Technical and operational characteristics of the vessel. The meaning of the word deadweight What is the deadweight of a ship
The displacement of a ship is the mass of water in tons displaced by the hull to the permissible load waterline, which, according to Archimedes' law, is equal to the mass of the ship. The weight of the vessel consists of the vessel's own weight and its carrying capacity (payload weight).
The vessel's light weight includes:
ship hull equipped with inventory and spare parts;
ready-to-use power plant with inventory and spare parts;
water in boilers, pipelines, pumps, condensers, coolers;
fuel in all operational pipelines;
carbon dioxide and brine or other operating materials in refrigeration units and fire protection systems;
residual water in bilges and tanks that cannot be removed by pumps, as well as waste water and moisture.
Carrying capacity in tons with hold volume and operating speed is the most important economic characteristic of a vessel; it must be guaranteed by the shipyard, since underestimation is punishable by contractual penalties.
Gross deadweight - the ship's deadweight - includes all masses that do not relate to the lightship displacement of the ship, such as:
payload (including mail);
crew and passengers with luggage;
all operating materials (fuel reserves, lubricants, oils, boiler feed water) in storage tanks;
ship supplies such as paints, kerosene, wood, resin, ropes;
supplies for the crew and passengers (drinking water, water for washing and provisions);
cargo securing equipment such as wooden supports, tarpaulins and masts, bulkheads for bulk cargo;
special equipment for special types of vessels, for example fishing equipment (nets, cables, trawls).
There are certain relationships between the most important components of the load, which also affect the efficiency of ships.
The ratio of the ship's light-laden displacement to its fully loaded displacement depends mainly on the type of vessel, the area of navigation, the speed of the vessel and the design of the hull.
For example, the displacement of a light-laden cargo ship at normal operating speed (14 - 16 kts) without ice reinforcements is approximately 25% of the displacement when fully loaded.
The icebreaker, which must have powerful engines and a particularly reinforced hull, has a light displacement of approximately 75% of its total displacement.
If a cargo ship has a full displacement of 10 thousand tons, then the lightship displacement is approximately 2.5 thousand tons, and its deadweight is approximately 7.5 thousand tons, while a large icebreaker of the same displacement has a lightship displacement of approximately 7.5 thousand tons and deadweight 2.5 thousand tons.
The ratio of the mass of the power plant to the total displacement is determined by the speed of the vessel, the type of engine (diesel, steam turbine, diesel-electric plant, etc.), as well as the type of vessel. An increase in the speed of the vessel with the same type of installation always leads to an increase in engine power and, consequently, to an increase in the named ratios.
Ships with a diesel installation have a larger engine weight than ships with other types of installations. Since the power plant also includes auxiliary mechanisms for the production of electrical energy and power plants for refrigerators, the mass of power plants on passenger, refrigerator and fishing vessels is greater than the mass of installations on conventional cargo ships of the same displacement.
Thus, the mass of the power plant of cargo ships is 5 - 10%, passenger ships- 10 - 15%, fishing vessels 15 - 20%, and tugs and icebreakers, as a rule, even 20 - 30% of the total displacement.
The ratio of the mass of the ship's hull to its displacement is determined by the mass of the bare hull of the ship and the mass of its equipment. All these masses depend on the type of vessel and, therefore, on its purpose.
The mass of a ship’s hull is affected not only by its main dimensions and their ratios, but also by the volume of superstructures and ice reinforcements. The casting system and the use of high-strength structural steels also play a significant role, especially for ships longer than 160 m.
The weight of the equipment depends on the purpose of the vessel; for example, in passenger ships due to passenger cabins, public, utility rooms, etc., or in fishing vessels (fishing and processing) due to crew cabins, fish processing machines and refrigerator equipment, it is significantly greater than that of conventional cargo ships and tankers.
