Recess marks. Landing of a vessel and determination of its draft by deepening marks Reserves and ship constant

The provisions on load lines are developed on the basis of the International Convention on Load Lines of 1966. The load line provisions apply to every ship that is assigned a minimum freeboard.

Freeboard- the distance measured vertically at the side in the middle of the length of the ship from the upper edge of the deck line to the upper edge of the corresponding load line.

Freeboard deck- this is the uppermost continuous deck, not protected from the effects of sea and weather, which has permanent means of closing all openings on its open parts and below which all openings in the sides of the ship are provided with permanent means for watertight closing.

The freeboard assigned to the vessel is fixed by applying on each side of the vessel a deck line mark, a load line mark and deepening marks marking the highest drafts to which the ship can be maximally loaded under various sailing conditions (Fig. 1). The load line corresponding to the season should not be immersed in water throughout the entire period from the moment it leaves the port until it arrives at the next port.

Ships with load lines marked on their sides are issued an International Load Line Certificate for a period of no more than 5 years.

The following load lines are used:

summer load line - L (S);
winter load line - W (W);
winter load line for the North Atlantic - ZSA (WNA);
tropical load line - T (T);
load line for fresh water - P (F);
tropical brand for fresh water - TP (TF).

The designation of the organization that assigned the load line is applied above the horizontal line passing through the center of the sign ring (Plimsoll disk). The designation of the Register of Shipping of the Russian Federation is RS.

Fig.1 Load line

There are load lines for timber carriers, passenger ships and sailing ships. The recess marks are intended to determine the draft of the vessel; they are applied on the outer plating of both sides of the vessel in the area of the stem, sternpost and on the midship frame (Fig. 2).

Recess marks are marked with Arabic numerals 10 cm high (the distance between the bases of the digits is 20 cm) and determine the distance from the existing waterline to the lower edge of the horizontal keel.

Until 1969, the markings of the recess on the left side were applied in Roman numerals, the height of which was 6 inches. The distance between the bases of the numbers is 1 foot ( 1 foot = 12 inches = 30.48 cm; 1 inch = 2.54 cm).

The load scale (Fig. 3) is a table for determining displacement (deadweight) based on the calculated or measured average draft of the vessel. It is usually calculated for two densities of water: sea - 1.025 t/m 3, fresh - 1,000 t/m 3.

To use a load scale, it is necessary to draw a horizontal line through a known value (for example, draft) and remove the values of interest (for example, displacement).

Rice. 2 Recess marks

Fig.3 Weight scale

Rules for the technical operation of the cargo device

The chief mate, chief engineer, boatswain, 4th engineer and electrician are responsible for the technical condition and maintenance of the cargo device.

Each ship must have a Register Book of ship lifting devices and relevant certificates, certificates, and instructions.
After repair or replacement of any of the non-removable critical structures of the lifting device, parts of the lifting mechanism, or the topping winch, operation of the lifting device is prohibited until it is tested in the presence of the Register inspector.
Blocks, staples, hooks, swivels, chain counterweights, tees must have marks and certificates.
It is prohibited to use even a slightly unbent cargo hook. The cargo hook brackets must lock securely. The blocks must be inspected, disassembled, cleaned of dirt, rust and lubricated with thick lubricant. The pulleys of all blocks and the swivels of the cargo hooks must be well lubricated, spread out and rotate freely.
Each vessel with a vertical cargo handling method and having a cargo device must be equipped and always have in the required quantity (in accordance with the supply sheet) serviceable slings and other cargo equipment that meets the requirements of the Safety Rules.
Weight shackles used to replace load hooks must have a pin held in place by a pin or pin.
Wooden blocks with cracks on the cheeks (so that the cheeks are accessible for inspection, they should be sanded), the fitting or pulley, as well as with a bent hook, a stretched bracket, a worn dowel or a damaged bushing should be replaced immediately.
All removable parts and cables of lifting devices that are not related to lifting devices must be checked at least once every 3 months. If broken wires are found in the cable, it should be inspected monthly. The results of the inspection and the measures taken to eliminate deficiencies should be recorded in the ship's log.
All cables of the running rigging of the cargo device must be free from splices, creases and tears in the strands.
Changing the horizontal position of the cargo boom at maximum reach using guy ropes is allowed when the ship has a list of no more than 5° and a trim of no more than 2°.
All lifting devices must be inspected before each use. Defects and measures to eliminate them are recorded in the ship's log. The lifting device is put into operation only after the detected defects have been eliminated.
Work with twin booms (“on the telephone”) and heavy booms must be carried out in accordance with the Instructions drawn up for each vessel and agreed with the Register. Simultaneous operation of a heavy and light boom of one mast is not allowed, unless this is provided for in the mentioned Instructions.
Each removable part (block, swivel, etc.), repaired or installed to replace a defective one, must have a Register stamp indicating that a test load test was carried out in the workshop, without which its use in a cargo device is prohibited.
The cargo equipment of the vessel must be inspected by the Register inspector and tested in his presence. Test reports must be included in the Register Book of ship lifting devices.
If any loading option requires liquid ballast, it must not be handled in any way during loading or unloading. However, if the information on stability, unsinkability and strength contains other instructions on the procedure for ballasting a ship with liquid ballast, you must be guided by these instructions.
During loading, passage and unloading, fuel and water should be consumed evenly on both sides.
When transporting cargo on deck, the following basic requirements must be met:
1. deck cargo must be stowed in such a way that there are safe passages for people with a width of at least 0.7 m to ladders, measuring and air pipes, fire stations, horns and fire extinguishers;
2. all passages must be through (without dead ends).
If timber cargo is carried on deck, these requirements must be met to the maximum extent possible.
The deck cargo must be fastened securely, but in such a way that in a critical position of the ship it is possible to quickly release the lashings or, in extreme cases, cut them.
When crossing by sea, the parts of the cargo device must be securely fastened in a traveling manner:
1. the ends of the arrows are well fixed in the sockets;
2. the hooks of the cargo pendants are laid behind the deck eyes (toes up with capping), and the cargo pendants are tightly fitted on the drums of the winches;
3. the lower blocks of guys are laid out from the eyes and laid at the spur of their boom, the hoist flaps are tightened, laid in a coil and suspended from the mast;
4. the cargo pendant and the slings of the guy hoists are secured to the boom in several places by lines.

