The oil and gas industry is rightfully considered one of the most high-tech industries in the world. Equipment used for oil and gas production numbers hundreds of thousands of items, and includes a variety of devices - from elements shut-off valves, weighing several kilograms, to gigantic structures - drilling platforms and tankers, of gigantic size, and costing many billions of dollars. In this article we will look at the offshore giants of the oil and gas industry.

Gas tankers of Q-max type

The largest gas tankers in the history of mankind can rightfully be called tankers of the Q-max type. "Q" here stands for Qatar, and "max"- maximum. A whole family of these floating giants was created specifically for the delivery of liquefied gas from Qatar by sea.

Ships of this type began to be built in 2005 at the company's shipyards Samsung Heavy Industries- shipbuilding division of Samsung. The first ship was launched in November 2007. He was named "Moza", in honor of the wife of Sheikh Moza bint Nasser al-Misned. In January 2009, having loaded 266,000 cubic meters of LNG in the port of Bilbao, a vessel of this type crossed the Suez Canal for the first time.

Q-max type gas carriers are operated by the company STASCo, but are owned by the Qatar Gas Transmission Company (Nakilat), and are chartered primarily by Qatari LNG producing companies. In total, contracts for the construction of 14 such vessels have been signed.

The dimensions of such a vessel are 345 meters (1,132 feet) long and 53.8 meters (177 feet) wide. The ship is 34.7 m (114 ft) tall and has a draft of about 12 meters (39 ft). At the same time, the vessel can accommodate a maximum volume of LNG equal to 266,000 cubic meters. m (9,400,000 cubic meters).

Here are photographs of the largest ships in this series:

Tanker "Moza"- the first ship in this series. Named after the wife of Sheikh Moza bint Nasser al-Misned. The naming ceremony took place on July 11, 2008 at the shipyard Samsung Heavy Industries in South Korea.

tanker« BU Samra»

Tanker« Mekaines»

Pipe-laying vessel “Pioneering spirit”

In June 2010, a Swiss company Allseas Marine Contractors entered into a contract for the construction of a vessel designed to transport drilling platforms and lay pipelines along the bottom of the sea. The ship named "Pieter Schelte", but later renamed , was built at the company's shipyard DSME (Daewoo Shipbuilding & Marine Engineering) and in November 2014 departed from South Korea to Europe. The vessel was supposed to be used for laying pipes South Stream in the Black Sea.

The ship is 382 m long and 124 m wide. Let us remind you that the height of the Empire State Building in the USA is 381 m (up to the roof). The side height is 30 m. The vessel is also unique in that its equipment allows laying pipelines at record depths - up to 3500 m.

in the process of completion afloat, July 2013

at the Daewoo shipyard in Geoje, March 2014

in the final stage of completion, July 2014

Comparative sizes (upper deck area) of giant ships, from top to bottom:

• the largest supertanker in history, "Seawise Giant";
• catamaran "Pieter Schelte";
• the world's largest cruise ship "Allure of the Seas";
• the legendary Titanic.

Photo source - ocean-media.su

Floating liquefied natural gas plant "Prelude"

The following giant has comparable dimensions to the floating pipe layer - "Prelude FLNG"(from English - “floating plant for the production of liquefied natural gas “ Prelude"") - the world's first plant for the production liquefied natural gas (LNG) placed on a floating base and intended for the production, treatment, liquefaction of natural gas, storage and shipment of LNG at sea.

To date "Prelude" is the largest floating object on Earth. The closest ship in size until 2010 was an oil supertanker "Knock Nevis" 458 meters long and 69 meters wide. In 2010, it was cut into scrap metal, and the laurels of the largest floating object went to the pipelayer "Pieter Schelte", later renamed to

In contrast, the platform length "Prelude" 106 meters less. But it is larger in tonnage (403,342 tons), width (124 m) and displacement (900,000 tons).

Besides "Prelude" is not a ship in the exact sense of the word, because does not have engines, having on board only a few water pumps used for maneuvering

The decision to build a plant "Prelude" was taken Royal Dutch Shell May 20, 2011, and construction was completed in 2013. According to the project, the floating structure will produce 5.3 million tons of liquid hydrocarbons per year: 3.6 million tons of LNG, 1.3 million tons of condensate and 0.4 million tons of LPG. The weight of the structure is 260 thousand tons.

Displacement when fully loaded is 600,000 tons, which is 6 times more than the displacement of the largest aircraft carrier.

The floating plant will be located off the coast of Australia. This unusual decision to locate an LNG plant at sea was caused by the position of the Australian government. It allowed gas production on the shelf, but categorically refused to locate a plant on the shores of the continent, fearing that such proximity would adversely affect the development of tourism.