The ratio of deadweight to total displacement (displacement utilization rate per deadweight) best characterizes the efficiency of cargo ships (not to mention the speed of the vessel). For tugs and icebreakers, the deadweight primarily determines the cruising range (voyage duration), since the deadweight of these types of ships is spent mainly on fuel materials and supplies.
The highest displacement utilization rates by deadweight are cargo ships and tankers (from 60 to 70%), the smallest are tugs and icebreakers (from 10 to 30%).
Deadweight or gross load capacity is the maximum amount of cargo a ship can accept when diving to the load line. Consists of all cargo, fuel, water reserves and supply weight.
180. What is the cargo capacity of a ship?
This is the volume of all cargo spaces. There is a distinction between grain and bale cargo capacity. The difference between them is 6 – 10%.
181. What is full register capacity?
This is the volume ship premises below the upper deck and in permanently covered superstructures in register tons obtained as a result of the measurement of the vessel. It includes the capacity of the wheelhouse, galley, bathrooms, double bottom, water tanks.
What is net register capacity?
This is the volume determined by deducting from the total registered capacity the volume of all residential, household premises, and auxiliary machinery premises outside the engine room. It is measured in a registered ton equal to 2.63 cubic meters.
Is pressing of water tanks allowed at low temperatures?
At low temperatures, pressing water tanks, including ballast tanks, is not allowed, because If ice plugs form in the air ventilation and measuring pipes, it will become impossible to empty and fill the tanks without thawing the plugs. Filling tanks is allowed to no more than 95% of its capacity.
Basic principles of the hydrodynamic theory of lubrication.
The essence of this theory is as follows. When at rest, the shaft journal is in contact with the bottom of the bearing (a wedge-shaped gap is formed between them) through a thin layer of adhered oil particles. When the shaft rotates, due to the difference in the diameters of the journal and bearing, a wedge-shaped gap is formed between them, into which oil adhering to the rotating journal of the shaft is drawn. In the narrow part of the gap, pressure is created, lifting the shaft. The maximum pressure value corresponds to an arc of up to 120 degrees of the bearing circumference.
Thus, at a certain rotation speed, an oil layer is formed between the surfaces of the journal and the bearing, and the shaft does not touch the bearing walls. The external load on the journal is balanced by the internal pressure of the oil wedge, the magnitude of which increases with increasing shaft speed. This can be explained by the fact that with increasing rotation speed, the thickness of the wedge-shaped gap increases due to an increase in the amount of oil pumped by the shaft journal.
The friction between the oil layers depends only on the viscosity of the oil and does not depend on the bearing material and the degree of roughness of its surfaces. However, it should be borne in mind that, in accordance with the laws of hydrodynamic friction, the viscosity of the oil is directly proportional to the load and the size of the gap between the shaft and the bearing.
In a properly designed bearing, during engine operation, a hydrodynamic regime is established, which is characterized by self-regulation between oil viscosity and friction force. Indeed, with increasing angular velocity, the friction force between the oil layers increases, which leads to strong heat generation. As the temperature increases, the viscosity of the oil decreases, and the process between friction force and temperature stabilizes.
What is the permissible diameter of the receiving mesh holes on the drainage system?
Receiving drainage branches must be equipped with receiving boxes or nets with holes with a diameter of 8 - 10 mm.
What response pressure is the safety valve of hydraulic systems set to?
Hydraulic mechanisms must be protected by safety valves, the response pressure of which should be no more than 1.1 times the maximum design pressure.
When there is a decrease in the performance of the evaporator installation, measures should be taken to clean the heating elements?
When performance decreases by more than 20% of the nominal .
To what pressure should the safety device of mechanically driven air compressors be adjusted?
A safety valve must be installed at each stage of the compressor, which does not allow the pressure in the stage to increase more than 1.1 calculated when the valve on the discharge pipeline is closed.
The valve must be designed so that it cannot be adjusted or switched off after installation on the compressor.
What requirements must devices for heating fuel in tanks meet?
