In the field of oil storage, oil storage tanks are indispensable equipment, and their accessories are vital components that ensure the safe operation of the tanks, enhance operational efficiency, and reduce oil losses. This article will provide a detailed introduction to the functions, design features, and importance of various oil storage tank accessories in practical applications.
The safe operation of oil storage tanks is crucial in the oil storage industry, and access and safety facilities form the foundation for ensuring the safety of operators and the normal operation of the tanks. These facilities not only provide convenient access for operators to ascend and descend the tanks but also ensure safety through various design details.
Operators frequently need to climb onto the tanks for tasks such as gauging, temperature measurement, sampling, and inspection. Therefore, ladders are essential facilities. There are two types of ladders: vertical and spiral. Small tanks usually have vertical ladders, while large tanks are equipped with spiral ladders. Vertical ladders have a simple structure suitable for small tanks with limited space, while spiral ladders better fit the structure of large tanks, utilizing space more efficiently and ensuring the safety of operators during ascent and descent. The height of ladders generally ranges from 800 to 1000 mm, with a width of 650 mm. This design provides operators with enough space to move while not occupying too much tank space.
Rest platforms are essential to ensure the safety of operators while ascending and descending the tanks. The width of the rest platform is 650 mm, and its counterclockwise rotation design allows operators to stand and rest more stably during the process. Additionally, the tank top is equipped with anti-slip steps, further enhancing the safety of operators walking on the tank top.
Manholes are designed for operators to enter and exit the tanks during cleaning and maintenance operations. Typically, vertical tanks have manholes installed on the bottommost ring plate of the tank wall, opposite the light hole on the tank top. This design facilitates quick access for operators during cleaning and maintenance and makes use of the light from the light hole to improve work efficiency. The diameter of manholes is usually 600 mm, with the center of the hole 750 mm from the tank bottom. Tanks with a capacity of less than 3000 cubic meters generally have one manhole, those between 3000 and 5000 cubic meters have 1 to 2 manholes, and tanks with a capacity of over 5000 cubic meters must have two manholes. Such arrangements meet the cleaning and maintenance requirements of tanks with different capacities.
Light holes, also known as ventilation holes, are designed for lighting and ventilation during tank cleaning or maintenance. They are usually located on the tank top above the inlet and outlet pipes, with a diameter of about 500 mm and an outer edge 800 to 1000 mm from the tank wall. The number of light holes is the same as that of manholes. This design ensures sufficient lighting and air circulation inside the tank during cleaning and maintenance, providing a good working environment for operators.
The design of oil inlet and outlet facilities directly affects the operational efficiency and safety of oil storage tanks. These facilities must ensure smooth oil flow while minimizing losses and environmental pollution during operations.
Inlet and outlet connection pipes are key components that connect the oil storage tank to external oil pipelines. They are available in three standard sizes: DN500, DN600, and DN750. Different sizes of connection pipes meet the oil flow requirements for various capacities, ensuring efficient oil inflow and outflow from the tank.
Drain holes are used for light oils, while cleaning holes are used for heavy oils. These holes come in three sizes: DN50, DN80, and DN100, with DN150 being the most commonly used. The primary function of drain and cleaning holes is to remove contaminated oil and residues from the tank, maintaining internal cleanliness. Regular cleaning of the tank reduces oil contamination and improves oil quality.
Gauging holes are designed for gauging, temperature measurement, and sampling. They are installed near the tank top platform, with each tank having only one gauging hole. The diameter of the gauging hole is 150 mm, and it is typically 1 meter away from the tank wall. The design of the gauging hole facilitates various detection operations on the tank top, ensuring accurate oil measurement.
Water drain pipes, also known as discharge pipes, are specifically designed to remove water and impurities from the tank and to clear residual contaminated oil from the tank bottom. A valve is installed on the external side of the discharge pipe. To prevent leakage or damage to the water drain valve, two valves are usually installed in series. During winter, insulation of the water drain valve is necessary to prevent freezing or valve rupture. The design of the water drain pipe effectively prevents the accumulation of water and residual contaminated oil, ensuring the normal operation of the tank.