Safety precautions when working with a cargo device

Cargo operations belong to the category of high-risk work. The safety regulations on naval vessels determine the requirements for the cargo equipment of the ship and regulate safe methods of working with hatch covers during the preparation and operation of the cargo equipment and the performance of cargo operations.

Cargo compartment

The places where the traction cables pass must be fenced off and the inscription “Passage closed” must be posted. It is prohibited to walk on the hatch sections during their opening, closing, or partial opening.

Sections installed in a vertical position must be securely locked. Do not leave them unlocked, even for a short time. Any work in the space between the open hatch sections can only be carried out with the permission of the watch officer or the work manager. During the entire period of work between the sections, there must be a sailor on deck who is obliged to ensure that no one removes the stoppers from the hatch sections, connects the traction cables to the sections, or turns on the hydraulically driven hatch cover control system.

It is prohibited to carry out any work on hatch sections that are not completely closed until a temporary railing is installed to prevent people from falling into the hold. The deck in areas where reloading operations are being carried out must be fenced off with handrails with prohibitory signs posted on the side towards which the cargo is moving.

You cannot go down into unlit and unventilated holds. Lighting chandeliers suspended on rods can only be carried when tension is removed and after all people have left the hold.

Persons involved in cargo operations undergo safety training before starting work. Qualified sailors and other crew members who have undergone special training and have special certificates are allowed to work on lifting mechanisms as a crane operator and winch operator, as well as as a slinger.

Only specially trained crew members at least 18 years old, whose names are announced by order of the ship after passing the exam, are allowed to work on heavy-duty devices. Only qualified sailors can be appointed as signalmen.

The winch or crane operator carries out all signals given only by the signalman, except for the emergency stop signal, which must be carried out regardless of by whom and in what way it is given. Any misunderstood signal should be taken as a stop signal. The signal for lifting a load can only be given after the slinger has confirmed that the load is properly slung and the signalman is satisfied that the movement does not endanger people working in the hold or on deck.

Signalman

It is prohibited to walk under a raised load, be on the line of cargo movement, under the boom, in the hatch opening, as well as go down into or out of the hold when lifting and lowering the load.

When working on winches and cranes, the following is prohibited:

allow uneven tension of all branches when lifting a load using multi-branch slings;
adjust the slings when the load is suspended;
unfasten the load before it sits firmly on the pads;
swing the load to place it outside the range of the booms or crane;
lift a load with people or loose objects on it, as well as a load that is in an unstable position or loaded with other loads;
pull back, turn and stop a swinging load while lifting, moving or lowering without the use of special guys.

In addition, when working on winches and cranes it is prohibited:

deliver cargo into the hold without a warning signal if there are people in the hold;
supply cargo into the hold before the previously supplied cargo is removed from the hatch opening and people retreat to a safe place;
carry cargo at a height of less than 0.5 m from ship structures or objects located in the path of cargo movement;
leave the load suspended at the end of work or during a break;
leave live mechanisms unattended;
adjust the pendant by hand, wind it alone or wind it onto the winch drum during its operation.

The operation of the lifting device must be stopped in cases of failure of the correct operation of the brakes, abnormal noise in the mechanism, damage to the cable, malfunction of switches and systematic operation of electrical protection systems.

When handling hazardous and flammable cargo, in addition to the above, you should also be guided by the transportation rules established for them.

Rice. 1. Load line for bulk carriers and tankers.

Rice. 2. Load line for ships transporting timber.

