How to Process and Manufacture Large Oil Storage Tanks?

Processing and manufacturing large oil storage tanks is a complex engineering project. The manufacturing of large oil storage tanks is usually divided into two methods: shop fabrication and field erection:

Shop Fabrication

• Steel Plate Processing:
  • Cutting and Forming: Using CNC cutting machines to cut steel plates into the required shapes (such as tank wall plates, tank bottom plates, and top plates). The steel plates may need to be roll-formed to fit the circular structure of the storage tank.
  • Prefabricated Components: The tank top, tank bottom, reinforcing rings, and accessories (such as flanges and nozzles) are prefabricated in the factory.
• Welding: Some components are initially welded in the factory, such as tank bottom plates or the overall welding of small storage tanks, using techniques such as MIG, TIG, or submerged arc welding.
• Surface Treatment: Prefabricated components are sandblasted, rust-removed, and coated with primer or anti-corrosion coatings (such as epoxy resin) to extend their service life.

Field Erection

• Site Preparation:
  • Foundation Construction: Leveling and excavating the ground at the selected location, and pouring reinforced concrete foundations to ensure the stability of the storage tank. The foundation must withstand the weight of the storage tank when fully loaded and environmental loads (such as wind and earthquakes).
  • Equipment Arrangement: Preparing cranes, scaffolding, and welding equipment, etc.
• Tank Assembly:
  • Tank Bottom Laying: Splicing and welding the prefabricated tank bottom plates one by one on the foundation, ensuring flatness and sealing.
  • Tank Wall Installation: Lifting and welding the steel plates ring by ring in the designed order, using vertical welding techniques. After each ring is welded, check the quality of the weld.
  • Tank Top Installation: Depending on the type of storage tank, install a fixed roof or a floating roof. Floating roof tanks require additional sealing systems to reduce evaporation losses.
• Accessory Installation: Installing inlet and outlet pipes, valves, breather valves, measuring devices, etc., to ensure the integrity of the storage tanks functions.

Quality Control and Testing

• Weld Inspection: Using non-destructive testing (NDT) techniques, such as ultrasonic testing and X-ray testing, to check for cracks or defects in the welds.
• Pressure Testing: Performing hydrostatic or pneumatic pressure tests on the storage tank to check for leaks. Large storage tanks usually use hydrostatic testing, filling with water and observing for leaks.
• Surface Inspection: Ensuring that the anti-corrosion coating is uniform and free of peeling, extending the life of the storage tank.
• Compliance Inspection: Ensuring that the storage tank complies with standards such as API 650, ASME Section VIII, and local environmental and safety regulations (such as the EPAs SPCC plan).

Transportation and Installation

• Transportation: Factory-prefabricated storage tanks or components are transported to the site by special trailers, railways, or barges. Large storage tank components need to be transported in sections to accommodate road restrictions.
• Field Installation: Using cranes to lift the components into place, completing the final assembly and connection. Perform final functional tests after installation to ensure seamless integration of the storage tank and piping system.

Post-Processing and Maintenance

• Corrosion Protection: Applying weather-resistant coatings to the outer surface of the storage tank, and special linings may be added internally to cope with corrosive media.
• Regular Inspection: According to API 653 standards, regularly inspect the structural integrity, welds, and anti-corrosion layer of the storage tank to prevent leakage or failure.