The emergence of a tanker fleet is a relatively new phenomenon. The first tankers appeared at the end of the 19th century. Until this time, technical solutions did not allow large quantities of bulk liquids, such as oil, to be transported in 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 19th century. The demand for oil has increased due to the development of energy in a number of countries, and technological innovations have made it possible to build a new class of ships - tankers designed to transport large quantities of crude oil and petroleum products in their 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 liquid cargo, such as petroleum products and crude oil, has caused an increase in the size and capacity of tankers.

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

Rice. 2. The location of the main channels limiting the growth of tanker fleet dimensions, and the corresponding maximum dimensions for each class of tanker.

Single-hull tankers built in 1970-80. around the world have been replaced by double-hulled tankers designed to prevent environmental pollution.

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

Oil - oil; Ocean - ocean; Steel 1-1/2” (or less thick) - steel 1-1/2” thick (or less); 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 - on a single-bottom tanker, only one layer of steel measuring 1-1/2” thick separates the transported oil and the ocean; Double bottom - double bottom.

A double bottom does not prevent an oil spill, but even in the most severe case, such as the Exxon Valdez tanker, experts say it can reduce the amount of oil that ends up in 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 runs aground, some oil will leak into the ocean. But ships of this project should be better protected from collisions than tankers with a double hull, although there is no practical evidence of this.
Double hull - double hull.
Double hull boats provide better cargo protection due to their double bottom and double sides. For a tanker with a double hull, the distance between the side and the longitudinal bulkheads should be 1/15 of the width of the tanker or from 2 to 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 along 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 safety measures are also taken. Basically, these are increased requirements for the strength of the hull and cargo tanks and the absence of cargo leakage in the event of an accident.

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

Mooring winches - mooring winches. Installing a superstructure over 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 pipelines can supply 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 - points for receiving and unloading cargo: 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-blade propellers move the ship forward. Each propeller weighs 53 tons and is the size of a three-story building; Rudders - rudders.

The main questions that arise when building a tanker:

Body contours

The hull contours of any vessel are one of its most important characteristics. The design of a tanker for transporting petroleum products is a weight-based design, that is, the dimensions of the vessel are directly related to the weight of the cargo being transported. (For other classes of ships, for example, for container ships, the design may depend on the volume of cargo transported - volume-based), where dimensions are determined by the volume of cargo space, cargo holds). Since it is desirable that the weight of the cargo transported during one voyage, in this case oil, be the maximum possible, it is necessary to provide the maximum possible dimensions of space for cargo tanks. Typically, tankers move at a relatively low speed, since the cargo is not perishable, as in the case of transporting food products. All these mentioned factors are taken into account when designing the tanker hull contours. In other words, a 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 actually determines the design of the tanker, is the General Arrangement Drawing. In Fig. Figure 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 ship, frame by frame, bulkheads and other main structure of the ship.

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

Bulbous nose

Today, almost all tankers have a bulbous bow, which increases efficiency when the vessel moves. 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 ships.

There are three types of nasal bulb, they are presented in Fig. 7 (when viewed from the bow to the stern of the ship).

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

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

The "Nabla" type bulb has a teardrop shape with a large volume at the top. This type of bulb is used on ships where special attention is paid to ensuring seaworthiness, for example, on Navy ships.

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

Tanker kit design

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

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

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

Double hull tanker set

As mentioned earlier, all tankers over 120m in length are now double-hulled to prevent marine pollution in the event of accidents, in accordance with MARPOL regulations. Tankers of the Panamax, Aframax, Suezmax, VLCC and ULCC classes have a double-hull set. The main reason for using a two-hull set 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 - knitsa; Inner bottom - internal bottom; Intermediate stringer - intermediate stringer; Wing tank - onboard tank; Longitudinal bulkhead - longitudinal bulkhead; Inner hull - inner housing; Deck-transverse web - below-deck frame frame; Center tank - central tank; Transverse web - frame frame.

In Fig. 8. shows a cross-section of the longitudinal frame of a double-hull tanker. In the right half of Fig. 8. shows a regular frame; sheets of inner and outer skin are attached to the stringers. The central tank is a cargo tank, and the side 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 cross-sectional strength of the vessel. Longitudinal stiffeners are welded to the frames. Stringers attached to the frames further increase the strength of the tanker hull.

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

Ship power plant (SPU) of a tanker

Since tankers are relatively slow-moving vessels (average maximum speed is 15.5 knots) and do not have spatial restrictions for engine placement, large low-speed marine diesel engines can be used as main engines. This type of engine takes up more space than high-speed marine engines, but provides more efficient power transfer to the propeller shaft, and there are no gearbox losses because the RPM of the engine shaft matches the RPM of the propeller. Tankers typically use large-diameter, low-rpm propellers to improve efficiency when propelling the vessel.

Tanker onboard systems

Tankers have a number of onboard systems that are unique in their purpose.

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

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 avoids the accumulation of hazardous vapors and gases in enclosed spaces of cargo tanks.

Overflow Control System:

This system uses level sensors and pressure sensors to monitor oil levels in cargo tanks to ensure that oil levels during loading and unloading operations do not exceed specified limits. Alarm sensors and drain valves are included in the system to prevent extreme situations.