Liquid fuel can only be heated using steam or water coils.
Fuel heating coils should be located in the lowest parts of the tanks.
The ends of the receiving fuel pipes in supply and settling tanks should be located above the heating coils in such a way that, if possible, the coils are not exposed.
The maximum temperature of heated fuel in tanks must be at least 10 degrees Celsius below the flash point of fuel vapor.
The heating steam condensate must be directed to a control tank with a sight glass.
The steam pressure used to heat the fuel should not exceed 7 kg/sq. cm (0.7 MPa).
To monitor the temperature of the heated fuel, thermometers must be installed in the required places.
What should be the capacity of the overflow tank?
The capacity of the fuel overflow tank must be at least 10 minutes of capacity of the fuel transfer pump.
The overflow tank must be equipped with a light and sound alarm that is triggered when it is filled over 75%.
Under what conditions should emergency power supplies maintain long-term functionality?
Emergency power supplies must remain operational under the following conditions: - long-term roll of 15 degrees;
Long trim 5 degrees;
Rolling +\- 22.5 degrees with a period of 7-9 seconds;
Pitching +\- 7.5 degrees;
Simultaneous action of roll of 22.5 degrees and trim of 10 degrees.
What is the required amount of contact between the gear teeth of the main mechanisms?
The contact of the gear drives of the main mechanisms must be at least 90% in forward motion, and in reverse 70% along the length and 60% in the height of the teeth.
What is the circulation ratio in a condenser?
This is the ratio of the amount of cooling water passing through the condenser to the amount of condensate formed:
M = ----- ; Usually M=100 – 110
Dk
Under what fluctuations in the supply air should pneumatic devices and elements operate reliably?
Pneumatic devices and elements must operate reliably with supply air fluctuations of +\- 20%.
What is minimum height pressure oil tanks in gravity lubrication systems for stern tube bearings?
The bottoms of tanks must be at least 3 meters above the highest load waterline.
Under what conditions can the steering gear stock be allowed to operate when twisted by 5 degrees or more?
The stock can be allowed to work provided it is annealed and the sector or tiller is replaced with a new key.
At what temperature should circulation oil separation be carried out?
Separation of oils containing additives should be carried out without washing with water and at a heating temperature of no more than 90 degrees Celsius (the upper limit is preferable for oils with high detergent properties). It is recommended to separate oils without additives by washing with water at a heating temperature of no more than 75°C.
What is the frequency of manual cleaning of the separator drum, and the permissible load on the surface of the working plates?
The frequency of manual cleaning of the separator drum should be determined in each specific case, depending on the nature of the released suspension, the productivity and sludge volume of the drum; Sludge deposits on the drum walls must not be allowed to reach the edge of the plate stack. The permissible contamination of the surface of the work plates should not exceed 30%.
What speed should the drive provide for pulling out the anchor chain when the anchor approaches the lock?
How many links should the anchor chain link consist of?
When lifting and releasing the anchor, all connecting brackets of the anchor chain must lie flat on the windlass (capstan) chain drum sprocket. To do this, each link of the anchor chain must consist of an odd number of links (not counting the connecting brackets).
At what reduction in diameter should anchor chain links be replaced?
Links must be replaced when the average diameter in the most worn part decreases by 1/10 or more of the original nominal diameter.
When should a mooring line be replaced?
A steel mooring cable must be replaced if it has broken wires of more than 10% of their total number over a length of the cable equal to eight of its diameters.
What is the time for shifting the propeller propeller blades from full forward to full rear?
The time should not exceed 20 seconds for screws with a diameter of up to 2 meters and 30 seconds for screws with a diameter over two meters.
At what rotations of the thruster blades should it be launched?
Start-up occurs only when the pitch of the variable-pitch propeller blades, which are usually installed on thrusters, is zero.
What is cavitation?
