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Tanker ships. The largest tanker in the world

§ 57. CARGO DEVICE OF TANKER

The cargo device of a tanker consists of a system of pipelines that serve to receive cargo, distribute it among cargo tanks and unload it, and pumps for pumping cargo.

Pipelines are divided into cargo and stripping, we will accept separate pumps for each pipeline system. The cargo system consists of large diameter pipes (250-350 mm) that allow the cargo to be pumped using the full capacity of the cargo pumps until the cargo level in the tanks drops almost to the level of the pipeline inlet openings, when the pump begins to "sweep" air. After that, the remaining relatively small amount of cargo is pumped out through the stripping system using stripping pumps, the performance of which is much less than cargo ones.

The cargo system is laid along the bottom of the cargo tanks, above the bottom set, and ends in the cargo pump room, joining the cargo pumps. From the pumps, one or more lines go to the upper deck, where they branch into offshoots going to both sides and to the stern. Flexible hoses are attached to the offshoots, connecting ship pipelines with coastal highways. Locking clinkets are installed at the ends of the processes.

From the same line, vertical pipes extend into the cargo tanks - risers, which serve to receive cargo directly from the deck to the tanks, bypassing the pump room. Each riser serves not one, but a group of tanks. In each cargo tank from the cargo line laid along the bottom, a branch with a receiver, called a snorer, departs. A clinket is installed on the offshoot, which has a stock extractor to the upper deck, ending with a flywheel. In addition to the receiving clinkets located in each tank, secant clinkets are located on the highway, separating a group (of two or three) tanks. In addition to cargo, ballast water is received and pumped out through the cargo line, which is necessary for the tanker during passages without cargo. On some tankers with separate ballast tanks, a special ballast pipeline is installed for pumping ballast, similar in design to the cargo one.

Numerous cargo piping systems are used on oil tankers. The most widespread are linear and ring systems, which create the greatest opportunities for cargo operations when transporting several types of cargo at the same time.

The linear system on a tanker with two longitudinal bulkheads (Fig. 149) consists of several lines 1, 2 and 3, each of which has its own pump 4, 5 and 6 and serves one specific group of tanks. Risers 7, 8 and 9 depart from each line to the upper deck, connected to deck lines 10, 11 and 12. With such a system of cargo pipelines, the vessel is able to simultaneously receive three types of cargo. To exclude the possibility of mixing cargo, two clinkets are installed on the jumpers between the highways. In the event of a failure of one pump and to enable the pump to work on "foreign" lines, the latter are interconnected by jumpers 13 and 14, which also makes it possible to speed up the possibilities for cargo operations even with one type of cargo.

With an annular system, along the bottom of the tanker (Fig. 150), which also has two longitudinal bulkheads, two lines are laid along the side, connected by bow 1 and stern 2 transverse jumpers into a ring. Receiving branches extend into each tank both from the left and from the right highways. To receive the cargo, in addition to the pump room, risers are brought to the upper deck. Cargo pumps 3 and 4 can operate on both lines separately and jointly. The ring system also provides the possibility of transporting two or more types of cargo, since there are several secant clinkets on the highways.

Ring systems can also be made in a slightly different form, for example, on ships with one longitudinal bulkhead, and also depending on the requirements for the ship.

The stripping line is located in the cargo tanks similarly to the cargo line, it is also equipped with receiving clinkets in each tank, flywheels are brought to the upper deck, secant clinkets are installed. Pipes with a diameter of 100-150 mm are used for the stripping line. The stripping line in the pump room is connected to stripping pumps, the pressure line from which does not go to the upper deck, but cuts into the cargo line, and sometimes, in addition, has a branch into the end cargo tank to collect stripped residues.

Stripping lines are usually laid along the same systems as cargo lines. The flywheels of the clinkets brought to the upper deck for quick orientation differ from each other in size and color. So, for example, all flywheels of the stripping system are smaller in diameter than the flywheels of the load system. The flywheels of the starboard tanks are painted in green color, left - in red, secant - in black, etc.

In the cargo pump room, the cargo, stripping and ballast lines are interconnected, forming a complex system of pipelines with a large number of clinkets. which makes it possible to carry out cargo operations in various options. For receiving and pumping outboard water, bottom kingstones are installed in the cargo pump room.

Cargo pump rooms can be located both in the middle and in the aft parts of the vessel. Some large-tonnage tankers have two pump rooms. With the aft location of the pump room, it is located between the cargo tanks and the engine room.

Preparation of the tanker to receive cargo. One of the main requirements for the carriage of cargo in bulk is to ensure the preservation of the quality of the transported cargo. Before accepting cargo
tanks must be cleaned of silt, dirt that enters the tanks along with ballast water, and rust that has fallen off the sides. This work is also carried out if homogeneous oil products were previously transported. When transporting fuel oil and crude oil, you should only remove dirt and solid residues that settle on the bottom.

The preparation of cargo tanks is carried out, as a rule, during ballast passages when proceeding to the port of loading. The tanks are washed and cleaned one by one. Washing water, if there are separators on the ship, is passed through them, and the separated residues are collected in tanks for delivery to the shore. To improve the working conditions in the tanks there are fans, and the air is sucked through the cargo pipeline from the bottom of the tank. Ventilation is carried out at night, when the washing of tanks stops.

All clinkets of the cargo and cleaning lines must be checked for tightness by water pressure in the pipeline created by the pump. All leaks noticed in joints and wedges must be eliminated. The density is checked immediately after the end of the washing of the tanks and the pipelines themselves. If the tanks have cargo heating coils, these should also be checked for defects that could allow cargo to enter the coils. If several types of cargo are accepted, then the transverse and longitudinal bulkheads separating different varieties must also be_tested for water tightness.

Immediately before the start of loading, all tanks are inspected and any foreign objects found are removed from the tanks. When performing cleaning work, non-sparking tools (shovels, shovels, buckets, scoops) should be used. All fire safety measures must be taken (grounding of washing hoses, prohibition of the use of shoes with metal nails, the possibility of sparks from the presence of static electricity is taken into account).

Cargo samples. The quality of oil products transported in bulk in cargo tanks may be reduced due to the ingress of water, mechanical impurities in the form of dirt or sludge, as well as mixtures with other oil products. To protect the interests of the shipowner and to prove that the transported oil products were of the same quality during delivery as during loading, samples of the cargo are periodically taken during the latter.

At certain intervals (1-2 hours), samples of the cargo are taken from the drain cock of the onshore pipeline at the side of the vessel. At the end of loading, all samples are mixed and the mixture is poured into two vessels with a capacity of about 1 liter each, which are sealed and stored for the required time - one at the consignor of the cargo, the other on the ship. Such samples are taken separately for each type of cargo. In case of presentation
the recipient of claims for the quality of the transported cargo, it is determined by the arbitrator by comparing control samples taken during loading with samples taken during unloading.