Inert gas supply system:

The space between the free surface of the cargo in the tank and the top sheets of the tank must be filled with inert gas to prevent the access of oxygen in order to avoid a fire hazard in case of accumulation of flammable vapors and gases. This is achieved by constantly supplying inert gas and monitoring its level in the tanks. Argon and carbon dioxide are most often used for these purposes.

Chapter 11 FEATURES OF WORK ON A TANKER

11.1. TANKER CATEGORIES

IN Depending on the deadweight (DWT), tankers are divided into the following categories:

− GP – small-tonnage tankers (6000 – 16499 DWT) are used for special transportation;

− GP - general purpose tankers (16500 – 24999 DWT) are used to transport petroleum products;

− MR – medium-tonnage tankers (25,000 – 44,999 DWT) are used to transport oil or petroleum products;

− LR1 – (Super Tanker) – large-capacity 1st class tankers (45,000 – 69,999 DWT) are used for transporting dark oil products;

− LR2 – (Mammoth Tanker) – large-capacity tankers of class 2 (70000 – 149999 DWT);

− VLCC – (Very Large Crude Carrier) – large-capacity tankers of class 3 (150,000 – 300,000 DWT);

− ULCC – (Ultra Very Large Crude Carrier) – supertankers (more than 300,000 DWT).

IN Depending on the type of cargo transported, tankers are divided into:

1. Tankers are liquid vessels designed for transportation in bulk in special cargo spaces - tanks (containers) of liquid cargo, mainly petroleum products (oil tankers) (Fig. 11.1).

2. gas carriers (Liquefied Gas Tankers) are tankers designed to transport natural and petroleum gases in a liquid state under pressure and (or) at low temperatures, in specially designed cargo tanks of various types. Some types of ships have a refrigerated compartment (Fig. 11.2).

3. Chemical tankers (Chemical Tankers) are tankers designed for transporting liquid chemical cargo; the cargo system and tanks are made of special stainless steel or coated with special acid-resistant materials.

11.2. TANKER HULL DESIGN FEATURES

The design of the tanker set is determined by the type of cargo being transported. The presence of free liquid surfaces in cargo tanks negatively affects the stability of the vessel, reducing its metacentric height. To reduce this effect, two or three longitudinal bulkheads are installed, passing through the entire ship, and transverse bulkheads, the distance between which is much less than in dry cargo ships.

Ensuring the strength of the hull of a large-capacity tanker (DWT >45,000 t) is achieved by using a longitudinal bracing system (Fig. 11.3, 11.4).

Rice. 11.3. Cross-section of a tanker hull with a longitudinal framing system: 1, 2, 3 – below-deck, side and bottom stiffeners;

4 – bottom brackets; 5 – vertical keel; 6 – flor; 7 – longitudinal bulkheads; 8 – frame frame; 9 – frame beam; 11 – carlings; 12 – below-deck brackets

Tankers designed to operate in ice conditions are built using a combined recruitment system.

Oil tankers with a deadweight of 20,000 tons or more and oil product carriers with a deadweight of more than 30,000 tons must have segregated ballast tanks (S.B.T. - Segregated Ballast Tanks), the capacity of which must be such that the ship can safely make ballast passages without resorting to the use of oil tanks for water ballast ( Fig. 11.5). The insulated ballast tanks are located in a double hull and double bottom.

Rice. 11.4. Tanker hull on stocks

Every tanker with a deadweight of more than 20,000 tons or more must be equipped with a system for cleaning cargo tanks by means of crude oil washing (Crude Oil Washing).

An oil tanker with a deadweight of 70,000 tons or more must have at least two slop tanks. The volume of these tanks must allow for tank washing with crude oil and subsequent separation of the collected oil residues from the water.

Rice. 11.5. Cargo tank

G.N. Sharlay. Features of working on a tanker

11.3. OIL TANKER CARGO UNIT

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

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

1) pipelines;

2) cargo pumps;

3) stripping system;

4) cargo heating system;

5) crude oil tank washing system;

6) inert gas system and gas exhaust system. Pipelines. For loading and unloading liquid cargo at oil loading

On all ships, a special cargo system is installed, consisting of receiving and unloading lines (Fig. 11.6).

Rice. 11.6. Deck piping

Receiving (suction) pipeline laid in cargo tanks.

Each cargo pump has a separate main pipeline, from which receiving branches, locked by valves or clinches, go to a certain group of tanks. Such wiring of the suction pipeline makes it possible to independently receive and pump out several different types of petroleum products.

Discharge (pressure) pipeline starts at cargo pumps ver-

teak pipes going to the upper deck. Then the main line is laid along the deck and branches go from it to the sides, to which during loading and lifting

The load is connected to flexible hoses or terminal stands supplied from the shore. Deck main pipelines are connected by vertical pipes (risers) to main pipelines laid in tanks.