Look carefully at the drawing. It is a circle and a figure that resembles a comb. A horizontal line is drawn through the center of the circle, the continuation of which on the “comb” is indicated by the letter L (summer mark). This is the so-called main brand. When sailing in winter, ships often encounter stormy weather. For safe navigation and successful fight against storms, the ship should not be overloaded, and, therefore, in winter it is necessary to take less cargo than in summer, and have a smaller draft and a larger freeboard, that is, a greater reserve of buoyancy . This is taken into account on the load line under the main letter 3 (winter line). But in winter, not all areas of the oceans are equally dangerous for a loaded ship.
The northern part of the Atlantic Ocean is the most “inhospitable”, and therefore, when sailing here, the ship should be the most lightweight. The permissible draft for such a voyage is marked by the ZSA line (winter mark for the North Atlantic).
Several “comb” lines are applied above the main – summer – mark. This suggests that the ship may have a greater draft than in summer. When does this happen? When sailing in the tropics, the weather is usually favorable for the voyage. There is no danger of icing, which increases the vessel's draft, and encountering a storm is less likely. The vessel here can take on more cargo, have a greater draft and less freeboard. This is marked with a T line (tropical mark). The vessel's draft depends on the density of the water. The greater the density of water, the greater the buoyant force; When a ship from the sea enters a river, its draft increases. Consequently, the stamp can be slightly “sinked” in the river. Therefore, two more lines are marked on the “comb” - P (fresh mark) and TP (tropical fresh mark).
For each ship, the load line is marked according to international rules, which are mandatory for all maritime powers in the world. Therefore, the shape of the load line is the same everywhere. The only difference is in the letters. On the load lines that are placed on the sides of our merchant ships, there are the letters P and S. They mean that the mark was applied to the side of the ship under the supervision of the Soviet classification society - the Register of the USSR.
Load lines of foreign merchant ships are indicated by letters of the English alphabet (see pictures). The letters of the Circle correspond to one or another name of the classification society. For example, L and R stand for Lloyd's Register, A and B for American Bureau of Shipping, etc.
On ships that transport timber, as well as either cargo or passengers, additional marks are applied. Each ship carries a freeboard certificate, and if the draft is greater than allowed by the load line, then its captain has no right to go to sea. In the event of overload, the port authorities responsible for the vessel's departure have the right to demand the removal of excess cargo and even detain the vessel in the port.
As a rule, the load line is attached in the form of steel strips to the side of the ship at the midship frame on each side and painted in a color different from the color of the surface of the hull. For example, if the board is black, then the stamp is painted white; if the side is spherical, then the stamp is painted green or black. The thickness of the load line line is the same: it is 25 mm. The diameter of the circle and the length of the “comb” lines are indicated in the drawing. Stamps for passenger and sailing ships have a simplified design. On timber carriers, on the load line towards the stern of the circle, an additional drawing is made with the addition of the letter L (L) - forest freeboard - to all letter names.
Deepening marks, or, as they are also called, “draft marks,” are applied on both sides of ships at the stems and on large ships on both sides near the midsection. Typically, on one side of the brand, the recesses are made in the metric system, and on the other - in feet. In the first case, the height of the numbers and the distance between them are equal to 1 inch and the numbers are applied every 1 inch. In this case, each meter of draft is indicated. If the mark of the recess is given in feet, then the height of the numbers and the distance between them are taken as 0.5 feet. The dredge marks should never be confused with the load line, as they serve only to measure the actual bow and stern draft at a given time.

Rice. 3. Load line for passenger ships.

Rice. 4. Load line for sailing ships.

Rice. 5. Load line for ships sailing on the Great Lakes (USA).

Rice. 6. Mark of the recess, or mark of the stems:
a) scale in feet; b) scale in decimeters.

The color of the copper, which varied from reddish to yellowish depending on the composition of the alloy, resembled the color of newly minted ancient copper coins. At sea, under the influence of salt water, the skin shone brightly, and in a port or dry dock, when it dried, it acquired a greenish tint, reminiscent of the color of the copper dome of a building.

Historical reference

The greed of the shipowner, who sought to load his ship as deep as possible, has been one of the main reasons for the death of merchant ships for many centuries. Since ancient times, sailors have been aware of the importance of freeboard and the danger of overload. We have reached some information that already ancient sailors limited the draft of their ships.
On an ancient ship raised by the French near Tunisia, a document dating back approximately two thousand years was preserved, corresponding to a modern charter agreement. The document contains the oaths of the skipper: “By Zeus and all the gods of Olympus, to keep the terms of the contract of carriage sacred and inviolable and not to accept additional cargo on your ship.” The collection of Venetian maritime regulations for 1255 mentions the oldest cargo marks-crosses, painted or burned on the sides of the ship . There were two stamps, for new and old ships over five years of age. Overloading was punishable by a fine. Subsequently, in Venice they even established the position of scribanus - a port supervisor for the loading of ships. And the laws of the Hanseatic city of Visby made it the responsibility of the Senate itself to inspect the ship.
Compared to medieval merchants, the shipowners of the “mistress of the seas” of Britain looked simply barbaric. At the beginning of the 19th century, the English merchant fleet accounted for almost half of the world. The accident rate in it was catastrophic. It grew steadily, and James Hall, a member of the New Castle Chamber of Commerce, bitterly stated in The Times: “It may be stated that the number of ships lost in England during 1867 was no less than 2,090, or about 6 ships a day.” In another article he wrote that as a result of the strong increase in the accident rate in the English merchant fleet, the number of insurance payments premiums to owners have doubled in twenty to thirty years; whereas previously insurers made a fortune in the merchant fleet, now they are losing money."
Hall himself was a large shipowner and at the same time the director of an insurance company. Every now and then faced with violations of navigation safety rules, he was the first to draw the attention of the English government to malicious overloading of ships. In 1869, in the House of Commons of the English Parliament, a draft of a new “Shipping Law” was discussed. Hall, who was present, proposed putting a load line on the sides to limit the draft of the vessel. Drawing public attention to the unacceptable situation in the English merchant fleet, Hall said: “It’s amazing It’s not that a large number of ships are lost at sea, but that this number is so small!”

