A cryogenic liquid storage tank is a specially designed pressure vessel used to store liquefied gases at very low temperatures. These tanks are commonly used for liquid nitrogen (LN₂), liquid oxygen (LOX), liquid argon (LAr), liquid carbon dioxide (LCO₂), LNG, and other cryogenic fluids.
Because cryogenic liquids must remain at low temperatures during storage, the tank is designed to minimize heat transfer from the surrounding environment. A typical cryogenic liquid storage tank uses a double-wall construction with an insulated space between the inner and outer vessels. Vacuum insulation and, in many designs, multilayer insulation help reduce heat ingress and limit liquid evaporation.
The basic storage process is simple: the cryogenic liquid is contained inside the inner vessel, heat transfer is minimized by the insulation system, and pressure is controlled as a small amount of liquid naturally vaporizes during storage.
What Is a Cryogenic Liquid Storage Tank?
A cryogenic liquid storage tank is an insulated vessel designed to safely contain liquefied gases at cryogenic temperatures and their corresponding operating pressures.
Unlike conventional liquid storage tanks, cryogenic tanks must address both extremely low temperature and pressure control. The tank must maintain the required mechanical strength at low temperatures while minimizing heat entering from the surrounding environment.
Commonly stored cryogenic liquids include:
- Liquid nitrogen (LN₂) for industrial gas, food processing, electronics, laboratories, and other applications.
- Liquid oxygen (LOX) for healthcare, metal processing, combustion, and industrial applications.
- Liquid argon (LAr) for welding, metallurgy, and industrial gas applications.
- Liquid carbon dioxide (LCO₂) for food and beverage processing, dry ice production, welding, and other applications.
- LNG for fuel and energy applications.
- Other cryogenic fluids for specialized industrial, research, and energy applications.
The required tank configuration depends on the stored liquid, capacity, operating pressure, installation conditions, applicable codes, and the intended method of liquid or gas withdrawal.
How Does a Cryogenic Liquid Storage Tank Work?
The working principle of a cryogenic liquid storage tank is based on low-temperature containment, thermal insulation, and controlled pressure management.
The basic process can be summarized as:
Cryogenic liquid → Inner vessel → Vacuum insulation → Reduced heat transfer → Controlled vaporization → Pressure management → Liquid or gas withdrawal
1. Cryogenic liquid is contained in the inner vessel
The inner vessel is the primary pressure-containing part of the tank. It is designed for the temperature and pressure conditions of the stored cryogenic liquid.
The inner vessel must maintain its mechanical integrity while exposed to very low temperatures and repeated temperature changes during filling, storage, and withdrawal.
2. The insulation system limits heat transfer
The inner vessel is separated from the outer jacket by an insulated annular space. Vacuum insulation significantly reduces heat transfer by limiting gas conduction and convection.
Additional insulation materials, such as multilayer insulation (MLI) or other suitable systems, can further reduce radiant heat transfer.
3. A small amount of liquid naturally vaporizes
No practical storage tank can completely eliminate heat input. Even with effective insulation, a small amount of heat reaches the stored liquid. This can cause a portion of the liquid to vaporize, producing boil-off gas.
The amount of vaporization depends on factors such as insulation performance, ambient conditions, tank condition, operating pressure, liquid temperature, and tank design.
4. Tank pressure is managed
As vapor forms inside the tank, pressure can change. Cryogenic storage systems therefore use appropriate pressure-control and pressure-relief arrangements to maintain safe operating conditions.
Depending on the system design, vapor may be used, returned to the process, managed through an economizer or pressure-building circuit, or released through an appropriate safety system.
5. Liquid or gas is withdrawn for use
Cryogenic liquid can normally be withdrawn directly from the tank for transfer to another vessel or process. Where gaseous product is required, the liquid can be sent through a cryogenic vaporizer and converted into gas before entering the gas supply system.
This makes a cryogenic storage tank an important part of a complete industrial gas storage and supply system.