The cargo and stripping pipelines are located at the bottom of the cargo tank. On combined OVO vessels, pipelines pass under the bottom in double bottom tunnels.

Various cargo line systems are installed on tankers, but three main systems should be noted: ring, linear and bulkhead.

Ring system(Fig. 11.7) - this system is used on small tankers with two longitudinal bulkheads and two pump rooms - bow and central. Two pump rooms divide the cargo tanks into 3 independent groups with independent deck pipelines, allowing three types of cargo to be loaded 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 the many jumpers and the difficulty in cleaning tanks located aft of the pump room when the tanker is trimmed aft.

Rice. 11.7. Ring freight line: Fig. 11.8. Linear cargo line: 1 – deck receivers; 2 – kingstons; 3 – cargo pumps; 4 – tank receivers

Linear system(Fig. 11.8) - used using centrifugal pumps located in the pump room at the stern 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 closes a group of tanks. Lines and groups of tanks closed on them can be connected and 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.

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

G.N. Sharlay. Features of working on a tanker

The advantage of the system is the small number of installed pipelines, which reduces the cost of building a tanker. The disadvantage is the limited capabilities 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 using gate valves or valves. The most common valves on tankers are the butterfly system valves, with a vertical or horizontal axis of rotation of the plate.

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

Load valves are usually controlled remotely using hydraulic systems that are widely used.

Cargo pumps (Fig. 11.9). For unloading, the tanker has 3–4 cargo pumps. They are located in the lower part of the pump compartment; the compartment itself is located between the engine room and the cargo tanks. Centrifugal-type cargo pumps are widely used on tankers, which have a number of advantages - simplicity of design, low weight and dimensions, high productivity. The vast majority of tankers use piston pumps as stripping pumps.

Rice. 11.9. Cargo pump

Rice. 11.10. Cargo heating system

Pumps supplying crude oil to cargo tank washers shall be cargo pumps or pumps specifically designed for this purpose.

Cargo heating system(Fig. 11.10). Oil tankers carrying viscous petroleum products have a cargo heating system. Petroleum 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. The coils are laid along the entire bottom of the tank at a height of about 10 cm from it. Sometimes the system consists of separate sections installed in different parts of the tanks. Valves for controlling the cargo heating system are usually located on the deck.

During the process of heating the cargo, the tightness of the coils is controlled through the drain valve. 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 condensation after use.

Crude oil tank washing system consists of tanks for washing solution, collection and storage of petroleum products, deck pipelines for supplying washing solution to washing machines, pump, heater, portable equipment.

Washing all or part of the tanks is necessary before changing cargo, before docking the tanker, or for repairs. Also, tanks are washed using clean ballast, with which the ship arrives at the port of loading and which can be discharged overboard in port waters.

Tank washing is carried out using special washing machines with rotating nozzles. Machines for washing tanks with crude oil must be stationary and have a design approved by the Register (Fig. 11.11). Each machine must be turned on using a shut-off valve. The number and location of washing machines must ensure effective cleaning 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 perform a full cycle of work within a certain time. Tank washers are powered by oil from the cargo pumps, which acts on the impeller, so proper line pressure is essential for effective washing. It is preferable to use an ejector for cleaning.

Programmable machines with one nozzle can be configured to wash certain areas of the tank in 4 cycles and allow you to change the angle of raising or lowering the nozzle in increments of 1.2, 3 and 8.50.

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 washing.

Rice. 11.11. Diagram of a stationary washing machine and its controls on the deck of a tanker

G.N. Sharlay. Features of working on a tanker

Tank washing is carried out in a closed cycle (Fig. 11.12), i.e. washing water is collected in one or two settling tanks (Slop Tanks). The cleaning duration, as well as the need to use hot water and chemicals, is determined in accordance with the Tank Cleaning Guide.

Washing with crude oil is only permitted with a properly functioning inert gas installation. No tank can be flushed with crude oil without filling it with an inert gas containing no more than 8% oxygen by volume.

Fig. 11.12. Intermediate state of a cargo tank during washing in an inertized environment (on the bulkhead there is soot from inert gases)

Waste wash water, after being separated from the water in one of the Slop Tanks, can be disposed overboard using an Oil Discharging Monitoring (ODM) system.

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

If the terms of the contract or the requirements of the oil port require, then after completing the washing of tanks with sea water, they are rinsed with fresh water for 10 - 15 minutes, then inerted.

Stripping system. Cleaning of cargo tanks refers to the process of removing oil residues from the bottom, walls and accumulation of 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 cleaning systems, the presence of heating, the design of the vessel, etc.

There are three methods for cleaning 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 in one way or another.

The manual method is a low-productivity method that requires a lot of time and money. The procedure for cleaning cargo tanks is as follows. After pumping with cold sea water, each tank is steamed for several hours. When the temperature in the tanks drops to 30−40 °C, they are ventilated and two washers are sent to spray all surfaces of the tanks with hot water (30−45 °C) from hoses. Cleaners must wear full protective clothing and use breathing apparatus or self-contained breathing apparatus.

