1. Task

2. Annotation

3. Summary

4. Description of the vessel

Description of the ship

5. Description of goods

6. Description of the cargo

7. Requirements for the cargo plan

8. Calculation of vessel loading

8.1 Determination of the estimated displacement, deadweight

8.2 Determining the flight time

8.2.1 Determination of the running time and the necessary stocks for the passage

8.2.2 Determination of net load carrying capacity

8.2.3 Determination of parking time and stocks in parking

8.2.4 Determining the amount of inventory

8.3 Determination of the moment of optimal trim

8.4 Allocation of supplies and cargo to cargo spaces

8.5 Checking the overall longitudinal strength

8.5.1 Determination of the bending moment due to the forces of gravity amidships of an unladen ship

8.5.2 Determination of the bending moment from the accepted loads and stores (deadweight forces)

8.5.3 Determination of the bending moment at midships from the holding forces

8.5.4 Determination of the bending moment

8.5.5 Determination of the allowable torque

8.6 Verification of local strength

8.7 Calculation of stability

8.8 Requirements of the Register of Russia for stability

8.9 Determination of the weather criterion

List of used literature

Average vessel draft dav 8.2 m

Aft trim 0.2 m

Length between perpendiculars L 140 m

Width of the vessel B 17 m

Coefficient of total completeness Sv 0.75

Calculated displacement Δр 12700 t

Displacement of the vessel light Δ0 3300 t

Abscissa Ts.T. light vessel X0 7.5 m

Tonnage W 17900 m3

Daily fuel consumption on the move 12 t

Daily fuel consumption in the parking lot 10 t

Daily water consumption 15 t

Supply stock Rsnab 40 t

Crew and baggage weight Rack 15 t

Provisions stock Rpr 40 t

Transition distance Lп 3000 miles

Average vessel speed Vav 12.5 knots

The daily rate of work in the port of loading Mss 2000 t / day

Daily rate of work in the port of unloading M’ss 1200 t / day

Time for auxiliary operations:

at the port of loading Tvsp 6 hours

at the port of unloading T'vsp 8 hours

Storm stock coefficient Ksht 10%

Delay time of the vessel on the way Tzad 0.3 days

Table No. 1. Cargo space volumes

Premises	Volume, m3	Premises		Volume, m3
Hold No. 1		Twindeck number 3
Twindeck number 1		Hold No. 4
Twindeck number 1 in		Twindeck number 4
Hold No. 2		Hold No. 5
Twindeck number 2		Twindeck number 5
Hold No. 3		Twindeck number 5 in
The total volume of cargo spaces of the vessel

Table No. 2.

Name and characteristics of goods presented for carriage

Table No. 3.