This is the occurrence of alternating pressure on the propeller blades or in the pipeline, in which a vacuum occurs in certain areas, leading to cold boiling of the liquid (formation of air bubbles), and then with a sharp increase in pressure, the bubbles collapse. Cavitation leads to rapid destruction of the surface of a part or component of a ship's technical equipment. means.
Basic units of measurement in SI.
These are kilogram, meter, second. Arbitrary values come from them. For example: Joule - expresses the energy and work done by a force equal to 1N along a path of one meter, coinciding in the direction of the force.
What is temperature?
This is a quantitative measure of the degree of body heating. Its existence is a property of the real world that underlies the zero law of thermodynamics; if the degrees of heating of two bodies do not change when they are brought into contact with a third body, then the degrees of heating of these two bodies do not change when they are brought into contact with each other.
What is density?
Body density is the ratio of body mass “M” to its volume “V”. Dimension kg/cu. meter.
What is viscosity?
This is the property of a liquid to resist the relative movement (shear) of its particles, which causes the appearance of a force of internal friction between the layers of the liquid if the latter have different speeds of movement.
The dynamic viscosity coefficient is a quantitative measure of viscosity and depends on the type of liquid, its temperature and pressure.
Kinematic viscosity coefficient = \, where is the density of the liquid.
What is the enthalpy of a body?
Enthalpy (heat content) is a function of quantities that determine the state of the body. It is the sum of internal energy and external work. Dimension kJ\kg.
Activity navy Russian Federation carried out on the basis of more than 200 enterprises and organizations, including 10 maritime shipping companies. 10 shipping companies, 21 seaport, 11 ship repair yards. Due to the importance of this industry for the country, the state retains control over the main infrastructure of seaports. For this purpose, since 1993. in all sea ports special state management bodies (seaport administrations) were created, into whose possession berths, breakwaters, approach channels, railway and road facilities of the ports were transferred. All these facilities are the property of the state and will be used by numerous clients. The operation of berths and terminals can be carried out by private companies.
For maritime transport The following indicators of the material and technical base, the operation of the fleet and ports are typical.
The vessel's displacement D - the mass of water displaced by the vessel - is equal to the vessel's mass in tons.
The total carrying capacity, or deadweight of the vessel DB,- this is the maximum amount of cargo in tons Q, as well as fuel supplies qT, water qB and supply cargo qCH that the ship can accept:
DB = Q + qT + qB + qCH.
Vessel's net tonnage D- this is the maximum amount of cargo (excluding water, fuel and supply cargo) in tons that a ship can accept for transportation:
DC = DB - (qT + qB + qCH).
Vessel cargo capacity- the volume of all cargo spaces of the ship in cubic meters.
Registered tonnage of the vessel (vessel volume)- measurement certificate. Registered capacity can be gross or full (gross) and net (net). Measured by volume register ton equal to 2.83 m3
Gross (full) registered tonnage of the vessel WBR- the volume obtained as a result of measuring the ship’s premises. Used as an indicator for calculating fees and duties at seaports.
The relationship between net and gross registered tonnage, deadweight (deadweight) and displacement can be characterized by the formula
W = 2/3W = 4/9D = 8/27D.
Vessel voyage- the time spent by the vessel from the start of loading at the port of departure until the vessel is positioned for new loading.
The duration of a vessel's voyage includes sailing and mooring time. Sailing time depends on the length of the voyage and the speed of the vessel, while parking time depends on the performance of loading and unloading equipment, as well as the level of organization of vessel servicing in ports.
There are simple, complex and circular flights. When transporting goods or passengers between two ports, a ship's voyage is called a simple voyage. When transporting goods between several ports, each of which is loaded or unloaded, the voyage is called complex. If a ship carries cargo between two or more ports and returns to the port of original departure, the voyage is called a round trip.
Running time coefficient KХ- the ratio of running time tХ to the total duration of the voyage TR:
KX = tX/TP.