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

Chemical-mechanized The method is to clean the tanks using 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 that allow the shutdown of any tanks that are not being stripped. The stripping pipeline is laid along the bottom of the cargo tank. The throughput of the stripping 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 for remote display of controlled parameters in the cargo operations control room (PUGO, Fig. 11.15).

To effectively monitor the operation of the stripping system, level indicators and means for manual level measurement in tanks must be provided.

To drain any cargo pumps and pipelines to shore reception facilities, a special small diameter pipeline must be provided, connected to the drain side of the inlet valves on both sides.

Gas exhaust system. If, during ballast receiving, loading, or internal movements of ballast or cargo, the internal pressure rises above the control level, the tank may rupture. If the internal pressure drops below atmospheric pressure, the tank can collapse inward, leading to the same catastrophic consequences.

Intense evaporation of petroleum products, especially light grades, changes in cargo volumes with sharp fluctuations in air and water temperatures necessitate the need to equip cargo tanks with gas exhaust systems (Fig. 11.13). There are two types of gas exhaust systems: separately for each cargo tank and for servicing a group of tanks. Individual gas outlet devices must rise above the cargo deck by at least 2.5 m.

The group gas exhaust system is supplied with a common line, to which pipes from each cargo tank are connected, removing gases from the upper points of the compartment. The common line ends with a vertical pipe laid along masts or columns that discharge vapors of petroleum products into the atmosphere.

Gas outlet pipes are made in such a way that water and oil cannot stagnate in them. In the lowest sections of the pipe, there should be drain taps, and the upper openings should be closed with protective caps to protect against precipitation. Fire-retarding structures must be installed on the pipes leading from each cargo tank. Their purpose

– prevent flames from a burning tank from reaching neighboring ones. The gas exhaust system is equipped with breathing valves (pressure

tion/vacuum), operating in automatic mode (Fig. 11.14). The purpose of these valves is to maintain a certain pressure in the tank.

Before loading begins, the breathing valves of the gas exhaust system (pressure/vacuum) must open.

Upon completion of cargo operations, the breathing valves are set to automatic mode. To prevent the entry of petroleum product vapors into the ship's premises, it is necessary to have portholes, doors, leading

G.N. Sharlay. Features of working on a tanker

into these rooms, close tightly. Switch the air conditioning system to closed cycle operation.

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

Sources of inert gas on tankers can be:

− flue gas from the main or auxiliary ship boilers;

− autonomous inert gas generator;

− gas turbine equipped with a fuel afterburning chamber.

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

Components of the system (Fig. 11.16):

1. The gas scrubber (SCRABBER) 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 with a large use of sea water).

2. Inert gas blowers are used to supply purified inert gas to cargo tanks.

Inert gas is loaded into ship tanks in two ways using:

− pipe bends of the main inert system for each tank;

− connecting the inert system to the cargo lines.

Cargo tanks must 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 water column. If the ship has been degassed, the tanks must be inerted before loading. During the crude oil washing process, inerting the tanks is mandatory.

Tankers are vessels designed to transport oil from production sites to oil refineries. Increasing needs and the desire to get maximum profit have led to the creation of supertankers, striking in their size and being the largest ships in the world.

They are also called tankers, emphasizing their purpose (for the delivery of liquid cargo: oil, gas, wine, oil, acids, and so on). This article will focus on the largest oil tankers in the world.

How tankers work

The body of these giants consists of a rigid frame, divided by longitudinal partitions into “tanks” (compartments filled with oil).

Modern supertankers have a double-hull structure, that is, they have an outer extremely strong hull that absorbs the impact of a possible collision, and an inner hull that is responsible for transporting dangerous cargo. These vessels received such a transformation in 1990 after a series of environmental disasters associated with the crash of the supertankers "Torey Canyon" (1967), "Amoco Cadiz" (1978), "Exxon Valdez" (1989), when thousands of gallons of oil spilled into the sea, causing irreparable damage to the ecosystems of Great Britain, France and Alaska.

Single and double hull oil tankers

Giant single-hull oil carriers include:

• "Crimea".
• "Torrey Canyon".
• Exxon Valdis.
• Amoco Haven and Amoco Cadiz.
• Idemitsu Maru.
• Esso Atlantic.
• Batillus.
• Knock Nevis.

They have a double-hull structure (selection from the top 10):

• Sirius Star.
• Hellespont Fairfax.

How oil ships work

Loading of “black gold” is carried out by powerful pumps located in special pumping stations equipped with ports. In order to unload the tanker, pumps are also installed on it and a special pipeline system is created, which has blocking and valves.

When the ship is loaded, the density of the oil is high, and the air temperature outside is quite low, the oil begins to be heated to reduce its viscosity and, therefore, facilitate pumping. Heating is carried out using water vapor, which flows through pipelines running directly in the tanks (compartments with oil). That is why tankers are equipped with steam boilers with enormous productivity.