Coordinates of the center of gravity of stocks

The ship is empty and supplies:	X g, m	Z g, m
The ship is empty
Provisions
Supplies
Application of the metacentre	-	The purpose of this course project is to study the technology of transporting these cargoes on a given type of vessel. In the course of the course project, you get acquainted with the characteristics of the goods presented for transportation and the type of vessel on which this cargo will be transported, as well as how the cargo is placed and loaded, according to their volumetric and weight characteristics and their compatibility. At the same time, it is necessary to understand how the strength of the hull of the vessel, the initial stability of the vessel when the reserves are expended during the voyage and after unloading the cargo at the ports of call, are respected. Consequently, the implementation of the course assignment sets as its task the study of technology and organization of cargo transportation by sea, which allows in the future to apply the knowledge gained in practice. 3. Summary The aim of the present project is studding procedure of the technology of the shipping of given cargoes on board the given ship. While working on the project one can get acquainted with characteristics of the cargoes necessary for the transportation the type of vessel on which board the cargo will be shipped, and with procedure of loading and stowing the cargoes in accordance with their weight and volume characteristics and compatibility of cargoes. One must understand it is necessary to pay attention to durability of the hull and stability of the vessel while spending stocks, during her sailing and after unloading cargoes at the first port of call. Consequently the main problems of this project are the procedure and organization the shipment of cargo by sea. This project helps to put knowledge into practice. The main part of the ship is the ship's hull. The hull of the ship is divided into three main parts: the bow (front) part, called the bow of the ship; the rear part, called the stern of the vessel; the part of the ship located between these two parts is called amidships ( middle part ship). The hull of the ship is the main part of the ship. This is the area between the main deck, sides and bottom. It is made of a frame covered with plating. The part of the ship's hull located below the water is the underwater part of the ship's hull. The distance between the waterline and the main deck is the ship's surface. The ship's hull is divided into a number of watertight compartments, decks and bulkheads. Bulkheads are steel vertical walls running along and across the vessel. The ship's hull consists of an engine room, cargo spaces and several tanks. In dry cargo vessels, the cargo space is divided into holds and twin decks. The forepeak tank is located in the bow of the hull, and the afterpeak tank is located in the aft (rear) part. They are designed for fresh water and fuel. If the vessel has double walls, then the space between the sides contains deck pockets. All permanent structures above the main deck are called superstructures. Currently, bulk carriers are built, standardized with the arrangement of the engine room and bridgework at the rear of the hull in order to gain more cargo space. The bow raised part of the deck is called the tank, and the aft raised part is called the hut. There are cargo handling equipment on deck such as cranes, winches, cargo booms, etc. The main body of a ship is called a hull. The hull is divided into three main parts: the foremost part is called the bow; the rearmost part is called the stern; the part in between is called midships. The hull is the main part of the ship. This is the area between the main deck, the sides (port and starboard) and the bottom. It is made up of frames covered with plating. The part of the below water is the ship's underwater body. The distance between the main deck is the vessel’s freeboard. The hull is divided up into a number of watertight compartments by decks and bulkheads. Bulkheads are vertical steel walls going across the ship and along. The hull contains the engine room, cargo spaces and a number of tanks. In dry cargo ships the cargo space is divided into holds. At the fore end of the hull are the forepeak tanks, and at the after end are afterpeak tanks. They are used for fresh water and fuel. If a ship has double sides, the space between the sides contains wing tanks. All permanent housing above the main deck is known as superstructure. Nowadays, cargo vessels are normally built with the after location of the engine room and bridge superstructure to gain more space for cargo. The forward raised part of the deck is called the forecastle and its after raised part is the poop. On deck their cargo handling facilities, such as cranes, winches, derricks etc. Iron ore (in bags) Iron ore is classified as a bulk cargo and is usually transported on bulk ore carriers. Transportation in bags is carried out only for small consignments. The main properties of ore as a bulk cargo are flowability, caking, freezing. A small specific loading volume is dangerous from the point of view of maintaining the strength of the ship's hull and the stability of the ship; therefore, the loading of ore on non-specialized ships must be carried out with strict observance cargo plan. Iron ore concentrate is subdivided into dry (gray, particle diameter less than 0.05 mm); wet (up to 10% humidity); wet (13% humidity). Moisture is an important indicator of a given cargo, as it determines its properties, such as freezing, liquefaction, etc. At a moisture content of up to 7%, the cargo should be considered non-freezing. At temperatures below 0 ° C and humidity above 13%, the ore freezes, which complicates its transportation, therefore, during transportation, it is necessary to maintain the specified temperature and humidity conditions, for which regularly measure the bilge air indicators, if necessary, perform natural or forced ventilation. Due to the high density of ore, the hold or tweendeck cannot be fully loaded with it, since in this case the requirement for the local strength of the hull is violated, according to which an unusable cargo space cannot be fully loaded with a load of less than 1.3 cubic meters. meters per ton. Specific loading volume of iron ore in bags is 0.5 cubic meters. meters per ton. White rice (in bags) Rice is transported in single and double bags from 80 to 100 kg. Rice differs from other cereals in its extreme susceptibility to various odors and active hygroscopicity. It has a high percentage of moisture and at the same time is able to absorb moisture or evaporate it, depending on the state of the air in the holds. Normal weight loss due to moisture evaporation is not more than 2.5% When transporting rice, in addition to the usual preparation of cargo spaces for the transport of grain, it is necessary to take a number of additional measures. Rice requires a very carefully designed and efficient ventilation system for two reasons. Firstly, the rice gives off some carbonic acid in the form of gas, and, secondly, the moisture content leads to fogging (condensation of moisture on the walls) of the holds. Consequently, condensation will drip onto the load from certain points of the metal structure, if the necessary precautions are not taken. Rice undergoes heating rather quickly, and this fact is associated with a decrease in humidity, which explains the decrease in weight in the "traditional" variation from 1 to 3%. The lower part (bottom, floor) of the hold should be covered with thin and battens laid across the vessel and boards laid in the distance of the vessel. Bottled vodka and wine (in boxes) Wine and vodka products are transported in barrels or in bottles packed in boxes. For packaging bottles, wooden or cardboard boxes are used. To protect the bottles from breaking, they are placed in cells and transferred with packaging material. All drawers must be specially marked "carefully fragile" or "do not turn over" to warn of the presence of glass inside the drawer and to show the top of the drawer. The loading of wine and vodka products is carried out with great care, excluding jerking mechanisms, swinging lifts, dropping boxes from a height. In the hold, the boxes are placed on a flat surface. Do not load heavy loads on top of boxes with wine and vodka products, which can damage the underlying loads. Upon receipt of wine and vodka products on the ship, strict control over the quality and quantity of cargo is required. Cargo with traces of opening, damage, smudges or damage will not be accepted for transportation. If the cargo is nevertheless loaded at the request of the consignor, then each damaged place is opened and checked in the presence of a commission. A special act is drawn up about the fact of the autopsy and the results. Specific loading volume - 1.7 cubic meters. meter per ton. Bananas (in bunches) Bananas are perishable goods of tropical origin. Their feature is a small temperature range at which they remain valid from 1 ° C to 5-8 ° C, so they are usually transported on special ships - banana carriers. On ordinary ships, their transportation is allowed only for a short time and subject to strict temperature regime. Before loading, the temperature in the holds should be 5-6 ° C below the optimum. Bananas are transported in bunches (whole branches), packed in plastic bags with holes or kraft paper or straw or cane branches. When loading, it is necessary to take into account the vulnerability of the cargo to chemical and mechanical stress, therefore, no other cargo should be placed on top of the bananas. For the safe transportation of this cargo, strict adherence to the temperature regime is necessary through regular ventilation. 1 ton of bananas in bunches takes 3.76 - 4.25 cubic meters. meters. Iron ore (in bags) Iron ore is bulk cargo and it is carried usually on bulk vessels. Carrying on usual ships is done only for small lots of cargoes. The main properties of ore as a bulk cargo are selffrizzing, selftightening and others. Small volume pertion of cargo maybe dangerous for ship stability and stronghess of hull, therefore the loading of ore on nonspecialized ships must be organized with whole according to cargo-plan. Iron ore is divided to dry (gray, diameter of pieces is than 0.05 mm); damply (to 10% of dampness); wet (13% of dampness). Dampness is important property of cargo because other properties depend on it. If dampness is less than 7%, then cargo is nonfreezing. At temperature below 0 and humidity above 13% ore freezes together, that complicates its transportation, on it during transportation it is necessary to support set temperature and humidity a mode for what on a regular basis to measure parameters of hold air if necessary to make natural or compulsory ventilation. In consequence of the big density of ore the hold or the twin deck cannot be loaded by her completely as the requirement to local durability of the case according to which be unusable a cargo premise in this case is broken cannot loaded completely by a cargo. Loading volume of iron ore - 0.5 m 3 / t White rice (in bags) Rice transport in unary and double bags from 80 up to 100 kg. Rice differs from others grain an extreme susceptibility to various smells and active hygroscopicity. It has high percent of humidity and thus is capable to absorb in itself a moisture or to evaporate it depending on a condition of air in holds. Normal loss of weight owing to evaporation of a moisture no more than 2.5% is considered By transportation rice, except for usual preparation of cargo premises for transportation grain, it is necessary to accept a number of additional measures. Rice demands very carefully developed and effective system of ventilation for two reasons. First, rice allocates a quantity of a coal acid in the form of gas, and, secondly, moisture content leads condensation of a moisture on walls holds. On it the condensate will drip on a cargo from the certain points of a metal design if necessary safety measures will not be accepted. Rice is exposed to heating quickly enough, and this fact is connected with downturn of humidity, than and reduction of weight in "traditional" change from 1 up to 3% speaks. The bottom part (the bottom, a floor) hold should be covered thin and battens, laid across a vessel and the boards laid afar of a vessel. Vodka and wine in bottles (in boxes) Alcohol is transported in cans or bottles packed in boxes. Wooden and cardboard boxes are used to packing of bottles. For protection bottles from beating they are in calls and separated. All boxes should have special marks "cautiously fragile" or “top handle with care” warning about presence inside of a box of glass and showing top of a box. Loading alcoholic products make with the big care excluding jerks of mechanisms, rocking of rises, dumping boxes from height. In hold boxes keep within on an equal surface. It is not necessary to load atop of boxes with alcoholic products heavy cargoes which can damage underlaying cargoes. While loading it is necessary to control guarantying and quality of cargo. Cargoes with spots of damage, beating or leaking don’t accepted to carrying. If it is loaded by requirement of special commission. This checking and its result must be fixed in special document. Loading volume of alcohol is 1.7 m 3 / tonn. Bananas (in bunches) Bananas concern to perishable cargoes of a tropical origin. Their feature is the small range of temperatures at which they keep the validity from 1 ° С to 5-8 ° С, on it their transportation is carried out on special banana-carriers. On usually ships they are can carrier only during small period and with proper temperature regime. Before loading temperature in holds mast is bellow optimal on 5-6 ° С. Bananas are carried in bunches (whole brunches), packed in palliation bags with ventilation or craft-paper or solemn or brunches of reed. At loading it is necessary to consider vulnerability of a cargo to chemical and mechanical influence, therefore atop of bananas other cargoes should not be placed. For safe transportation of the given cargo strict observance of a temperature mode by regular ventilation is necessary. 1 ton of bananas in bunches requires 3.76-4.25 m 3 The placement of cargo on the ship must ensure that the following basic conditions are met: 1. Elimination of the possibility of damage to cargo from their mutual harmful influence (the action of moisture, dust, odors, the occurrence of chemical processes, etc.), as well as damage to the lower layers of the cargo from the pressure of the upper ones; 2. Creation of the possibility of unimpeded unloading and loading at intermediate ports of call; 3. Ensuring maximum labor productivity during cargo operations; 4. Elimination of mixing of goods from different consignments of bill of lading; 5. Ensuring the acceptance on board of a whole number of consignments of bill of lading; 6. Maintaining the general and local strength of the vessel; 7. Ensuring optimal (or at least close to it) trim during transitions; 8. Guarantee that at all stages of the voyage the stability of the vessel will not fall below the limits stipulated by the Register norms; at the same time, the occurrence of excessive stability must be excluded; 9. Maximum use of the vessel's carrying capacity and cargo capacity (depending on which of the indicated values ​​will be the limiting one); 10. Ensuring the loading of receiving the maximum possible freight under the given conditions of carriage. Such numerous and sometimes conflicting requirements make the preparation of a cargo plan time-consuming. The usual workflow for calculating ship loading is as follows: 1. Determination of the total amount of cargo that can be accepted for carriage on a given voyage; 2. Selection of cargo, based on the conditions of full use of the vessel's carrying capacity or its cargo capacity, or obtaining the maximum freight; 3. Distribution of the load over the cargo compartments, taking into account the need to ensure the strength of the hull (a cargo compartment means a hold plus tweendecks above it); 4. Placement of cargoes in cargo spaces depending on the possibility of joint transportation and ensuring safety, as well as the sequence of unloading at intermediate ports; 5. Determination, correction and check of trim; 6. Determination, correction and verification of stability. If a ship is making a voyage with intermediate ports of call, then the calculations begin from the last intermediate port, in the reverse order: first, stocks are placed for the last passage and cargo for the last port, then for the penultimate passage and cargo, etc. The cargo plan is drawn up even before the start of loading - the so-called preliminary plan. During loading, sometimes deviations are made from it due to non-delivery of the planned cargo, discovered inaccuracies in the calculation, readdressing of consignments, etc. therefore, after the end of cargo operations, an executive cargo plan is drawn up, corresponding to the actual loading of the vessel. According to it, the characteristics of strength, stability and trim are finally specified. It is this plan that is sent to the port of destination. The cargo plan is most often performed in the form of a schematic vertical section along the diametrical plane for a dry cargo ship and horizontally for a tanker. With especially complex cargo compositions on navigable ships, sometimes the location of cargo is also shown on horizontal sections. Such cargo plans can have two or more schemes and are called multi-plane. 8. Calculation of vessel loading Load calculations are performed point by point in accordance with the proposed methodology. 8.1 Determination of the estimated displacement, deadweight The estimated displacement is determined as follows: 1. According to the specified draft, which will not violate the draft of the seasonal zones. 2. According to the load line corresponding to the sailing season, ie. if the vessel is moving from one navigation area to another, which may be in the area of ​​the seasonal mark L - summer zone, W - winter zone, ZSA - winter North Atlantic, P - fresh, T - tropical zone, TP - tropical fresh zone. 3. In our case, we find d cf = 8.2 m, which corresponds to D p = 12700 t. Let us determine the total carrying capacity D w (deadweight), which is equal to: D w = D p - D 0 = 12700 - 3300 = 9400 t. 8.2 Determining the flight time 8.2.1 Determination of the running time and the necessary stocks for the passage t x = + T back. , days; t x = + 0.3 = 10.3 days; P zap. = K pcs t x q t x + K pcs t x q in x, t; P zap. = 1.1 10.3 12 + 1.1 10.3 15 = 305.91 t. Full lifting capacity (deadweight) D w = D p + D 0. Deadweight can be expressed as the sum of the weights of cargo and stores that can be taken on board the ship at a certain draft d cf. D w = P load + P t + P in + P sn. + P eq. + P pr. D w = 12700 - 3300 = 9400 t. Net carrying capacity D h is the weight of the cargo without the weight of fuel, water, ship supplies, crew, provisions. D h = D w - S (P cargo + P t + P in + P snab + P eq + P pr) P nf.gr. = 2300 + 3000 + 1400 = 6700 t. W nf.gr. = 1150 + 4410 + 2380 = 7940 m 3. W of the vessel = 17900 m 3 P f.gr. = (W - W nf.gr.) / m d.gr. P f.gr. = (17900 - 7940) / 4 = 9960/4 = 2490 t. D h = SR 1 + R 2 + R 3 + R 4; D h = 2300 + 3000 + 1400 + 2490 = 9190 t. 8.2.3. Determination of parking time and stocks in the parking lot t Art. = + t aux + + t ¢ aux. ; t Art. = + 0.25 + + 0.33 = 12.8 days; P t st = t st. Q t st = 12.8 10 = 128 t. P in st = t st. Q in st = 12.8 15 = 193t. SR zap. = R zap.toy + R z.st. + R pr + R snub + R eq. = 305.91 + 321 + 40 + 40 + 15 = Determination of fuel and water reserves for crossing and parking R t = R x t + R st t = K pcs t x q x t + R t st = 1.1 10.3 12 + 127 = 135.96 + 128 = 264 t; R in = R x in + R in st = K pcs t x q x in + R in st = 1.1 10.3 15 + 193 = 169.95 + 193 = Determine the average shoulder of the bow X n and aft X k compartments: X n = SW j n x j n / SW j n, X k = SW j k x j k / SW j k, where W j n and W j to the cargo capacity j of the bow and stern cargo space; x j n and x j to the abscissa of the center of gravity of the cargo to the bow and stern from the midsection, i.e. the horizontal distance of its center of gravity from the midsection in meters. The total variable load is taken to be equal to the net tonnage of the vessel: D h = P n + P k Having solved the equations for the total distributed mass of the bow P n and aft P k compartments, we get: Then the distributed mass in each particular compartment will be: P i n, P i k - the weight of the cargo for any cargo space; W i n, W i k - the volume of any cargo space. P 1 hold = 937 (4583/11228) = 382 t P 1up.tv. = 738 (4583/11228) = 301 t P 2 hold = 2417 (4583/11228) = 987 t P 3 hold = 2783 (4583/11228) = 1136 t P 4 hold = 2752 (4607/6672) = 1900 t P 5 hold = 417 (4607/6672) = 288 t P 5up.tv. = 1096 (4607/6672) = 757 t 8.4 Allocation of supplies and cargo to cargo spaces Premises Weight, t X g (+) M x (+) X g (-) M x (-) Z g M z 7,5 7,24 -43 3,94 1041,316 -48 10,23 3707,864 -40 17 Provisions -72 7,2 Supply -17,1 3,27  1 R 4022 + Σ 1 M x 24750 -Σ 1 M x -32926,213 Σ 1 М z 29314,98 Hold 1 51,5 4 50 4,6 50 5,39 Twindeck 1 51 8,7 51 9,7 51 11,2 Twindeck 1 in 52 13,7 51 15,04 Hold 2 30 1,1 wine and vodka 32 1,4 31 2,9 30,5 4,51 Twindeck 2 31 8,5 30 9 30 9,5 Hold 3 5 1,55 wine and vodka 5 2 5 2,9 5 4 Twindeck 3 5 8,5 5 8,6 5 9 5 10 Hold 4 -16 2 -16 2,9 -16 3,5 -16 5 Twindeck 4 wine and vodka -16 9 -16 9,5 -16 10,6 Hold 5 -55 4,7 wine and vodka -55 5,3 -55 6 -55 6,4 Twindeck 5 -56 8,7 wine and vodka -56 9,5 -55 9,9 -55 10,4 Twindeck 5 V -55 -14093,376 12,5 -55 -9805,5164 12,9 -55 -13589,022 13,2 -55 -4146,8866 13,8 8678 Σ 2 M x 111436,4 Σ 2 M x -103240,45 Σ 2 M z 59585,1 P total 12700 Σ о M x 136186,4 Σ о M x -136166,66 Σ о M z 88900 X g = 0,002 Z g = 7 Hold 1. P = 382 0 + 40.7 + 196.6 + 144.7 = 382 W = 937 1.7 * 40.7 + 1.47 * 196.6 + 4 * 144.7 = 926.99 Twindeck 1. P = 402 8.9 + 233.9 + 159.2 = 402 W = 985 4.45 + 343.8 + 636.8 = 985 Twindeck 1 top P = 301 0 + 0 + 46 + 167.6 = 213 W = 738 67.6 + 670.4 = 738 Hold 2. P = 987 7.5 + 51.7 + 547.8 + 380 = 987 W = 2417 3.75 + 88 + 805.3 + 1520 = 2416.9 Twindeck 2. P = 701 312.5 + 157.3 + 231.2 = 701 W = 1717 156.3 + 267.4 + 339.8 = 763.7 Hold 3. P = 1136 235.3 + 214 + 435.1 + 252.6 = 1136 W = 2783 117.7 + 363.8 + 639.6 + 1010.4 = 2131.5 Twindeck 3. P = 674 192.4 + 81.1 + 201.1 + 199.4 = 673 W = 1651 96.2 + 137.9 + 295.6 + 797.6 = 1327.3 Hold 4. P = 1900 921.2 + 306.5 + 363.2 + 309.1 = 1900 W = 2752 460.5 + 521.9 + 533.6 + 1236 = 2752 Twindeck 4. P = 1132 0 + 214 + 276 + 218 = 708 W = 1640 214 * 1.7 + 276 * 1.47 + 218 * 4 = 1640 Hold 5. P = 288 145.1 + 28.2 + 109.8 + 4.9 = 288 W = 417 72.6 + 48 + 161.4 + 20 = 302 Twindeck 5 P = 530 221 + 128.3 + 112.7 + 68 = 530 W = 767 110.5 + 217.6 + 166.1 + 272 = 766.2 Twindeck 5 top P = 757 256.2 + 178.2 + 247.1 + 75.4 = 756.9 W = 1096 128.1 + 302.9 + 363.2 + 301.6 = 1095.8 8.5 Checking the overall longitudinal strength The general longitudinal strength of the ship's hull is checked by comparing the greatest bending moments in the midship area of ​​the M outgrowth. with the standard value of the permissible bending moment M add. 8.5.1 Determination of the bending moment due to the forces of gravity amidships of an unladen ship M o = k o D o L ^^ k o = 0.126 (for dry cargo ships with a machine in the stern) a) The amplitude of the roll: q ir = x 1 ∙ x 2 ∙ Y = 1.0 ∙ 1.0 ∙ 24.0 = 24.0 deg (according to tabular values) b) The resulting value is plotted on the q-axis to the right of the origin. c) Restore the perpendicular to the intersection with the DDO. We get point A. d) Set aside from point A the segment equal to 2 ∙ q ir to the left. Got a point A ' e) From point A we draw a tangent line to the DDO. f) From point A to the right, set aside a segment equal to 57.3 ˚ (1 glad.) g) From point B, restore the perpendicular to the intersection with the tangent. Received L def. L def = 0.12 m. The Register of Russia imposes certain requirements on the stability of transport vessels, the verification of the fulfillment of which is mandatory when drawing up a cargo plan before a vessel leaves the sea. The stability requirements of the Register of Russia are detailed in the Rules for the Classification and Construction of Sea-Going Ships of the Register of Russia and are summarized as follows. For transport vessels with a length of 20 m and more, the stability criteria must be met: a) the dynamically applied heeling moment from the wind pressure M v must be equal to or less than the overturning moment M s, determined taking into account the conditions of the pitching amplitude, i.e. the condition must be met K = M s / M v ³ 1.0 where K is the weather criterion; b) the maximum shoulder of the static stability diagram l max should be at least 0.25 m for vessels with a length of L ³ 80 m and at least 0.2 m for vessels with a length of L ³ 105 m. For intermediate values ​​of lengths, the value of l max is determined by linear interpolation ; c) the roll angle at which the stability arm reaches a maximum q m must be at least 30 ˚ , i.e. q m ³ 30 ˚ ; d) the sunset angle of the diagram of static stability q v must be at least 60 ˚ , i.e. q v ³ 60 ˚ ; e) the initial metacentric height for all load cases, with the exception of the ship without light, must be positive (h o ³ 0). Stability for ships is considered to be sufficient according to the weather criterion K, if at the worst, in terms of stability, the load case, the dynamically applied heeling moment from wind pressure M cr is equal to or less than the overturning moment M ref, i.e. if the conditions are met: k = M def / M cr M def / M cr ³ 1 М cr = 0.001 ∙ p v ∙ A v ∙ z, where р v - wind pressure, Pa p v = 1196 Pa (taken according to the Register table depending on the area of ​​navigation of the vessel and the sail area). And v is the sail area of ​​the vessel given to us, m 2. And v = 110 m 2. z - distance of the center of windage from the plane of the current waterline M cr = 0.001 ∙ 1196 ∙ 110 ∙ 7 = 921 tm. K = 1524/921 = 1.65> 1. Consequently, stability is sufficient for the calculated vessel. 1. Zhukov EI, Pismenny MN “Technology of sea transportation”. 2. Belousov L.N. "Technology of sea transportation". 3. Kozyrev V.K. "Cargo management". 4. Nemchikov V.I. "Organization of work and management of sea transport." 5. “Safety rules for the carriage of general cargo by sea. 4 - M ”Volume 2. 6. Kitaevich B.E. “Marine cargo operations. Educational and practical guide to the English language ”. 7. Snopkov V.I. "Carriage of goods by sea", "Carriage of goods by sea." 8. Encyclopedic Dictionary "Ensuring the safety of cargo in sea transport."

