The largest tanker in the world. The largest oil tanker in the world. Offshore giants of the oil and gas industry Cargo tanker

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 around the world have been replaced by double-hulled tankers designed to prevent environmental pollution.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 vessel).

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.

Construction and operation of cargo and

To load and unload oil products or other liquid cargo and distribute cargo among tanks, tankers are equipped with special cargo pipeline systems that allow these operations to be carried out. The remaining cargo from the tanks, not selected by the cargo system, is pumped out through a stripping system, which is basically similar in design to the cargo system, but has a significantly lower capacity, a higher pump suction height and smaller pipeline diameters. On ships of small deadweight, they are limited to one system that combines the functions of cargo and stripping.

Cargo systems on tankers provide for the possibility of receiving and delivering cargo from any side and from the stern of the vessel. For this purpose, the inlet and outlet pipes of the cargo system are located in the middle part of the main deck along both sides of the vessel symmetrically to the center plane. From the system of inlet and outlet pipes, the cargo line is extended to the stern of the vessel.

Cargo operations (draining and loading of petroleum products) must be carried out with closed inspection eyes of tanks, which, in turn, are equipped with fire-retardant nets.

Displacement of air and gases from tanks during loading, as well as filling of tanks with them during draining, must be carried out through a gas outlet (“breathing”) system (see section 5).

There are several standard solutions for the implementation of cargo systems on tankers. The ring system is used on tankers in which the cargo pump room (CPS) is located in the middle of the vessel, between the cargo compartments; linear system - on tankers in which the pump room is located behind all tanks, between the cargo tanks and the MKO; cargo system with bulkhead bypass clinkets - on tankers with aft-mounted gas pumping equipment.

Ring system cargo pipeline is common on ships of early construction and small deadweight.

The system has relatively high maneuverability and survivability. The disadvantage is the high cost, large number of fittings and complexity of operation.

Linear system cargo pipeline has become most widespread, especially on large-capacity tankers. This system, compared to the ring one, is easier to operate and cheaper to build, but has less survivability (see Figure 1.1).

I-IV - group of tanks; - - - - cargo, -.-.-.-.- ballast pipelines

Figure 1.1 - Diagram of the cargo and ballast pipelines of the Leonardo da Vinci tanker

The requirements developed by Shell and British Petroleum apply to the large-tonnage tankers they charter:

The cargo system, taking into account the breakdown of the cargo tank area, must ensure the transportation of at least 2 types of cargo in the proportion of 50%:50%, or 25%:75%;

Both simultaneous and sequential unloading should be possible (partial mixing of cargo in pipelines is allowed);

The performance of the cargo system must ensure unloading (including stripping) within 15 hours at a pressure of at least 1.15 MPa;

Loading of homogeneous cargo must be carried out at an intensity of 10% per hour of the net carrying capacity, and ballast operations must be carried out simultaneously so that at any time the vessel has a load of at least 30% of the full deadweight to ensure seaworthiness;

The middle of the cargo manifold must be located amidships of the ship or no more than 3 m from it in any direction;

The height of the centers of the connecting flanges above the deck should be 0.9 m; at a higher height, a stationary working platform should be installed, spaced from the centers of the flanges at a distance of 0.9 m;

The cargo manifold must have at least four branches with flanges with a diameter of 406 mm, installed so that the distance between centers is at least 2.1 m, and the distance from the side to the DP is 4.6 m.

To connect the cargo manifold from standard valves to shore hoses, the requirements stipulate that the vessel be equipped with a set of adapter connections for flanges 101x203 mm, 101x254 mm, 101x 304 mm;

Between the clinkets of the cargo manifold and the adapters, spacers 400 mm long are installed, the support of which must be designed for a load from the hoses equal to 4 tf.

In the cargo pumping room, 2...4 cargo pumps (FP) with a capacity of (3...6) are installed. 10 3 m³/h and (9…12) . 10 3 m³/h on supertankers. Large tankers use centrifugal pumps with a steam turbine or electric drive (horizontal or vertical). The horizontal drive located in the MKO increases its length. The vertical drive (Figure 1.2) is shorter, the main drives are located lower, but it creates difficulties with its alignment.

1 - turbo drive; 2 - gas-tight seal;

3 - swivel joint; 4 - pump

Figure 1.2 - Vertical cargo pump

The GN pressure is 1.13 – 1.45 MPa. The total power of the gas pump reaches 0.5 Ne of the tanker. On old and small tankers, horizontal piston hydraulic pumps are used with a productivity of 100-400 t/h. They are characterized by a higher suction height, which ensures their use as stripping pumps (SP). Rotary pumps can also be used as pumps.

Some product carriers, gas carriers and chemical carriers use hydraulically driven submersible hydraulic pumps.

GN and ZN differ in productivity, so the time for complete stripping is 30% of the total tanker unloading time.