Each time after raw materials are pumped out of the vessel, the tanks are thoroughly cleaned and degassed to prevent the ignition of vapors released from the cargo residues.

Characteristics

All oil carriers included in the group of supertankers have similar properties:

• Big sizes. As a rule, the length and width of these vessels are very large. Thus, the largest tanker in the world, whose dimensions are truly enormous, had a length close to 500 meters and a width of about 70 m.
• High draft when transporting cargo (For example, the Sirius Star draft when loading is 22 m).
• Huge displacement (for example, Hellespont Fairfax has a displacement of 234 thousand tons).
• Fairly high speed for ships of this size. On average 13-17 knots.
• Highest carrying capacity (Exxon Valdis transported 235 thousand tons of oil).
• Huge deadweight (total weight, which includes the weight of cargo, necessary fuel, equipment, etc.). For example, the deadweight of Batillus is almost 554 thousand tons.
• The crew size is 30-40 people.

The largest tankers in the world. Top 10

10. Supertanker "Crimea" is the largest tanker of the USSR and modern Russia. Built at the Kerch Shipyard. Launched in 1974. In 1989 it was sold to Vietnam under the name Chi Linh. Length - 295 m, width - 44.95 m, deadweight - 150,500 tons.

9. "Torey Canyon" - manufactured in the USA, this tanker crashed in 1967 on its way to England. The length of the tanker is 296.8 m.

8. "Exxon Valdis" - was built in 1985. in San Diego (California). In 1989, it crashed off the coast of Alaska, resulting in the release of 700 thousand barrels of oil. After eliminating the consequences, it was towed to the shores of San Diego and put back into service. In 2012, the tanker was scrapped in Singapore. Length - 300 m, width - 51 m, deadweight - 209,836 tons.

7. Sirius Star - was manufactured in 2008 in Geoje (South Korea). Captured by Somali pirates in November 2008. Released in 2009. The length of the tanker is 332 m, width is 58 m.

6. MT-Haven (Amoco Milford Haven) - launched in 1973 in Cadiz (Spain). Transported oil from the Middle East to ports on the Mediterranean Sea. Sank in 1991 near Genoa (Italy) as a result of a missile hit during the conflict between Iran and Iraq. Now it is one of the most visited wrecks by divers. Length - 334 m, width - 51 m, deadweight - 233,690 tons.

Amoco Cadiz is a sister tanker to MT-Haven. Amoco Cadiz began its voyage in 1975 from Cadiz (Italy). And in 1978, as a result of running aground, it broke into three parts and sank off the coast of France. The death of the ship led to one of the largest environmental disasters. About 200,000 tons of oil spilled into the sea. The length of the tanker is 334 m, width - 51 m, deadweight - 233,690 tons.

5. Idemitsu Maru - built in 1966 in Yokohama (Japan). Transported oil from the Persian Gulf to the shores of Japan. Decommissioned in 1980. Currently completely dismantled. Length - 344 m, width - 49.84 m, deadweight (absolute load capacity) - 209,413 tons.

4. Hellespont Fairfax - created in South Korea in 2002. Transports oil from Saudi Arabia to Houston. Length - 380 m, width - 68 m.

3. Esso Atlantic is the brainchild of Japanese shipbuilding masters. It was launched in 1977. Under the flag of Liberia, it transported oil from the Middle East to Western Europe. In 2002 it was disposed of in Pakistan. Length - 406.5 m, deadweight - 516,891 tons.

2. Batillus - launched in France in 1976. Transported oil from the Persian Gulf to Northern Europe. Decommissioned and completely dismantled in Taiwan in 1985. Length - 414.22 m, width - 63 m, deadweight - 553,662 tons.

1. Knock Nevis is the largest oil tanker in the world. Was built in 1976 in Japan. Let's pay a little more attention to the leader.

Knock Nevis. Giant's story

The largest oil tanker in the world began its journey in 1976 in Japan, and was then transferred to the ownership of a Greek tycoon. Initially, the dimensions of the vessel were as follows: length - 376.7 m, width - 68.9 m, and deadweight - 418,610 tons. It was propelled by a huge steam turbine with a capacity of 50 thousand horsepower, and a speed of 16 knots was provided by an incredibly large propeller with four blades. During factory tests, strong vibration of the hull was detected, which became the reason for the refusal of the Greek owners to accept the vessel. In 1976, the largest tanker in the world was transferred to SHI, where it was given the name Oppama.

After this, the tanker came into the possession of a Hong Kong shipowner, and large-scale processing of the vessel began. In 1981, the giant received the name Seawise Giant, now its length has increased to 485 m, its width to 68.86 m, and its deadweight is 564,763 tons.

The largest tanker in the world was supposed to transport oil from the Middle East to US ports. In 1986, during the conflict between Iran and Iraq, the ship was damaged by an anti-ship missile and was officially considered sunk.