Alas, it was the voice of one crying in the wilderness.
And only Samuel Plimsol heard it. Oddly enough, he was neither a shipowner nor a sailor at all. A brewery manager and later a coal merchant, Plimsol made a considerable fortune and in 1868 achieved election to parliament from the city of Derby. Not being particularly picky about his means, he used the material collected by Hall and wrote the book “Our Sailors.” The picture it presented of English shipping at that time turned out to be so unattractive that the government appointed a royal commission on unseaworthy ships. However, after several months of work, the commission declared that there was no question of universal rules for limiting the draft of ships, and any law regarding the minimum permissible freeboard height would be malicious! In the summer of 1875, at a parliamentary debate, English Prime Minister Disraeli said that the next shipping bill under consideration should be rejected. Then Plimsol jumped up and, turning to his opponents, shouted:

Scoundrels!

For this he was suspended from his post for a week. Plimsol was forced to publicly ask parliament for an apology, but he became extremely popular and increased the number of his supporters in parliament.
The very next year a law was passed
According to it, ships were required to have a load line on their sides in the form of a circle, the center of which would indicate the maximum draft... which was determined by the shipowner himself. Naturally, he tried to declare the load lines “with a reserve” “just in case,” often dooming the ship to certain death. In 1882 alone, 548 British ships sank and 3,118 sailors died. This turn of events caused numerous protests and unrest. However, the British government, always distinguished by conservatism, introduced a load line law only in 1890. The height of the freeboard began to be determined by the classification society, and the permissible draft indicator, mandatory for all British merchant ships, acquired its current form.
It is curious that, despite the originality and simplicity of the load line, which subsequently ensured such a long life for it, Plimsol did not even try to patent it. However, if this had happened, it is unlikely that he would have received even a penny from the shipowners who hated him. However, the former brewer became so popular among sailors that he was even elected chairman of the English Union of Sailors and Firemen.
Before the First World War, the load line was already widely used in Belgium, France, Germany, Japan, Holland, Sweden, and Portugal. True, shipowners
they were still trying to catch. Calcutta, Norfolk, and the ports of the West Indies and the Gulf of Mexico were especially notorious. They even developed special techniques on how to deceive the vigilance of inexperienced supervisors. Usually, an overloaded ship was artificially heeled so that the mark would rise out of the water and be visible from the pier. As for the huge American merchant fleet by that time, the conscience of the shipowner still remained the measure of the permissible draft of the ship. That was until the Vestris died. In November 1928, this cargo ship, being loaded 7 inches above the load line, lost stability during a storm in the Atlantic, capsized and sank. The news of the Vestris tragedy spread throughout the world and made a deep impression on the public of the United States. In 1929, the US Congress approved the Load Line Act. A year later, a conference was held in London, which adopted the first “International Convention” on the “load line”. It was signed by representatives of more than 40 states, including our country, which by that time had long ago implemented Plimsol’s useful proposal.

Methodology for determining the weight of cargo on board a ship using the draft survey method

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

The purpose of a draft survey is to determine the weight of cargo on board a vessel. By measuring the draft, using the ship's cargo documentation and information on calculating the loaded 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 which are not the weight of the cargo, the difference being 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 ship builders’ information about the ship varies. It is very difficult to accurately measure precipitation and find out the actual weight of ballast.

The time it takes to conduct a draft survey will depend on many factors: the size of the vessel, the amount of ballast, the number of tanks, and the condition of the vessel. It is common practice for a surveyor to be present from the beginning to the end of cargo operations. On large ships, two surveyors are required to carry out a draft survey.

The accuracy of measurements during a draft survey is affected by the situation on the vessel and time constraints. Minor errors will not cause significant damage if the vessel is small in size. However, when transporting large quantities of valuable cargo, 1% of the weight of this cargo represents a large amount of money. The surveyor must demonstrate that he has made every effort to take the most accurate measurements possible using standard methods. The surveyor must be confident in what he is doing and be able, as far as possible, to prove that he is right.

1.0. Determination of cargo mass based on the vessel's draft.

1.1. Removing the vessel's draft.

The vessel's draft (T) is the depth to which the vessel's hull is immersed in water. To measure the draft values on the bow and stern perpendiculars (stem and stern, respectively), recess marks are applied on both sides. Marks of recesses are also applied on both sides in the middle (midship) of the vessel to remove sediments in the midships.

Recess marks may be indicated by Arabic numerals and presented in metric measurement (meters, centimeters - Appendix 1), as well as Arabic or Roman numerals - English measurement system (feet, inches - Appendix 2).

With the metric draft measurement system, the height of each digit is 10.0 cm, the vertical distance between the digits is also 10.0 cm, the thickness of the digits on sea vessels is 2.0 cm, on river vessels 1.5 cm. With the English draft measurement system, the height of each The digits are 1/2 foot (6 inches), the vertical distance between the digits is also 1/2 foot, and the thickness of the digits is 1” (inch).