Safety and protective facilities are essential components for the operation of oil storage tanks. These facilities are designed to prevent and respond to various potential safety risks, ensuring the safe operation of the tanks under all conditions and protecting personnel, equipment, and the environment from damage.
Fire foam chambers, also known as foam generators, are fixed fire extinguishing devices installed on oil storage tanks. One end of the foam generator is connected to the foam pipeline, while the other end is welded to the uppermost ring plate of the tank wall with a flange. When the fire extinguishing foam passes through the air intake of the fire foam chamber, it absorbs a large amount of air to form foam, which then breaks through the isolation glass and enters the tank (the glass thickness is no more than 2 mm), achieving the purpose of extinguishing the fire. The design of the fire foam chamber effectively prevents the occurrence and spread of tank fires, ensuring the safety of the tank.
Grounding wires are devices for eliminating static electricity on oil storage tanks. During the storage and transportation of oil, the accumulation of static electricity can lead to dangerous situations such as fires and explosions. Grounding wires can channel the static electricity from the tank into the ground, eliminating the hazard of static electricity and ensuring the safe operation of the tank.
Compared to general dome tanks, internal floating roof tanks have unique structures and performance requirements, and they are equipped with various special accessories.
Since the internal floating roof covers the oil surface and virtually eliminates the vapor space, the evaporation loss is minimal. Therefore, mechanical breathing valves and safety valves are not installed on the tank top. However, in practice, there may still be some vapor leakage from the annular gap around the floating roof or other accessory joints. To prevent the accumulation of vapors to a dangerous level, vent holes are opened on both the tank top and tank wall. The design of the vent holes ensures normal gas circulation inside the tank, preventing the accumulation of vapors that could pose a danger.
During oil loading and unloading operations in internal floating roof tanks, a large amount of static electricity accumulates on the floating roof. Since the floating roof and tank wall are often sealed with insulating materials, the static electricity on the floating roof cannot be conducted away through the tank wall. To dissipate this static electricity, static electricity conductor wires are installed between the floating roof and the tank top. Typically, two bare copper stranded wires are used, with one end connected to the light hole and the other end pressed onto the cover strip of the floating roof. The design of the static electricity conductor wires effectively prevents the accumulation of static electricity, avoiding the risk of fires and explosions caused by static electricity.
To prevent deformation of the tank wall and ensure the smooth vertical movement of the floating roof, two stainless steel cables are vertically tightened between the top and bottom of the internal floating roof tank. The two cables are symmetrically arranged at the ends of the floating roof diameter. Under the restriction of the cables, the floating roof can only move vertically, thus preventing its rotation. The design of the stainless steel cables effectively ensures the smooth vertical movement of the floating roof, preventing deformation and damage to the tank wall caused by the rotation of the floating roof.
Automatic vent valves are installed in the center of the floating roof. They are designed to allow the tank to breathe normally when oil is being loaded or unloaded while the floating roof is in its supporting position, preventing the area below the floating roof from being evacuated or over-pressurized. The design of the automatic vent valve ensures that the pressure below the floating roof remains stable during oil loading and unloading operations, thus ensuring the safe operation of the tank.
Diffuser pipes are connected to the inlet pipes inside the tank. The diameter of the diffuser pipe is twice that of the inlet pipe, and numerous 2-mm-diameter holes are evenly drilled on both sides. They play a role in reducing the flow velocity during oil loading, protecting the supports of the floating roof. The design of the diffuser pipe effectively reduces the velocity of the oil entering the tank, minimizing the impact on the supports of the floating roof, thereby extending their service life and ensuring the normal operation of the tank.
Oil storage tank accessories play a crucial role in the operation of oil storage tanks. From access and safety facilities to oil inlet and outlet facilities, from safety and protective facilities to special accessories for internal floating roof tanks, each accessory is carefully designed to meet the safety and efficient operation requirements of the tanks. Proper configuration and use of these accessories not only effectively reduce oil losses and extend the service life of the tanks but also ensure the safety of operators and the stable operation of the tanks. Therefore, a thorough understanding and correct use of oil storage tank accessories are essential knowledge for practitioners in the oil storage industry.