In 1988, the Norwegian company Norman bought, raised and restored the ship, giving it the name Happy Giant.

In 1991, the tanker again changed its name and owner. It became known as Gehre Viking and was owned by the Norwegian company Loki Stream AS.

Due to its structure (the tanker was single-hulled), the ship could not enter the ports of Europe and the USA (in accordance with the law on double-hulled ships), and therefore in 2004 it changed owners again, was named Knock Nevis and was converted into an oil storage facility off the coast of Qatar.

In 2010, the largest tanker in the world was renamed for the last time (it was now called Mont) and, under the flag of Sierra Leone, was sent to India for disposal.

One of the anchors of this huge ship is on display at the Hong Kong Maritime Museum.

What is the largest tanker in the world

There is still debate among experts about which of the giant tankers should be given the well-deserved first place. This is due to the fact that the original dimensions of the Knock Nevis were: length - 376.7 m, and deadweight - 418,610 tons, and only after reworking the ship turned into a real colossus with a length of 458.45 m, deadweight of 564,763 tons and a displacement of 657,000 tons.

The initial dimensions of his opponent Batillus were as follows: length - 414.22 m and deadweight - 553,662 tons, in addition, Batillus was not subject to modifications and did not change its purpose.

Future technologies

Very soon, the largest tanker in the world (photo above) will hand over the palm among the largest ships to truly huge floating cities with offices, parks, residential buildings and roads. The project of such a city called "Green Float" was developed by a Japanese company and will soon be implemented.

Another equally ambitious plan for a floating city, Eco Atlantis, is being implemented by a company from China, China Communications. The city is being built near the coast of Nigeria.

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 structure of a tanker is a whole complex of special devices and systems. It includes:

1. pipelines;
2. cargo pumps;
3. stripping system;
4. cargo heating system;
5. crude oil tank washing system;
6. inert gas system and gas exhaust system.

Rice. 1 Scheme 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

Receiving (suction) pipeline laid in cargo tanks. Each cargo pump has a separate main pipeline, from which receiving branches, locked by valves or clinches, go to a certain group of tanks. Such wiring of the suction pipeline makes it possible to independently receive and pump out several different types of petroleum products.

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

The cargo and stripping pipelines are located at the bottom of the cargo tank. On combined OVO vessels, pipelines pass under the bottom in double bottom tunnels.

Various cargo line systems are installed on tankers, but three main systems should be noted: ring, linear and bulkhead-clinquet.

Ring system(Fig. 3) - this system is used on small tankers with two longitudinal bulkheads and two pump rooms - bow and central. Two pump rooms divide the cargo tanks into 3 independent groups with independent deck pipelines, allowing three types of cargo to be loaded 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 the many jumpers and the difficulty in cleaning tanks located aft of the pump room when the tanker is trimmed aft.

Linear system(Fig. 4) - 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 closes a group of tanks. Lines and groups of tanks closed on them can be connected and 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 - kingstons; 3 - cargo pumps; 4 — tank receivers
Rice. 4 Linear cargo line: 1 - deck receivers; 2 - kingstons; 3 - cargo pumps; 4 — tank receivers

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

The advantage of the system is the small number of installed pipelines, which reduces the cost of building a tanker. The disadvantage is the limited capabilities 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 using gate valves or valves. The most common valves on tankers are the butterfly system valves, with a vertical or horizontal axis of rotation of the plate.

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

Load valves are usually controlled 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 compartment; the compartment itself is located between the engine room and the cargo tanks. Centrifugal-type cargo pumps are widely used on tankers, which have a number of advantages - simplicity of design, low weight and dimensions, high productivity. The vast majority of tankers use piston pumps as stripping pumps.

Rice. 5 Cargo pump on a ship

Pumps supplying crude oil to cargo tank washers shall be cargo pumps or pumps specially designed for this purpose.

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

During the process of heating the cargo, the tightness of the coils is controlled through the drain valve. 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 condensation after use.

Rice. 6 Cargo heating system

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

Washing all or part of the tanks is necessary before changing cargo, before docking the tanker, or for repairs. Also, tanks are washed using clean ballast, with which the ship arrives at the loading port and which can be discharged overboard into.

Tank washing is carried out using special washing machines with rotating nozzles. Machines for washing tanks with crude oil must be stationary and have a design approved by the Register (Fig. 7). Each machine must be turned on using a shut-off valve. The number and location of washing machines must ensure effective cleaning 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 perform a full cycle of work within a certain time. Tank washers are powered by oil from the cargo pumps, which acts on the impeller, so proper line pressure is essential for effective washing. It is preferable to use an ejector for cleaning.

Programmable machines with one nozzle can be configured to wash certain areas of the tank in 4 cycles and allow you to change the angle of raising or lowering the nozzle in increments 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 washing.