The presence of two redundant systems increases the cost of the ship, clutters the gas and cargo equipment, and complicates the automation of cargo operations, so there is a tendency to abandon the stripping system. Listed below are some ways to resolve this issue.

Gravity drain systems from British Petroleum (see Figures 1.3, 1.4). They are also used on the domestic tankers Sofia (see Figure 1.5).

The system is based on the free flow of oil through the bulkhead clinker doors that connect all the cargo tanks, the oil flows into the aft compartment and is taken by the gas pump, which operates at maximum productivity, and as the tanker empties, the trim to the stern increases.

An ejector is used to ensure reliable suction, operating on oil, which sucks oil from the aft compartment and pumps it into a settling tank located above the gas pump, so that the oil from it creates sufficient suction support for the gas pump (Figure 1.6).

1 - additional cutting blade on the receiving branches of the stripping pipeline; 2 and 3 - cargo and stripping pumps; 4 - deck cargo pipeline; 5 - secant blades between the inlet pipes

Figure 1.5 - Diagram of a cargo pipeline with bulkhead bypasses and clinkers for a tanker of the Sofia type (first series)

1 - stripping ejector; 2 - settling tank; 3 - pump room;

4 - cargo pump; 5 - cargo tank; 6 - receiving pipe of the cargo pump;

7 - receiving pipe of the stripping ejector

Figure 1.6 - Method of filling the cargo pump during stripping

cargo tank

"Sentry-Strip" system is equipped with a vacuum tank at the gas pump suction, in which, when the head pressure decreases, a vacuum is created, sucking in oil and increasing the gas pump head (Figure 1.7). As the level in this tank decreases, the valve on the HN suction closes (see section 2).

1 - air separator; 2 - differential pressure sensor; 3 - valve drive on discharge; 4 - butterfly valve; 5 - pneumatic valve; 6 - vacuum tank; 7 - vacuum valve; 8 - non-return valve; 9 - vacuum pump; 10 - electric drive of the vacuum pump; 11 - air filter; 12 - air filter refrigerator; 13 - vacuum gauge; 14 - pressure gauge; 15 - air supply valve.

Figure 1.7 - Scheme of the "Sentry-strip" system

There is a system with a vacuum tank that reduces the speed of the GN turbo drive as the pressure falls.

The Prima-vac system (Figure 1.8), with a decrease in backwater, increases the recirculation of oil at the suction of the centrifugal pump and prevents its failure.

All these systems increase the operating time of the GN at full capacity. An advantage is given to tankers with a double bottom, which constantly have sufficient GN support (Tankers “Crimea”, “Pobeda”, Figures 2.1, 2.2, “Mobil-Pegasus”).

1 - cargo pump; 2 - recirculation tank; 3 - Prima-vac valve;

4 - automatic valve; 5 - air outlet pipe; 6 - recirculation line; 7 - valve on the pressure line; 8 - air line control valve

There are many classifications.

4 main features of ship classification:

Transport or cargo ships

Fishing vessels

Service vessels (tugs, off-shore)

Technical fleet vessels (dredging vessels)

Classification by means of movement:

Self-propelled

Non-self-propelled

By way of movement:

Hydrofoil or hovercraft

Submarines

By sailing area:

Sea vessels of unlimited navigation

Limited sailing (up to 200 miles)

Coastal vessels

Inland navigation vessels

Mixed swimming

For special purposes:

Civil

Main types of specialized vessels

Bulk carriers: these are vessels for transporting various bulk cargoes, usually without cargo devices with large covers (Self-unloader, PIBO, OBO)

Universal vessels: these are double-deck tween-deck vessels with cargo arrangements for general cargo

Container ships: for transporting containers, have high speed, maximum utilization of cargo capacity

Refrigerated vessels: for transporting goods that require special treatment. Capable of maintaining climate and temperature conditions.

Ro-Ro vessels: ships with a horizontal loading method, for transporting cars, containers and general cargo. Cargo decks along the length of the vessel, side tanks

Lighter carriers: large floating containers. Mainly on rivers.

Semi-submersible vessels: for transporting large and heavy cargo.

Extra lifting: for transporting large and heavy loads.

Passenger ships: for transportation of liquid cargo, luggage, mail

Tanker: for transportation of liquid cargo

Offshore vessels: support vessels, fire vessels, pipe and cable laying vessels, reconnaissance vessels.

3. Classification of tankers.

GP (General Purpose) - small-tonnage tankers (6000-16,499 tons); used for special transportation, including transportation of bitumen;

GP - general purpose tankers (16,500-24,999 t); used for transportation of petroleum products;

MR (Medium Range) - medium-tonnage tankers (25000-44999 tons); for transportation of oil or petroleum products;

LR1 (Large/Long Range1) - oiler - large-capacity tankers of class 1 (45,000-79,999 tons); used for transportation of dark oil cargoes;

LR2 - large-capacity tankers of class 2 (80,000-159,999 tons);

VLCC (Very Large Crude Carrier) - large-capacity tankers of class 3 (160,000-320,000 tons);

ULCC (Ultra Large Crude Carrier) - supertankers (more than 320,000 tons); for transportation of oil from the Middle East to the Gulf of Mexico.