Graphical representation on the ship's drawing of the location of each consignment of cargo in the ship's cargo spaces and on the deck for a given voyage. The cargo plan of the vessel is drawn up on the basis of general requirements for the optimal placement of cargo, taking into account the conditions of the upcoming voyage. To fulfill these requirements, it is necessary to ensure:

Maintaining the necessary stability, strength and trim of the vessel; - the most profitable use of the cargo capacity and cargo capacity of the vessel;

Ability to ensure loading and unloading of cargo in the shortest possible time; - safe navigation of the vessel; - safe and timely delivery of goods; - observance of the sequence of loading cargo with the calculation of unloading the vessel in intermediate ports without additional transshipments; - observance of safety standards and labor protection of the ship's crew and port workers.

In addition to technical and organizational requirements, when drawing up a cargo plan, the need to achieve the highest economic efficiency of the ship's operation is taken into account.

To draw up a cargo plan, you need to know detailed information about the vessel, cargo and sailing conditions. A cargo plan can only be accepted for execution when it ensures the safety of navigation, i.e. the vessel has sufficient stability longitudinal strength allowable heel and trim. This is ensured by the normal distribution of weight loads along the length, width and height of the vessel.

The next most important stage in drawing up a cargo plan is the distribution of cargo between various cargo spaces of the vessel, for which all physical, mechanical, chemical and other properties of cargo are studied and taken into account. The correct distribution of cargoes among the holds affects not only their safety, but also the safety of the ship's navigation. The placement of cargoes on board that emit moisture, odors, or present a fire and explosion hazard should be done with extreme caution. Liquid cargo in containers, heavy weights and cargo in fragile containers also require special measures when loading. Joint transportation of incompatible goods in the same room can lead to their damage due to harmful effects on each other. When drawing up a cargo plan, the issue of maximizing the use of cargo capacity and carrying capacity should be resolved. This is achieved by selecting the appropriate combination of light and heavy loads. The amount of cargo that a vessel can accept for transportation is determined by its specific loading volume.

In the practice of the fleet, two types of cargo plans are distinguished - preliminary and executive.

A preliminary cargo plan can be drawn up by the port authority, the ship's agent or the cargo mate on the ship itself. When drawing up a cargo plan, it is necessary to know the operational and technical characteristics of the vessel, as well as the transport characteristics of the cargo and its physical and chemical properties.

The operational and technical characteristics of the vessel include: 1. Linear characteristics - length, width, depth of the vessel and its draft;

2. Weight characteristics - vessel's empty displacement, vessel's displacement to cargo, carrying capacity (deadweight); 3. Volumetric characteristics of the vessel.

The main transport characteristics of the cargo are its mass, volume, linear characteristics and specific loading volume. To solve problems associated with the possibility of transporting various goods in one cargo compartment, properties such as flammability, toxicity, radioactivity and its aggressive properties are important: dust, odors, hygroscopicity, the possibility of quarantine contamination and a number of other properties.

After placing the cargo in the holds, the following parameters of the vessel are calculated: - stability; - ship landing (roll and trim); - loads on ship structures; - the elements of the rolling of the vessel.

The developed preliminary cargo plan must be approved by the master. During the loading process, an executive cargo plan is drawn up. When drawing up a cargo plan for a Ro-Ro vessel, the preliminary cargo plan should be linked to the vessel's handling schedule.

- Types of cargo plans.

A one-plane drawing of the cargo plan is always drawn up.

In the case of a large number of small consignments of cargo, it is necessary to draw up a cargo plan that has several planes. In such a plan, an additional section is given along the twindeck, upper deck, etc.

The coordinates of the cargo inside the vessel can be determined from the drawing of the vessel by sections along the water lines (approximately every meter), along the frames (by spacing), as well as by buttocks (approximately every meter). In this case, each consignment of cargo can be accurately identified by the number of the waterline, buttocks and frame (Golubev system).

--The procedure for drawing up a cargo plan.

1. Check if there are any goods dangerous to the ship and passengers.

2. Determine the possibility of stowage of goods in terms of their compatibility and uniform distribution in the holds, draw up a list from which it should be seen that

a) incompatible cargo was able to be distributed to different cargo spaces;

b) the use of the cubic capacity of the holds and the distribution of weight loads in individual compartments will not cause harmful stresses in the ship's hull.

3. To check the influence of loading on the stroke cargo works to subdivide cargoes according to the classification adopted in the regulation on ship-daily norms of cargo operations in ports, and to determine the coefficient of uneven distribution of cargo in the holds.

4. Having a scheme for placing the cargo in the holds, draw up a cargo plan (Fig. 1).

5. Check lateral stability.

H some details of the draft survey

Inquisitive - already senior mates

and more to the cadets.

In the world, billions of tons of cargo are transported in bulk by sea vessels. Obviously, the question of how much cargo is loaded on the ship or how much has been removed from it will always be relevant.

This quantity can be determined both by onshore measuring systems and by the draft of the vessel - by the draft survey method.

Arranging onshore measurements can be cumbersome and a compact draft survey is a good alternative to onshore measurements. At modern terminals there are no problems with organizing the weighing of cargo, but then a draft survey can be, as practice shows, a very useful independent (control, if you like) means of determining the amount of cargo on the ship.

The usefulness of a draft survey is understandable. All that remains is to worry about its currently reasonably achievable reliability and accuracy.

The direct participants in the draft survey are the chief (cargo) mate of the vessel and an independent surveyor.

The surveyor does not bear any responsibility for the inaccuracy of determining the amount of cargo, and can only fly out of work for his non-observance of the Instructions head -office. Let's leave him alone.

But the CEOs, perhaps, should understand the problems of the draft survey in more detail.

So, the vessel accepted bulk cargo at the port, the amount of cargo was determined by the operator of the onshore measuring complex and / or an independent surveyor and entered into the Bill of Lading.

At the port of unloading, the new operator and / or new surveyor determined the amount of cargo less than in the Bill of Lading. Disputes and vessel demurrage. Both the operator and the port of loading surveyor are absent. In this case, losses and troubles arise primarily from the shipowner. Obviously, the chief executive officer needs to start the fight for knowing the reliable amount of cargo in advance at the port of loading. At the port of unloading, he will already defend his own, and not someone else's numbers. The Chief Officer, as the only participant in both loading and unloading, is a key figure in the draft survey.

The chief executive officer knows the structure and specifics of his vessel better than the surveyor of the most stellar company, it remains only to know better than him and the draft survey technique.

This is not difficult.

The most complete existing draft survey standards are given in the International Code (Internet address: unece. org / energy / se / pdfs / ece _ energy _19 r. pdf).

Let's look through it.

General scheme

The standard procedure requires an initial survey to be carried out prior to loading:

· Determine draft by marks of deepening and calculate displacement D i;

· Measure liquid ballast levels and calculate the amount Bl i;

· Measure the levels of ship's stores and calculate their quantity St i;

· Write out the empty displacement from the ship's documents LS and calculate the so-called "constant":

Const = D i - Bl i - St i - LS (1)

After loading, a final survey is required:

· Define accordingly D f, Bl f, St f;

· Calculate the amount of cargo received:

Cargo = D f - Bl f - St f - LS - Const (2)

Note that in this case, a certain mixture (each time different) from the errors of measurements and calculations of the initial survey will be included in Const , and then by chance it can be neutralized or aggravated by a similar mixture of errors in the final survey. The result according to formula (2) turns out to be unreliable, which is confirmed by practice - Const not stable and sometimes within very wide limits.

Codex assurances what if hesitation Const do not exceed 10%, the draft survey was carried out qualitatively, not enough. Just from voyage to voyage, both during loading and unloading, one (and maybe more than one) and the same systematic error can be repeated. This is instantly revealed if one compares not only the survey results, but also the survey results with the measurements of the coastal complex.

Substituting into formula (2) the expression for Const, we get:

Cargo = (D f - D i) - (Bl f - Bl i) - (St f - St i) - (LS - LS) (3)

It turns out that the amount of cargo received is numerically equal to the algebraic sum of changes in displacement, ballast and reserves between the initial and final surveys .

For draft survey Const is completely unnecessary and can only be used when planning a voyage, so that, for example, you do not promise to carry more cargo than is allowed by the draft of the load line.

Consider possible errors in formula (3).

Empty displacement

In the vast majority of cases, the change LS LS - LS = 0 does not occur between the initial and final surveys, and an error does not arise here.

However, there are the following options:

· The anchor was laid on the ground, and then the anchor-chain was released (there was a hauling of the vessel along the berth);

· The boat was lowered (for measuring the draft, for example), and at the final survey it was already in its regular place;

· Before loading, hatch covers were removed and laid on the shore (there are such ships), and at the final survey they were already on the ship;

· And finally, the outboard ladder was lowered all the way to the berth (sometimes through an oversight of the watch), and then raised above the berth or replaced with a light gangway.

In any case, according to the ship's drawings and certificates for this equipment, it is possible to determine its mass in advance and calculate the change LS without (from the point of view of survey) errors.

Ship stores

Consumable ship supplies of fresh water and provisions are discharged into the ship's bulk tanks, so the sum of the supplies and polluted waters taken in the initial survey should be equal to their sum in the final survey, the change is zero, and the error to the cargo will be zero.

The requirement of the Code to determine the amount of fresh water reserves both in the initial and in the final surveys only provokes a general error due to measurement errors and errors in the calibration of ship tanks. For draft survey purposes, these measurements and calculations are harmful.

For the same reason, fuel and lubricating oil measurements are not necessary. The operating time of the main engine (if there was, for example, the transition of the vessel from the berth to the berth), the auxiliary diesel engine and the boiler are known from the Machine Log, the hourly consumption of fuels and lubricants is known from the passport data of the mechanisms, so these changes can be calculated practically without (from the point of view of a survey) errors.

By the way, many vessels use not only fresh water for sanitary purposes, but also outboard water (up to about 50 liters per person per day), which also ends up in collecting tanks almost completely compensating for the usual consumption of fuels and lubricants.

Ballast

In view of the above, real problems of accuracy arise when calculating the load according to the formula:

Cargo = (D f - D i) - (Bl f - Bl i) (4)

Errors in determining the amount of ballast is the most cumbersome topic in the description, so we will single it out in a separate article.

For most ships and in most cases, the ballast of a vessel in transit can be pumped out in advance before the start of loading, and even more so it is possible not to change it until the end of loading. The change in ballast will be equal to zero and there will be no excessive error for the amount of cargo.

Displacement of the vessel

Cargo = (D f - D i) (5)

Seawater density

The procedure for sampling and measuring the density of water is fairly fully set out in the Code. We only note that a hydrometer (of good quality) and a glass for samples (a simplified form is also possible) are better to have their own shipboard ones. This eliminates errors from the use of different devices at the port of loading and at the port of unloading.

In the example given in the Code, the density is indicated as 1.0285 t / m 3, the last figure being guessed only. There may be 4 and 6, that is, the error can reach 0.0001 t / m 3.

For small vessels (carrying capacity of the order of 1000 t), this gives an error in the amount of cargo of about 0.1 t. For large vessels ( Handysize - about 30,000 tons of cargo), the error will be only about 5 tons, and on supers ( Capesize , 100-150 thousand tons of cargo), the error will be about 10-15 tons.

This is perfectly acceptable today and in the future. There is no need to organize more accurate measurements.

Measurement of sediment

As a matter of fact, in most cases no measurement is made, the precipitation is visually assessed according to a very rough (decimeter, half-foot) scale of indentation marks:

· In the middle of the ship - at an acute angle in a narrow gap between the side of the ship and the berth or in acrobatic positions from the storm ladder from the sea side;

· At the ends - squinting from the dock, remotely half the width of the ship's hull.

All this is often done in unfavorable weather, rough water surface, poor lighting conditions. And the technical condition of the indentation marks and the accuracy of the positioning of their edges in height often make much to be desired.

