Vessel deepening marks. Plimsol disc (load lines)

Draft marks

Draft marks (depression marks)

signs on the outer plating in the bow, stern and amidships of the ship, applied at some level from the keel to determine the draft of the ship. Draft marks - numbers or letters with a height and a distance of 100 mm between them. The magnitude of draft fore and aft can be determined only by knowing the distance of each draft mark from the keel (given in a special draft mark layout)

Edwart. Explanatory Naval Dictionary, 2010

See what "Precipitation marks" are in other dictionaries:

- (Draught marks) see Load line. Samoilov K.I. Marine Dictionary. M. L .: State Naval Publishing House of the NKVMF of the USSR, 1941 ... Marine Dictionary

DEEP GRADES- vertical scales applied on the outer skin of both sides of the vessel in the area of ​​the stem and sternpost, and for large vessels also the midsection of the frame. They are marked with Arabic numerals 10 cm high, located at the same height from each other and ... ... Marine encyclopedic reference book

Draft value- the value of the difference in the marks of the sedimentary mark, obtained in different cycles of measurements. Source …

Indentation marks showing the ship's draft Draft ... Wikipedia

the consignment- 3.3 batch: Rails of the same type, one or more heats, one heat treatment mode (for heat-strengthened rails), simultaneously presented for acceptance in an amount of not more than 100 pcs. Source: GOST R 51685 2000: Rails ... ... Dictionary-reference book of terms of normative and technical documentation

Petrol- (Petrol) Gasoline is the most common fuel for most modes of transport Detailed information about the composition, production, storage and use of gasoline Contents >>>>>>>>>>>>>> … Encyclopedia of the investor

magnitude- 2.26 c value (c value) dimensionless quantity which expresses the degree of thermal contact between temperature sensors and the medium whose temperature is to be measured. Source … Dictionary-reference book of terms of normative and technical documentation

Nautical term, the angle of deviation of the ship's hull from the horizontal position in the longitudinal direction, the difference between the draft of the stern and the bow of the ship. In aviation, the term is used to refer to the same angle that specifies the orientation of the aircraft ... ... Wikipedia

MDS 13-22.2009: Methodology for geodetic monitoring of the technical condition of high-rise buildings and unique buildings and structures- Terminology MDS 13 22.2009: Methodology for geodetic monitoring of the technical condition of high-rise buildings and unique buildings and structures: Absolute (total) settlement - total settlement from the beginning of observations, obtained relative to the original high-rise ... ... Dictionary-reference book of terms of normative and technical documentation

MDS 13-22.2009: Methodology for monitoring the technical condition of high-rise and other unique buildings and structures by geodetic methods- Terminology MDS 13 22.2009: Methodology for monitoring the technical condition of high-rise and other unique buildings and structures by geodetic methods: Absolute (total) sediment is the total sediment from the beginning of observations, obtained relative to the original ... ... Dictionary-reference book of terms of normative and technical documentation

3.1. Determining the values ​​of draft fore and aft:

m.

3.2. The above-determined values ​​of draft fore, aft and mean draft correspond to the calculated values ​​on the perpendiculars. If it is necessary to check the correctness of the calculation after loading the vessel, the values ​​of the draft on the marks of the vessel's recesses should be taken - from the port and starboard sides (visually). The resulting settlement values ​​on the grades will differ from the calculated settlement values ​​on perpendiculars due to the following factors:

- the location of the marks of the recesses does not coincide with the position of the perpendiculars;

- marks of recesses are applied to the ship's hull, while repeating the spatial curvature of the shape of the ship's contours at the ends;

- the presence of a deflection arrow from the general bending of the body;

- a significant change in the shape of the waterline relative to the design in the presence of trim;

– the actual value of the outboard water density differs from the accepted value.