Cryogenic Liquid Storage Tank Construction
A typical vacuum-insulated cryogenic liquid storage tank consists of an inner vessel, outer jacket, vacuum space, insulation system, structural supports, piping, instrumentation, and safety devices.
The basic construction can be represented as:
Outer jacket → Vacuum space → Insulation → Inner vessel → Cryogenic liquid
Inner Vessel
The inner vessel directly contains the cryogenic liquid. Its material and design must be suitable for the stored medium, operating temperature, pressure, and applicable design requirements.
Outer Jacket
The outer jacket surrounds the inner vessel and protects the insulation and vacuum space from the external environment. It also provides the external structural enclosure of the tank.
Vacuum Space
The space between the inner vessel and outer jacket is evacuated to reduce heat transfer. Maintaining an effective vacuum is an important part of cryogenic tank thermal performance.
Supports and Connections
Internal and external supports maintain the position of the inner vessel while limiting unwanted heat conduction. Piping and connections provide the required paths for filling, liquid withdrawal, gas withdrawal, pressure control, instrumentation, and safety functions.
Why Are Cryogenic Storage Tanks Vacuum Insulated?
Vacuum insulation is used because conventional insulation alone cannot provide the same level of thermal isolation required for long-term cryogenic liquid storage.
Heat can reach the stored liquid through three primary mechanisms:
- Conduction: heat transfer through structural supports, piping, and other physical connections.
- Convection: heat transfer through gas movement in the space surrounding the inner vessel.
- Radiation: heat transfer between surfaces caused by thermal radiation.
Creating a vacuum around the inner vessel greatly reduces gas conduction and convection. Multilayer insulation or other low-heat-transfer insulation systems can further reduce radiant heat transfer.
The objective is to minimize heat ingress, which helps reduce evaporation and improves the thermal performance of the storage system.
What Happens to Cryogenic Liquid During Storage?
Although cryogenic storage tanks are highly insulated, the stored liquid is not completely isolated from ambient heat. A small amount of heat will eventually enter the tank, causing some liquid to change into vapor.
This process is commonly referred to as boil-off.
The basic relationship is:
Ambient heat → Heat enters tank → Part of liquid vaporizes → Vapor accumulates → Pressure changes
Effective cryogenic tank design therefore focuses on controlling heat ingress and managing the resulting vapor.
Boil-Off Gas
Boil-off gas (BOG) is vapor generated when heat enters a cryogenic storage tank and causes part of the stored liquid to evaporate.
Reducing BOG is important because excessive evaporation can result in product loss and increased tank pressure. Good vacuum performance, effective insulation, suitable tank design, and appropriate operating conditions can help minimize unnecessary vaporization.
BOG management should therefore be considered together with the tank’s pressure-control system and the downstream gas-use requirements.
Vertical vs. Horizontal Cryogenic Liquid Storage Tanks
Cryogenic liquid storage tanks are available in different physical configurations. Vertical and horizontal designs are commonly selected according to capacity, available installation space, site conditions, and application requirements.
| Configuration | Typical Consideration |
|---|---|
| Vertical | Efficient use of ground area and commonly used for stationary bulk storage. |
| Horizontal | Useful where available height is limited or where the site layout favors a horizontal configuration. |
| Flat-bottom | Used for larger storage applications where site, foundation, capacity, and engineering requirements support this configuration. |
For a broader comparison of cryogenic tank types, configurations, components, sizing, and applications, see our Cryogenic Tanks Guide.
What Liquids Can Be Stored in Cryogenic Tanks?
The same basic cryogenic storage principle can be applied to different liquefied gases, but the tank design must be matched to the properties and operating conditions of the specific medium.
| Cryogenic Liquid | Common Applications |
|---|---|
| Liquid Nitrogen (LN₂) | Industrial gases, food processing, electronics, laboratories, and cooling applications. |
| Liquid Oxygen (LOX) | Healthcare, metal processing, combustion, and industrial gas applications. |
| Liquid Argon (LAr) | Welding, metallurgy, metal processing, and industrial gas applications. |
| Liquid CO₂ (LCO₂) | Food and beverage, dry ice, welding, and industrial processes. |
| LNG | Fuel, energy, industrial, and transportation applications. |
What Should You Consider When Selecting a Cryogenic Liquid Storage Tank?