The error of such a definition of 1-2 cm is by no means uncommon (it happens even worse!).

Meanwhile, the number of tons per 1 cm of draft on small vessels is about 5 tons, on large vessels up to 40 tons, and on supers up to 70-80 tons and an error of tens, or even a hundred or two tons of cargo is quite probable.

For the purposes of safety of navigation, the indentation marks are usually quite good, but for the purposes of draft survey (commercial! - the price of cargo is 100, 500, or even 1000 USD for every ton) they are not at all suitable.

The ship afloat has the beginning of the axis " Z »For hydrostatic calculations is under water and is not available as a base for measuring the draft.

On the ship along the upper deck at the side in the dock, strips (similar to the deck line above the Plimsol disc) should be welded, the elevation of which above the keel in the dock can be measured with an accuracy of 1 mm. (Attention! Due to shipbuilding tolerances, including the height of the side, the elevation of the planks should be taken actual, not calculated.)

Standing on the deck, in comfortable conditions, using a device based on a conventional tape measure and a stilling tube (similar to those specified in the Code), you can measure the freeboard from the planks with an accuracy of 1 mm and then calculate the draft with an error of 1-2 mm, that is, by the amount of cargo up to 1 ton on a small vessel, up to 10 tonnes on a large one and up to 15 tonnes on a super.

It is even better to have on board a laser tape measure with an averaging device, which will give a reliable measurement result from the planks to the water, even if the vessel itself sways during the measurements.

If you consider these measures cumbersome, then take into account that doubts and disputes in the usual "determination" of precipitation take longer than an indisputable instrumental measurement.

If this does not convince you, then try to visually determine with acceptable accuracy (1 cm) the draft in photo 1 under excellent weather conditions. Do you think you succeeded?

Then try the same thing on photo 2. Decided on some value? Now, note that the top edge of the 4M mark (that's 410 cm) matches the bottom edge of the 42 mark (that's 420 cm). So what is the sediment in reality?

Cases of this kind are by no means isolated on a variety of courts. The author was sometimes bewildered on Panamax. Meanwhile, tens, and even hundreds or two tons of cargo, tens and hundreds of thousands of dollars are in uncertainty. Dependence on other people's flaws is very unpleasant.

It is clear that both the cargo and the money are not your own. And if you are still a supporter of not MEASURING draft, but DEFINITION of its "sea bulging eye", then this article is not for you, but at least think about your professional honor and at least some responsibility to the shipowner.

Body shape

With advanced methods of building ships, a mathematical model is used to describe the shape of the hull, the exact calculation of the displacement for which is not difficult. We only note that the electronic version of this mathematical model must be on board the ship.

Here we will consider ships of the traditional method of construction, when the shape of the hull is described by a Theoretical drawing, which is being developed at the stage of still conceptual design, as a rule, with 10 theoretical frames.

On the stage technical project a revised drawing with 20 frames is being carried out, according to which the revised hydrostatic data of the vessel are calculated.

Further refinement of the drawing (especially at the ends) happens at the stage of the working project and here the Plaza building for the shipyard is drawn on an enlarged scale with full set practical frames. Hydrostatic data are generally not recalculated.

When drawing on a plaza on a scale of 1: 1, additional clarifications are made and a table of plaza ordinates is published.

And finally, the assembly of the ship on the slipway will make further adjustments to the shape of the hull, which will be indirectly reflected in the delivery certificate of the main dimensions of the ship.

A systematic analysis of changes in the shape of the hull in these circumstances is hardly possible. Let's take for granted the individual opinions of experts that the error in calculating the displacement according to the Table of Plazovy Ordinates will not exceed 0.1%, that is, for a cargo of about 1 ton on small vessels, about 35 tons on large vessels, and up to 100-150 tons on supers. It is possible that for individual ships it will be necessary to take into account deviations under the Act of main dimensions.

Meanwhile, ship designers in the overwhelming majority of cases use the theoretical drawing of a technical or even a draft design for hydrostatics calculations.

Or such a case. For older vessels, the Stability Information (and in them also hydrostatics) was massively recalculated in accordance with the requirements of the SOLAS MK. For one group of ships this was done by one design bureau, for other ships of the same series - another (maybe there is a third, but so far it has not come across). Calculation of the amount of cargo according to different Information with the same initial data gave a difference of 30 tons with a total amount of cargo of about 3000 tons.

For the accuracy of calculating the seaworthiness of the vessel, all this is not important, but, as in the case of deepening marks, it is completely unacceptable for the needs of a draft survey, about which no one has ever said anything to the designers.

For ships under construction, it may become the norm to perform all hydrostatic calculations for operational documents according to the Tables of Plazovy Ordinates. For ships in operation, it is advisable to order such hydrostatics specifically for draft survey without re-issuing (possibly) other valid documents.

It is possible that for a number of vessels the results will turn out to be quite close to the previous ones, but the costs should not be considered in vain, and in this case, there will be evidence of minimizing errors.

Preliminary results

As follows from the above, the usual record of draft survey results of the type 13473.685 and even 3473.685 tons of cargo is ridiculous. Three digits after the decimal point are always fiction. The pseudo-precision only distracts from the real problems of the draft survey. You need to worry about the three digits before the comma.

The Code says that the determination of the amount of cargo by draft survey with an accuracy of 0.5% is accepted by the world practice.

This is not very clear. Now, if someone knew the truth, then ± 0.5% would be understandable.

Onshore measurements indicated 20,100 tons of cargo, and the draft survey gave 20,000 tons. The difference does not exceed 0.5%, and the true value is less than a lesser or more than a greater one? Or is it between?

If the difference is more than 0.5% - what to believe? Arithmetically fitting? And where to?

The cargo is about 20,000 tons and 0.5% is 100 tons. Even with a very modest price of 100 USD for 1 ton either the seller or the buyer will be infringed by 10,000 USD ... Does the victim agree to compensation in the form of an assurance of accepted world practice? Maybe you need to ask him first?

It is clear that it is not the chief executive officer or the shipowner who should ask for consent, but the right to freely dispose of someone else's cargo is highly questionable.

Perhaps it is time for logistics specialists to divide the draft survey into "survey - proforma" (a rough estimate of the amount of cargo) and "survey - MEASUREMENT" of the amount of cargo.

We emphasize once again that it is impossible to completely abandon the draft survey. It is needed at least as an independent control over the coastal measuring complex - it has its own curious "details" and the results of its measurements are by no means indisputable truths.

If the vessel is also used as a meter for the amount of bulk cargo, then EVERY draft "survey - measurement" error with acceptable efforts should be minimized. On small ships, integer units of tons of cargo can be reliable, on large ships - tens, and on supers - hundreds.

If readers are interested, they can refer to subsequent articles, which will be devoted to the refined calculation of the terms D f - D i and Bl f - Bl i in formula (4).

Photo 1. (Option)

Photo 1. (Option)

Photo 1.

Photo 2.

calculation of displacement during draft survey

The displacement of the vessel is determined by the shape of its hull and the draft at a given density of seawater.

Problems with the shape of the hull, water density and the accuracy of measuring the draft are discussed in the previous article "Some details of the draft survey", here we will consider the problems of accurate calculation of the displacement.

Design waterline

The landing of the vessel is uniquely determined by the trace of the waterline on its hull.

All vessels afloat have a greater or lesser bend in the longitudinal direction, more or less changing with changes in the amount and location of cargo, liquid ballast and ship's stores.

Let us take the shape of the hull unchanged and then the waterline will bend, which is mathematically absolutely adequate, but much more convenient for analysis.

The bend of the waterline can be with one inflection point (parabolic shape as in Fig. 1) and with two or even three inflection points ( S -shaped form).

International Draft Survey Code (Internet address: unece. org / energy / se / pdfs / ece _ energy _19 r. pdf ) it is planned to measure the draft according to the indentation marks in only 3 points along the length of the vessel T f, T m, T a and the shape of the bend therefore remains unknown.

Having comprehended the formulas of the Code for amendments to the mentioned T, we will understand that it is required to connect the dots T f and T a a straight line and, extending it to the perpendiculars of the vessel, obtain draft d f and d a on perpendiculars, and drawing a parallel line through T m , get a draft midships d m ... It is assumed that precipitation d lie on the parabolic waterline.

The waterline bend arrow is

F = df + da / 2-dm f = d f + d a- d m (1)

The figure clearly shows that in this case, errors are obtained, and the larger, the larger the bending arrow and the distance l f, l m, l a from groove mark lines to perpendiculars and midships.

Exact distance values

With the General Ship Location drawing, walk along the quay and across the deck, using your fingers to count the number of spacing from the nearest main transverse bulkheads of the ship to the corresponding lines of the deepening marks - this is the only way you can reliably determine which practical frames the marks are placed on. Drawings of stamps applied on a ship may be unreliable and not reporting.

Now I would very much like, but never succeeded, to see the designer's indication of how many millimeters in the bow or in the stern are the perpendiculars and midship of the Theoretical Drawing from the nearest practical frames.

Using the Theoretical Drawing, calculate this relationship yourself and only after that you will be able to correctly determine the distances l f, l m, l a.

There are Theoretical drawings without applied practical frames or drawings on the ship simply are not. Get the designer by requesting accurate official information about this relationship. Indirect signs may turn out to be unreliable.

For a draft survey, only and exclusively the perpendiculars and midship of the Theoretical Drawing are needed, since the hydrostatics of the vessel is calculated according to this drawing.

Despite quite extensive practice, I have never been able to see in the Stability Information a competent record "Length of the vessel between the perpendiculars of the Theoretical drawing ... m". But to see someone else's there LBP (from the Load Line Rules) had to. Moreover, there have been cases when by the diligent hand of a certain inspector with the assurance of a "wet" seal, the correct numbers were corrected for the wrong ones.

Length of vessel between perpendiculars LBP for draft survey - this is the length on the Theoretical drawing according to constructive waterline, and the middle of this length is the desired midship.

In the LBP Code is interpreted incorrectly - as the length of cargo waterline. The midsection is also interpreted incorrectly - the middle of the length is taken special waterlines (read the Load Line Rules). The Plimsol disc denotes (if it is also correctly installed) a completely different midship, which has nothing to do with the draft survey.

When taking office on a ship, do not consider it a job, deal with the distances again and again, draw up a Distance Scheme or check it, if any. It is important.

Guided by the Code, the surveyor at the loading port took the wrong position amidships and made a mistake in the amount of cargo by several tens of tons. The surveyor at the port of unloading, also respecting the Code, repeated the mistake, and the amount of cargo was the same for both. But there is still weighing of the cargo by the coastal complex! It will show that both surveyors are wrong. Again disputes, again a simple ship.

(By the way, there is a similar story with precipitation: there must be exact knowledge from the upper or lower edge of the keel, the hydrostatics are calculated and what thickness of the keel is accepted by the calculator. Otherwise, an unnecessary error may again occur, although only a few tons of cargo.)

Average draft

Moving on to Fig. 2, which clearly depicts the essence of the requirements of the Code, we will see that the straight line d f - d a considered a trim line TRIM , and the tangent parallel to it is considered to cut off the fore and aft parabolic wedges (shaded), equal in volume to each other.

The center of the volume of each parabolic wedge for a rectangular body rises above the tangent by exactly 3/10 f ... Since the ends of the ship are rounded in plan and the center of the volume is therefore somewhat reduced, in the Code its position is expertly reduced to 2.5 / 10, that is, to 1/4 f.

The equivalent parabolic straight waterline will pass through the centers of the volumes in parallel d f - d a and the average draft will be

MMM = d m + 1/4 f (2)

In the Codex, for some reason, this expression is substituted with an expression for f and obtained a mathematically adequate, but completely obscuring the physical meaning of the faceless formula

MMM = 1/8 (d f + 6 d m + d a) (3)

It is clear that the chief executive officer should calculate the draft only after f while observing the bend arrow, which is functionally important for the vessel, which on some vessels is directly required by the Strength Information.

Here the Code again admits a number of errors: the constructions based on real measurements of the draft at 5 points along the length of the vessel never gave a parabolic waterline, and detailed calculations on the Bonjean Scale did not give either the equality of the volumes of the wedges, or the coefficient 1/4. Deviations are both small and significant. Lottery.

Some survey firms trying to refine the formula (3), for ships of complete formations consider S -shaped bend is inevitable and always take 1/3 for them f:

MMM = 1/6 (d f + 4 d m + d a) (4)

Others consider the bend to be always parabolic, but for vessels of full formations, the wedges do not round off and always take 3/10 f:

MMM = 1/20 (3 d f + 14 d m + 3 d a) (5)

It looks like the interval 1/4 - 1/3 covers the whole range possible changes coefficient for f but, unfortunately, no one indicates the border between full and sharp contours. To the taste of the surveyor at the loading port? But it may not be divided by the surveyor at the discharge port or the operator of the onshore measuring complex. But the greater the algebraic difference between the bending arrows of the vessel with and without cargo, the greater the uncertainty with the amount of cargo.

Gentlemen, first mates, observe the bow arrow of your vessel and estimate for yourself the difference in tonnes of cargo when applying different formulas.