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

Sediment removal is carried out from both sides of the vessel with the greatest possible accuracy from the pier and/or boat.

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

The 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 recess marks in the bow, amidships and aft on one side.

For the obtained settlement values, the average settlement is calculated (formula 1) :

Where T'- average draft, m;

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

B - transverse distance between the recess marks of the right and left sides, m;

q is the angle of roll (read from the inclinometer located on the navigation 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 vessel).

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

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

Determination of draft amidships

Designations for Fig. 2. :

1 - main deck line;

2 - waterline;

3 - freeboard height to waterline;

4 - draft to the waterline;

5 - draft to summer load line;

6 - summer freeboard;

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

8 - keel line.

1. 2. Determination of the average of the average calculated draft, taking into account corrections to the draft in the bow and stern parts of the vessel, as well as the trim and deformation of the vessel.

Measurements of draft in the bow of the vessel are recorded according to the marks of the recesses marked on the stem, and not along the bow perpendicular, which is the design line. As a result, an error appears, which is eliminated by introducing a correction (see Fig. 3., formula 5):

Introduction of amendments to draft in the bow and stern of the vessel and amidships

f - distance from the stem to the bow perpendicular, m;

LBM = LBP – (f + a) - trim - the difference in draft of the vessel in the bow and stern, m;

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

When trimming the vessel, measurements of the draft of the stern part of the vessel are recorded according to the marks of the recesses on the stern post, and not along the stern perpendicular; therefore, the same correction must be introduced for the draft taken in the stern part (formula 6):

a - distance from the recess marks to the stern perpendicular, m.

Distances A And f can be determined using a scale drawing of the ship or a longitudinal section of the ship.

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

The drafts of the bow and stern parts of the vessel, taking into account 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 deepening scale is shifted to the bow or stern of the vessel from the plimsol circle (formula 10):

Where diff.'- trim determined after introducing amendments to the drafts of the bow and stern parts of the vessel;

m is the distance from the plimsol circle to the midship recess mark, m.

The sign of the correction is negative when the mark of the recesses is shifted towards the stern and positive when the mark of the recesses is shifted towards the bow from the plimsol circle.

Precipitation at midships, taking into account the correction, is calculated using formula 11:

The average settlement is calculated using formula 12:

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

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

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

The total carrying capacity of the vessel is deadweight – is determined as follows (formula 15, 16):

If we take the mass of the ship's stores and the mass of the “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 quantity of cargo determined in this way must be clarified taking into account changes in the mass of ship supplies during cargo operations.

Part ship's stores includes:

mass of fuel and lubricating oils;
mass of drinking and technical fresh water;
the mass of ship supplies of provisions and supplies (paint, 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, remaining water in tanks, etc.

The vessel's displacement is determined by load 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;
trim moment scale, tm/cm;
the tons per cm draft scale shows, for a particular draft, the amount of cargo that must be removed or loaded to change the ship's draft by 1 cm (can be expressed in tons per inch);
freeboard scale, m and/or feet.

When using a load scale, the values of displacement and deadweight must be determined using the fresh water scale (g = 1.000) if the ship is in fresh water, and using the sea water scale (g = 1.025) if the ship is in sea water. The value 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) determined before and after loading (unloading) of the vessel by the average average design draft on the load scale, hydrostatic table (Appendix 4) or hydrostatic curve (Appendix 5). Typically, displacement is indicated for sea water (r = 1.025 t/m3).

1. 4. Corrections for ship trim.

Cargo hydrostatic tables or hydrostatic curves, which give displacement at different drafts, are calculated for a vessel on an even keel. The true displacement of a vessel trimmed to the stern or bow differs from the displacement given in the load scale or table, therefore, must 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, you must first add 50 cm (6 inches) to the draft value and remove the value from the hydrostatic tables of the trimming moment, and then subtract 50 cm (6 inches) from it and use this data to 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 general correction for trim is expressed by formula 22:

Displacement corrected for trim is determined according to formula 23:

1. 5. Correction for seawater density.

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

Seawater samples to determine actual density should be taken at a depth corresponding to approximately half the vessel's draft and approximately halfway through the vessel. To obtain more accurate data, samples can also be taken near the bow and stern of the vessel.

If an ariometer (hydrometer) calibrated at a temperature of 15°C is used to determine the density of water, then the actual density is determined using the following table 2 based on measured density and actual water temperature.

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

The displacement, taking into account the correction for the density of sea water, 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 deducted from the displacement as not related to the payload.

TO variable ship supplies relate:

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

To determine the mass of variable reserves, immediately after the vessel's draft is removed, all ship's tanks should be checked.

Determination of the amount of fresh water and ballast.

On a ship, fresh water can be stored in galley and sanitary tanks, in forepeak and afterpeak tanks, in deep tanks and bottom tanks (boiler water).

The bottom part of the vessel consists of a double bottom, which houses double-bottom tanks intended for ballast. Double-bottom tanks run either across the entire width 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 that serve to ensure the safety of the vessel in case of a hole.

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

Water on the ship can also be found in bilges (ship drainage reservoirs) located along the sides. Sewage tanks must be emptied before measuring sludge.