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

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

Washing with crude oil is only permitted with a properly functioning inert gas installation. No tank can be flushed with crude oil without filling it with an inert gas containing no more than 8% oxygen by volume.

Waste wash water, after being separated from the water in one of the Slop Tanks, can be disposed overboard using an Oil Discharging Monitoring (ODM) system.

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

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

Rice. 8 Intermediate state of a cargo tank during washing in an inertized environment (on the bulkhead there is soot from inert gases)

Stripping system. Cleaning of cargo tanks refers to the process of removing oil residues from the bottom, walls and accumulation of 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 cleaning systems, the presence of heating, the design of the vessel, etc.

There are three methods for cleaning 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 one degree or another.

Manual method- This is a low-productivity method that requires a lot of time and money. The procedure for cleaning cargo tanks is as follows. After pumping with cold sea water, each tank is steamed for several hours. When the temperature in the tanks drops to 30-40 °C, they are ventilated and two washers are sent to roll all the surfaces of the tanks with hot water (30-45 °C) using hoses. Cleaners must wear full protective clothing and use breathing apparatus or self-contained breathing apparatus.

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

Chemical-mechanized method- this is cleaning tanks using 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 that allow the shutdown of any tanks that are not being cleaned. The stripping pipeline is laid along the bottom of the cargo tank. The throughput of the stripping 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 for remote display of controlled parameters in the cargo operations control post (CUGO).

To effectively monitor the operation of the stripping system, level indicators and means for manual level measurement in tanks must be provided.

To drain any cargo pumps and pipelines into onshore reception facilities, a special small-diameter pipeline must be provided, connected to the drain side of the inlet pipe valves on both sides.

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

Intense evaporation of petroleum products, especially light grades, changes in cargo volumes with sharp fluctuations in air and water temperatures necessitate equipping 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. Individual gas outlet devices must rise above the cargo deck by at least 2.5 m.

Rice. 9 Common gas outlet pipe

The group gas exhaust system is supplied with a common line, to which pipes from each cargo tank are connected, removing gases from the upper points of the compartment. The common line ends with a vertical pipe laid along masts or columns that discharge vapors of petroleum products into the atmosphere.

Gas outlet pipes are made in such a way that water and oil cannot stagnate in them. In the lowest sections of the pipe, there should be drain taps, and the upper openings should be closed with protective caps to protect against precipitation. Fire-retarding structures must be installed on the pipes leading from each cargo tank. Their purpose is to prevent flames from a burning tank from reaching 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. Before loading begins, the breathing valves of the gas exhaust system (pressure/vacuum) must open.

Upon completion of cargo operations, the breathing valves are set to automatic mode. To prevent petroleum product vapors from entering the ship's premises, it is necessary to close the portholes and doors leading to these premises tightly 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 to prevent explosion or fire in cargo tanks. This is explained by the fact that the inert gas has a low oxygen content. SIG 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 ship boilers;
• autonomous inert gas generator;
• gas turbine equipped with a fuel afterburning chamber.

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

Components of the system:

1. The gas purifier (SCRABBER) 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 when seawater is used).
2. Inert gas blowers are used to supply purified inert gas to cargo tanks.

Inert gas is loaded into ship tanks in two ways using:

• pipe bends of the main inert system for each tank;
• connecting the inert system to the cargo lines.

Cargo tanks must 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 ship has been degassed, the tanks must be inerted before loading. During the crude oil washing process, inertization of tanks is mandatory.

Replacing the tank atmosphere. If the gas-air mixture from the tank could be displaced by an equal volume of inert gas, then the atmosphere of this tank would end up having the same level of oxygen content as in the incoming inert gas. In practice this is 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 inert gas by inerting or purging. In both cases, one of two processes will predominate - dilution or substitution.

Dilution(dilution). The incoming inert gas is mixed with the initial atmosphere of the tank to obtain a homogeneous gas mixture throughout the entire volume of the tank. When starting the SIG, the supplied inert gas must have a high speed, 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 hydrocarbon gas, being heavier than 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 flow rate. This method allows several tanks to be inerted or purged simultaneously.

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

• lean is an atmosphere in which combustion is prevented due to the deliberate reduction of hydrocarbon gas to a value less than the lower flammability limit (LEL);
• with an unknown gas composition - this is an atmosphere whose gas content may be below or above the ignition limit, or in this range;
• supersaturated is an atmosphere whose gas content exceeds the established flammability limit;
• inerted is an atmosphere whose combustion is prevented due to the introduction of an inert gas into it with a subsequent 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 must 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 inertized atmosphere;
• a gas analyzer that determines the concentration of hydrocarbon gas over 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 the SIG depends on proper operation and maintenance of the system as a whole. It is important to ensure proper functioning of gas return controls, especially deck water seals and non-return valves to prevent the flow of petroleum gas or liquid petroleum products into the engine room and other areas of the ship where the inert gas plant is located (Fig. 15).

Rice. 15 Deck hydraulic valve

Suggested reading: