LNG storage tanks, as critical equipment for the storage and transportation of liquefied natural gas (LNG), have been widely used in various industrial fields due to the increasing demand for natural gas. Since LNG is a cryogenic, flammable, and explosive gas, the design, operation, and maintenance of LNG storage tanks must comply with strict safety standards. To ensure the safe use of LNG storage tanks, in addition to high-quality design and construction, it is also necessary to strengthen management and conduct regular inspections during operation. This article will provide a detailed discussion on the safe use of LNG storage tanks, focusing on their structure, material selection, safety design, operational standards, and risk prevention measures.
Structure and Material Selection of LNG Storage Tanks
LNG storage tanks are essential equipment for storing cryogenic liquefied natural gas. Since LNG storage tanks must maintain natural gas in a liquid state at extremely low temperatures (-163°C), their design and material selection must fully consider cryogenic performance, safety, corrosion resistance, and long-term durability. Below is a detailed introduction to the structure and material selection of LNG storage tanks.
1. Main Components of LNG Storage Tanks
The basic components of LNG storage tanks include cryogenic storage vessels, pipeline systems, and control instrumentation systems. The design of storage tanks must consider the cryogenic storage characteristics of LNG while meeting high safety requirements. Key technologies include:
Cryogenic Storage Vessel: The inner tank of the storage tank is made of special materials to adapt to the extremely low-temperature environment of LNG storage.
Pipeline System: The pipeline system connecting the storage tank to other equipment must have excellent cryogenic performance to ensure stable gas transportation at low temperatures.
Control Instrumentation System: Includes pressure control, temperature monitoring, and leak detection systems to ensure stable operation of the storage tank.
2. LNG Storage Tank Material Selection
The design and manufacturing of LNG storage tanks impose extremely strict requirements on material selection:
Inner Tank Material: Since LNG storage tanks operate at -163°C, the inner tank material must have ultra-low-temperature performance. The most commonly used material is 9Ni steel (Ni9 steel), with a nickel content of 8.5%~9.5%, which ensures sufficient strength, toughness, and plasticity at extremely low temperatures, along with good formability and weldability.
Outer Shell Material: The outer shell of LNG storage tanks is typically made of stainless steel with excellent fire resistance, providing strong corrosion and impact resistance.
Pipeline Material: The pipeline system of the storage tank uses austenitic stainless steel, which has excellent cryogenic performance, ensuring stability and safety during gas transportation.
Safety Design of LNG Storage Tanks
The safety design of LNG storage tanks is key to ensuring long-term reliable operation. Major safety design measures include:
Fire-Resistant Outer Shell Design: The outer shell of LNG storage tanks is made of stainless steel with high fire resistance, effectively containing leaked LNG and preventing fire accidents caused by high temperatures.
Cold Box and Airtight Design: Joints, valves, and vaporizers are installed in airtight cold boxes to prevent LNG leakage. Cold boxes can contain leaked LNG, preventing the spread of flammable gases and reducing the risk of fire and explosion.
Integrated Design: LNG storage tanks, cold boxes, and heat exchangers are integrated into a "gas supply unit." This design enables overall risk control, improves equipment efficiency, and facilitates product certification and inspection.
Safety Operation Management of LNG Storage Tanks
To ensure the safe use of LNG storage tanks, operators must strictly follow safety operation standards and conduct regular inspections and maintenance. Key aspects of safety operation management include:
1. Pressure Monitoring and Regulation
The internal pressure of LNG storage tanks must be monitored at all times. Special attention should be paid to avoiding overpressure during liquid oxygen storage. Monitoring equipment should have real-time transmission and alarm functions to ensure operators can promptly identify and address issues.
2. Acetylene Concentration Control
Liquid oxygen in LNG storage tanks may react with acetylene, leading to fire or explosion. Therefore, the acetylene concentration in liquid oxygen must be regularly analyzed and kept below 0.1×10^-6. If the concentration is too high, immediate measures must be taken to discharge the liquid oxygen.
3. Temperature Control and Ice Prevention
The internal temperature of LNG storage tanks is very low, and measures must be taken to prevent moisture from entering the tank and causing pipeline icing. For tanks emptied of liquid, all valves must be closed if immediate heating is not possible to prevent moisture ingress and pipeline blockage.
Safety Precautions for LNG Storage Tanks
The following safety precautions must be observed during the use of LNG storage tanks:
Liquid Oxygen Splash Protection: Contact with liquid oxygen can cause frostbite, so operators should avoid splashing liquid oxygen on exposed skin. In case of accidental contact, immediate treatment is required to prevent frostbite.
Regular Cleaning and Inspection: Equipment such as low-pressure solenoid valves and pressure regulators must be regularly cleaned and inspected to ensure normal operation and avoid accidents caused by equipment failure.
Emergency Shutdown Measures: In the event of a leak or equipment failure, the emergency shutdown procedure must be activated immediately to cut off the gas supply and ensure the safety of the operating area.
Risk Prevention and Emergency Response
Although LNG storage tanks are designed with high safety standards, the stored liquefied natural gas is still a flammable and explosive gas. Therefore, comprehensive risk prevention and emergency response measures are essential. Key prevention measures include:
Leak Detection and Alarm Systems: LNG storage tanks are equipped with advanced leak detection systems to monitor gas concentrations in the surrounding environment in real time. In the event of a gas leak, the system will automatically alarm and activate shut-off devices to prevent fire and explosion.
Emergency Drills and Training: Regular emergency drills ensure that operators are proficient in handling accidents such as leaks, fires, or explosions. Emergency responders must be familiar with the use of various emergency equipment to take effective measures in the shortest possible time.
Conclusion
LNG storage tanks play a vital role in the storage and transportation of liquefied natural gas. With the increasing global demand for natural gas, the safety and reliability of LNG storage tanks are more important than ever. Through scientific design and reasonable material selection, LNG storage tanks can operate stably in extremely low-temperature environments. Advanced safety control systems and risk prevention measures maximize the protection of personnel and property. Proper operation management, regular equipment inspections, and strict safety standards are key to ensuring the safe use of LNG storage tanks. Only in this way can the safe and efficient storage and transportation of liquefied natural gas be achieved.