Therefore, the values ​​of the draft taken from the marks of the recesses are recalculated to the values ​​on the perpendiculars (based on the data of the ship's documentation), after which corrections are introduced to the displacement determined on the cargo scale for the average draft, taking into account all of the above factors:

a) Correction for water density

where ρ f is the actual density of outboard water, t / m 3; ρ is the density of water according to the load scale, t/m 3 ; D- displacement, determined by the cargo scale, t;

b) correction for trim

,

where q 0 – number of tons per 1 cm of precipitation, t/cm; x f 0 – abscissa of the center of the waterline area, m; M dif - moment trimming by 1 cm, tm / cm;

c) correction for hull contours at the extremities

,

where is the distance of the bow mark of the recesses from the bow perpendicular, m; is the distance of the stern mark of the recesses from the aft perpendicular, m;

d) correction for hull bending

where is the hull deflection arrow, cm (for this calculation, for educational purposes, we accept cm).

Thus, the final displacement value is obtained by summing the value determined on the load scale and its corrections. This final value must match the value calculated when drawing up the ship's cargo plan.

3.3. Recalculation of settlements on perpendiculars to settlements on grades:

where is the trim angle of the vessel; a- the distance of the bow mark of the recesses from the bow perpendicular; b- distance of the stern mark of the depressions from the stern perpendicular; With- the distance of the middle mark of the recesses from the plane of the midship frame.

(m)

3.4. The results of ship landing calculations after loading as of departure:

landing called the position of the vessel relative to the calm surface of the water. In the general case, the landing of the 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 diametral plane is inclined at some angle to the vertical plane, then this parameter will be the angle θ, which is called bank angle (Fig.5 a); if the plane of the midsection - the frame is inclined at some angle with respect to the vertical plane, then this parameter will be the angle ψ, called trim angle (Fig.5 b).

The landing of the vessel in the general case is determined by three parameters:

D- average draft(midship draft), m;

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

-θ – bank angle– (inclination of the ship in the plane of the midship frame), deg.;

The trim angle is related to the trim D f:

tg ψ \u003d (d n - d c) /L = Df/L

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

The following landings are possible:

BUT. The ship sails straight and straight 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 sails straight but trimmed (θ = 0, ψ ≠ 0). In this case, the landing is characterized by two parameters in one of the following combinations:

Medium draft d and trim angle ψ ;

Medium draft d and trim Df;

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

The above parameters are interconnected by the following dependencies: ψ ○ = 57 0 ,3(d n – d c / L) ; d \u003d (d n + d k) / 2

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

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

d, ψ and θ; d n, d k and θ; d , Df and θ.

To control the ship's draft when its load changes, as well as to determine its trim, use recess marks . Marks of recess are applied on both sides of the vessel in the bow and stern, as well as in the area of ​​​​the midship - frame. The height of the figures, measured according to the norms for the OP, is 1 dm (100 mm), the distance between them is also 10 cm, or 50 mm and 50 mm, respectively; when marking depressions in feet, the height of the digits and the spacing between them is assumed to be 0.5 feet (6 inches). Metric marks are applied in Arabic numerals, foot marks in Roman numerals (Fig. 6)

Rice. 6 Grades of depressions (sediment).

According to the marks of the recess, the overall draft is measured, since the lower edge of each number shows the vertical distance to the lower edge of the horizontal keel. In addition, recess marks are not necessarily located on the ship's fore and aft perpendiculars.

The ship's documentation, which serves to assess the seaworthiness of the vessel, is calculated and built for draft, counted on perpendiculars from the ship's OP. Therefore, in order to obtain them, it is necessary to correct the settlement values ​​taken from the depression marks using a special scale (Fig. 7).

In the absence of the specified scale, precipitation at perpendiculars is determined by the formulas:

d n \u003d d nm ± δ nm + (L / 2 - ℓ 1) ψ;d to \u003d d km ± δ km - (L / 2 - ℓ 2) ψ, where: δ nm and δ km- 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 plane of the midsection - frame.

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

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

Questions for self-control:

1. What parameters determine the landing of the vessel?

2. What landing cases are typical for ships?

3. Why, where and how are the indentation marks applied?

4. Is there a difference between the drafts taken from the marks of the deepening and the draft calculated in the ship's documentation, and what is it?