Ballast mileage coefficient KB is determined by dividing the ballast mileage LB by the total mileage of the vessel L:
Displacement is one of the main characteristics of a vessel, which indirectly characterizes its size.
The following displacement values are distinguished:
- mass or weight and volume,
- surface and underwater (for submarines and underwater vessels),
- · empty displacement, standard, normal, full and maximum.
The total displacement is equal to the sum of the lightship displacement and the deadweight.
The displacement of a ship is the amount of water displaced by the underwater part of the ship's hull. The mass of this amount of water is equal to the weight of the entire vessel, regardless of its size, material and shape. (According to Archimedes' law)
Ш Mass (weight) displacement is the mass of a ship afloat, measured in tons, equal to the mass of water displaced by the ship.
Since during operation the mass of the vessel can vary within wide limits, two concepts are used in practice:
Fully loaded displacement D, equal to the total mass of the ship's hull, all mechanisms, devices, cargo, crew passengers and ship stores at the maximum permissible draft;
Lightweight displacement D0, equal to the weight of the vessel with equipment, permanent spare parts and supplies, with water in boilers, machinery and pipelines, but without cargo, passengers, crew and without fuel and other supplies.
Ш Volumetric displacement - the volume of the underwater part of the vessel below the waterline. With a constant weight displacement, the volumetric displacement varies depending on the density of the water.
That is, the volume of fluid displaced by a body is called volumetric displacement.
The center of gravity of the volumetric displacement W is called the center of displacement.
Standard displacement is the displacement of a fully equipped ship (vessel) with a crew, but without fuel, lubricants and drinking water in tanks.
Normal displacement is a displacement equal to the standard displacement plus half the supply of fuel, lubricants and drinking water in the tanks.
Full displacement (loaded displacement, full load displacement, designated displacement) - displacement equal to standard displacement plus full reserves of fuel, lubricants, drinking water in tanks, cargo.
Displacement reserve is an excess addition to the weight of the vessel taken during design to compensate for the possible excess of the weight of its structure during construction.
Maximum displacement - displacement equal to standard displacement plus maximum reserves of fuel, lubricants, drinking water in tanks, cargo.
Underwater displacement is the displacement of a submarine (bayscaphe) and other underwater vessels in a submerged position. Exceeds the surface displacement by the mass of water received when immersed in the main ballast tanks.
Surface displacement is the displacement of a submarine (bayscaphe) and other underwater vessels in a position on the surface of the water before diving or after surfacing.
Load capacity
Carrying capacity is one of the most important operational characteristics - the mass of cargo for which the ship is designed to transport - the weight of various types of cargo that the ship can transport, provided that the design landing is maintained. Measured in tons. There is net tonnage and deadweight.
Net load capacity (Useful load capacity) is the total weight of the payload carried by the ship, i.e. weight of cargo in holds and weight of passengers with luggage and intended for them fresh water and provisions, the mass of fish caught, etc., when loading the vessel according to the calculated draft.
Deadweight (full load capacity) - DWT - deadweight tons. It represents the total mass of the payload carried by the ship, constituting the net carrying capacity, as well as the mass of fuel supplies, water, oil, crew with luggage, supplies of provisions and fresh water for the crew when loading the ship according to the design draft. If a vessel with cargo takes on liquid ballast, the mass of this ballast is included in the deadweight of the vessel. Deadweight at summer load line draft sea water is an indicator of the size of a cargo ship and its main operational characteristic.
Carrying capacity should not be confused with cargo capacity, and even more so with the register capacity (register cargo capacity) of a vessel - these are different parameters, measured in different quantities and having different dimensions.
Today transport system throughout the world is significantly distributed between different modes of transport. Any thing that comes to us from abroad is delivered by road, rail, air or transport. The role of the latter is especially great in connecting continents and continents, since water covers most of the earth's surface, making transportation by trucks and trains impossible . Air travel is too expensive. Moreover, the aircraft is capable of carrying not so much weight. There remains one type of transport that has been in demand for hundreds of years - sea.
