What is the difference between deadweight and gross tonnage? Technical and operational characteristics of the vessel. What is cavitation
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Meaning of the word deadweight
deadweight in the crossword dictionary
New explanatory dictionary of the Russian language, T. F. Efremova.
deadweight
m. The main characteristic of a vessel is its total carrying capacity, including the weight of cargo, people on board, as well as all fuel, water, etc., necessary for navigation.
Encyclopedic Dictionary, 1998
deadweight
DEADWEIGHT (full carrying capacity of the ship) is the mass of cargo (payload, ship supplies, crew) accepted by the ship. Deadweight at draft load line- the main operational characteristics of a sea vessel.
Deadweight
(eng. deadweight), the total weight of cargo that the ship accepts. D. at summer load line draft sea water is an indicator of the size of a cargo ship and its main operational characteristic. Numerically, D. is equal to the difference between the displacement and the dead weight of the vessel with the mechanisms ready for action (with filled fuel pipelines, with water in boilers, cooling pipelines, etc.). The main part of the cargo ship's weight is the weight of the cargo; on passenger ship the weight of the cargo (passengers and luggage) constitutes a smaller part of the ship, and the majority of it is consumable ship supplies (fuel, water).
Wikipedia
Deadweight
Deadweight- a value equal to the sum of the masses of the ship’s variable cargo, measured in tons, that is, the sum of the mass of the payload carried by the ship, the mass of fuel, oil, technical and drinking water, masses of passengers with luggage, crew and food.
Deadweight is the difference between full displacement and empty displacement.
In commercial shipping, a distinction is made between the net deadweight capacity (abbreviated as DWCC) and the deadweight or gross deadweight of the vessel.
The first is maximum weight cargo that a ship can accept up to its maximum load line draft. This value may vary depending on the actual load of the ship with fuel and supplies.
The total or gross deadweight is a constant and includes, in addition to the total weight of the cargo, also the total weight of the crew members, removable equipment and ship stores
The term "deadweight" is used only for merchant ships, and for purely cargo ships. Deadweight at load line draft is an indicator of the cargo capacity of a cargo ship and its main operational characteristic.
The main technical and operational characteristics (not only of transport ships) usually include:
Displacement;
Load capacity;
Travel speed;
Cruising range;
Autonomy in terms of water and provisions supplies;
Gross and net tonnage.
Sometimes, instead of carrying capacity, the deadweight of the vessel appears - DW.
Vessel displacement- this is the mass of the volume of water in tons displaced by the ship’s hull to a certain waterline (usually the cargo line), which, according to Archimedes’ law, is equal to the mass of the ship.
Displacement Δ is usually represented in the form of two components:
where Δ 0 - empty displacement;
DW - deadweight - the mass of all variable cargo on the ship that does not relate to the lightness displacement.
IN light displacement included
Hull weight
Equipment weight
Inventory weight
Weight of ready-to-use power plant with spare parts and necessary supplies
Mass of residual water in bilges and tanks, etc.
« Lightweight displacement - vessel displacement (in tons) without cargo, fuel, lubricating oil, ballast, fresh and boiler water in tanks, ship stores, as well as without passengers, crew and property"
Lightweight displacement determined by the manufacturer upon completion of construction of the vessel and is subject to adjustment during operation. This is due to a change in the amount of residual water that cannot be pumped out of the ballast tanks, the build-up of layers of paint applied during daily maintenance of the ship, etc.
Deadweight includes all masses that do not relate to the lightship displacement of the ship.
"Deadweight -difference between the displacement of a ship in water with a density of 1.025 along the load waterline corresponding to the designated summer surface boat, and empty displacement."
Deadweight includes the weight of transported cargo, crew and passengers with supplies and luggage, supplies of fuel, lubricants, ship supplies (paint, cables, etc.), equipment for securing cargo, special supplies (for example, for fishing vessels - trawl, nets, etc.) etc. The weight of the ship's crew with luggage is determined at the rate of 1 ton of luggage for 12 people.
Load capacity- the amount of cargo that can be placed on the ship in holds*, tween decks**, or on the upper deck. This value is usually measured in metric tons.
(*Hold is an internal space on a ship, located below the lowest deck. **Tweendeck is the space between decks on ships with several decks.)
But for sea transport to and from the UK, a different unit may be used - English or long ton (long tone ). It is equal to 1016 kg (2240 lb).
If transportation is carried out in the North American region, then apply North American or short ton (short tone ). It is equal to 907 kg (2000 lb).