The Code gives a recommendation to “specify” the coefficient according to a certain Schedule for the Factor. Plot the factor points 0.75 and 0.67 (corresponding to 1/4 and 1/3) and you will see that for a waterline fullness factor of less than 0.65, the Code considers the bend to be always parabolic (and even worse), and with a factor greater than 0 , 85 always S -shaped (and even worse), and between them a bend of an incomprehensible shape.

The Code does not bring any clarity, the question remains open. The search for new formulas continues, but the required accuracy (1-2 mm) has not yet been achieved.

Meanwhile, the uncertainty with the coefficient for f , like the rest of the above-mentioned errors, are completely eliminated by instrumental measurements of the draft at 5 points along the length of the vessel.

Let me remind you that it will take no more time (taking into account the discussions at each of the 3 points during the usual "reading" of stamps) than with instrumental and therefore indisputable measurements at 5 points.

Previously, a 5-point curved waterline was drawn using flexible slats or patterns. It is laborious and unacceptable for a draft survey. Now, the computer program can easily and accurately approximate the waterline in a polynomial series, which gives both the shape of the bend and the exact values ​​of the draft at any point along the length of the vessel.

Calculation of Displacement

D let's omit that by a blind chance the surveyor, guided by the Code, still received the meanings MMM and TRIM with apt precision.

Further, the Code requires to write out from the Table of hydrostatics of an even keel at a draft of MMM the values ​​of displacement ∆, the number of tons per 1 cm of draft TRS and the position of the center of the waterline area along the length of the vessel LCF ... May one more luck await him - the table is calculated accurately enough. And even with this, unnecessary errors are possible: with large trims at the stern of vessels with a bulb, it will be at least partially above the water, and from the Table it will be taken submerged, or, conversely, - the aft gauge is submerged, and it will be taken floating.

The Code then requires you to rotate the waterline around a point LCF to the position of a new even keel and, using the elementary proportion formula, calculate the change in draft in meters x = LCF / LBP ∙ TRIM , and then the first amendment to the tabular displacement in tons

∆1 = LCF / LBP ∙ TRIM ∙ 100 TRS (6)

Ever since the time of the classics of the theory of the ship, it is known that the formula is accurate only for a conventional ship with straight-walled sides along the entire perimeter of the waterline and is permissible for solving the buoyancy equations with trims of no more than 1% LBP (and for some vessels even up to 0.5%).

For draft survey purposes, the accuracy should be much higher, and then the actual trims reach 3 or even 5% (for a vessel without cargo, for example).

To take into account the indirectness of the sides, the Code proposes a second amendment to the tabular displacement:

∆2 = 50 / LBP ∙ TRIM 2 ∙ (MTS + - MTS -) (7)

which essentially means by approximate differentiation to find the rate of change of the trimming moment of the MTS (the values ​​of which are also inaccurate) in the range of only 1 m (from 0.5 m down from MMM to 0.5 m up from MMM), and then approximately integrate it, but already in the range actual trim. For a vessel without cargo with significant trims, these are again possible significant errors.

The displacement sought by the Code is obtained by the formula:

D = ∆ + ∆1 + ∆2, (8)

all terms e which, as we can see, may have unnecessary errors. The formula does not guarantee the reliability of the result.

At the same time, all vessels, in accordance with paragraph 2.1.3.4 of IMO Resolution A.749 (18), must have a Hydrostatics Table that allows, without approximate calculations, simple interpolation to determine the displacement in the entire range of trims possible during operation.

Vessels, which will persistently approximate the waterline by only 3 points, must be equipped with at least a Hydrostatics Table with trim. Calculations according to formulas (6), (7), (8) should be excluded in all cases. This, incidentally, will reduce the duration of the calculations.

Pay attention, since for obtaining the Table of an even keel the shape of the hull is described for a computer, then it is possible to obtain a Table with a trim at a penny cost. Shipowners, probably out of ignorance, save money, and the Classification Societies, for unknown reasons, en masse admit the absence of such a Table on ships, ignoring the requirements of the SOLAS MK.

Ships, on which they still prefer the waterlines in the form of a polynomial series, should have (also at a penny cost) a Table of conditional hull volumes by spacing (analogue of the Bonjana Scale) in electronic form. Displacement can be obtained without unnecessary errors by using an electronic curved waterline.

On ships, the shape of which is described by the mathematical model, in order to obtain the correct value of the displacement, in general, it is only necessary to know the actual density of the seawater and the draft at 5 points along the length of the ship.

Conclusions

Existing draft survey techniques are based on hydrostatics that are quite accurate enough to assess the safety of navigation. Specific - commercial - the purpose of the draft survey requires calculations of increased accuracy. Nothing prevents the use of these calculations for other purposes.

The outlined marginal error in determining the amount of cargo by draft survey up to 0.1% can and should be achieved. To do this, shipowners only need (not difficult and inexpensively) to provide the possibility of instrumental measurements of the draft at 5 points along the length of the vessel and to supply the vessels with high-quality hydrostatic data.

Those who are persistent in measuring only 3 points of draft must be provided with at least Hydrostatics Tables with trim.

It is high time to get rid of the practice of using archaic approximate calculations.

How not to lose accuracy on ships where between the initial and final surveys you have to operate with liquid ballast - in the next article.

Rice. 1 Determination of sediment d at the perpendiculars of the vessel.

Rice. 2 Determination of the average draft MMM

liquid ballast during draft survey

Inquisitive - already senior mates

And more to the cadets.

In the previous articles "Some details of the draft survey" and "Calculation of displacement for a draft survey" it was shown that for the most accurate measurement of the draft survey of the amount of bulk cargo on the ship, EVERY possible error should be minimized.

In this final article, we will consider the possibilities of minimizing the error in determining the CHANGE in the amount of ballast between the initial and final surveys, well, we will draw a general conclusion about the draft survey.

Obviously, the smaller the ballast change Bl f - Bl i , the smaller the error in calculating this change. And when the ballast does not change at all, the error to the load is generally zero.

First, let's try to reduce the ballast change on a large scale - with whole tanks.

OPERATIONAL BALLAST

Let's make a virtual voyage for bulk cargo on a ship of an unlimited navigation area, for example, 120 m long, which, in addition to the forepeak and afterpeak, has 5 pairs of bottom ballast tanks (about 1500 t) and 5 pairs of below deck tanks (about 1000 t).

In anticipation of a severe storm in the ocean (wavelength comparable to the length of the vessel), all bottom and below deck tanks were ballasted according to the requirements of the Strength Data Sheet. In this case, the requirements of the Stability Information are fulfilled with a margin.

The storm does not last forever, and our ship, steadily moving towards the port of loading, entered the closed sea, the wavelength was 2-3 times shorter than the length of the vessel. According to the requirements of the Stability Information, ballast is required in only 4 pairs of bottom tanks (about 1200 t); The requirements of the Strength Information are fulfilled with a margin.

In port and port waters, to ensure stability (roll, normalized roll angle from the wind) and strength (already in practically calm water), ballast is not required on our vessel at all.

However, it is necessary to have a normal landing to ensure maneuverability at low speeds (immersion of the propeller, controllability, sufficient visibility from the wheelhouse), and possibly to maintain the operability of mechanisms and to provide a checkpoint (bridges, mooring loading devices) the surface gauge of the vessel. In this case, our vessel requires only 3 pairs of bottom tanks (about 900 tons of ballast).

This minimum possible ballast will be called “operational”. For another ship, as a percentage of the full one, it will be more, and for some it will not be required at all. Operational ballast during loading should be pumped out completely if the full cargo capacity of the vessel is required, or partially if a smaller cargo will be accepted.

Now the senior man only has to prove to the surveyor that between the initial and final surveys

Ballast residues in "empty" tanks have not changed;

Such and such a volume of operational ballast has been pumped out of the "full" tanks.

But more on that later.

In the meantime, a remark for the unloading ship: in this case, a certain minimum sufficient amount of operational ballast can be determined.

Let it be, for example, also 900 t, which can be accepted as unloading between the initial and final surveys. The capacity of ballast pumps is 2x 162 m 3 / h and after the measurements of the final survey there will always be 2 hours before the ship leaves for pumping 600 tons of ballast into the remaining 2 pairs of "empty" bottom tanks. Safe in terms of stability, access to the open sea will be ensured, and if there is a threat of severe storms, then in 3 hours it is also possible to have time to add another 1000 tons of ballast to the below-deck tanks without any problems.

Ballast change is minimized.

Now separately for each tank.

Tank equipment

A very important point! Indeed, according to one single measurement point, and even obtained blindly, it will be necessary to judge the entire volume of ballast in the tank.

The gauge tube must provide access of the tide rod (practically vertically and without bends) to the lowest point of the tank: it is necessary to measure the FILLING LEVEL. The tube should be located at the aft end of the tank.

Let's divide tanks into two types - those with a flat bottom part (bottom) and those without such a part (forepeak, afterpeak, below deck).

If in a tank of the first type the measuring tube is located at the side of the vessel, it is necessary to achieve its transfer to a point on the deck above the flat part of the bottom. Otherwise, a tide-rod in the form of a rigid rod will stick into the rounding of the cheekbone with an undermeasured filling level, and a tide-rod in the form of a tape measure with a weight, bending when sliding along the rounding of the cheekbone, will give “blue haze” instead of high-quality measurement.

In tanks of the second type because of their design features often it is not possible to ensure the full depth of the tide rod sinking. The value of this undershoot must be determined when the vessel is docked.

For all tanks in the dock, it is necessary to determine the actual height of the deck above the zero point as the reference depth of lowering the tide rod.

The coordinates of the measuring tube from the bulkheads of the tanks in the plan and the values ​​of the control depths must be given to the designer for calculating the Tables of the volumes of tanks. Without this data, the Tables of volumes turn into a coded puzzle.

Additional requirements for the equipment of tanks arise from the specifics of the correct measurement of levels.

MEASURING LEVELS

The vessel was under loading with a large trim at the stern. A clear line of 9 cm level appeared on the tide rod in the tank. According to the table of volumes, this is 3 m 3 of ballast. Let's measure the depth of the footstock lowering. The height of the side and the loss of the deck plus the thickness of the deck and the height of the deck sleeve, and now minus the depth of lowering - turns out to be undershoot by a foot stock of 18 cm! There are fewer, but there are more. This means that the design of the tube came across not through, but with a bottom and a side cut. The end of the tube rotted, and in the repair it was cut off, and then not restored, but a new bottom was welded as simply as possible - along the cut. And so - in every repair.

With a loading depth of 9 + 18 = 27 cm according to the Table of Volumes, this is 30 m 3 of ballast. So how much is actually 3 or 30?

It doesn't matter yet. The main thing is whether the amount of ballast will change by the final survey.

Loading completed, no trim. Measurement in the same tank gives a clear 0. Is the ballast spread over the bottom or pumped out? Neither one nor the other is unprovable.

But this does not happen in one tank. Draft survey is not even a formality, but just a "linden".

The bottoms of the tubes must be cut off and thus open the tubes for the free passage of the tide rod. With a through tube underneath it, a weld is provided on the bottom. Ideally, it is not needed either. Just use a treadle, the end of which is covered with leather (rubber, plastic), when measuring the paintwork protecting the bottom inside the tank from damage.

On another vessel, during the initial survey with a large stern trim, but with normal tubes, the level measurements were 2-3-4 cm, which gives a negligible amount of ballast.

During the final survey, the trim turned out to be even slightly on the bow, the level measurement in each of the tanks became different, but the order of the numbers is also from 0 to 3-4 cm. What happened? Ballast has not flowed as it is clogged, is the flow silted up? Or increased due to the slow flow of the hull (filtration)? Or ballast valves not holding? Or maybe an accidental mistake of mechanics when operating the system? Uncertainty again with tens of tons of ballast.

Free overflow of residual ballast should be carefully checked when the ship is taken over from new building or refurbishment. Between repairs, the crew should at least occasionally flush the crossflows by pumping and pumping out a small amount of clean seawater.

Washing should be especially intensive after ballasting of river mouths, surf zone, etc. with turbid water. Such ballast must be replaced with a clean one as soon as possible to prevent sedimentation of suspended matter on the bottom of the tanks.

Some vessels, after loading, get a bow trim and measurements in the stern tubes will show zero ballast. No need to guess whether the same residues have flowed over or increased, or even completely evaporated. On such ships, metering tubes are also required in the bow of the bottom tanks.

In tanks of the second type, the second tube may not be installed, but the residual ballast must be of such a size that, even with a differential on the bow, a real measurement in the aft tube is possible. The free surfaces of these residues will have practically no effect on stability, and their values ​​will practically not reduce the carrying capacity of the vessel.

WITHwe figured out the lower levels of ballast, let's move on to the upper ones.

Measurement of "full" tanks is obligatory as well as "empty" ones. o °

Before measuring the "full" tank, the stopper of the measuring tube must be open, ensuring free drainage of ballast from the tube along its upper edge. Do not torment the tank and the system by pressing - the air cushion in the tank will still be of unknown volume.

Level measurement in a "full" tank should be carried out with a naturally free ballast surface, without the influence of a compressed air cushion. You will pressurize the tank after the draft survey.

Only being confident in the correct determination of the change in the levels of ballast filling, one can proceed to the correct determination of the change in its volume.