The appropriate tank depends on the characteristics of the stored liquid and the requirements of the complete storage and supply system.
- Stored medium: Identify the cryogenic liquid and its operating temperature.
- Required capacity: Determine the required storage volume based on consumption and replenishment requirements.
- Operating pressure: Select a suitable pressure rating for the intended application.
- Installation space: Consider available height, footprint, access, foundations, and surrounding equipment.
- Withdrawal requirements: Determine whether the system requires liquid withdrawal, gas withdrawal, or both.
- Applicable standards: The design and manufacturing requirements should correspond to the applicable local and international codes and regulations.
- Future demand: Consider expected changes in consumption and system expansion.
Cryogenic Liquid Storage Tank Standards
Cryogenic storage tanks are pressure-containing equipment, so their design, fabrication, inspection, testing, and certification must follow the requirements applicable to the installation and destination market.
Depending on the project, requirements may include standards and regulatory frameworks such as ASME, CE/PED, GB, or other applicable national and international codes.
The appropriate standard should be determined according to the tank design, operating conditions, installation location, transport requirements, and local regulatory requirements.
Cryogenic Liquid Storage Tanks for Industrial Gas Supply
A cryogenic liquid storage tank is often only one part of an industrial gas supply system. In a typical installation, liquid is delivered to the storage tank, stored under controlled conditions, and then supplied to the point of use.
When gaseous product is required, the stored liquid can pass through a vaporizer before entering the distribution system. Depending on the application, the complete system may also include pressure-building equipment, valves, instrumentation, safety devices, vaporizers, pumps, and gas distribution equipment.
This integrated approach allows cryogenic liquid storage to support continuous gas supply for industrial and commercial applications.
Cryogenic Liquid Storage Tank vs. Cryogenic Tank
The terms cryogenic tank and cryogenic liquid storage tank are closely related but can have different scopes.
Cryogenic tank is a broad term covering different types of equipment used to contain or transport cryogenic fluids.
Cryogenic liquid storage tank more specifically refers to a tank designed for storing liquefied cryogenic gases, particularly in stationary or bulk storage applications.
Therefore, a cryogenic liquid storage tank can be considered a specific application within the broader category of cryogenic tanks.
Types of Cryogenic Vacuum-Insulated Tanks
Cryogenic vacuum-insulated tanks are engineered for the safe storage and delivery of liquefied gases at extremely low temperatures. They are primarily classified into two types:
1. VIT (Vacuum-Insulated Tank)
- Designed for pressures up to 5 bar (g).
- Used for storage of liquid intended for delivery to a pump or tanker.
- Features a double-walled structure with vacuum insulation for minimal heat ingress.
2. VIE (Vacuum-Insulated Evaporator)
- Designed for pressures up to 35 bar (g).
- Operates with a vaporiser to supply gas directly to customers.
- Ideal for supplying large quantities of gas over a short period.
- Construction: inner vessel made of stainless steel, outer vessel of carbon steel.
- Insulation: vacuum interspace filled with perlite for excellent thermal performance.
- Often supplied with instrumentation such as level indicators and pressure protection devices.
Operational Safety
To ensure safe operation, a dedicated person should be responsible for regular inspection of the cryogenic liquid storage tank. Key checks include:
- Ensure the inner vessel pressure does not exceed the tank’s working pressure. If it does, take immediate pressure relief measures.
- Inspect all valves and fittings for leaks or abnormal conditions.
- Verify instrumentation is functioning correctly, including level indicators and pressure protection systems.