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

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 the ship. By measuring the draft, using the vessel's cargo documentation and information on the calculation of the submerged volume of the vessel, using the density of the water in which the vessel is located, the surveyor can calculate the weight of the vessel. 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 information of ship builders about the ship varies. It is very difficult to accurately remove precipitation, to know the actual weight of the ballast.

The time for 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. The usual practice is the presence of a surveyor from the beginning to the end of cargo operations. On large vessels, two surveyors are required to produce a draft survey.

The accuracy of measurements during a draft survey is affected by the situation on the ship and time constraints. Minor errors will not cause significant damage if the vessel has small dimensions. 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 mass of cargo by the draft of the ship.

1.1. Removing the draft of the ship.

Vessel's draft (T) - the depth to which the ship's hull is submerged in water. To measure the draft on the bow and stern perpendiculars (stem and stern, respectively), marks of recesses are applied on both sides. Marks of depressions are also applied from both sides in the middle (midships) of the vessel to remove sediment amidships.

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

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

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

The sediment is removed from both sides of the vessel with the maximum 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 washing by water of each brand of depression, which will be the actual draft of the vessel in this 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 depression marks in the bow, amidships 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 amidships, m;

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

q - roll angle (taken from the inclinometer located on the ship's navigation bridge) of the ship's sides with the maximum possible accuracy from the berth, °

(1° list is approximately equal to the width of the vessel).

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

The draft amidships 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

Symbols for fig. 2. :

1 - main deck line;

2 - waterline;

3 - freeboard height to the waterline;

4 - draft to the waterline;

5 - draft to the summer load line;

6 - year freeboard;

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

8 - keel line.

1. 2. Determination of the average of the average design draft, taking into account corrections 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 ship are recorded according to the marks of the recesses, applied on the stem, and not according to the bow perpendicular, which is the calculation line. As a result, an error appears, which is eliminated by introducing an amendment (see fig. 3., formula 5):

Introduction of a draft correction in the bow and stern parts of the ship and amidships

f - 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 - distance between perpendiculars passing through the points of intersection of the load 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 trimmed, the measurements of the draft of the stern of the vessel are recorded according to the marks of the recesses on the stern, and not along 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 marks of the recess to the aft perpendicular, m.

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

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

The 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 ship is determined by formula 9:

A correction for the draft amidships is introduced if, when the draft is removed amidships, the depth scale 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 circle of the plimsol to the mark of the recess on the midships, m.

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

Precipitation amidships, taking into account the correction, is calculated from formula 11:

The average draft is calculated from 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 ship's displacement.

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

The total carrying capacity of the vessel is deadweight – is defined 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 specified taking into account the change in the mass of ship stores during the time of cargo operations.

Part ship stores includes:

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

Part "dead" cargo includes the mass of unrecovered ballast, the remaining water in the tanks, etc.

The displacement of the vessel 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 scale of the number of tons per 1 cm of draft 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 the cargo scale, it is necessary to determine the values ​​of displacement and deadweight on the scale for fresh water (g = 1.000) if the ship is in fresh water, and on the scale for sea water (g = 1.025) if the ship is in sea water. The value of the indicator of the number of tons per 1 cm of draft must be taken from the load scale only in the region of the found average draft.

Displacement (D) is determined before and after loading (unloading) of the ship according to the average design draft on the load scale, hydrostatic table (Appendix 4) or hydrostatic curve (Appendix 5). Usually displacement is given for sea water (r = 1.025 t/m3).

1. 4. Corrections for the ship's trim.

Cargo hydrostatic tables or hydrostatic curves, which give displacement at different drafts, are calculated for a ship on an even keel. The true displacement of a ship trimmed to the stern or bow is different from the displacement given in the load scale or table, therefore, must be applied corrections for trim(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 draft and take the value from the hydrostatic trim tables, and then subtract 50 cm (6 inches) from it and determine the value of the trim moments from this data. 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 correction for trim is expressed by formula 22:

The trim corrected displacement is determined by formula 23:

1. 5. Correction for the density of sea water.

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 taken according to the data of the port meteorological service to the trim-corrected displacement.