TABLES OF TANK VOLUMES

The table of volumes of each tank should be preceded (in addition to the metering tube data) with a Scheme of the tank with its geometric characteristics. The surveyor has no time to decipher small-scale general diagrams or dig into working drawings (moreover, they are often absent on the ship). The diagram will make it possible to always get a correct idea of ​​the configuration of the free ballast surface in the tank, taking into account protrusions, ledges, independent tanks,echo sounder mines,bilge drainage wells, etc. Even for the simplest bottom tank - from side to diameter and from bulkhead to bulkhead - there is a need to know the radius of rounding of the chine or the degree of narrowing of the tank to the bow or stern.

The volume table should be calculated only and exclusively by the Plaza ordinates. andonly from the lowest point / plane of the tank to the highest point of the metering tube. The first column should be called (and be!) "Filling level". All kinds of "Count on the tide rod", "Subdivision of the subway", "Level" " Sound "and T.NS. not unambiguous, not informative. 0

It is very necessary in the Tables that the range of calculated trims of the vessel is obviously sufficient - from possible onthe bow at full carrying capacity to more than that of the unladen vessel (the rest of the ship's stores, as a rule, increase it).

Hundreds of revised Tables, and most of them have shorter ranges than needed. Survey societies recommend each time by ballasting to drive the actual trim of the vessel into the framework available in the Tables. Unlikely this is a reasonable recommendation. Obviously, it is more expedient to count the Tables once for the rest of the vessel's life.

Standard coefficient of permeability of tanks (0,98 etc.) should not be applied vDraft survey tables. Body kit volume, pipelinedov(including transit), mines, wells, etc. should be taken by designtive drawings and correctly distributed over the height of the tank. A summary of the deductible volumes taken into account should be shown on the Tank Scheme. Painstaking, but not difficult at all!

Example: The simplest cylindrical tank - from side to diameter 6.5m and from the bulkhead before bulkheads 19.8m with a radius of rounding of the cheekbone 0.5m. H on one vessel in the Table of volumes (the entire booklet is in attestation signatures and stamps) at the level filling0.5m volume indicated 62,87 m 3, and on another vessel of the same series, but with a Booklet of another design organization (also signatures and stamps), the volume is indicated 60,61 m 3, and such cisterns 8. Almost 20 t difference when the vessel's carrying capacity is only 3000 T.

In the Booklets, the filling levels are newfangled, given in 1cm intervals. It would be possible to print them after 1mm - the accuracy of the Tables will not improve from this .

Ambiguity in the results of measurements of filling levels and sloppy Tables of volumes can completely sweep awayall other efforts to clarify the amount of cargo on board. The first mate will always be a bit in disputes about the lack of cargo. O

With correct measurements and tables, it is possible to convincingly prove both the invariability of the residual ballast and the magnitude of the change in ballast.

The amount of ballast between the upper and lower loading levels is determined according to the Tables. The density of the received ballast is always known from seawater samples for calculating the displacement. To determine the density of the ballast pumped out during loading, it is necessary to have a sampler that is adapted to be inserted into the measuring tube.

Thus, the change in the amount of ballast between the initial and final surveys can and, therefore, must be taken into account quite correctly.

Considering the previous articles, these are, perhaps, all the main problems of the draft survey. The rest of the details can be solved along the way.

CONCLUSION

Draft survey was, is and will be. However, by joint efforts it is time to raise his methodology to a higher level.

From a very uncertain accuracy of 0.5% (only because of the ballast, the error can be greater), it is possible and necessary to proceed to the guaranteed accuracy of the draft survey of no more than 0.1% for the load.

Very importantself-education of senior officers (surveyor - only an independent witnesstel of measurements), but the main thing is to persuade the shipowners for SIMULTANEOUS and relatively small costs for providing the vessel:

· Possibility of instrumental measurements of the settlement at 5 points along the length;

· Reasonably spaced gauge tubes in ballast tanks;

· Correct data on the hydrostatics of the vessel and the volume of ballast tanks.

Let's call such vessels STANDARD in the sense of a draft survey.

They, of course, should not only be the pride of the ship owner, but also receive a variety of preferences. At least in the form of the right to go on a voyage without wasting time in ports for disputes over the amount of cargo, saving port costs and running time ship. But this is all the concern of logistics specialists and P&I clubs.

Happy sailing!

Well, something extraneous:

Or maybe the modernized draft survey will also replace the petroleum survey, which is very bulky in its present form?

Surveyor Yakovenko Gennady Pavlovich

Sevastopol

Tel. 8 0692 54 72 22

mob. 8 067 233 44 65

E-Mail: [email protected]

2.12 Technique for drawing up a cargo plan

Load and unload cargo in accordance with cargo plane on consignments of lading, avoiding their mixing. When handling a vessel, the ports are obliged to: place cargo in accordance with the cargo plan agreed by the master. Layout of cargoes on the ship; is compiled with the aim of the most rational use of cargo spaces and giving the ship

necessary stability. Distinguish between preliminary (before loading) and final (executive) G. p. (after the end of loading); single-lane (cross-section of the vessel along the diametrical plane, which shows the placement of cargo in holds, twin decks and on the deck) and multi-lane G. p. (compiled for container ships and universal ships with a large number of consignments of lading, when it is necessary to know the location of goods in the horizontal plane). Compilation by G. p. is made taking into account the compatibility of goods. Data on the goods presented for carriage on the ship are summarized in special. tab. First, in this table. enter data on non-optional cargo (packaging, weight, specific loading volume, time for loading in accordance with the norms of loading and unloading, etc.). Then the number of passing cargo is calculated and the rest of the table is filled in. When calculating the set of goods, the stowage ratio and the volume of separation materials are taken into account. G. p., Compiled for specialized cargo ships, have their own specifics. G. p. a container ship is called a container plane; it is complemented by a rotational plan, on which decomp. the colors are circled around the consignments of containers sent to the appropriate port of unloading. When the vessel is ready to start loading, an Act of the vessel's readiness for loading is signed by the Captain and Stevedore. Before the start of loading, a Cargo plan- a graphic representation of the placement of the cargo. Preliminary - drawn up by the port before the start of cargo operations. Executive - draws up an assistant after the end of loading. Freight plan types: single-lane and multi-lane. When drawing up a cargo plan, the following is taken into account: cargo capacity (W) - capacity (volumetric) of all cargo spaces; lifting capacity (P) - capacity (mass) of all cargo spaces; stability of the vessel; body strength (general and local). Distribution of cargo on the ship. When transporting heavy loads (ore), the strength of the decks must be taken into account. The shipping company must prescribe the norms for the loading of individual spaces of the vessel. Cargoes on board the ship should be arranged by weight, in proportion to the volume of individual cargo spaces. In this case, the strength of the vessel will be preserved. The amount of cargo intended for loading into any of the ship's spaces can be determined by the formula: p = wP/ W, where R- the required weight of the cargo; w- the volume of the cargo space; W- cargo capacity of the vessel (respectively in bales or grain); R- the weight of all cargo accepted by the ship. In practice, longitudinal strength is fully ensured if the weight amount of the load differs from the result obtained by the above formula within 10-12%. When loading the deck of any ship, it should be borne in mind that its strength in the ends of the ship is greater than in the middle. Likewise, at the sides and bulkheads, the deck has greater strength than in the middle, unless, of course, the deck is reinforced with pillars. AAAAAAAAAAAAAAAAAAAAAAAAAAA

A properly prepared cargo plan should provide: seaworthiness of the vessel; safety of goods; the ability to accept and issue cargo according to bills of lading (by lot); simultaneous handling of holds, characterized by the coefficient of unevenness of the holds, Km = W / N Wmax, where Km is the coefficient showing the ratio of the vessel's cargo capacity W to the cargo capacity of the largest hold Wmax, multiplied by the number of holds; NS-number of holds. If there is different cargo in the holds, then the coefficient showing the ratio of the total number of hatch hours to be worked throughout the ship to the number of hatch hours in the largest hold multiplied by the number of holds will be more accurate. CL = L /nLmax ensuring high-speed handling of ships in ports; full use of the carrying capacity and cargo capacity, that is, the full load of the vessel. The procedure for drawing up a cargo plan. Check if there are any goods dangerous to the ship and passengers. Determine the possibility of stowage of goods in terms of their compatibility and uniform distribution in the holds, draw up a list from which it should be seen that incompatible goods were successfully distributed to different cargo spaces; the use of the cubic capacity of the holds and the distribution of weight loads in individual compartments will not cause harmful stresses in the ship's hull. To check the effect of loading on the progress of cargo operations, subdivide the cargo according to the classification adopted in the regulation on ship-daily norms of cargo operations in ports, and determine the coefficient of uneven distribution of cargo in the holds. Having a scheme for placing cargo in the holds, draw up a cargo plan. Check lateral stability .

2.13 Production relations of the stevedore with the ship administration, client's representative, warehouse workers, dispatcher, railway

Ports are required to provide high quality carrying out work on the handling of the vessel; loading up to full carrying capacity and cargo capacity; stowage of cargo in holds, ensuring the safety of cargo and the seaworthiness of the vessel; elimination of damage during handling. Reducing the processing time of a vessel in the port allows you to increase its carrying capacity, reduce capital investments in the fleet, and reduce the cost of cargo transportation by reducing the time spent in the port. Acceleration of the processing of ships in ports makes it possible to improve the use of the main production assets of maritime transport and increase the profitability of its work. Upon the arrival of the vessel at the port and obtaining free practice (after registration of the arrival, customs and border inspection), as well as after the end of unloading, if the vessel goes under loading, the captain must give the port workers a notification (notification) of the vessel's readiness for handling. Notis is issued in duplicate; it contains the name of the vessel, the time of arrival at the port, the numbers of the hatches. and the time of their readiness for cargo operations, the time the vessel is ready to receive the bunker and water. If not all hatches are ready for processing, the captain hands over a new notification to the port for each subsequent hatch. Upon arrival of the vessel (after the end of border and customs inspection) or after the end of unloading, if the vessel is being loaded, a representative of the port must arrive at the vessel within 30 minutes, regardless of the time and location of its location (in the roadstead or at the berth) and receive a notification. On the duplicate of the Notice, the port representative must indicate the date and change of the beginning of the processing of the vessel under the NPFRP, and for which vessel this vessel is accepted for processing. In addition, they establish the procedure for the entry or exit of the vessel from the port and agree on the terms of the work on the vessel with organizations that are not under the administrative subordination of the port. All the main issues of organizing the processing of the vessel are developed and set out in the technological plan - the schedule of its processing. No vessel can be handled in the port without a stevedore leader. Stevedoring includes work on the preparation and organization of loading - unloading and servicing of ships, development of TPGOS, registration of cargo and transport documentation, as well as work on loading and unloading on a straight line; the option of railway cars, barges and vehicles. Stevedoring works are carried out by a staff of stevedores working under the guidance and control of the Deputy District Chief for Operations. Stevedore staff consists of senior and shift stevedores assigned to a specific group of berths and specializing in the handling of certain cargo or cargo of one direction. Senior stevedore subordinates to three or four changeable stevedores, he represents the port on the ship and is the responsible manager and organizer of work on this ship. Prior to the arrival of the vessel at the port, the senior stevedore takes part in preparing the port for handling the vessel, participates in drawing up a cargo plan, develops the TCDP, prepares the berth for receiving the vessel, controls the preparation of warehouses for receiving and issuing cargo, draws up applications for wagons, mechanization equipment, inventory, labor force. Further, the senior stevedore organizes and supervises loading and unloading operations and provides service to the vessel during the entire processing period, coordinates with the vessel's administration the scheme and methods of securing cargo. Replaceable stevedore works under the direction of a senior stevedore. During the absence of the senior stevedore on the ship, the shift person performs his functions. The shift stevedore on his shift is operatively subordinate to the shift dispatcher of the area. He is a manufacturer of cargo operations, who directly supervises the work of crews and has the right to stop working on ships and wagons if the ship and representatives of the railway station act contrary to the rules for transshipment of goods, to remove from work those under his authority who violate the technology of reloading and labor safety rules. Before the start of the shift, the replaceable stevedore must check the serviceability of the technological equipment and its compliance with the current technology, instruct the workers on labor safety and reloading technology, together with the foreman arrange the workers at the work sites, indicate the places and methods of stowing the cargo. During the shift, he organizes work in accordance with the approved technology and TPGOS so that there is no downtime for workers, machines and transport, controls the quality and intensity of the work of the teams, organizes the receipt of cargo from the warehouse, submits applications on time for re-supply of wagons, replacement of reloading machines and cargo handling devices and inventory, supervises loading - unloading and fastening - unsealing of goods. One of the most important tasks of the shift stevedore should be considered the preparation of the work of the next shift. 2 hours before the start of the shift, the stevedore must analyze the state of affairs for each hold, compare it with the task for the TPGOS and the shift - daily plan, and draw up an application for the shift dispatcher for workers, vehicles and transport. When loading the vessel, the stevedore must pick up all orders for cargo that will be loaded during the shift, establish their location and the possibility of receiving from the warehouse or the possibility of warehouses to receive cargo when unloading the vessel. If it is impossible to receive any consignment of cargo from the warehouse, the stevedore through the shift dispatcher must arrange for the replacement of the cargo and think over the ways of its transportation. Having clarified all the questions on the organization of the shift, the shift stevedore informs the ship's administration about the upcoming work, agrees on the work plan, submits an application for ship cargo equipment, opens or closes mechanically driven hatches. The stevedore must ensure the supply of separation and equipment by the workers of the previous shift, as well as the opening and closing of the hatches of the holds. After the end of the shift, the stevedore monitors the cleaning of the workplace, the delivery of reloading machines, technological equipment and inventory, fills in orders - tasks for the work performed. In the process of performing his duties, the stevedore is associated with a large circle of employees of the region, other farms and the port authority, with officials of related transport organizations, state control bodies and inspections. As a rule, the senior stevedore receives all instructions on the organization of work, on the transfer and clearance of cargo, on loading or unloading the vessel and many other emerging issues from the head of the area, his deputies for operation and storage, senior dispatcher, technologist and safety engineer. and the shift stevedore - from the senior stevedore and the shift dispatcher. He is obliged to know what issues are within the competence of the officials of the port, related transport organizations, regulatory authorities in order to properly build their business relations and quickly resolve difficulties with all participants in the handling and maintenance of the vessel.