Water test. When receiving cargo, it may contain water that has got there from shore tanks or from ship pipelines, in which it may remain after washing tanks or pumping out ballast. The presence of water in the cargo and its amount are determined using water-sensitive paste or paper. A weight attached to a measuring tape, which is used to measure the height of the level of the cargo in the tank, has a small groove, or flat, on which the paste is applied. If paper is used, then it is simply attached to the weight. The tape measure is lowered into the tank through a measuring tube and, when the weight reaches the bottom of the tank, it is kept for some time, necessary for the paste to dissolve with water. Having lifted the tape with a weight, they notice the height reading at the boundary of the dissolution of the paste on the weight and, using calibration tables, determine the volume of water, which is then excluded from the volume of the load.

Cargo measurements. Upon completion of loading, to determine the weight of the accepted cargo, its measurements are made. The level of the cargo in each tank can be measured with a metal tape, graduated in centimeters, which is lowered into the measuring tube. After the weight, suspended at the end of the tape measure, touches the bottom, the tape measure is lifted and, according to the wetting level of the tape, a reading is noted corresponding to the height of the load level in the tank with an accuracy of fractions of a centimeter. To speed up the measurement process, which is especially necessary at the end of loading, a metro rod is used instead of a tape measure - a wooden slat with a length of

1.5-2.5 m with a crossbar in the upper part and having the same graduation along the entire length as the tape measure. The metro rod is quickly lowered to the stop by the crossbar into the measuring tube or into the viewing neck. Noticing the level of wetting of the footstock, the height of the void in the tank is noted from the level of the load to the conditional point - the stop of the cross.

To determine the volume of cargo in tanks, there are calibration tables on the ship, with the help of which, according to the measurements of the cargo level or emptiness in the tank, the number of cubic meters of cargo is determined. By amending specific gravity cargo, its temperature and trim of the vessel, receive the weight of the cargo in tons, which is entered into the cargo documents.

Unloading. Preparatory work for unloading should be carried out before the vessel arrives at the port. If viscous oil products are transported, then for a certain time before arriving at the port they need to be heated using standard steam heating coils located on the bottom of the tanks. It is necessary to prepare the necessary equipment - pallets, transition pipes, mats, rags, etc.
Upon arrival at the unloading port, all outboard scuppers on the cargo deck are closed with specially made wooden plugs. After mooring on the ship, in the presence of the representatives of the recipient of the cargo and the quality inspector, the cargo is sampled and its quantity is measured.

Unloading from tanks is carried out in the order provided for by the unloading plan drawn up by the cargo assistant and approved by the captain of the vessel.

The duties of the sailor on duty during unloading include: opening and closing clinkets on the upper deck at the direction of the cargo assistant; measurement of voids; monitoring the position of the cargo level in the tanks for the timely switching of cargo pumps to stripping ones; monitoring for the absence of possible leaks from flange connections of pipelines and drain cocks, etc.

During unloading, the ship rises in relation to the berth, so the sailor must monitor the condition of the cargo hoses, preventing them from chafing against the protruding parts of the ship's hull, and also promptly loosen the mooring cables.

Upon completion of the unloading and cleaning of the tanks, the recipient's representative, together with the cargo assistant, makes sure that there is no cargo in each tank, making measurements using a tape measure, as well as visually using an explosion-proof electric torch.

In some cases, cargo operations, such as refueling other ships, may be carried out at sea both underway and while the ships are drifting. When transferring cargo on the move, the vessel receiving the cargo or bunker is towed by the tanker astern. Then, with the help of a conductor, a hose is transferred from the tanker to the towed vessel, where it is connected to the receiving line.

Unloading may also be carried out at a time when * the ships, not having a course, are moored side by side to each other. Such an operation can be successfully carried out without the use of special soft fenders of large size only when total absence unrest, which is extremely rare on the high seas or ocean. Even a slight wave causes rolling, in which ships standing in a lag can easily receive damage to their hulls and superstructures. To avoid damage, it is necessary to use large fenders, which must be made either specially, as is done for fishing floating bases, or from auxiliary material - logs, old car tires, etc. In the practice of whaling fleets, the carcasses of the dead are used as fenders whales.

The mooring ends of ships lying side by side in the sea are always subject to strong jerks due to uneven movements of ships in waves, which often leads to cable breaks. To avoid this, it is recommended to use synthetic cables or combined - steel with a spring from a synthetic cable. It is not recommended to feed short cables, as they break quickly.

The successful implementation of the transfer of liquid cargo or fuel at sea, which is a complex operation, requires coordinated actions of the entire crew.

Management of cargo operations on a tanker and their mechanization. The production of cargo operations on tankers, due to the explosive nature of the transported goods, creates a number of specific conditions. For example, cargo and stripping pumps are located in the cargo pump room, and their drives, both electric motors and steam turbines, are located behind an impenetrable bulkhead in the engine room. Therefore, to control the pump drives, a control panel is installed in the area of the pump room at the level of the transition bridge. In order to avoid overly complicated designs, especially for steam drives, the pumps are not intended to be started from the control panel. This operation is performed by the shift engineer in the engine room by order transmitted from the console by telephone or voice tube. For the same purpose, on some ships, a telegraph is installed in the cargo pump room, through which the necessary orders are transmitted to the engine room.

The console has the necessary instruments - pressure gauges, vacuum gauges and others that are used to control the operation of pumps. Changing the number of revolutions of the pumps, as well as stopping them, can be done from the remote control. For an emergency stop of pumps, for example, in the event of a hose break or cargo overflow, an emergency stop button for pumps is installed, usually in the area of the gangway, where the sailor on duty is constantly located.

Measuring the level of cargo on modern large tankers with 30-40 cargo tanks, and the operations of opening and closing a large number of clinkets when moving from one tank to another, are very laborious. In some cases, for example, at the end of loading, as a result, it is necessary to reduce the loading speed, due to the fear of overflowing the cargo, since actions with large-section clinkets and with a large number of handwheel turns are manually limited by human capabilities. However, despite the seeming simplicity of mechanization of relatively simple processes - manipulations with clinkets and measuring levels, these works have not yet been embodied in a convenient, reliable and simple mechanized system. The main obstacle to this is the lack of an explosion-proof remote system for measuring the level of cargo in tanks, which gives reliable readings with the necessary constant accuracy. However, on some tankers these
the work is still mechanized, although the performance of these systems does not reach the required level of accuracy.

On a vessel equipped with such systems cargo work can be performed by one person - the operator at the central control panel. All clinkets, cargo, stripping and secant, located both in tanks and in the cargo pump room, have a hydraulic drive located directly on the clinket body and are controlled from the remote control by simply pressing a button. On the remote control there are indicators of the positions of the clinkets "open - closed". From the same console, all pumps are remotely controlled and the operation of their drives is monitored. Measurement of cargo levels is also carried out remotely using a pneumometric system with the conversion of the pressure of the height of the liquid column in the tank into an electrical impulse transmitted to the central control post. A device that converts an air pressure signal into an electrical one is installed outside the tank in a safe place.

Such a system does not have the accuracy necessary to calculate the amount of cargo received, and gives an approximate reading of the level. To accurately determine the amount of accepted cargo, it is necessary to measure the voids manually.