Determination of the amount of fuel and lubricating oils.

Fuel (diesel, fuel oil) is located in bottom, service and settling tanks, as well as in deep tanks. There are small lubricating oil tanks in the engine room. Responsibility for measuring the amount of fuel and lubricating oil lies with the chief engineer, who has calibration tables compiled in tons or cubic meters. Data from measurements and calculations of all reserves are summarized in table 3, 3a.

3.0. Time required to conduct a draft survey.

To conduct a draft survey on a small standard vessel and obtain effective results, a qualified surveyor will need about half an hour. If this is a large 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 average in size and can be placed between the two examples above. Much also depends on the type of vessel and the crew involved.

There is a huge difference in the time and effort required to conduct the 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 - precipitation, variable ship supplies (ballast and fresh water, fuel, lubricants, etc.). It is believed that this method helps eliminate errors that could arise when determining the light weight of the ship and the weight of the ship's stores, and gives a more accurate result. Measurements of ballast tanks and sediment removal are carried out upon the vessel's arrival at the port and upon completion 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 if the ship constantly transports a certain type of cargo along a certain route, all its variables are known and the ship constant (constant) is accurately calculated. This method has some other benefits besides saving time. Since measurements are taken with the ship loaded, it is possible to avoid deviations that occur when measurements are taken on a ship with a large trim.

4.0. Accuracy of measurements.

An experienced surveyor, working under ideal conditions, will measure to within ±0.1 - 0.3% on a large vessel and to within ±0.4 - 0.7% on a small vessel. If you look at things realistically, it is almost impossible to provide ideal working conditions. Therefore, measurements are carried out with an accuracy of 0.5% of the total mass of the cargo.

If the instruments used to take measurements are of insufficient quality, the measurement accuracy will fluctuate within 1%. Technical errors may go unnoticed by the surveyor, and even more so by his employer, who has no idea about the operating principle of this method. Even with the best technology, adverse weather conditions and lack of crew assistance can affect the measurement accuracy by up to 0.5%. Since the measurements taken represent only initial information, inaccurate measurements will lead to errors in further calculations. Disagreements in the work of the surveyor and the crew, its inconsistency will also affect the flow of the draft survey, such as:

crew recalculation of ballast and fuel mass during survey;
blocking of measuring tubes;
changing documents;
creating other obstacles to the normal work of the surveyor.

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

The surveyor's only defense is attention to the smallest details, as well as the dexterity acquired along with sea experience. A detailed study of the ship's plans also often reveals inaccuracies and errors, but since not every plan can exactly correspond to a given ship, any conclusions must be drawn on this basis very carefully.

5.0. Draft.

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

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

Water fluctuations make it difficult to remove sediment. Special measuring tubes are used. Water passes 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 ship's roll (if any) with a special device - an inclinometer. Next, precipitation is calculated using simple trigonometry. However, accurate inclinometers are very rare, so 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 sediment, significantly changing its values. If the ship moves relative to the water, especially if there is a small under-keel clearance (the distance between the ship'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 current speeds up to four knots on changes in draft and trim is insignificant. If the current speed is four knots or more, the draft can increase to 6 cm, depending on the shape of the vessel.

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

In bright sunshine and low water temperatures, there is a tendency for ships to bend their hulls. The deck expands, but the bottom of the ship does not, which leads to a bowing of the ship's hull. The way out of this situation is to use special adjustment methods to help avoid errors in calculations.

6.0. Density.

The next step of the draft survey after removing sediments is to measure the density of the water in which the vessel is located. It is important to measure the density of water immediately after removing sediment, since it can change with the tide, as well as with changes in water temperature. 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 errors are as follows:

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

The best option for determining water density is to take samples three times at different depths in the bow, stern and amidships (9 values). The number of samples may be smaller if the vessel is small or if experience shows that for a given berth the water density is constant at a certain depth. In total, at least a liter of water samples should be taken. The water is then placed in a special transparent vessel for testing. This must be done immediately while the seawater temperature remains constant.

There is no need to measure the water temperature when using a glass hydrometer. It is important to determine the water density values at the time of the draft survey. Applying corrections to density measured with a hydrometer leads to distortion of the obtained values. As the temperature changes, the ship's hull will expand and contract, and 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 the water and record the value of the intersection of the water level and the device scale. It is important that your eyes are opposite the device and not at an angle. The hydrometer must be designed specifically 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 special indicator of gravity (relative density). The surveyor will need to determine the weight of the cargo in air as this is the generally accepted commercial weight. Therefore, in his calculations he must use the apparent density or mass per unit volume in air.

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

To summarize, we highlight the main thing for a 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 volume in air, kg/l.

7.0. Masses to be determined.

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

Light weight of the vessel.

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

Ballast.

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

It is ideal for the ship to have no list 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 be time-consuming and may result in problems associated with pumping ballast during the survey, which will affect its accuracy. Introducing a heel correction for each ballast tank is also a labor-intensive operation, which is not required if the heel is small.

A ship in ballast always has a large trim to the stern. Some ships are equipped with appropriate tables for adjusting trim when performing 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 filled, takes measurements of the remaining empty tanks. This procedure will not take much time; it is acceptable for small tank ships that do not have too much trim.