During operation, the actual carrying capacity of the vessel can be determined as the difference between the actual displacement (minus the ship's stores) and Δ 0.
Travel speed ships are measured in knots. One knot is equal to one nautical mile per hour. One nautical mile is equal to l/60 degrees of the arc of the Earth's meridian and is 1852 meters or 10 cables.
Cruising range- the distance in miles that a ship can travel without replenishing fuel.
Autonomy in terms of water and provisions supplies- the time in a day during which a ship can remain at sea without replenishing these supplies.
Cargo capacity- along with carrying capacity, it is a characteristic that ensures the profitability of sea transportation. It is determined by the volume of cargo holds and tween decks, which are calculated taking into account the volume of cargo hatches.
The amount of cargo that can be loaded on a ship depends on both cargo capacity and cargo capacity.
Cargo transported by sea is divided into dry And liquid Separately - this liquefied gases and chemical cargo.
Among dry cargoes there are: containerized, piece, bulk And bulk.
Tare are called goods that are transported in packaging (containers). Boxes, bags, barrels, cans, etc. are used as containers.
Piece cargo is usually transported without packaging and is accepted onto the ship not by weight, but by number of places.
Bulk are called cargoes that are supplied to the ship in bulk, without counting places. These include: ore, coal, ore concentrates, crushed stone, stone, sand, etc.
To the number bulk cargo includes: grain, wheat and cotton seed, sunflower, etc., if they are transported in bulk. Bulk cargo differs from bulk cargo greater flowability and are usually stored indoors. Bulk and bulk cargo have a number of similar characteristics, on the basis of which they are classified into a single category and called massive.
A set of containerized or containerized and piece goods of various compositions, differing in weight, size and packaging, is called general
In a number of sources, separate groups are divided into refrigerated cargo, cargo transported in packages, containers, trailers, barges etc.
Regardless of the classification considered, there are large cargo, heavy, dangerous and etc.
When designing a vessel, cargo capacity is determined based on the type of cargo being transported and its quantity. In accordance with this, they distinguish
Bulk cargo capacity
Bale capacity.
Both differ from the theoretical capacity (i.e. the capacity determined from the theoretical drawing).
Bulk cargo capacity obtained by subtracting from the theoretical capacity the volumes occupied by the housing set, the volume of floors, bilges, etc.
When determining bale capacity The volume of holds and tween decks is determined to the inner edges of the fish and the lower edge of the beams. When determining the capacity of ships carrying liquid cargo, only the volumes per hull set are excluded, and a reserve is introduced for the volume required for thermal expansion of the cargo.
The volume of refrigerated holds is calculated minus the volume of insulation and volumes that cannot be used to accommodate cargo (coils, pipelines, ventilation ducts, etc.)
Bale capacity differs from bulk cargo capacity by 8-10%.
The capacity for bulk cargo differs from the theoretical one by 5-6%.
The capacity of refrigerated holds differs from the theoretical one by 25-30% due to large insulation losses.
In addition to cargo capacity, the fleet operates gross (GT) And net tonnage (NT) of the vessel, which act as measures of the size of the vessel and are determined in accordance with the International Convention on Tonnage of Ships . In the practice of operating ships, in the specialized literature, these capacities have another name - tonnage.
Today transport system throughout the world is significantly distributed between different types 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, a quantity that no aircraft in the world can lift. What is also important is the relatively low cost of transporting large quantities of 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 the 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 by 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.
The vessel is a complex engineering structure designed to move on water with various loads. Like any transport structure, it is characterized by a number of operational qualities: lifting capacity, cargo capacity, autonomy, reliability, etc. Since the vessel is also a floating structure, it is also characterized by seaworthiness - buoyancy, stability, unsinkability, propulsion, pitching and controllability.
vessel performance
lifting capacity
Load capacity name the weight of various types of cargo that a ship can transport. A distinction is made between net tonnage and deadweight.
Net load capacity- this is the total weight of the payload carried by the ship, i.e. the weight of the cargo in the holds and the weight of passengers with luggage and fresh water and provisions intended for them, the weight of caught fish, etc., when loading the ship according to the design draft.