Sampling of sea water 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 an ariometer (hydrometer) calibrated at 15°C is used to determine the density of water, then the actual density is determined from the following tab. 2 measured density and actual water temperature.

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 stores.

Before and after the loading (unloading) of 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 stores relate:

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

To determine the mass of variable reserves, 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, fresh water can be stored in galley and sanitary tanks, in fore peak and after peak tanks, in deep tanks and bottom tanks (boiler water).

The bottom of the vessel consists of a double bottom, which accommodates double-bottom tanks intended for ballast. Double-bottom tanks run either along 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 the tanks is measured using measuring tape (roulette) through measuring tubes. After determining the water level calibration tables available on the ship, is determined by the amount of water in tons or cubic meters. 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 with a significant trim requires the introduction of a correction for trim according to the calibration tables or by calculating the correction for trim using the “wedge” calculation method (Annex 6).

Water on the ship can also be in bilges (ship drains) located along the sides. The sump tanks must be emptied before measuring the sludge.

Determination of the amount of fuel and lubricating oils.

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

3.0. The time required to conduct a draft survey.

It will take a qualified surveyor about half an hour to conduct a draft survey on a small standard vessel and obtain effective indicators. If this is a large ship carrying bulk cargo and arrived in ballast, it will take at least four hours to process it with the participation of at least two surveyors. The size of most ships is average, they can be placed between the two examples above. A lot also depends on the type of vessel and the participation of the crew.

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 - precipitation, ship's variable stores (ballast and fresh water, fuel, lubricants, etc.). It is believed that this method helps to eliminate errors that could occur when determining the light ship mass and ship stores mass, 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 vessel is already fully loaded. It is used in the event that the vessel constantly carries out transportation of 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 advantages besides saving time. Since measurements are taken with a loaded boat, it is possible to avoid the deviations that occur when measurements are taken on a boat with a large trim.

4.0. Accuracy of measurements.

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

With insufficient quality instruments used to take measurements, the measurement accuracy will fluctuate within 1%. Technological errors may go unnoticed by the surveyor, and even more so by his employer, who has no idea about the principle of operation of this method. Even when using the best technology, adverse weather conditions and lack of crew assistance can affect the accuracy of measurements 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 by the crew of the mass of ballast and fuel during the survey;
• blocking of measuring tubes;
• change of documents;
• creating other obstacles to the normal operation of the surveyor.

It would seem that such insignificant things that occur during draft removal, 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 protection is the attention to the smallest details, as well as the dexterity acquired along with sea experience. A detailed study of ship plans also often reveals inaccuracies and errors, but since not every plan can exactly match a given ship, it is necessary to draw any conclusions based on this very carefully.

5.0. Draft.

The first step of a draft survey is sediment removal. Draft will be 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 take more accurate readings of the draft. 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 the gangway can lead to an error of up to 100 tons.

It is important to pay attention to the clarity of cargo marks. On some ships, load lines are marked with Arabic numerals (metric measurement) on one side and Roman numerals (English measurement - feet) on the other. In this case, at the end of the removal of the sediment, 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 weight scale.

Another way to remove sediment from the sea side is to measure the ship's roll (if any) with a special device - a rollometer. Further, using simple trigonometry, precipitation is calculated. However, accurate inclinometers are a rarity, 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 the sediment, significantly changing its values. If the boat is moving through the water, especially if there is a small clearance under the keel (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 the current speed up to four knots on the change in draft and trim is insignificant. If the current speed is four knots or more, the draft can increase up to 6 cm, depending on the shape of the vessel.

The current is a real problem for river moorings. Theoretical and practical work carried out to calculate the “sucking effect” is insufficient. Therefore, there is only one choice for the surveyor - to rely on his professional experience.

With bright sun and low water temperatures, there is a tendency for ships to bend their hull. The deck expands, but the bottom of the ship does not, which leads to the bowing of the ship's hull. The way out of this situation - special methods of adjustment will help to avoid errors in the 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, as 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 mistakes are as follows:

• improper sampling of water;
• neglecting the use of 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 the density of water is to take samples three times at different depths in the bow, stern and amidships (9 values). The number of samples may be less if the vessel is small or if practice shows that for a given berth the water density is a constant value at a certain depth. In total, water samples should be taken at least per liter. Then the water is placed in a special transparent vessel for testing. This should be done immediately while the sea water temperature is maintained.