In view of the extent to which trade relations have developed today, many types of ships have begun to be used in practice. For example, there are dry cargo ships (including universal ships, bulk carriers, lighter carriers), refrigerators (vessels for transporting products), container ships (for transporting classic sea 8-foot containers) and others. These are adapted for transporting a certain type of product; all of them are equipped with special equipment. Thus, almost any product can be transported by sea anywhere in sufficient volume!
How are vessels used?
Most goods that move in large volumes are delivered by sea. The ship is capable of carrying thousands of tons of cargo, which is more than any aircraft in the world can lift. What is also important is the relatively low cost of transportation large parties cargo by sea. For comparison, if the largest aircraft An-225 (Mriya) is capable of transporting 120 tons, then the deadweight of the vessel (this is the gross tonnage) of even a small ship is 3-5 thousand tons. What can we say about large floating platforms for transportation. It is now obvious that the application water transport much more rational when it comes to transporting goods. The only drawback of the ships is the long duration of their voyage. However, this is not scary, because you can plan the supply of goods, calculating the time for their delivery by sea.
How much can the ship hold?
As already noted, the capacity of a ship is characterized by such an indicator as the deadweight of the vessel. This designation comes from the English deadweight, which means “dead weight”. This means that this is the maximum mass that a ship can transport while moving at normal speed. This figure cannot be exceeded. Knowing it is important in order to effectively charter a ship without forcing it to sail with empty seats and not overloading it. For ships, deadweight is calculated by subtracting the mass of an empty ship ready to sail from the mass at which the ship is completely submerged in water to the load mark (full displacement).
What does this characteristic mean?
Essentially, the deadweight of a ship is the difference in mass that is missing before the ship is fully loaded, minus the ship's basic equipment. When loading, this characteristic is taken into account as an extreme value, the maximum that a ship can transport. Transport companies chartering sea ships and those engaged in transportation on a regular basis, knowing that the deadweight of a vessel is its most important characteristic, are able to distribute cargo as efficiently as possible among available vessels. This value can also be called the carrying capacity of an individual floating craft.
Why do you need to calculate deadweight?
In addition to knowing the maximum weight that can be transported on a particular ship, using deadweight you can also effectively calculate the mass of the “payload” and cargo that is necessary for navigation. The first includes those goods and things that, according to the contract, the ship must transport from point A to point B. As for the second, cargo for navigation, it should include reserves of fuel and other combustible materials, food reserves, and also the weight of all people on board the ship.
As maritime experts note, the deadweight of a ship is usually two parts, distributed in a ratio of 90% to 10% in favor of the so-called payload.
Examples of deadweight of various ships
In order to more clearly represent the size of this value, let's consider some examples. So, there is a bulk carrier “Omsky”, which belongs to the R2/R3 RSN class. This is a motor ship with a body 108 meters long and 15 meters wide. This vessel is driven by two propellers. According to data from the Maritime Register of Shipping, the deadweight of the Omsky vessel is 3070 tons, both when moving along the river and by sea. It turns out that about 200 tons will constitute reserve reserves and almost 2800 tons can be placed on this ship as cargo. It should be noted that for a bulk carrier the ratio will be more likely 90% to 10%, and somewhere around 95% to 5% - more in favor of cargo capacity than on passenger ships.
Other characteristics of the vessel
Obviously, such a characteristic as the deadweight of the vessel is an important parameter, extremely necessary for the expedition of the vessel and its final cost. However, it is obvious that this is not the only such important indicator. For example, when chartering a floating craft, you should also pay attention to the total capacity of the holds and their sizes. In addition, the type of cargo ship and its intended purpose (for which cargoes it is primarily used) play an important role.
In general, such an indicator as carrying capacity plays a huge role. Transportation organizers have to deal with it every time a ship is loaded.