Measurements made in full ballast tanks on a heavily trimmed vessel will be a source of error. Measurements in empty tanks will be more accurate, but there remains the possibility of residual ballast water in the tanks, the amount of which cannot be determined.

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

Having carried out the necessary measurements and received the values of the depth of water in the tanks, the surveyor, using calibration tables or by calculations, converts these values into m. Knowing the density of 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 water in the ballast tank, and it is not enough to believe the statements of the chief mate that the ballast was taken on board on the high seas. An error in the value of ballast water density for large ships can lead to a change in cargo weight of up to 150 tons or more.

Thus, the surveyor must, by any available means, take samples of water from all or several of the ballast tanks and determine its density using the same hydrometer with which he measured the density of sea water.

To summarize, we highlight the main thing for a surveyor who determines the amount of ballast on board a ship:

carefully read the plans for the location of ballast tanks;
take measurements of ballast tanks using a steel tape measure with water marking paste;
determine the density of water in each tank;
calculate the volume occupied by water in each tank, applying the necessary corrections for heel 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 similarly to the amount of ballast. It is less labor intensive, there are fewer fresh water tanks, and there is usually no need to determine the density of the water.

Heavy and diesel fuel, lubricating oils.

If the ship did not take fuel on board during its stay in the port, the surveyor uses in the calculations the amount of fuel and lubricating oils specified in the fuel quality certificate (Bunker Receipt - see. table 3). If the vessel took on fuel 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 adjustments for roll and trim are made as for ballast tanks. For fuels and lubricating oils, density values at 15°C are typically used. To measure fuel tanks, it would be more advisable to use a special hydrometer for fuel, which determines the exact density value. However, such hydrometers are not used because the amount of fuel and oil is not large and the possibility of error is also very small. It must be remembered that cooled fuel or oil moves very slowly, so if there is a change in trim, it may be time to determine the exact depth of the liquid in the tank. In this case, measuring voids in the tank will give a more accurate result.

Reserves and ship constant.

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

The constant includes crew supplies, paint, remaining dirt in tanks, minor discrepancies in load line marks, and inaccuracy in determining the ship's light weight.

During the initial draft survey, carried out on a ship 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 fastening materials and supplies on board, as well as with the appearance of ice and snow on the deck. Due to these factors, which cannot be determined by calculation, the light weight of the vessel can change by 60 tons.

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

A negative constant can result for the following reasons:

Offset of the weight scale.
Some vessels use ballast tank calibration charts and hull data developed for another vessel of the same type. Vessels of the same type differ slightly from each other, but the same tables are used.
On some ships, the cause of significant errors is trim that is much greater than permissible. Such vessels are a kind of scourge for draft surveyors. If the chief officer is unable to provide constant values from previous voyages in the event of a theoretically unacceptable result, the accuracy of the results of this draft survey will be questionable.

When conducting a deadweight survey, the surveyor either determines the value of the ship's constant approximately or takes its value on faith based on the vessel'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.

A deadweight survey is often more accurate than a full draft survey, since it is possible to avoid the mistakes of the initial draft survey associated with the large trim of the vessel. Measurements are carried out on a loaded ship, all calculations are carried out as for a ship on an even keel, which allows you to avoid many mistakes.

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

On cargo ships, determination and calculation of draft are required for various purposes. For example, to determine the mass of loaded or unloaded cargo, to give the ship a given trim, etc. The draft of the vessel is measured at the bow, stern and middle marks of the depression.

Recess marks these are numbers and horizontal lines welded on both sides of the ends of the ship’s hull and in the midsection area. The draft of the vessel in the area where the mark is applied is equal to the vertical distance from the lower edge of the number to the lower edge of the keel. In everyday work, the term “removal of precipitation” is used to measure settlement, i.e. determine the draft of the vessel by the marks of the recess or determine the draft by measuring the height of the freeboard.

Recess marks are painted white on a dark background or dark on a light background.

Marking of recess marks can be carried out:

In the metric system (Arabic numerals), draft is measured in meters - the height of the numbers and the distance between them (perpendicular to the main plane) is 100 mm.

In the English system (Roman numerals), draft is measured in feet (1 ft = 0.3048 m. There are 12 inches in one foot, 1 inch = 2.54 cm). In this case, the height of the numbers and the distance between the numbers (perpendicular to the main plane) is 0.5 feet (6 inches).

If both systems are used on the ship, then on the left side the indentation marks are applied in Roman numerals, and on the starboard side in Arabic numerals.

It should be noted that the accuracy of the calculations associated with them depends on the accuracy of sediment removal. Therefore, navigators must learn to take photographs of precipitation under various unfavorable conditions: low light, waves, snow, ice, poor visibility of marks due to a large viewing angle or poor coloring of marks.

In addition, it is necessary to acquire the skills to measure the height of the freeboard at the locations of the recess marks. Based on the measured freeboard height, the vessel's draft at the measurement location is also calculated.

An example of sediment removal on English and metric recess marks is shown in Figure 1.

English system Metric system

Measuring draft by deepening marks

The shape of the ends of the ship's hull does not always allow the marking of recesses on the bow and stern perpendiculars. Therefore, for the convenience of removing sediment, they are applied at a certain distance from the corresponding perpendicular.