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. The application of corrections to the density measured with a hydrometer leads to a distortion of the obtained values. With a change in temperature, the hull of the ship will expand and contract, the same changes will occur with the hydrometer - therefore, it is not necessary to introduce corrections for 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 fix the value of the intersection of the water level and the scale of the device. It is important that the eyes are opposite the device, and not at an angle. The hydrometer must be designed specifically for sea water.

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 needs to determine the mass of the cargo in the air, since this is a generally accepted commercial mass. Therefore, in calculations, he must use the apparent density or mass of a unit volume in air.

Units of measurement are usually kg/l. If the hydrometer is intended to measure mass in a vacuum or read a gravity reading, a correction of 0.0011 gm/ml is applied and must be subtracted from the obtained density value to obtain a mass value in air.

Summing up, we 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 per unit volume in air, kg/l.

7.0. Masses to be determined.

Once the draft and water density values ​​are 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 empty weight of the vessel, the amount of ballast, ship stores, as well as the value of the ship constant or ship constant are determined. On a small vessel, one surveyor can handle this task. If it is a very large vessel waiting to be loaded or preparing to leave for a voyage, the surveyor will need an assistant. While the first one will determine the values ​​of draft and water density, the second one will measure the ship's tanks.

The weight of the ship is empty.

The value of the light weight of the vessel is taken on faith according to the information of the vessel. If the same erroneous lightship weight was used during the initial and final draft survey, this will not result in 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 error in determining the light weight of the ship will lead to an erroneous value of the weight of the cargo.

Ballast.

Determining the amount of ballast is 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.

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

A ship in ballast always has a large trim to the stern. Some ships are equipped with appropriate tables for adjusting the trim when making calculations in ballast tanks, some are not. To avoid calculating trim corrections, many surveyors insist that ballast tanks be either empty or full at the time of the survey. The surveyor, having made sure that some of the ballast tanks are full, measures 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 the full ballast tanks of a heavily trimmed ship will be a source of error. Measurements in empty tanks will be more accurate, but there remains the possibility of the existence of ballast water residues in tanks, the amount of which cannot be determined.

Measurement of ballast holds is a complex operation and also a source of possible errors. The hold must be empty and dry before 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 with which he will enter the calibration tables.

Having made 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 determines the amount of water in the tanks. However, it is difficult to determine the density of water in a ballast tank, and it is not enough to believe the statements of the chief officer that the ballast was taken on board on the high seas. An error in the value of the ballast water density for large ships can lead to a change in the mass of the cargo up to 150 tons or more.

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

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

• carefully study the plans for the location of ballast tanks;
• measure ballast tanks using a steel tape 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 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 similarly to the amount of ballast. This is a less labor intensive job, there are fewer fresh water tanks, and it is usually not necessary to determine the density of the water.

Heavy and diesel fuel, lubricating oils.

If during the stay in the port the ship did not take on fuel, the surveyor uses in the calculations the amount of fuel and lubricating oils indicated in the fuel quality certificate (Bunker Receipt - see below). tab. 3). If the ship between the initial and final draft survey took on fuel or if a deadweight survey is 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 commonly used. For measuring fuel tanks, it would be more appropriate to use a special fuel hydrometer that 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 change in trim, it can take some time to determine the exact depth of the liquid in the tank. Measurements of voids in the tank in this case will give a more accurate result.

Reserves and ship's constant.

The ship's constant, contrary to the name, is a non-constant value. It is the difference between the net displacement and the value of all ship's variable stores (ballast, fresh water, fuel and lubricants, slop water, etc.).

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

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-built ships have a larger constant than new-build ships. The value of the constant will fluctuate with a change in the amount of fixing materials on board, stocks, as well as with the appearance of ice and snow on the deck. Due to these undetermined by calculation factors, the empty weight of the ship can change by 60 tons.

