Comprehensive Guide to Cryogenic Double Wall Storage Tanks

Cryogenic double wall storage tanks are essential components in the storage and transportation of liquefied gases at ultra-low temperatures. These tanks are designed to maintain the integrity and safety of stored substances like liquid nitrogen (LN₂), liquid oxygen (LO₂), liquefied natural gas (LNG), and other cryogenic liquids. This article delves into the various aspects of cryogenic double wall tanks, including their design, materials, working principles, applications, and more.

1. Introduction to Cryogenic Double Wall Tanks

Cryogenic double wall tanks are specialized vessels designed to store liquefied gases at extremely low temperatures, typically below -150°C. The double-wall construction comprises an inner tank, which holds the cryogenic liquid, and an outer tank that provides structural support and secondary containment. The space between these two walls is evacuated to create a vacuum, offering excellent thermal insulation.

2. Design and Construction

2.1 Structure and Materials

• Inner Tank: Constructed from materials with high resistance to cryogenic temperatures, such as austenitic stainless steel (e.g., SA240 304 or S30408).cimchonto.en.made-in-china.com

• Outer Tank: Made from carbon steel (e.g., Q345R or SA516 GR.70), providing structural integrity and resistance to external pressures.cimchonto.en.made-in-china.com

• Insulation: The annular space between the inner and outer tanks is filled with high-performance insulating materials like perlite or multilayer super insulation, and then evacuated to create a vacuum. This setup minimizes heat transfer and maintains the low temperatures of the stored liquids.krisonengineering.com+1cryogenindia.com+1

2.2 Tank Configurations

• Vertical Tanks: Ideal for installations with limited ground space, vertical tanks are commonly used in industrial settings.

• Horizontal Tanks: Suitable for applications requiring larger storage capacities and easier access for maintenance.

3. Working Principle

The cryogenic double wall tank operates on the principle of thermal insulation and pressure containment:

1. Inner Tank: Holds the cryogenic liquid at ultra-low temperatures.krisonengineering.com+1Cryospain+1

2. Vacuum Insulation: The space between the inner and outer tanks is evacuated to create a vacuum, significantly reducing heat transfer.cryogenindia.com+1cimchonto.en.made-in-china.com+1

3. Outer Tank: Provides structural support and serves as a secondary containment layer, ensuring safety in case of leaks or failures in the inner tank.

This design ensures the maintenance of cryogenic temperatures and the safety of the surrounding environment.cryogenindia.com

4. Cryogenic Tank Materials

• Inner Tank: Materials like austenitic stainless steel (SA240 304 or S30408) are preferred for their resistance to brittle fracture at cryogenic temperatures.cimchonto.en.made-in-china.com+1energy-steel.com+1

• Outer Tank: Carbon steels such as Q345R or SA516 GR.70 are commonly used, offering strength and toughness suitable for low-temperature applications.cimchonto.en.made-in-china.com+1energy-steel.com+1

• Insulation Materials: Perlite is widely used due to its effectiveness in insulating against cryogenic temperatures.energy-steel.com

5. Cryogenic Tank Capacity and Temperature

• Capacity: Cryogenic double wall tanks are available in various capacities, ranging from small-scale units (e.g., 5 m³) to large-scale tanks (e.g., up to 312 m³), catering to different industrial needs.cryogenindia.com

• Temperature Range: These tanks are designed to operate within a temperature range of -196°C to +50°C, accommodating the storage requirements of various cryogenic liquids.cryogenindia.com+1krisonengineering.com+1

6. Cryogenic Tank Vacuum and Insulation

The vacuum between the inner and outer tanks serves as a crucial component for thermal insulation:cimchonto.en.made-in-china.com+2cryogenindia.com+2energy-steel.com+2

• Vacuum Level: Typically maintained at 5 × 10⁻² mbar, ensuring minimal heat ingress.cryogenindia.com

• Insulation Materials: High-performance materials like perlite or multilayer super insulation are used to enhance thermal resistance.cryogenindia.com+4krisonengineering.com+4ambicacryogenic.com+4

This setup effectively reduces boil-off rates and maintains the low temperatures of stored cryogenic liquids.

7. Double Wall Vessel and Double Integrity Tank

The terms "double wall vessel" and "double integrity tank" refer to the design philosophy of incorporating two layers of containment:

• Double Wall Vessel: Consists of an inner and outer tank, providing primary and secondary containment.

• Double Integrity Tank: Emphasizes the structural integrity of both walls, ensuring safety and compliance with stringent regulations.

These designs are critical in preventing environmental contamination and ensuring the safety of personnel.

8. Cryogenic Tank Design Standards

Cryogenic double wall tanks are designed and manufactured in compliance with various international standards:

• ASME VIII Div.1: Provides guidelines for the design, fabrication, and inspection of pressure vessels.sjcryos.com

• EN 13458: Specifies the design and construction of cryogenic tanks.

• PED: The Pressure Equipment Directive ensures the safe design and operation of pressure equipment within the European Union.

• ISO 9001: Certifies quality management systems, ensuring consistent product quality.

Adherence to these standards ensures the reliability and safety of cryogenic storage tanks.

9. Cryogenic Tank Uses: LN₂, LO₂, and LNG

Cryogenic double wall tanks are versatile and can store various liquefied gases:en.wikipedia.org

• Liquid Nitrogen (LN₂): Used in medical applications, food freezing, and industrial processes.

• Liquid Oxygen (LO₂): Essential in healthcare for respiratory support and in industrial applications.

• Liquefied Natural Gas (LNG): Utilized as an energy source in power generation and transportation.

The design of these tanks accommodates the specific requirements of each gas, ensuring safe and efficient storage.