The mechanization of cargo operations should not only improve the operational performance of the ship, reducing lay time, but also significantly facilitate the work of the crew and create prerequisites for comprehensive mechanization ship work and reducing the number of crew.

Protection of tanks against corrosion. The surfaces of cargo tanks and the equipment located in them (pipelines, clinkets, stock ducts, ladders, etc.) when transporting light oil products (gasoline, kerosene, naphtha, etc.), as well as crude oil, especially with a high content of sulfur connections are subject to severe corrosion. During ballast crossings, which sometimes take up to 50% of the operating time, salty outboard water is taken into the cargo tanks for ballast, which also contributes to the rapid oxidation of steel.

Pipelines that carry liquids at high speeds are most susceptible to corrosion. The resulting electrochemical processes also contribute to the formation of general corrosion or separate, deep local lesions and fistulas. As a result, after four to six years of operation, a significant part of the pipelines needs to be replaced with the withdrawal of the tanker for repairs for a considerable time.

To protect the internal surfaces of cargo tanks from corrosion, protective coatings are applied to all surfaces in the form of a paint film, as well as electrochemical protection.
For painting, various compositions are used that are resistant to the action of petroleum products, made on the basis of ethinol varnishes, epoxy and vinyl resins and many other chemical compounds. The application of protective coatings, however, causes a number of difficulties, since most of them are toxic and require the use of special protective devices and intensive ventilation. Vapors of these paints are explosive and require careful implementation of all fire prevention measures. In addition, to ensure the strength of the coating, its good adhesion - stickiness to the metal - its surface must be very carefully cleaned.

The best result is the treatment of all surfaces with sandblasting or shot blasting machines. Therefore, the application of protective films, as well as the correction of local damage, can only be carried out in the factory during the construction of the vessel or its repair.

A protective system is used as electrochemical protection. It consists of protectors - castings of magnesium or aluminum-magnesium alloys in the form of discs or cones, evenly placed in close proximity to the inner surfaces of the tank. Possessing a reduced potential with respect to steel and being in salt water during ballast transitions, which in this case is an electrolyte, the magnesium electrode begins to work as a cathode, the particles of which are transferred to the steel surface, creating a protective film on it. The protector itself is destroyed.

It should be borne in mind that aluminum-magnesium alloys, when struck against corroded steel, cause a spark, so the fall of such a protector in a non-degassed tank can lead to an explosion. This property largely limits the use of tread protection on tankers.

Inhibitors are also used to protect tanks from corrosion - special chemicals that are introduced into the transported cargo, and they settle on the surface of the tank, creating a protective film.

Measures to prevent pollution of the sea by oil products. On modern transport ships, whose mechanisms and boilers operate on diesel fuels and fuel oils, oil products waste is inevitably formed, accumulating in the bilges of engine rooms and tanks for collecting dirty and used oils. A large number of oil tankers perform tank washing operations during ballast passages, as a result of which a large amount of water is heavily polluted with oil products. Pumping overboard of bilge water, and in particular washing water, from tankers creates a serious

threat of pollution sea water oil products, leading to the death of fish, birds and marine animals, as well as oil pollution of seashores, beaches, canals, rivers and ports.

Therefore, back in the twenties of our century, this issue began to be seriously studied in order to create effective measures to combat marine pollution with oil products. Various recommendations have been developed. However, the first document was the Resolution of the International Convention for the Prevention of Marine Oil Pollution, adopted in 1954.

In the following years after the adoption of this Convention, practice has shown the need for additional measures to prevent the discharge of oil from ships. To this end, the Intergovernmental Marine Consultative Organization (IMCO) convened the International Conference on the Prevention of Marine Oil Pollution, which was held in London in the spring of 1962. The Conference significantly revised the 1954 Convention, supplemented it, clarified the scope, rules and requirements.

The resolutions of the conference state that the only known and fully effective method To prevent oil pollution of the sea is a total ban on the discharge of persistent oils into the sea. However, before the dumping of oil into the sea is completely prohibited, it is necessary to equip ships with appropriate devices for receiving oil-polluted ballast from them.

Therefore, the Convention did not set a date for a complete ban on the discharge of polluted waters into the sea, but established exclusion zones as a temporary measure. Oil-contaminated water can be pumped overboard within these zones only through devices that provide water purification to an oil content of not more than 100 mg per 1 liter of the mixture. In the absence of such devices on the ship, contaminated water must be pumped out outside the restricted areas or, upon arrival of the ship at the port, into special containers.

Each ship is required to keep a special log, which indicates the time and place of discharge of polluted water, the reception and discharge of ballast water, the washing of cargo tanks, etc.

The Soviet Union has developed a whole range of organizational and technical measures to combat marine pollution by oil products. In April 1961, the Ministry of the Navy put into effect the Temporary Guidelines for the Prevention of Oil Pollution of the Sea, prepared taking into account the basic requirements of the 1954 Convention, the control of which was entrusted to port captains.

In September 1968, the Council of Ministers of the USSR adopted a resolution "On measures to prevent pollution of the Caspian Sea."
Transportation on tankers of loose and other cargoes. In addition to oil products, other cargoes such as vegetable oils, alcohols, molasses, ammonia, liquefied gases, etc. are transported in bulk on tankers. The transportation of products such as vegetable oils, alcohols or molasses does not require special devices and devices. It is only necessary to wash and ventilate the tanks very carefully, since one of the main requirements for cargo tanks is the cleanliness of their surfaces and the absence of odors in them. Some edible oils, such as coconut oil and molasses, have a high pour point and must be warmed up before unloading. It must be borne in mind that each product has its own heating temperature, the excess of which leads to a loss in the quality of the cargo.

Sometimes tankers also carry raw sugar.

Bulk grain cargoes are transported by tankers relatively often. The preparation of tanks for the transport of grain also consists of thoroughly washing and ventilating the tanks until the oil odors are eliminated. Receiving snores of cargo and cleaning lines, in order to avoid getting grain into pipelines, must be carefully tied with canvas. If the flight involves a transition from one climate zone to another, with a sharp drop in water and air temperature, at which the internal surfaces of the tanks begin to sweat, then to protect the cargo from moisture, all surfaces of the bottom and sides must be covered with insulating material before loading, sometimes even in several layers. Straw mats are good insulators, but burlap or canvas can also be used.

For the transportation of liquefied gases, specialized tankers are used, adapted for the transportation and loading and unloading of liquids under relatively high pressure.

The emergence of the tanker fleet is a relatively new phenomenon. The first tankers appeared at the end of the 19th century. Until that time, technical solutions did not allow the transportation of large quantities of bulk liquids, such as oil, in the holds. And the markets did not require such transportation, the demand for oil was satisfied by local processing and transportation by land.

At the end of the XIX century. increased demand for oil due to the development of energy in a number of countries, and technological innovation made it possible to build ships of a new class - tankers designed to carry large quantities of crude oil and oil products in the holds. This is how this separate specialized class of ships began to develop.