In some cases, the surveyor receives a negative constant. This is usually a sign of an 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 weight scale.
• Some ships use ballast tank calibration charts and ship hull data developed for another ship of the same type. The same type of vessels are slightly different from each other, but the tables are the same.
• On some ships, the cause of significant errors is a trim that is much larger than the allowable one. Such vessels are a kind of scourge for draft surveyors. If the Chief Officer fails to provide 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 carrying out a survey for deadweight, the surveyor either determines the value of the ship's constant 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.

A deadweight survey is often more accurate than a full draft survey, as there is an opportunity to avoid initial draft survey errors associated with a large ship trim. The 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 handled regularly, it is useful to compare the values ​​of the constant over several trips and determine the value with which the survey was most accurate.

That is how English sailors call the load line, which, on the basis of the rules of an international convention, is applied to the sides of every merchant ship launched, if its tonnage exceeds one hundred and fifty registered tons. Such a name can be considered justified, if we recall that for the first time their compatriot Samuel Plimsol proposed to legalize it. His idea, which prevented the death of hundreds of thousands of human lives at sea, was simple and concrete - a brush and a bucket of paint put an end to the overloading of ships, which was practiced by shipowners for many centuries. It turned out that this Englishman, a brewer from the city of Derby, a man who had virtually nothing to do with shipping, left a good memory of himself to the sailors on board every merchant ship.
The history of the establishment of a cargo line is one of the most dramatic pages in the history of merchant shipping. Here we will show what a load line is and how to use it.
depict on the sides of the model of a merchant ship.
Judging records of model boat competitions show that many modellers have lost a lot of points on the stand just because they forgot to put load lines and indentation marks on their models or applied them incorrectly.
What is a "Plimsol disc" and how does it differ from the deepening marks?

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

Rice. 2. Load line for ships carrying timber.

Look closely at the drawing. This is a circle and a figure resembling 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 stamp). This is the so-called main brand. When sailing in winter, ships often encounter stormy weather. For safe navigation and successful fight against a storm, 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 margin of buoyancy . This is taken into account on the load line under the main letter 3 (winter mark). But in winter, not all areas of the oceans are equally dangerous for a loaded ship.
The most “inhospitable” is the northern part of the Atlantic Ocean, and therefore, when sailing here, the ship should be most lightened. The allowable draft for such navigation is marked with the WSA line (winter mark for the North Atlantic).
Several "comb" lines are applied above the main - summer, brand. This suggests that the vessel 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 ship's draft, and a meeting with a storm is less likely. The ship here can take more cargo, have a larger draft and a smaller freeboard. This is marked by the T line (tropical mark). The ship's draft depends on the density of the water. The greater the density of water, the greater its buoyant force; when a ship enters a river from the sea, its draft increases. Therefore, in the river it is possible to “sink” the brand a little. Therefore, two more lines are marked on the "comb" - P (fresh grade) and TP (tropical fresh grade).
For each ship, the load line is marked according to international rules, which are mandatory for all maritime powers of the world. Therefore, the shape of the load line is the same everywhere. The only difference is in the letters. On the cargo marks, which are applied on the sides of our merchant ships, there are letters P and C. They mean that the mark was applied on board the vessel under the supervision of the Soviet classification society - the Register of the USSR.
Load lines of foreign merchant ships are marked with letters of the English alphabet (see pictures). The letters near 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 - "American Bureau of Shipping", etc.
On ships that transport timber, as well as cargo and passengers, additional stamps are applied. Each ship has 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 an overload, the port authorities responsible for the vessel's entry into the voyage 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 steamed in the form of steel strips on the side of the vessel on the midship frame from 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 with white paint; if the board is ball-colored, then the mark is painted green or black. The thickness of the load line line is the same: it is equal to 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 the ships at the stems and on large ships on both sides at the midships. Usually, on one side of the stamp, the indentations 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 I dm and the numbers are applied after 1 dm. In this case, each meter of precipitation is indicated. If the mark of the recess is given in feet, then the height of the figures and the distance between them are taken as 0.5 feet. Indentation marks should in no case be confused with the load line, as they only serve to measure the actual fore and aft draft at the moment.