Methods for determining the weight of cargo on board the vessel by the draft survey

After the vessel receives free practice, a surveyor arrives on board to conduct a draft survey.

The purpose of the draft survey is to determine the weight of the cargo on board. By measuring draft, using the ship's cargo documentation and information to calculate the immersed volume of the ship, using the density of the water in which the ship is located, the surveyor can calculate the weight of the ship. From this total, he subtracts the weight of the vessel and other weights on board the vessel that are not the weight of the cargo, the difference will be the weight of the cargo. (see attached forms 1, 2, 3, 4)... However, in practice, it must be taken into account that the ship is flexible and is not at rest, the information of the ship builders about the ship varies. It is very difficult to accurately remove sediments, to find out the actual weight of the ballast.

The time taken to carry out a draft survey will depend on many factors: the size of the vessel, the amount of ballast, the number of tanks, the condition of the vessel. It is common practice for a surveyor to be present from start to finish of cargo operations. On large vessels, two surveyors are required to carry out a draft survey.

Measurement accuracy during draft survey is influenced by the situation on the vessel and time constraints. Minor mistakes will not cause significant damage if the vessel is small. However, when transporting large consignments of valuable cargo, 1% of the mass of this cargo represents a large amount of money. The surveyor must prove that he has made every effort to make the most accurate measurements using standard methods. The surveyor must be confident in what he is doing and be able, as far as possible, to prove his case.

1.0. Determination of the weight of the cargo by the draft of the vessel.

1.1. Removing the draft of the vessel.

Draft of the ship (T) - the depth to which the hull of the ship is immersed in the water. To read the sediment values ​​on the fore and aft perpendiculars (stem and stern, respectively), recess marks are applied from both sides. Recess marks are also applied on both sides in the middle (midship) of the vessel to remove sediment midships.

Recess marks can be designated with Arabic numerals and are presented in metric measurement system (meters, centimeters - Appendix 1), as well as Arabic or Roman numerals - English measurement system (feet, inches - appendix 2).

With the metric system of measuring the draft, the height of each figure is 10.0 cm, the vertical distance between the figures is also 10.0 cm, the thickness of the figure on sea vessels is 2.0 cm, on river vessels 1.5 cm. In the English system of measuring the draft, the height of each the number is 1/2 foot (6 "), the vertical spacing is also 1/2 foot, the thickness of the number is 1" (inch).

The line of contact of the ship's hull with water (actual waterline) at the intersection of the indentation marks in the bow of the ship gives the draft of the bow (Tn), in the middle of the ship - the draft at the midship (Tm), in the stern - the draft of the stern (Tc).

Draft removal is performed from both sides of the vessel with the highest possible accuracy from the berth and / or boat.

When the sea is rough, it is necessary to determine the average value of the amplitude of water washing of each mark of the depression, which will be the actual draft of the vessel in a given place. (fig. 1.):

Actual draft (fig. 1.) is: (22'07 "+ 20'06") / 2 = 21'06.5 ". If it is impossible to remove the draft from both sides, the draft is removed from the indentation marks in the bow, midships and aft from one side.

For the obtained values ​​of the draft, the average draft is calculated (formula 1):

where T ’- average draft, m;

T - draft taken in the bow, stern and midships, m;

B is the transverse distance between the marks of the deepening of the right and left sides, m;

q is the heel angle (taken from the inclinometer located on the navigating bridge of the vessel) of the sides of the vessel with the maximum possible accuracy from the berth, °

(1 ° of heel is approximately equal to the width of the boat).

The sign of the correction is negative if the roll is towards the observed side, and is positive if the direction of the roll is opposite. . The calculation of the average draft in the bow, stern and midships is carried out separately.

The amidships draft can be determined by measuring the freeboard from the line of the main deck to the surface of the water, which is then subtracted from the height from the keel to the main deck. (fig. 2.):

Determination of draft amidships

Legend for Fig. 2.:

1 - line of the main deck;

2 - waterline;

3 - freeboard to waterline;

4 - draft to the waterline;

5 - draft up to the summer load line;

6 - year freeboard;

7 (H) - height from keel to main deck;

8 - keel line.

1. 2. Determination of the average of the mean design draft, taking into account the amendments to the draft in the bow and stern of the vessel, as well as the trim and deformation of the vessel.

Draft measurements in the bow of the vessel are recorded according to the marks of the recesses marked on the stem, and not according to the forward perpendicular, which is the calculated line. As a result, an error appears, which is excluded by the introduction of the amendment (see fig. 3., formula 5):

Introduction of a draft correction in the bow and stern of the vessel and amidships

f is the distance from the stem to the forward perpendicular, m;

LBM = LBP - (f + a) - trim - the difference between the ship's draft in the bow and stern, m;

LBP is the distance between the perpendiculars passing through the points of intersection of the cargo waterline with the leading edge of the stem and the axis of the rudder stock (distance between the bow and stern perpendiculars), m.

When the vessel is differentiated, the measurements of the draft of the stern of the vessel are recorded according to the marks of the indentations on the sternpost, and not according to the stern perpendicular, therefore, the same correction must be introduced for the draft taken in the stern (formula 6):

a is the distance from the indentation marks to the aft perpendicular, m.

Distances a and f can be defined using a scaled drawing of a ship or a longitudinal sectional drawing of a ship.

In most cases, on modern ships there are tables or graphs of the dependence of the magnitude of the corrections on the trim.

Drafts of the bow and stern parts of the vessel, taking into account the corrections for the deflection of the stems, are calculated according to formulas 7, 8:

The average draft between the bow and stern of the vessel is determined by formula 9:

A correction to the midship draft is introduced if, when removing the midship draft, the scale of the deepening is shifted to the bow or stern of the vessel from the plimsol circle (formula 10):

where diff. '- trim, determined after the introduction of amendments to the draft of the bow and stern of the vessel;

m - distance from the plimsol circle to the mark of the deepening midships, m.

The sign of the correction is negative when the mark of the depressions is displaced to the stern and positive when the measure of the depressions is displaced to the bow from the plimsol circle.

Precipitation amidships, taking into account the amendment, is calculated by formula 11:

The average draft is calculated by formula 12:

The average of the average design draft, taking into account the deformation of the vessel (bending-deflection), is determined by formula 13, 14, 14 A:

1. 3. Determination of the displacement of the vessel.

Displacement by weight - the mass of the vessel, equal to the mass of water displaced by the vessel. Since the displacement of the vessel changes depending on the degree of its loading, any value of the draft (deepening of the vessel's hull into the water) corresponds to a certain displacement.

Gross tonnage of the vessel - deadweight - is determined as follows (formula 15, 16):

If we take the mass of ship's stores and the mass of “dead” cargo unchanged, then the mass of the cargo will be equal to the difference between the deadweight of the vessel with cargo (DWTg) and the deadweight of the vessel before loading / after unloading (DWT0). The amount of cargo determined in this way must be clarified taking into account the change in the mass of ship's stores during the production of cargo operations.

Part ship stores includes:

• mass of fuel and lubricating oils;
• the mass of drinking and technical fresh water;
• the mass of ship's stocks of provisions and supplies (paints, spare parts, etc.);
• weight of the ship's crew with luggage at the rate of 1 ton of luggage for 12 people.

Part Dead weight includes the mass of unpumped ballast, residual water in tanks, etc.

The displacement of the vessel is determined by cargo scale(appendix 3), which is a drawing-table, consisting of a number of scales with divisions:

• deadweight scale, t;
• displacement scale, t;
• draft scale, m and / or feet;
• scale of trim moments, tm / cm;
• the scale of the number of tons per 1 cm of draft shows, for a specific draft, the amount of cargo that must be removed or loaded to change the draft of the vessel by 1 cm (can be expressed in tons per inch);
• freeboard scale, m and / or feet.

When using the cargo scale, it is necessary to determine the displacement and deadweight values ​​on the scale for fresh water (g = 1,000), if the vessel is in fresh water, and on the scale for seawater (g = 1.025), if the vessel is in sea water. The value of the indicator of the number of tons per 1 cm of draft should be taken from the load scale only in the area of ​​the found average draft.

Displacement (D) is determined before and after loading (unloading) of the vessel by the average design draft of the cargo scale, hydrostatic table (Appendix 4) or hydrostatic curve (Appendix 5). Usually the displacement is indicated for seawater (r = 1.025 t / m3).

1. 4. Corrections for ship trim.

Cargo hydrostatic tables or hydrostatic curves, which give displacement at different draft, are calculated for a vessel on an even keel. The true displacement of a vessel trimmed to the stern or bow is different from the displacement given in the cargo scale or table, therefore, should be applied. trim corrections(formulas 18, 19 - if calculations are carried out in the metric system; formulas 20, 21 - if calculations are carried out in the English system):

To do this, first add 50 cm (6 inches) to the value of the draft and remove the value from the hydrostatic tables of the differentiating moment, and then subtract 50 cm (6 inches) from it and from this data determine the value of the trimming moments. The difference between the trimming moments will be this value.

The sign of the first amendment is obtained algebraically (Table 1):

The sign of the second amendment is positive. The total trim correction is expressed by Equation 22:

Trim-corrected displacement is determined by formula 23:

1. 5. Correction for the density of seawater.

In cases where the actual water density differs from the accepted one (r = 1.025 t / m3), it is necessary to introduce a correction to the trim-corrected displacement for the density measured by a hydrometer, hydrometer, or taken from the data of the port meteorological service.

The sampling of seawater to determine the actual density should be carried out at a depth corresponding to approximately half of the ship's draft and approximately in the middle of the ship. To obtain more accurate data, samples can also be taken near the bow and stern of the vessel.

If, when determining the density of water, an ariometer (hydrometer) is used, calibrated at a temperature of 15 ° C, then the actual density is determined according to the following tab. 2 according to the measured density and actual water temperature.

The correction for the density of water is determined by formula 24, 24 A:

The displacement, taking into account the correction for the density of seawater, is determined by formula 25:

2.0. Determination of the mass of ship's stores.

Before and after loading (unloading) the vessel, it is necessary to determine the amount of variable stores that must be subtracted from the displacement, as not related to the payload.

TO variable ship's stores relate:

• fuel (diesel, fuel oil);
• lubricating oil;
• fresh water (drinking, technical);
• ballast water.

To determine the mass of variable stocks, immediately after the removal of the ship's draft, all ship's tanks should be checked.

Determination of the amount of fresh water and ballast.

On board the vessel, fresh water can be stored in galley and sanitary tanks, in forepeak and after-peak tanks, in deep tanks and bottom tanks (boiler water).

The bottom part of the vessel consists of a double bottom, in which double bottom tanks are located, intended for ballast. Double bottom tanks run either across the entire beam of the vessel, or are divided along the axis of the vessel into two symmetrical tanks. Often double bottom tanks are separated from each other by special tanks, which serve to ensure the safety of the vessel in the event of a breach.

The water level in the tanks is measured using measuring tape (tape) through the measuring tubes. After determining the water level by calibration tables the amount of water available on the ship is determined in tons or cubic meters. If the amount of water is given in units of volume, then it is converted into tons, multiplying the volume by the density at a given temperature. Measuring the amount of water with a significant differential requires the introduction of a trim correction according to calibration tables or by calculating the trim correction using the "wedge" calculation method (Appendix 6).

The water on the ship can also be in bilges (water collectors for ship's sewage) located along the sides. The sewage tanks must be emptied before sludge measurement.

Determination of the amount of fuel and lubricating oils.

Fuel (diesel, fuel oil) is stored in bottom, supply and slop tanks, as well as in deep tanks. In the engine room there are small tanks of lubricating oil. The chief mechanic is responsible for measuring the amount of fuel and lubricating oil, who has calibration tables in tonnes or cubic meters. Measurement and calculation data of all reserves are summarized in tab. 3, 3a.