FSO (Floating Storage and Offloading unit) - supertankers (more than 320,000 tons); for storing and unloading oil onto smaller tankers.

4. Types of service and auxiliary fleet vessels.

Service and auxiliary vessels are divided into:

auxiliary vessels: tugs, transshipment vessels, supply vessels, floating jetties

Service vessels:

Special purpose vessels: research vessels, expeditionary vessels, hydrographic vessels, training vessels.

Service vessels: icebreakers, medical and sanitary vessels, rescue vessels, fire vessels, pilot vessels, lightships,

5. Classification of container ships.

Name	Capacity(TEU)	Characteristics
Ultra large Container ship	More than 15000	L=397mB=56mT=15.5mEmmaMaersk class vessels exceed NewPanamax class limits
New Panamax		Width up to 43m. The size of vessels of this class allows passage through the Panama Canal using new locks
Post-Panamax
Panamax		The maximum dimensions of ships of this class are: length 294.13 m, width 32.31 m, draft 12.04 m in TFW (tropical fresh water). Capable of passing through old Panama Canal locks
Fidermax
Small feeder

6. Design features of container ships

1) cargo holds are box-shaped

2) the volume of the cargo space is a multiple of the volume of a 20-foot container

3) holds have guides for containers

4) To protect deck containers, an extended side or bumper is made

5) A large number of ballast and fuel tanks

6) There are wide opening holds

7) Removable pontoon type hold covers are opentop

7. Types of containers

1) Standard 20ft and 40ft are designed for general cargo

2) Open top with removable lid

3) FLATRack type containers

4) Refrigerated containers are designed for transportation of sensitive cargo

5) Container tank

6) SideDoors container

7) 45ft containers

8) High Cube h=9.5 ft

8. Features of transportation of refrigerated containers

1) refrigerated containers must be placed in accordance with the plan of these containers

2) The use of additional electrical cables is not allowed

3) Refrigerated containers can only be placed on deck

4) Refrigerated containers cannot be stacked in more than 2 tiers

5) Refrigerated containers cannot be placed on the sea side (along the edges of the sides)

6) Refrigerated containers can only be installed in places where there are power sources intended for these containers (sockets)

Vessels carrying crude oil and petroleum products are divided into sizes. The global oil and petroleum product tanker fleet uses a classification system to standardize contract terms, set shipping costs, and classify vessels for charter contracts. The system, known as the Average Rate Assessment (AFRA) system, was created by Royal Dutch Shell six decades ago, and the London Tanker Brokers Group (LTBP), an independent group of trading brokers, oversees the system.

AFRA uses a scale that classifies tanker ships according to deadweight tons, a measure of a ship's capacity to carry cargo. A ship's estimated barrel capacity is determined using an estimated 90% of the ship's deadweight, which is multiplied by the barrel per metric ton conversion factor specific to each type of petroleum product and crude oil as the density of the liquid fuel. Vary by type and grade.

The smaller vessels on the AFRA scale - general purpose (GP) and medium range (MR) tankers - are typically used to transport cargo of petroleum products over relatively short distances, for example from Europe to the US East Coast. Their smaller size allows them to access most ports around the world. A GP tanker can carry between 70,000 barrels and 190,000 barrels of motor gasoline (3.2-8 million gallons), and an MR tanker can carry between 190,000 barrels and 345,000 barrels of motor gasoline (8-14.5 million gallons).

Long Range (LR) vessels are the most common vessels in the global tanker fleet as they are used to transport both petroleum products and crude oil. These ships can access the largest ports that supply crude oil and petroleum products. The LR1 tanker can carry between 345,000 barrels and 615,000 barrels of gasoline (14.5-25.8 million gallons) or between 310,000 barrels and 550,000 barrels of light crude oil.

The majority of the global tanker fleet is classified as AFRAMAX. AFRAMAX ships - ships from 80,000 dwt and 120,000 dwt. This ship size is popular with oil companies for logistics purposes, and many ships have been built to these specifications. Because the AFRAMAX range exists somewhere between the LR1 and LR2 AFRA scales, LTBP does not publish freight estimates specifically for AFRAMAX vessels.

Throughout AFRA's history, tankers have grown in size and new classifications have been added. With the expansion of global oil trade, the Very Large Crude Carrier (VLCC) and Ultra Large Crude Carrier (ULCC) were added, and larger vessels provided better economics for crude oil shipments. VLCCs are responsible for the majority of crude oil supplies around the world, including in the North Sea, where Brent oil prices benchmark. The VLCC can carry between 1.9 million and 2.2 million barrels of West Texas Intermediate (WTI) crude oil.

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

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