Low prices for the construction and charter of tankers contributed to the development of long-distance maritime trade in oil and petroleum products. Demand for the transport of bulk cargoes such as oil products and crude oil has caused an increase in the size and capacity of tankers.

The increase in the dimensions of tankers for long-distance transportation turned out to be limited by the size of the locks of the two channels through which the main routes pass - the Suez and Panama, as well as the Strait of Malacca. Demand necessitated the expansion of the Panama Canal locks, which led to the division of tankers into existing tankers of the “old Panamax” class and those built already taking into account the new dimensions of the “new Panamax” locks (see Fig. 2).

Rice. 2. The location of the main channels that limit the growth of tanker fleet dimensions, and the corresponding limit dimensions for each class of tankers.

Single-hull tankers built in 1970-80 worldwide have been replaced by double-hulled tankers whose design prevents pollution environment.

Rice. 3. Development of constructive technical solutions that prevent environmental pollution in case of damage to the tanker hull.

Oil - oil; Ocean - the ocean; Steel 1-1/2” (or less thick) - steel 1-1/2” (or less) thick; Bulkheads - bulkheads; Protective space - protective space; Cargo tanks - cargo tanks; Single Bottom - single bottom; On a single-bottom tanker, only one layer of steel measuring 1-1/2” inches thick separates oil from the ocean Double bottom - double bottom.

Double bottoms do not prevent oil spills, but even in the worst case, such as the Exxon Valdez tanker, experts say it can reduce the amount of oil entering the ocean.
Mid-deck - a tanker with an intermediate deck.
On a tanker with an intermediate deck, the lower tanks have a single bottom and when the ship is grounded, some oil will enter the ocean. But the court this project should be better protected from collisions than double-hulled tankers, although there is no practical evidence for this.
Double hull - double body.
Double hull ships provide better cargo protection due to the double bottom and double sides. For a double hull tanker, the distance between the side and the longitudinal bulkheads shall be 1/15 of the tanker's breadth or between 2 and 2.9 m.

The basic design of the tanker is extremely simple. As shown in Figures 4 and 5.

Oil tanker (Front view) - tanker (front view); Center cut view - cross section in the center of the vessel; Double hull - double hull; Oil tanks - oil tanks; Segregate Ballast tank - separate ballast tanks.

Oil tanker (side view) - tanker (side view); Bridge - bridge; Fuel Tank - fuel tank; Engine room - engine room (MO); Pump Room - pump room; Double Hull - double hull; Empty - empty compartments; Oil Tanks - oil tanks.

When building a tanker, the maximum possible measures to ensure safety are also provided. Basically, these are increased requirements for the strength of the hull and cargo tanks and the absence of cargo leakage during an accident.

This ULCC class tanker is unusual in that it has a twin-shaft rig that propels it, including two engines and two propellers, as well as two rudders.

Mooring winches - mooring winches. Mounting the superstructure above the MO saves construction costs. Hot water pipelines and electrical cables can be laid directly from the MO; Radar - radar; Cabins - cabins; Cargo pump room - room for loading pumps; Navigation deck - navigation deck; Helicopter landing pad - helipad; These pipes carry water for cleaning the tanks and firefighting - these pipes can carry water for cleaning tanks and fire fighting systems; Anchor windlass - anchor windlass; Mooring winch - mooring winch; Tank hatches - hatch covers over tanks; Discharging and loading points - cargo acceptance and unloading points: Hydraulic cranes lift shore hoses which discharge and load cargo - hydraulic cranes lift shore hoses for unloading and receiving cargo; Oil cargo tanks - oil cargo tanks; Engine room - MO; Steam turbines - steam turbines; Two five-bladed propellers drive the ship forward - two five-bladed propellers drive the ship forward. Each screw weighs 53 tons and is the size of a three-story building; Rudders - rudders.

The main questions that arise when building a tanker:

Hull contours

The contours of the hull of any vessel are one of its most important characteristics. The design of a tanker for the transportation of petroleum products is a design that depends on the weight of the cargo - weight-based, that is, the dimensions of the vessel are directly related to the weight of the transported cargo. (For other classes of ships, for example, for container ships, the design may be volume-based, where the dimensions are determined by the volume of cargo space, cargo holds). Since it is desirable that the weight of the cargo carried in one voyage, in this case oil, be the maximum possible, it is necessary to provide for the maximum possible dimensions of the space for cargo tanks. Usually tankers move at a relatively slow speed because the cargo is not perishable, as in the case of transportation food products, All these mentioned factors are taken into account when designing the contours of the tanker hull. In other words, the tanker has a higher Coefficient of Buoyancy compared to ships of other classes.

General location

The most important drawing in the tanker design process, which, in fact, determines the design of the tanker, is the General Arrangement Drawing. On fig. 6 shows this drawing of the general arrangement of compartments, rooms, systems and equipment, side view. It shows the location of all the internal compartments of the vessel, frame by frame, bulkheads and other main structures of the ship's set.

Some of the ship's structural details are clear from this drawing. Cargo tanks (oil tanks - C.O.Ts) usually have the same dimensions, determined by the designer at the initial design stage, depending on the total weight of the cargo carried by the ship. Access to each tank is provided separately by ladders or elevators. The engine room (MO) and superstructures are usually located in the aft part of the vessel. But a special room, absent on ships of other classes, - pumping station, usually located in front of MO. It houses all the pumps required for loading and unloading operations.

bulbous nose

To date, almost all tankers have a bulbous bow, which increases efficiency when the vessel is moving. Although tankers are slow-moving vessels, the bulbous bow significantly reduces wave resistance when the vessel is moving. At the same time, the geometry of the bow bulb of tankers differs significantly from the similar geometry of the bulb of high-speed vessels.

There are three varieties of the nasal bulb, they are shown in Fig. 7 (when viewed from the bow to the stern of the vessel).

Bulb type "Delta" has a larger volume in the lower part. This feature makes such contours of the bow of the vessel more advantageous on ships with frequent changes in waterline level, since a larger volume in the lower part of the bulb ensures its immersion in water at a different range of waterline levels and load conditions.

Bulb type "O" has a maximum volume in the middle part. This type of bulb is used on ships with cylindrical bows, for example, for bulk carriers.

Bulb type "Nabla" has a teardrop shape with a large volume in the upper part. Bulb of this type is used on ships where special attention is paid to ensuring seaworthiness, for example, on ships of the Navy.

Most tankers carry cargo along the route and return empty under ballast. The level of the waterline when empty is different from the level of the waterline when fully loaded. But this frequent change in the level of the waterline requires that the bow bulb, under all sailing conditions, be submerged in water. Therefore, tankers usually have a Delta-type bow bulb.

tanker set design

The structural set of the tanker depends on the class and dimensions of the tanker. So far, many of the existing small tankers for the transportation of petroleum products by inland waterways and coastal tankers have a single hull set. Although MARPOL (Marine Pollution) regulations require a double hull set for all vessels over 120 m in length, regardless of the type of cargo. Such tankers will be replaced and are being replaced by double-hulled ones.

The gangway is a structure raised above the deck and running along the entire length of the tanker, this bridge provides access to all cargo tanks. Bottom plating, deck sheets, and gangway sheets are parts of the longitudinal set of the tanker's hull and increase the strength of its hull in the longitudinal direction.

The side plating on single-hull tankers was attached to the frames transverse set. The reason for using the transverse framing structures for attaching the side plating was the accumulation of oil residues on the stiffening ribs of the longitudinal framing. And then, after pumping out the cargo, a certain amount of oil products remained in these hard-to-reach places. This had two consequences: 1) it led to contamination of the cargo, 2) the continued accumulation of cargo residues led to corrosion of the stiffeners of the set.

Set of double-hulled tankers

As previously mentioned, all tankers over 120m are now double-hulled to prevent marine pollution in case of accidents, in accordance with MARPOL regulations. Panamax, Aframax, Suezmax, VLCC and ULCC class tankers have a double hull framing. The main reason for using a double-hull kit is to prevent contamination of the environment during an oil spill in the event of an accident and damage to the hull.

Stringer - stringer; Floor - floor; Plate bracket - knee; Inner bottom - inner bottom; Intermediate stringer - intermediate stringer; Wing tank - side tank; Longitudinal bulkhead - longitudinal bulkhead; Inner hull - inner hull; Deck-transverse web - underdeck frame frame; Center tank - central tank; Transverse web - frame frame.

On fig. 8 shows a cross-section of the longitudinal framing of a double-hulled tanker. In the right half of Fig. 8. shows a conventional frame, sheets of inner and outer skin are attached to the stringers. The central tank is a cargo tank and the wing tanks are segregated ballast tanks (SBT). Ballast water tanks are coated with epoxy resin to prevent corrosion.

The transverse set shown on the left side of fig. 8, is installed every three to four spacings to increase the strength of the vessel in cross section. Longitudinal stiffeners are welded to the frames. Stringers attached to the frames additionally increase the strength of the tanker hull.

Currently, regardless of which classification society approves the design of a double-hull tanker, tanker hull framing is carried out in accordance with the Harmonized Common Structural Rules - CSR for tankers developed by the International Association of Classification Societies - IACS.

Power ship installation (SPP) of a tanker

Since tankers are relatively slow ships (average max. speed is 15.5 knots) and have no space constraints for engine placement, they can use large low-speed marine diesel engines as main engines. This type of engine takes up more space than high speed marine engines, but delivers more efficient power to the propeller shaft and there is no gear loss because the engine shaft RPM matches the propeller RPM. Typically, tankers use large-diameter, low-rpm propellers to improve efficiency when moving the ship.

Tanker onboard systems

Tankers have a number of on-board systems that are unique in their purpose.

Cargo heating system:
Crude oil tankers are equipped with such a system because crude oil is a viscous and dense liquid, especially at low temperatures. This can interfere with the operation of pumps and the movement of liquid through pipelines during loading and unloading operations. Therefore, a special heating system is used to maintain an acceptable temperature and viscosity of the cargo in the holds.

Cargo tank ventilation system:

Cargo tanks are almost never completely filled, but the accumulation of flammable and explosive gases in the tanks is unacceptable. An adequate ventilation system prevents the accumulation of hazardous vapors and gases in the enclosed spaces of cargo tanks.

Overflow Control System:

This system uses level sensors and pressure sensors to control the oil level in the cargo tanks so that the oil level during loading and unloading operations does not exceed the prescribed limits. Alarm sensors and drain valves are part of the system to prevent an extreme situation.

Inert gas supply system:

The space between the free surface of the cargo in the tank and the top plates of the tank must be filled with an inert gas to prevent access to oxygen in order to avoid a fire hazard in case of accumulation of flammable vapors and gases. This is achieved by constant supply of inert gas and control of its level in the tanks. The most commonly used for these purposes are argon and carbon dioxide.

The main part of tankers carrying oil, gas and products of their processing is the area of cargo tanks (cargo area), which contains cargo tanks (tanks), a cargo system, cargo pump and / or compressor rooms adjacent to them or located above them. rubber dams.

The main part of the cargo area are tanks - moisture-proof shells that serve as the primary container for cargo.

In the construction of modern tankers, various designs of cargo tanks are used, which can be conditionally classified into four main types:

Type 1 - built-in cargo tanks, which are part of the ship's hull and contribute to its overall and / or local strength. They are intended for the carriage of goods with a design vapor pressure of up to 24.5 kPa (in some cases up to 68.64 kPa) that do not affect any part of the hull with temperatures below 263K.

Type 2 - membrane cargo tanks - consist of a thin shell supported through insulation by adjacent vessel hull structures. The membrane compensates for thermal expansion or contraction of the load and reduces its effect on the hull. The design vapor pressure of the cargo in membrane tanks is the same as for built-in tanks (type 1).

Type 3 - semi-membrane cargo tanks, consisting of a thin shell partially supported through insulation by adjacent ship hull structures.

Type 4 - independent cargo tanks that do not have a rigid connection with the hull, but rely on the internal set of the hold and / or deck. Integral cargo tanks (type 1) are widely used on most tankers. It is a typical hold for the transportation of bulk cargo, the basic design of which was considered by us in the description common device tankers.

Resistant in a wide temperature range in the environment of petroleum products, vegetable oils and alcohols is the coating of carbon steel with zinc silicate, fluoroplastic elastomers, and some brands of polyurethanes. Coatings based on epoxy resins are resistant to most light petroleum products, acids and alkalis, however, they are not sufficiently resistant to certain types of vegetable and synthetic oils when exposed to elevated temperatures and alternating loads (including vibrations).

Modern tankers are gigantic ships. The impressive size is explained by the economic "scale effect". The cost of transporting one barrel of oil on ships is inversely proportional to their size. In addition, the number of crew members of a large and medium tanker is approximately the same. Therefore, giant ships significantly reduce the cost of transportation for companies. However, not all seaports able to host a supertanker. Such giants need deep-sea ports. For example, most Russian ports are unable to receive tankers with a deadweight of more than 130,000-150,000 tons due to fairway restrictions.

Tanker accidents are among the so-called man-made disasters, the cause of which is economic activity people, often associated with the adoption of ill-considered decisions, negligence, and sometimes simply with unprofessionalism and ignorance of natural patterns. Technogenic environmental disasters caused by oil spills during accidents on tankers are among the most common. According to international organization IMCO, only in 1970 about 5 million tons of oil got into the seas and oceans, now this figure has increased. Moreover, this danger grows with an increase in the tonnage of tankers and their number. According to experts, the total probability of an accident is 0.4 per 1000 flights. The probability of spill risk is assumed to be 0.05 per 1000 voyages on the high seas and 0.25 in hazardous locations. Considering the likely frequency of grounding and collision accidents the average size oil spill can be estimated as 1/48 of the amount of oil transported per flight.

That is, being able to transport, say, frozen chickens, it will be considered as cargo.

Types

Bulk carriers

Bulk carrier- the general name of ships intended for the carriage of solid, bulk, and packaged cargo, including containers and liquid cargo in containers. Includes universal general cargo ships equipped with handling facilities, bulk cargo ships, bulk carriers with a deadweight of less than 12 thousand tons, some other ships, for example, sinter carriers.

bulk carriers

bulk carrier(Also bulk carrier) - a ship for the transport of bulk cargo in bulk in the hold (that is, without containers). Bulk carriers are used to transport ore, coal, cement, etc. In addition to universal bulk carriers, there are specialized ones equipped for the transportation of certain types of cargo, such as ore carriers, cement carriers, etc. There are ships that can simultaneously transport both bulk and liquid cargo (then there are those that are both a bulk carrier and a tanker), for example, oil ore carriers.

container ships

Container ship- a vessel for the carriage of goods in standardized containers.

ro-ro

ro-ro(also: ro-ro ship) - a ship with a horizontal way of loading and unloading. Ro-Ros are most often used to transport (lorries) cars and other wheeled vehicles. The main advantage of the ro-ro is the speed of unloading and loading the vessel. For these operations, cranes are not needed: trucks with cargo simply drive in / out on the cargo decks of the vessel along the ramp.

Lighter carriers

Lighter carrier- a vessel carrying special barges - lighters. Lighter carriers are often used where large vessels cannot approach the berth due to insufficient depth or for other reasons. Lighters are loaded at the berth, transported by tug to the lighter carrier and lifted on board the lighter carrier. Unloading is done in reverse order. In Russia, there is the world's only nuclear-powered lighter carrier "Sevmorput" serving the villages of the Arctic Ocean. This lighter carrier is part of the Federal State Unitary Enterprise Atomflot of the State Corporation Rosatom.

tankers

Tanker - a ship for the carriage of bulk cargo.

refrigerated ship

Refrigerated ship - a ship, the holds of which are equipped with cooling units. Refrigerated ships are used to transport perishable foodstuffs. Because of this, among the sailors they received the nickname "banana carriers".

Size classification

There is a worldwide classification of cargo ships by size. It relies on the capacity of ports and terminals to receive vessels of various sizes and on the capacity of the most important canals (Suez and Panama). There are several interpretations of these classes: Lloyd's scale, AFRA scale, flexible market scale.

Tanker classes

Name and decoding	Alternative name	Scale characteristics (dwt in tons)			Description	Example
Name and decoding	Alternative name	Lloyd	AFRA	flexible market	Description	Example
ULCC: Ultra Large Crude Carriers (Ultra Large Oil Carriers)		300-550 thousand	320-550 thousand	320-550 thousand	Very large oil tankers carrying crude oil over long distances. Transportation routes originate in the Persian Gulf and deliver oil to Europe, America, and Southeast Asia. Due to the fact that it is impossible for such large ships to pass through the Suez Canal, they usually go around Africa by passing through the Cape of Good Hope. Again, due to their large size, these vessels cannot unload in normal ports and are accepted by purpose-built terminals.	Knock Nevis
VLCC: Very Large Crude Carriers (Very Large Oil Carriers)		200-300 thousand	160-320 thousand	200-320 thousand	They follow a route similar to that of larger tankers, but due to their smaller size, they have flexibility in choosing ports. This allows VLCC ships to operate routes to the ports of the Mediterranean, West Africa and reach the Northern Marine Terminals. In addition, such tankers can return with ballast through the Suez Canal.	Exxon Valdez
Suezmax	AFRA: LR2 (Large Range 2)	180-200 thousand	80-160 thousand	120-200 thousand	As of 2012, ships with a deadweight of up to 200 thousand tons pass through the Suez Canal, larger ships can pass in ballast. There are plans to widen the canal to accommodate larger vessels.
Aframax Lloyd: capemax	AFRA: LR2 (Large Range 2)	100-180 thousand	80-160 thousand	80-120 thousand	As of 2012, ships with a deadweight of up to 200 thousand tons pass through the Suez Canal, larger ships can pass in ballast. There are plans to widen the canal to accommodate larger vessels. Historically, the name arose when such ships could not cross this channel and were sent with cargo around the African continent.
Panamax	AFRA: LR1 (Large Range 1); Lloyd: Aframax	Up to 80 thousand	45-80 thousand	60-80 thousand	Vessels with limit dimensions to pass through the Panama Canal
product tanker	AFRA: medium range tanker	XXXXXXX	25-45 thousand	60-80 thousand
product tanker	AFRA: General Purpose tanker	XXXXXXX	10-25 thousand	60-80 thousand
separate class for Lloyd are tankers Malaccamax that can cross the Strait of Malacca in Malaysia

Classes of bulk carriers (dry cargo carriers) according to Lloyd classification

Name	Characteristic (deadweight in tons, approximately)	Description
Capesize	100-400 thousand	The largest dry bulk carriers not intended for navigation in (through) the Panama and Suez Canals. Draft and other characteristics vary. The class has internal gradation (VLOC and VLBC).
Panamax	65-100 thousand	Vessels with the maximum allowable dimensions for the passage of the Panama Canal (length 225.0 meters, width 32.25 meters, cage 12.5 meters). Vessels of this class are not equipped with cargo cranes and have 7 holds. The maximum draft in cargo is up to 15.0 meters.
Supramax	50-70 thousand	An intermediate class between Handymax and Panamax. Equipped with cranes, have 5 holds. The maximum draft in cargo is up to 13.0 meters.
Handymax	35-45 thousand	Vessels equipped with cranes and having a loaded draft of up to 12.0 meters. As a rule, they have 5 holds.
handysize	20-35 thousand	Vessels equipped with cranes and having a maximum loaded draft of up to 10.0 meters. As a rule, they have 5 holds.
mini bulk carriers	Up to 10 thousand	Small sea freighters for short and coastal voyages

Notes

Cargo ship; Navalochnik // Great Soviet Encyclopedia: [in 30 volumes] / ch. ed. A. M. Prokhorov. - 3rd ed. - M.: Soviet Encyclopedia, 1969-1978.

On a tanker, all cargo operations are carried out by a cargo system (Fig. 1), which consists of pumps and pipelines laid along the upper deck and in cargo tanks.

The cargo device of a tanker is a whole complex of special devices and systems. It includes:

pipelines;
cargo pumps;
cleaning system;
cargo heating system;
crude oil tank washing system;
inert gas system and gas exhaust system.

Rice. 1 Schematic of tanker cargo system

For loading and unloading liquid cargo on oil tankers, a special cargo system is installed, consisting of receiving and unloading lines (Fig. 2).

Rice. 2 Deck piping

Inlet (suction) pipeline laid in cargo tanks. Each cargo pump has a separate main pipeline, from which receiving branches go to a certain group of tanks, locked with valves or clinkets. Such wiring of the suction pipeline allows you to independently receive and pump out several different grades of oil products.

R unloading (pressure) pipeline begins at the cargo pumps with vertical pipes going to the upper deck. Further, the highway is laid along the deck and from it to the sides there are branches, to which, during loading and unloading, flexible hoses or a terminal stander supplied from the shore are connected. Deck main pipelines are connected by vertical pipes (risers) with main pipelines laid in tanks.

On the bottom of the cargo tank are the cargo and stripping pipelines. On OBO combined ships, pipelines run under the bottom in double bottom tunnels.

Installed on tankers various systems cargo lines, however, three main systems should be noted: ring, linear and bulkhead-clinket.

ring system(Fig. 3) - this system is used on tankers of small sizes with two longitudinal bulkheads and two pump rooms - bow and center. Two pump rooms divide the cargo tanks into 3 independent groups with independent deck pipelines, which allow loading three types of cargo without the risk of mixing.

Pump rooms are usually located in the middle part of the tanker. As a rule, piston pumps are used. The disadvantage of the system is a lot of jumpers and the difficulty in cleaning tanks located aft of the pump room, when the tanker is trimmed to the stern.

Linear system(Fig. 4) - is used using centrifugal pumps located in the pump room in the aft part of the tanker, behind all cargo tanks. There can be two, three, four cargo lines, depending on the size and design of the tanker. Each of them has an independent cargo pump and a group of tanks closes. Lines and groups of tanks closed on them can communicate and be separated by valves, of which there must be at least two. This ensures the transportation of different types of cargo placed in different groups of tanks.

Rice. 3 Ring cargo line: 1 - deck receivers; 2 - kingstones; 3 - cargo pumps; 4 - tank receivers

Rice. 4 Linear cargo line: 1 - deck receivers; 2 - kingstones; 3 - cargo pumps; 4 - tank receivers

Bulkhead-clinket- the system differs from the two previous ones in that pipelines are not laid in cargo tanks. Holes are cut out in the bulkheads at the bottom, closed with special valves. During loading and unloading, the cargo flows through these openings from the tanks to the tank, where cargo and stripping pipelines are installed, near the pump room. This system is also called the system free flow(FREE FLOW).

The advantage of the system is a small number of installed pipelines, which reduces the cost of building a tanker. The disadvantage is the limitations of the possibilities when transporting several types of cargo at the same time.

At all stages of transshipment operations, it is necessary to control the movement of cargo through ship pipelines. This control is carried out with the help of gate valves or valves. Butterfly valves with a vertical or horizontal axis of rotation of the plate have received the greatest distribution on tankers.

Pipelines and valves are subjected to a hydraulic tightness test with water pressure equal to one and a half working pressure, it is lifted slowly by a cargo pump. The absence of leakage indicates the tightness of pipelines and valves.

The control of cargo valves, as a rule, is carried out remotely using hydraulic systems that are widely used.

Cargo pumps(Fig. 5). For unloading, the tanker has 3-4 cargo pumps. They are located in the lower part of the pump (pump) compartment, the compartment itself is located between the engine room and cargo tanks. Centrifugal-type cargo pumps have been widely used on tankers, which have a number of advantages - simple design, low weight and dimensions, high productivity. Piston pumps are used as stripping pumps on the vast majority of tankers.

Rice. 5 Cargo pump on a ship

The pumps supplying crude oil to the cargo tank washers shall be cargo pumps or pumps specially provided for that purpose.

Cargo heating system(Fig. 6). Oil tankers carrying viscous oil products have a cargo heating system. Oil products are heated to reduce viscosity, which facilitates their flow. The heating system has the form of coils made of steel pipes, through which steam is passed. Viki kites are laid along the entire bottom of the tank at a height of about 10 cm from it. Sometimes the system is individual sections installed in various parts of tanks. Valves for controlling the cargo heating system are brought to the deck.

In the process of heating the cargo, the tightness of the coils is controlled through the drain cock. If clean water comes out of the faucet, and then steam, the coil is working. If condensate contaminated with oil comes out of the faucet, this is a signal of a system malfunction. In winter, the system must be drained of condensate after use.

Rice. 6 Cargo heating system

Tank washing system crude oil consists of tanks for cleaning solution, collection and storage of oil products, deck pipelines for supplying cleaning solution to washing machines, pump, heater, portable equipment.

Washing of all or part of the tanks is necessary before changing the cargo, before placing the tanker in the dock, for repairs. Also, tanks are washed under clean ballast, with which the vessel arrives at the port of loading and which can be drained overboard into.

Tanks are washed with special washing machines with rotating nozzles. Machines for washing tanks with crude oil shall be stationary and have a design approved by the Register (Fig. 7). The inclusion of each machine must be carried out using a shut-off valve. The number and location of washers should ensure effective washing of all horizontal and vertical surfaces of tanks.

There are two types of washing machines:

non-programmable with two nozzles;
programmable with one nozzle.

Machines with two nozzles are not programmed and always complete a full cycle of work in a certain time. Tank washing machines are powered by oil from cargo pumps that act on a paddle wheel, so proper line pressure must be maintained for efficient cleaning. For stripping, it is preferable to use an ejector.

Programmable machines with one nozzle can be configured to wash certain sections of the tank in 4 cycles and allow you to change the angle of rise or fall of the nozzle with a resolution of 1.2, 3 and 8.5 0 .

Portable washing machines can also be used to wash tanks. To connect portable washing machines to the washing line, special rubber hoses are used. The cars are lowered into the tank through special washing hatches located in the upper part of the tank. These machines can be installed at different tank heights and are very effective at the final stage of tank cleaning.

Rice. 7 Scheme of a stationary washing machine and its control on the deck of a tanker

Washing of tanks is carried out according to a closed cycle (Fig. 8), i.e., washing water is collected in one or two settling tanks (Slop Tanks). The duration of the wash, as well as the need to use hot water and chemicals, is determined according to the Tank Cleaning Guide.

Washing with crude oil is only permitted if the inert gas installation is in good working order. No tank may be washed with crude oil without being filled with an inert gas with an oxygen content of not more than 8% by volume.

Waste wash water after separation from the water in one of the Slop Tanks can be removed overboard using the Oil Discharging Monitoring (ODM) system.

After washing the tanks with crude oil, it is necessary to flush the entire washing pipeline with sea water into the settling tank, then bring the oxygen content to 21% by ventilation, reduce the concentration of explosive substances and gases to the required levels. Then select the residues, while monitoring the content of O2, RH, explosives with constant ventilation.

If the terms of the contract require, then after the completion of the washing of the tanks with sea water, they are rinsed with fresh water for 10-15 minutes, then they are inert.

Rice. 8 Intermediate condition of a cargo tank during washing in an inert atmosphere (soot from inert gases on the bulkhead)

Stripping system. Cleaning of cargo tanks is understood as the process of removing oil residues from the bottom, walls and a layer of oil residues after the main cargo has been drained. After unloading oil products, about 1% of the cargo remains in the tanks, which depends on the cargo and stripping systems, the presence of heating, the design of the ship, etc.

There are three ways to clean the surfaces of cargo tanks of oil tankers: manual, mechanized and chemical-mechanized. This division is conditional, since each of these methods uses manual labor to some extent.

