How to select a high pressure PVC hose
The loading and unloading process of petrochemical terminals is mainly based on “ship ← → loading and unloading arm ← → shore”. However, some terminals are limited by factors such as ship type, berths, and operating density. The loading and unloading process of “ship←→oil hose←→shore” is often used as a supplement. Small petrochemical terminals often use this process for loading and unloading. In addition, the offshore anchorage barge operation completely adopts the loading and unloading process of “ship → oil hose → ship”.
Analysis on the usage of hoses in petrochemical terminals
The oil hoses used in petrochemical terminals are generally divided into two categories: rubber hoses and composite hoses. Rubber hoses are generally composed of flanges (joints), short pipes (the connecting medium between the flange and the hose), and hoses (multi-layer composite). Composite hose is a flexible oil pipe. The inner and outer skeleton of the pipe is formed by winding steel wires and is made of polymer materials.
The oil transfer hoses used in petrochemical terminals are generally based on refined oils and chemicals such as gasoline, diesel, aviation kerosene, and toluene, and are specially used for special purposes. Its operating temperature is generally normal temperature, and its operating pressure is generally 0.1-0.7MPa. The oil transfer hoses used for anchorage transfers are generally based on fuel oil and crude oil. The higher temperature can reach 60℃ depending on the oil quality. The operating pressure is generally 0.1-0.6MPa. Wharf anchorages mainly use rubber hoses, supplemented by composite hoses. Composite hose is not suitable for use in anchorages.
Recommendations for safe use of petrochemical terminal hoses
Hose service life
Rubber hose: Recommended for use no more than 7 years.
Composite hose: Recommended for use no more than 4 years.
Disposal of hoses
1. If the static pressure test fails, the hose should be scrapped. It is also recommended that this batch of hoses be scrapped.
2. If the resistance between the two pipe joints of the oil delivery hose is less than the maximum allowable resistance of 2×106Ω/m specified in GB/T 9572, the hose should be scrapped. All hoses in this batch should be tested for conductivity at the same time.
3. The surface of the hose is severely worn, has deep cracks, or the steel wire is exposed and rusted.
4. The inner bladder of the hose is bubbling and falling off.
5. The hose is bent or deformed.
6. The hose makes abnormal noise during operation.
Regular inspection of hoses
1. Test content.
(1) Appearance inspection: No deformation, wear, rust, exposed steel wire, severe discounting, aging, etc.
(2) Inner tank inspection: no blistering, damage, aging, etc.
(3) Static pressure testing: Sampling is carried out according to the hose purchase batch, and testing is performed once a year. During testing, water is used as the pressure testing medium. Conduct a static pressure test at a pressure of 1.5~2.4Mpa for 10~15 minutes to measure the elongation of the hose.
(4) Conductivity detection.
2. Static pressure detection
(1) Lay the hose flat and straight, and measure its length L0.
(2) Seal one end of the hose with a blind plate and connect the other end to the pressure testing equipment.
(3) Use water as the medium, increase the pressure of the hose to 1.5MPa, maintain it for 10 minutes, and measure the length of the hose L1. Depressurize the hose to zero and, at least 15 minutes apart, measure hose length L2.
(4) Elongation = (L1-L0)/L0×100%. Permanent elongation = (L2-L0)/L0×100%.
3. Conductivity detection. Use a multimeter to check the resistance between the two joints of the hose.
4. Qualification standards.
(1) The hose should be kept under test pressure for 10 to 15 minutes without leakage, bubbling, deformation, etc.
(2) The elongation is less than or equal to the specified standard. Permanent elongation is used as a reference.
(3) The resistance between the two pipe joints of the hose is greater than the maximum allowable resistance 2×106Ω/m specified in GB/T 9572.
(4) Scope of application of hoses
1. Transport medium: Rubber hoses are usually used for loading and unloading of crude oil and refined oil. Composite hoses are usually used for loading and unloading chemicals.
2. Operating location: Composite hose is only suitable for dock operations. Not suitable for ship-to-ship transfer operations at offshore anchorages.
3. Ship type: Rubber hoses should be used for loading and unloading operations on ships of 10,000 tons and above.
Requirements for safe operation of hoses
1. Transportation of hoses. Rubbing of hose surfaces or joints on the ground should be avoided. Avoid bending the hose excessively; it is recommended to use a dedicated hose cart for transportation.
2. Inspection before operation. Before operation, check to confirm that there is no deformation, wear or serious discount on the surface. Make sure there are no blisters or damage to the inner tank. At the same time, confirm that the joints are not loose or deformed.
3. Hose connection. A gasket should be placed in the connection between the two pipes. All bolt holes should be filled with bolts and tightened in a diagonal counterbalance. The length of the hose connection should be able to accommodate changes in ship/shore differences and displacements. Avoid excessive stress that could damage the hose.
4. Hoisting operations. When hoisting hoses, special hoists should be used to avoid deformation of the hoses (such as flat belt lifting).