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

History reference

The greed of the shipowner, who sought to load his ship as deep as possible, for many centuries was one of the main reasons for the death of merchant ships. From the earliest times, sailors have been aware of the importance of freeboard and the danger of overloading. Some information has come down to us that already ancient navigators limited the draft of their ships.
On an old ship raised by the French near Tunisia, a document of about two thousand years ago, corresponding to a modern charter agreement, has been preserved. The document contains the skipper's oaths: "Zeus and all the gods of Olympus to keep the terms of the contract of carriage sacred and indestructible and not to accept additional cargo on their ship." There were two marks, 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 loading ships. And the laws of the Hanseatic city of Visby made it a duty of the Senate to inspect the ship.
Compared with medieval merchants, the shipowners of the "mistress of the seas" of Britain looked simply barbarians. At the beginning of the 19th century, the English merchant fleet accounted for almost half of the world's. in The Times: "It can be stated that the number of ships lost in England in 1867 was not less than 2090, or about 6 ships a day. " In another article, he wrote that as a result of a strong increase in the accident rate in the English premiums to owners have doubled in twenty to thirty years; if earlier insurers made a fortune on the merchant marine, now they are suffering losses.
Hall himself was a major shipowner and at the same time director of an insurance company. Every now and then faced with violations of the safety rules of navigation, he was the first to draw the attention of the British government to the malicious overloading of ships. In 1869, in the House of Commons of the English Parliament, a draft of a new “Navigation Act” was discussed. Hall, who was present at the same time, proposed putting a load line on board that limits the ship’s draft. Drawing public attention to the unacceptable situation that has developed in the English merchant fleet, Hall said: “Amazing is not that a large number of ships perish 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. The manager of the brewery, and later a coal merchant, Plimsol amassed considerable kali-tal, in 1868 he achieved election to parliament from the city of Derby. Not being particularly selective in his means, he took advantage of the material collected by Hall and wrote the book "Our Sailors". The picture of the then navigation of England presented in it turned out to be so unsightly that the government appointed a royal commission on non-seaworthy ships. However, after a few months of work, the commission declared that universal rules for limiting the draft of ships were out of the question, and any law regarding the minimum allowable freeboard would be malicious! In the summer of 1875, in a parliamentary debate, England's Prime Minister Disraeli declared 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 for a week. Plimsol was forced to publicly ask for an apology from Parliament, but he became unusually popular and increased the number of his supporters in Parliament.
The following year, a law was passed
According to it, ships were required to have on their sides a load line in the form of a circle, the center of which would show the maximum draft ... which was determined by the shipowner himself. Naturally, he sought "just in case" to declare cargo lines "with a margin", often dooming the ship to certain death. In 1882 alone, 548 English ships sank and 3,118 sailors died. This turn of events caused numerous protests and unrest. However, the British government, always distinguished by conservatism, only in 1890 introduced a law on the load line. The classification society began to determine the height of the freeboard, and the indicator of permissible draft, 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 provided her with such a long life, Plimsol did not even try to patent it. However, if this happened, he would hardly 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 trade union of sailors and stokers.
Before the First World War, the load line was already widely used in Belgium, France, Germany, Japan, Holland, Sweden, Portugal. True, shipowners
still trying to catch up. Especially notorious were Calcutta, Norfolk, the ports of the West Indies and the Gulf of Mexico. They even developed special tricks on how to deceive the vigilance of inexperienced supervisors. Usually, an overloaded vessel was artificially rolled up so that the mark rose from the water and was 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. So it was until the death of "Vestris". This cargo steamer in November 1928, being loaded 7 inches above the load line, lost stability during a storm in the Atlantic, capsized on board and sank. The news of the tragedy of "Vestris" spread all over the world and made a deep impression on the public of the United States. In 1929, the US Congress approved the Load Line Act. And 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 since adopted Plimsol's useful proposal.