Manual way This is a low performance method that requires a lot of time and money. The procedure for stripping cargo tanks is as follows. After pumping with cold sea water, each tank is subjected to steam steaming for several hours. When the temperature in the tanks drops to 30-40 ° C, they are ventilated and two washers are sent, who roll up all the surfaces of the tanks from hoses with hot water (30-45 ° C). Washers should be fully dressed in protective clothing and use hose or self-contained breathing apparatus.

mechanized way is carried out with water, which is supplied to the tanks under pressure through special washing machines. Washing is carried out mainly with outboard water of various temperatures or detergent solutions.

Chemical-mechanized method- this is the cleaning of tanks with the same means as with the mechanical method, but instead of water, various detergents are used.

The stripping system includes positive displacement pumps, centrifugal self-priming pumps or ejectors; must be equipped with valves to enable the shutdown of any tanks that are not being stripped. The stripping pipeline is laid along the bottom of the cargo tank. Bandwidth cleaning system should be 1.25 times greater than the flow of all washing machines operating simultaneously at any stage of washing.

The stripping system must be equipped with control devices: counters, pressure gauges, which must have means of remote display of controlled parameters in the cargo operations control post (PU-GO).

To effectively control the operation of the stripping system, level indicators and means of manually measuring the level in the tanks should be provided.

To drain any cargo pumps and pipelines to the onshore reception facilities, a special pipeline of small diameter should be provided, connected to the drain side of the valves of the intake and discharge pipes on both sides.

Gas exhaust system. If, during ballast acceptance, loading, or internal movements of ballast or cargo, the internal pressure rises above the control level, the tank may burst. If the internal pressure drops below atmospheric pressure, then the tank can collapse inward, which will lead to the same catastrophic consequences.

Intensive evaporation of oil products, especially light grades, changes in cargo volumes with sharp fluctuations in air and water temperatures necessitate the equipment of cargo tanks with gas exhaust systems (Fig. 9). There are two types of gas exhaust systems: separately for each cargo tank and for servicing a group of tanks. Separate venting devices should rise above the cargo deck by at least 2.5 m.

Rice. 9 Common exhaust pipe

The group gas venting system is supplied with a common line, to which pipes from each cargo tank fit, venting gases from the upper points of the section. The common line ends with a vertical pipe laid along the masts or columns that discharge oil vapors into the atmosphere.

Gas pipes are made in such a way that water and oil cannot stagnate in them. In the lowest sections of the pipe, drain cocks should be provided, and the upper holes should be closed with protective caps to protect against atmospheric precipitation. Pipes from each cargo tank shall be provided with fire-protective structures. Their purpose is to prevent the flame from a burning tank from entering the neighboring ones.

The gas exhaust system is equipped with breathing valves (pressure/vacuum) operating in automatic mode (Fig. 10). The purpose of these valves is to maintain a certain pressure in the tank. Prior to loading, the breathing valves of the venting system (pressure/vacuum) must be opened.

At the end of cargo operations, the breathing valves are set to automatic mode. To prevent the ingress of oil vapors into the ship's spaces, it is necessary to close the portholes and doors leading to these spaces before loading. Switch the air conditioning system to closed-loop operation.

Rice. 10 Pressure/vacuum valve

Inert gas systems(WHITEFISH). Cargo tanks are filled with inert gas in order to prevent an explosion or fire in the cargo tanks. This is explained by the fact that the inert gas has a low oxygen content. CIG produces an inert gas with an oxygen content typically not exceeding 5% of the total volume.

Sources of inert gas on tankers are:

flue gas from marine boilers;
autonomous inert gas generator;
gas turbine equipped with a fuel afterburner.

Any source of inert gas must be cooled and flushed with water to remove soot and sulfuric acid before being supplied to cargo spaces.

Components of the system:

The scrubber (SCRUBBER) is designed to cool the flue gas coming from the boiler, remove sulfur dioxide almost completely and separate soot particles (all three processes take place using sea water).
Inert gas blowers are used to supply purified inert gas to cargo tanks.

The inert gas is loaded into the ship's tanks in two ways using:

branch pipes of the main inert system for each tank;
connection of the inert system to the cargo lines.

Cargo tanks should be inerted when they contain a cargo of oil, dirty ballast or when they are empty after unloading but not degassed. The oxygen content in the tank atmosphere should not exceed 8% by volume with a positive gas pressure of at least 100 mm of water column. If the vessel has been degassed, the tanks must be inerted before loading. In the process of washing with crude oil, inertization of tanks is mandatory.

Replacing the atmosphere of the tank. If the gas-air mixture from a tank could be displaced by an equivalent volume of inert gas, then the atmosphere of this tank would have the same oxygen content as the incoming inert gas. This is practically impossible, and a volume of inert gas equal to several tank volumes is introduced into the tank before the desired result is achieved. The atmosphere in the tank is replaced with an inert gas by inerting or by blowing. In both cases, one of the two processes, dilution or substitution, will predominate.

Dilution(dilution). The incoming inert gas is mixed with the original atmosphere of the tank to obtain some kind of homogeneous gas mixture throughout the entire volume of the tank. When starting the SIG, the supplied inert gas must have a high velocity sufficient to reach the bottom of the tank. To do this, it is necessary to limit the number of tanks that can be inerted at the same time.

substitution(displacement). This is when the hydrocarbon gas, being heavier than the inert gas, is squeezed out through a pipeline connected to the bottom of the tank. When using this method, the inert gas must have a very low speed filing. This method allows you to inertize or purge several tanks at the same time.

Cargo tank atmosphere control. The states of the atmosphere of cargo tanks are subdivided as follows:

depleted - this is the atmosphere, the ignition of which is excluded due to the deliberate reduction of hydrocarbon gas to a value below the lower flammable limit (LEL);
with an unspecified gas composition is an atmosphere whose gas content may be below or above the flammable limit, or in this range;
supersaturated is an atmosphere whose gas content exceeds the established flammability limit;
inertized is an atmosphere whose ignition is excluded due to the introduction of an inert gas into it, followed by a decrease in the oxygen content in it (not higher than 8% by volume).

Rice. 11 Gas analyzer - tankoscope

To measure the gas composition of cargo tanks, the following instruments should be on board the ship (Fig. 11 - 14):

flammable gas indicator, which determines the percentage of gas in the depleted atmosphere of the tank;
tankoscope - a gas analyzer for determining the percentage of hydrocarbon gas in an inerted atmosphere;
a gas analyzer that determines the concentration of hydrocarbon gas in excess of 15% by volume in a supersaturated atmosphere;
oxygen meter - oxygen content analyzer;
a device that determines the concentration of toxic gases within the limits of their toxic effects on humans.

Rice. 12 Device - gas analyzer of the environment

Rice. 13 Device - oxygen meter

Rice. 14 Hand pump with drager tubes

The degree of protection provided by SIG depends on proper operation and Maintenance systems as a whole. It is important to ensure the correct functioning of the means of protection against the return of gas, especially deck water seals and non-return valves to prevent the outflow of petroleum gas or liquid oil into the engine room and other areas of the ship where the inert gas installation is located (Fig. 15).

Rice. 15 Deck hydraulic lock