The bow mark is applied either on the bow perpendicular or aft of it.

The stern and middle recess marks can be applied both forward and aft from the corresponding perpendicular.

Sometimes part of the recess mark is applied on the perpendicular, and the other part at some distance from it.

Figure 2 shows an example of the arrangement of recess marks relative to the bow and stern perpendiculars and the midship of the vessel. Typically, ship diagrams indicate the distance between the mark of the recess and the corresponding perpendicular. Since in all calculations related to determining the landing of a vessel and determining the mass of cargo by drafts, drafts on perpendiculars are used, the drafts taken on the marks of the recess must be corrected with appropriate corrections so that they correspond to the drafts on the perpendiculars. Correcting the sediments taken on the depression marks means “bringing” them to the corresponding perpendiculars. To do this, use the formulas given in the article “Reducing precipitation to perpendiculars.”

An example of the arrangement of recess marks.

Symbols used in Figure 2:

KVL – structural waterline corresponding to the draft of the vessel along the summer load line.

lн– Distance of the nasal mark of the recess from the nasal perpendicular.

lsr– Distance of the middle mark of the recess from the midsection.

lcr– Distance of the stern mark of the recess from the stern perpendicular.

Landing called the position of the vessel relative to a calm water surface. In general, the landing of a vessel is determined by parameters that fix the position of the vessel relative to the surface of the water or the position of the waterline relative to the vessel.

Fig.5 Landing of the vessel.

If the center plane is inclined at a certain angle to the vertical plane, then this parameter will be the angle θ, which is called roll angle (Fig.5 a); if the midsection - frame plane is inclined at a certain angle relative to the vertical plane, then this parameter will be the angle ψ, called trim angle (Fig.5 b).

The landing of a ship is generally determined by three parameters:

D – average draft(midship draft), m;

D f – trim(difference between bow and stern draft D f = d n – d k), m;

-θ – roll angle– (inclination of the vessel in the midship – frame plane), degrees;

The trim angle is related to the trim D f:

tg ψ = (d n – d k) /L = Df/L

With the adopted coordinate system, the trim on the bow is considered positive (ψ > 0), and the roll angle is to starboard (θ> 0) .

The following landing cases are possible:

A. The vessel floats upright and on an even keel (θ = 0, ψ = 0). In this case, the landing is characterized by only one parameter - the average draft d.

B. The ship floats straight, but with trim (θ = 0, ψ ≠ 0). In this case, the landing is characterized by two parameters in one of the following combinations:

Average draft d and trim angle ψ ;

Average draft d and trim Df;

Precipitation by nose d n and stern d to, measured respectively at the bow and stern perpendiculars.

The above parameters are interconnected by the following dependencies: ψ ○ = 57 0.3(d n – d k / L); d = (d n + d k) /2

IN. The ship floats on an even keel, but with a list (ψ = 0, θ ≠ 0). In this case, the landing is characterized by two parameters - average draft d and roll angle θ .

G. General case of landing (the ship floats with a list and trim). Landing is characterized by three parameters in one of the following combinations:

d, ψ And θ ; dn, dk And θ ; d , D f And θ.

To control the draft of the vessel when its load changes, as well as to determine its trim, use recess marks . Recess marks are applied on both sides of the vessel in the bow and stern, as well as in the midship - frame area. The height of the numbers, measured according to the standards for OP, is 1 dm (100 mm), the distance between them is also 10 cm, or 50 mm and 50 mm, respectively; When marking indentations in feet, the height of the numbers and the interval between them are taken to be 0.5 feet (6 inches). Metric stamps are applied in Arabic numerals, foot stamps in Roman numerals (Fig. 6)

Rice. 6 Marks of depressions (sediment).

The overall draft is measured by the marks of the recess, since the lower edge of each number shows the vertical distance to the lower edge of the horizontal keel. In addition, the recess marks are not necessarily located on the bow and stern perpendiculars of the vessel.

Ship documentation, which serves to assess the seaworthiness of the vessel, is calculated and constructed for drafts measured at perpendiculars from the vessel's base. Therefore, to obtain them, it is necessary to correct the sediment values taken from the recess marks using a special scale (Fig. 7).

In the absence of the specified scale, settlements on perpendiculars are determined by the formulas:

d n = d nm ± δ nm + (L/2 - ℓ 1) ψ;d к = d km ± δ km - (L/2 - ℓ 2) ψ , Where: δ nm And δ km– the distance from the main plane of the lower edge of the keel in the planes of the bow and stern marks of the recess (the “+” sign when the edge passes below the OP, the “-” sign - above the OP), ℓ 1 And ℓ 2 – the distance of the bow and stern marks of the recess from the midship plane - the frame.

On some ships, precipitation gauges are installed to determine draft, the readings from which are automatically transmitted to the bridge.

Rice. 7 Scale connecting precipitation on perpendiculars with precipitation on the deepening marks of the m/v “A. Safontsev."

Questions for self-control:

1. What parameters determine the landing of a ship?

2. What types of landings are typical for ships?

3. Why, where and how are recess marks applied?

4. Is there a difference between the drafts taken using the deepening marks and the drafts calculated in the ship’s documentation and what does it consist of?