5. Inspection during operation. Regularly record pipeline, medium temperature, pressure and other working parameters. Avoid over-temperature and over-pressure use. According to factors such as changes in ship draft, tide, current, wind direction, etc. Adjust the hose appropriately and promptly. Maintain a moderate bend to prevent the hose from being bent, broken or worn.
6. Store after operation. When storing at the dock, avoid sunlight, flooding, and rain. Prevent accelerated aging of hoses and shorten their service life.
Connect the ground wire
The ground wire should be grounded first, and then the oil pipe arm should be installed. The oil terminal requires that after the oil tanker berths, a joint cable should be connected between the ship and the shore to provide a circuit for static electricity and current. The bonding cable should be equipped with a closed insulating switch before installing the earth wire. Place the switch in the “off” position, and then place the switch in the “connected” position after installation. However, this practice is not advocated internationally. In order to prevent the flow of current between the ship and the shore, it is usually required to install an insulating flange on the oil pipeline arm on the shore. The flange is a connection joint composed of insulating gaskets, bushings and washers. It is used to prevent the flow of current between pipelines and oil pipeline arms to ensure safety.
Hoses should be inspected before use
The ship has the right to refuse to use any defective oil hose. Hoses should be pressure tested annually. Test data shall be marked on the hose. They should be inspected before each use for swelling, wear, flattening, leaks or other defects.
Hose connection, lifting and hanging
Use caution when connecting hoses. The hose should not be pulled hard, and should not be twisted and squeezed by the berth and the tanker. And should prevent bending to less than the deflection radius specified by the manufacturer. The parts where the hose has friction and contact with the berth or other structural parts of the ship should be protected. Also avoid contact between the hose and hot metal surfaces, such as steam lines, etc. The oil transfer hose should have sufficient slack characteristics to accommodate minor movements of the ship.
When hoisting the hose, direct contact between the outer surface of the hose and the lifting wire should be absolutely avoided. It is not allowed to use single-point lifting with the hose end hanging down. Multi-point lifting should be used. And make the hose have a deflection radius not less than that specified by the manufacturer. Where a single lifting point is used, such as a jib crane, the entire set of hoses should be supported using specialized slings and brackets. The weight placed on the cargo main should not be excessive. The connected oil hose should be hung in an appropriate manner.
Hose adjustment
When the oil tanker rises and falls with the tide and loading and unloading cargo, the hose should be adjusted accordingly to avoid excessive stress on the connection between the hose and the ship’s main pipe, which may cause accidents.
Use and adjustment of oil transfer arm
Most of the new oil tanker terminals now use metal oil transfer arms. When using them, you should pay attention to:
The oil transfer arm should be in line with the oil tanker pipeline;
Prevent the oil transfer arm from exceeding its free rotation limit and causing overload displacement due to loading, unloading, tides, etc.;
If an emergency disconnection device is installed, it should be checked at any time to prevent accidental disconnection;
When disassembling and assembling, care should be taken to prevent residual oil in the pipe from flowing out;
Oil pans and oil barrels should be placed under the ship-to-shore connection pipes to collect cargo oil that drips when the pipes are removed or cargo oil that leaks due to loose joint sealing.
Prevent oil spills and prepare fire-fighting equipment
Before loading, all deck drainage holes on the ship should be blocked with wooden plugs or cement to prevent oil from flowing overboard in the event of oil spillage. The sea valve should be closed and monitored at all times to prevent cargo oil from leaking from the sea valve.
Before loading oil, fire-fighting equipment should be placed at the connecting point and two fire-fighting hoses should be connected nearby.
Connect the emergency tow cable (fire tow cable)
The emergency tow rope is usually carried at the bow and stern of the outer side of the oil tanker. One end is fastened to the tow bitt, and the other end with the connecting eye ring is passed to the outboard through the fairlead, and is tied to the eye ring. Return the lead cable to the deck for operation. The total length is about 100m, and the length coiled on the deck is usually 36.6m according to the regulations of each port, in case of fire emergency. During cargo operations, adjust the distance between the eye ring and the water surface in a timely manner and always keep it 1~2m away from the water surface. When towing is required, one person is required to connect the eye ring of the emergency tow cable to the tow rope of the tugboat within 15 minutes.
Conditions for stopping loading and unloading operations
When the wind speed exceeds 15m/s (Beaufort wind scale is about 7), the wave height is 1m and is expected to continue to increase;
thunderstorm weather;
There is a fire nearby, endangering the ship;
There is a ship approaching or sailing next to it, which may endanger the ship.
Conditions for stopping berthing operations
Winds above level 6 will pass through the oil area;
When the wind speed exceeds 15m/s (Beaufort wind scale is about 7) and the wave height is 1m;
thunderstorm weather;
The visibility at sea in the oil area is less than 1000m.
Conditions for emergency departure
Wind speed exceeds 18m/s and wave height exceeds 1.5m;
There is a fire in the adjacent area, endangering the ship.
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