Deadweight- sometimes called the full load capacity, and represents the total weight of the payload carried by the ship, constituting the net load capacity, as well as the weight of fuel reserves, boiler water, oil, crew with luggage, supplies of provisions and fresh water for the crew - also when the ship is loaded according to the design draft. If a cargo vessel takes on liquid ballast, the weight of this ballast is included in the vessel's deadweight. The deadweight value for each ship is constant and is determined by the total weight of variable cargo that can be accepted on the ship when loading it according to the design draft. In contrast to deadweight, the light weight of a ship or light displacement is the sum of all permanent weights that make up the weight of the structure of the constructed ship (the weight of the hull, mechanisms, ship devices, systems and equipment), and the weight of permanent inventory equipment. This also includes the weight of those parts of the fuel, water and oil reserves that are located in the boilers, mechanisms and pipelines of the ship's mechanical installation prepared for launch, as well as the weight of those remains of various liquid cargoes and tanks that cannot be removed during pumping.
cargo capacity
Cargo holds and other spaces intended to accommodate cargo are characterized by volume. The total volume of all cargo spaces is called cargo capacity vessel, which is measured in cubic meters.
register capacity
Cargo capacity holds just like the carrying capacity of the vessel, it does not give a complete idea of its size. Therefore, for a uniform assessment and, first of all, the size of its premises, the concept of registered capacity, or registered tonnage, has been adopted in world practice. In this case, a registered ton equal to 2.83 cubic meters is taken as a unit of volume. m (or 100 cubic feet). The registered ton, which is a measure of volume, should not be confused with the ordinary ton, which is a measure of weight.. There are different gross tonnage of a ship - gross and net capacity - net.
travel speed
Travel speed is the most important operational quality of a vessel, determining the speed of transport operations. For river boats, speed is measured in knots, for river boats - in kilometers per hour.
cruising range
Cruising range call the distance that ship or vessel can pass at a given speed without replenishing fuel, boiler feed water and oil. The cruising range is determined by the purpose of the vessel.
autonomy
Autonomy called the length of stay ship or vessel on a flight without replenishment of fuel, provisions and fresh water necessary for the life and normal activities of people on board (and passengers).
seaworthiness of the vessel
buoyancy
Buoyancy called the ability of a vessel to float in a certain position relative to the surface of the water for a given number of people in it.
stability
Stability is the ability of a vessel, removed from a position of equilibrium by the action of external forces, to return to a state of equilibrium after the action of these forces ceases.
unsinkability
Unsinkability of the ship they call its ability, after flooding of part of the premises (for example, when) to remain afloat and maintain stability and a certain reserve of buoyancy.
speed of the vessel
Speed of the vessel is called its ability to move through water at a given speed, under the influence of a driving force applied to it. A distinction is made between the speed of the vessel during testing and the operational speed, i.e. the speed in the operating mode of the power plant.
pitching
Pitching are called oscillatory movements near the equilibrium position performed by a vessel freely floating on the surface of the water.
controllability
Vessel controllability characterized by two qualities: agility, i.e. the ability of the vessel to change the direction of movement at the request of the navigator, and stability on course, i.e. the ability of the vessel to maintain the direction given to it forward direction without deviation to the sides. Unstable on course ships are called prowling.
diagram of the general layout and structure of a dry cargo ship
1 - upper deck; 2 - bulwark; 3 - cargo boom; 4 - ventilation head; 5 - cargo winch; 6 - cargo mast (column); 7 - recovery boiler; 8 - radar antenna; 9 - wheelhouse; 10 - railing; 11 - ventilation deflector; 12 - cargo hatch coaming; 13 - cargo hatch closure covers (open hatch); 14 - foremast; 15 - saling platform; 16 - hatch cover; 17 - mooring hawse; 18 - mooring bollards; 19 - windlass; 20 - visor; 21 - anchor chain stoppers; 22 - ; 23 - forepeak; 24 - forepeak (collision) bulkhead; 25 - pillers; 26 - transverse waterproof bulkhead (corrugated); 27 - second bottom flooring; 28 - second (lower) deck; 29 - bottom stringer; 30 - flor; 31 - deck set; 32 - cargo twindeck; 33 - cargo hold; 34 - zygomatic keel; 35 - engine room; 36 - diesel generators; 37 - main engine; 38 - thrust bearing; 39 - corridor propeller shaft; 40 - shafting; 41 - propeller (); 42 - steering wheel; 43 - tiller compartment; 44 - steering gear;
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 it permissible to press-fit water tanks when?
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.
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 evaporation unit, 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?
Heating of liquid fuel can only be carried out 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-term 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 the minimum height of oil pressure 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 that 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).
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?
Starting is carried out only at zero pitch of the adjustable pitch propeller blades, which, as a rule, are installed on thrusters.
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. facilities.
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.