3.0. The time required for a draft survey.

It will take a qualified surveyor about half an hour to carry out a draft survey on a small standard vessel and get effective indicators. If this is a large-sized vessel carrying bulk cargo and arriving in ballast, it will take at least four hours to process it with the participation of at least two surveyors. Most vessels are medium in size and can be placed between the two examples above. Much also depends on the type of vessel and crew involvement.

There is a huge difference in the amount of time and effort required to conduct an initial, final draft survey and determine the weight of the cargo. During the initial and final draft survey (before and after loading), all variables are measured - draft, variable ship's reserves (ballast and fresh water, fuel, lubricants, etc.). It is believed that this method helps to eliminate errors that could arise in determining the ship's light weight and the mass of ship's stores, and gives a more accurate result. Ballast tank measurements and sediment removal are carried out upon arrival of the vessel at the port and at the end of loading.

A simpler method is a deadweight survey. It includes measurements of draft and variables only when the ship is already fully loaded. It is used in the event that a ship constantly transports a certain kind of cargo along a certain route, all its variable values ​​are known and the ship's constant (constant) is accurately calculated. This method has several other benefits besides saving time. Since the measurements are taken with a loaded boat, it is possible to avoid deviations that occur when measurements are made on a boat with a large trim.

4.0. Accuracy of measurements.

An experienced surveyor working in ideal conditions will take measurements to within ± 0.1 - 0.3% on a large vessel and to within ± 0.4 to 0.7% on a small vessel. Realistically speaking, it’s almost impossible to provide ideal working conditions. Therefore, measurements are carried out with an accuracy of 0.5% of the total weight of the cargo.

With insufficient quality instruments used for taking measurements, the measurement accuracy will fluctuate within 1%. Technological errors can go unnoticed for the surveyor, and even more so for his employer, who has no idea about how this method works. Even when using the best technology, adverse weather conditions and lack of crew assistance can affect the measurement accuracy up to 0.5%. Since the measurements taken are only initial information, inaccurate measurements will lead to errors in further calculations. Disagreements between the work of the surveyor and the crew, its inconsistency will also affect the course of the draft survey, such as:

• recalculation of the mass of ballast and fuel by the crew during the survey;
• blocking of measuring tubes;
• change of documents;
• creation of other obstacles to the normal work of the surveyor.

It would seem that such minor things that occur during sediment removal, such as opening or closing holds, vibrations caused by the movement of cranes, can lead to a significant change in trim and draft.

The surveyor's only protection is the attention to the smallest detail, as well as the dexterity acquired through maritime experience. A detailed study of the plans of the vessel also often reveals inaccuracies and errors, but since not every plan can exactly correspond to a given vessel, it is necessary to draw any conclusions on the basis of this very carefully.

5.0. Draft.

The first step in a draft survey is to remove the sediment. The draft is removed in the bow, stern and amidships from both sides of the vessel (six values). The surveyor should be as close to the water as possible to obtain more accurate settlement readings. When handling large vessels, it is imperative to use a boat to remove sediment from the sea side. An attempt to read the draft indicators of a large bulk carrier in ballast from the ladder can lead to an error of up to 100 tons.

It is important to pay attention to the clarity of the load marks. On some seagoing vessels, load marks are marked with Arabic numerals (metric) on one side and Roman numerals (English feet) on the other. In this case, at the end of sediment removal, all readings should be transferred to one system.

Water fluctuations make it difficult to remove the sediment. Special measuring tubes are used. Water flows inside a narrow glass tube and, having reached a certain level, stops. Then readings are taken on the load scale.

Another way to remove sediment from the sea side is to measure the roll of the vessel (if any) with a special device - an inclinometer. Next, precipitation is calculated using simple trigonometry. However, accurate inclinometers are very rare, therefore this method is applicable only in conjunction with another for further comparison of the obtained indicators.

The draft survey report must contain a description of the weather conditions during the survey. In urgent cases, it is better to postpone the survey due to bad weather conditions.

Currents and shallow water also make it difficult to remove the sediment, significantly changing its value. If the boat is moving in relation to the water, especially if there is little clearance under the keel (the distance between the boat's hull and the ground), it will sink more into the water, increasing the draft as a result of the “suction effect” and changing the trim. It has been experimentally established that the influence of the current velocity of up to four knots on the change in draft and trim is insignificant. If the current speed is four knots or more, the draft may increase up to 6 cm, depending on the shape of the vessel.

The current is a real problem for river berths. The theoretical and practical work carried out to calculate the “suction effect” is insufficient. Therefore, the only choice for a surveyor is to rely on his professional experience.

In bright sun and low water temperatures, there is a tendency for vessels to bend the hull. The deck expands but the bottom of the ship does not, which causes the hull to buckle. The way out of this situation is that special correction methods will help to avoid errors in calculations.

6.0. Density.

The next step in the draft survey after sediment removal is to measure the density of the water in which the vessel is located. It is important to measure the density of the water immediately after the removal of the sediment, since it can change with the tide, as well as with the temperature of the water. The very concept of "density" is often misunderstood - we are talking about the ratio of mass and volume.

All errors in determining the density of water are the result of insufficient practice and misunderstanding of the relationships between different densities. Typical mistakes the following:

• improper water sampling;
• neglect of the use of corrections for water temperature;
• using specific gravity (density) indicators in vacuum instead of using air mass indicators.

The best option for determining the density of water is to take samples three times at different depths in the bow, stern and midships (9 values). The number of samples may be lower if the vessel is small or if practice shows that for a given berth the water density is constant at a certain depth. In total, water samples should be taken at least per liter. Then the water is placed in a special transparent test vessel. This should be done immediately as long as the seawater temperature is maintained.

There is no need to measure the temperature of the water using a glass hydrometer. It is important to determine the density values ​​of the water at the time of the draft survey. Applying corrections to the density measured with a hydrometer distorts the readings. As the temperature changes, the hull of the vessel will expand and contract, the same changes will occur with the hydrometer - therefore, there is no need to introduce corrections to the density.

The surveyor must ensure that the base of the hydrometer and the surface of the water are not contaminated with oil or grease. Then lower the device into water and record the value of the intersection of the water level and the scale of the device. It is important that the eyes are in front of the instrument and not at an angle. The hydrometer must be specially designed for seawater.

Density values ​​will be in the range of 0.993 - 1.035 t / m3. To take measurements, you need a hydrometer capable of measuring mass in air (apparent density), mass in vacuum (actual density), and a specific gravity (relative density). The surveyor needs to determine the mass of the cargo in the air, as this is a common commercial mass. Therefore, in his calculations, he must use the apparent density or mass per unit volume in air.

The units are usually kg / l. If the hydrometer is designed to measure mass in a vacuum or to take a gravity index, a correction of 0.0011 gm / ml is applied, it must be subtracted from the obtained density value to obtain the mass value in air.

Summing up, let's highlight the main thing for the surveyor when determining the density of water:

• take the required number of samples;
• use an accurate hydrometer;
• do not apply temperature corrections;
• determine the mass of a unit of volume in air, kg / l.

7.0. Weights to be determined.

After the values ​​of sediment and water density have been determined, the values ​​of all masses are set, which will then need to be subtracted from the displacement to determine the mass of the cargo. The ship's light weight, the amount of ballast, ship's stores, as well as the value of the ship's constant or ship's constant are determined. On a small vessel, one surveyor can handle this task. If this is a very large vessel awaiting loading or preparing to leave for a voyage, the surveyor will need an assistant. While the former will determine the values ​​of sediment and water density, the latter will be engaged in measuring ship's tanks.

The weight of the vessel is unladen.

The value of the lightweight of the ship is taken on faith according to the information of the ship. If during the initial and final draft surveys, the same erroneous light weight of the vessel was used, this will not entail an error. If, on the initial draft survey, one value was used, and on the final one another, this will lead to an error. When carrying out a survey for deadweight, any mistake in determining the light weight of the vessel will lead to an erroneous value for the weight of the cargo.

Ballast.

Determining the amount of ballast represents the largest amount of work. The surveyor should measure all ballast tanks and determine the amount of ballast in them. For this, it is best to use a steel tape with a paste marking the water.

Ideally, the vessel should not have a roll and be on an even keel, but in practice this is almost impossible to achieve. The roll can be corrected by moving ballast from one tank to another. However, this operation will take a long time and may cause problems with pumping ballast during the survey, which will affect its accuracy. Entering a roll correction for each ballast tank is also a time consuming operation that will not be necessary if the roll is small.

A vessel in ballast always has a large stern trim. Some ships are provided with appropriate trim tables for calculations in ballast tanks, some are not. To avoid calculating trim corrections, many surveyors insist that ballast tanks be either empty or full during the survey. The surveyor, having made sure that some of the ballast tanks are full, takes measurements of the remaining empty tanks. This procedure does not take much time, it is acceptable for small tanks of ships that do not have too much trim.

Measurements made in full ballast tanks of a ship with a large trim will be a source of error. Measurements in empty tanks will be more accurate, but there is still the possibility of residual ballast water in the tanks, the amount of which cannot be quantified.

Measuring ballast holds is a complex operation and also a source of potential errors. The hold must be empty and dry prior to the initial draft survey. If this is not possible, the surveyor must measure the voids in different parts of the hold to obtain the correct depth value to enter the calibration tables.

Having made the necessary measurements and having obtained the values ​​of the water depth in the tanks, the surveyor, using calibration tables or by calculations, converts these values ​​into m. Knowing the density of the water in each tank, which he also had to determine, the surveyor sets the amount of water in the tanks. However, it is difficult to determine the density of the water in a ballast tank, and it is not enough to believe the senior officer's assertion that the ballast was taken on board on the high seas. An error in the value of the density of ballast water for large ships can lead to a change in the weight of the cargo up to 150 tons or more.

Thus, the surveyor must take water samples from all or several ballast tanks in any way possible and determine its density using the same hydrometer with which he measured the density of the seawater.

Summing up, let's highlight the main thing for the surveyor, who determines the amount of ballast on board the vessel:

• carefully read the plans for the location of ballast tanks;
• take measurements of ballast tanks using a steel tape with a paste marking the water;
• determine the density of water in each tank;
• calculate the volume occupied by water in each tank, applying the necessary corrections for roll and trim;
• determine the amount of ballast water in each tank using the product of volume and density.

Fresh water.

The amount of fresh water is determined in the same way as the amount of ballast. It is less labor intensive, there are fewer fresh water tanks and usually no water density determination is required.

Heavy and diesel fuels, lubricating oils.

If, while staying in the port, the vessel did not take on board fuel, the surveyor uses in the calculations the amount of fuel and lubricating oils specified in the fuel quality certificate (Bunker Receipt - see. tab. 3). If the vessel took fuel on board between the initial and final draft survey, or if a deadweight survey is being carried out, the surveyor must measure the fuel tanks and determine the amount of fuel and lubricating oils by calculation. Calculations and corrections for roll and trim are performed as for ballast tanks. For fuels and lubricants, densities at 15 ° C are generally used. For measuring fuel tanks, it would be more expedient to use a special fuel hydrometer, which determines the exact density value. However, such hydrometers are not used because the amount of fuel and oil is not large and the probability of error is also very small. It must be remembered that cooled fuel or oil moves very slowly, so if there is a trim change, it can take some time to determine the exact depth of the fluid in the tank. Measurements of voids in the tank in this case will give a more accurate result.

Stocks and ship constant.

The ship's constant, contrary to the name, is not a constant value. It is the difference between the net displacement and the value of all variable ship stocks (ballast, fresh water, fuel and lubricants, sediment water, etc.).

The constant includes the crew, the ship's stores, paint, remaining dirt in the tanks, minor discrepancies in the marks of the load marks, inaccuracy in determining the unladen weight of the ship.

During the initial draft survey carried out on the vessel in ballast, the surveyor determines the constant by calculation. For a small bulk carrier, the normal value of the constant is about 250 tons. Older ships have a higher constant than newer ships. The value of the constant will fluctuate with changes in the amount of anchorage materials on board, stocks, and when ice and snow appear on the deck. Due to these factors, which are not determined by calculation, the weight of the ship unladen can change by 60 tons.

In some cases, the surveyor receives a negative constant. This is usually a sign of error. However, if the constant remains negative after repeated measurements and calculations, this value should be used.

A negative constant can be obtained for the following reasons:

• Offset of the weight scale.
• Some ships use ballast tank calibration tables and hull data developed for another ship of the same type. Vessels of the same type differ slightly from each other, but the tables are the same.
• On some vessels, significant errors are caused by trims that are much larger than the allowable trim. Such vessels are a kind of scourge for draft surveyors. If the Chief Officer is unable to provide the constant values ​​for previous flights in the event of a theoretically unacceptable result, the accuracy of the results of this draft survey will be questionable.

When conducting a survey for deadweight, the surveyor either determines the value of the ship's constant approximately, or takes its value on faith according to the ship's information. The deviation of the constant from its actual value means the same deviation of the amount of cargo from its actual amount on board.

Deadweight surveys are often more accurate than full draft surveys, as there is an opportunity to avoid initial draft survey errors associated with large trim of the vessel. Measurements are carried out on a loaded vessel, all calculations are carried out as for a vessel on an even keel, which avoids many errors.

If the vessel is regularly surveyed, it is useful to compare the constant values ​​across several voyages and determine the value with which the survey was most accurate.