VIT vs VIE vs Flat-Bottom Tanks
| Type | Function | Pressure Range | Application |
|---|---|---|---|
| VIT | Liquid storage | Low pressure | Storage before pumping |
| VIE | Gas supply | Medium to high | Direct industrial gas supply |
| Flat-bottom | Bulk storage | Near atmospheric | LNG terminals & large plants |
Cryogenic Storage Tank Design – Flat-Bottom Tanks
- Atmospheric storage slightly above ambient pressure
- Designed for large quantities of a single product
- Inner vessel: stainless steel; Outer vessel: carbon steel
- Typically site-built with emergency flap valves on main inlets/outlets
- Insulation: perlite-filled interspace with nitrogen purge
Maintenance Recommendations:
- Regularly check the jacket vacuum. If it deteriorates, conduct additional vacuuming via a professional service or manufacturer
- Identify and correct equipment or accessory failures promptly to ensure safe and continuous operation
How to Choose the Right Cryogenic Tank
- Small demand (labs / medical): Dewars or small cryogenic cylinders
- Medium demand: VIE systems for continuous gas supply
- Large-scale storage: Flat-bottom LNG tanks
- Transport applications: ISO cryogenic tanks
Selecting the correct system depends on capacity, pressure requirements, and end-use application.
Capacity Range and Applications
- Small-scale: 50 – 500 L (laboratories, medical)
- Medium-scale: 1 – 50 m³ (industrial gas supply)
- Large-scale: 100 – 200,000 m³ (LNG storage)
Typical Applications:
- Industrial gas supply systems
- LNG storage and distribution
- Medical oxygen systems
- Food freezing and preservation
- Electronics and semiconductor manufacturing
Boil-Off Gas (BOG) Management
Advanced cryogenic tank systems are designed to minimise boil-off gas through:
- High-efficiency vacuum insulation
- Perlite or multilayer insulation systems
- Pressure control and recondensation systems
Effective BOG management reduces product loss and improves overall system efficiency.
Safety and Maintenance
- Continuous pressure and level monitoring
- Regular inspection of valves and pipelines
- Verification of pressure relief devices
- Vacuum performance monitoring
Maintenance:
- Periodic vacuum re-evacuation
- Leak detection and repair
- Compliance with international standards
Codes and Standards
Internationally recognized codes and standards regulate cryogenic storage tank design, manufacturing, and operation. These guidelines ensure the safety, quality, and reliability of the specialisedzed containers that manage substances at extremely low temperatures. Adherence to these standards is crucial to mitigate risks and prevent accidents.
Key codes and standards cover various aspects of cryogenic storage tank design, construction, and operation, including:
Table 2: Codes and Standards for Cryogenic Storage Tanks
| CODE/STANDARD | FOCUS |
|---|---|
| ASME B&PV Code Section VIII | Design principles for pressure vessels, including cryogenic tanks |
| API 620 | Design and construction of large welded low-pressure storage tanks |
| API 625 | Tank systems for refrigerated liquefied gas storage |
| NFPA 55 | Storage, use, and handling of gases in cryogenic systems |
| ISO 13458 | Cryogenic vessels – Safety devices for protection against excessive pressure |
| EN 13445 | Unfired pressure vessels, including cryogenic storage vessels |
| AISC 360 | Structural design of steel elements used in cryogenic tanks |
These codes provide comprehensive guidelines for design principles, materials, construction, safety devices, and structural considerations. Compliance with these standards ensures that cryogenic storage tanks are designed and constructed to withstand the unique challenges of extremely low temperatures and the associated hazards of cryogenic fluids.
Why Choose DSW Cryogenic Tanks
- Full compliance with ASME, API, and ISO standards
- Custom-engineered solutions for LNG and industrial gases
- Advanced vacuum insulation technology
- Global export experience
- Competitive pricing with factory-direct supply
DSW delivers high-performance cryogenic storage solutions tailored to your operational requirements.
TECHNICAL QUESTIONS
Frequently asked questions about Cryogenic Liquid Storage Tanks
A cryogenic storage tank is a vacuum-insulated, double-walled pressure vessel designed to store liquefied gases below −150°C. It uses a stainless steel inner vessel, carbon steel outer shell, and a vacuum-perlite or multilayer insulation system to minimise heat ingress and boil-off gas.
A VIT (Vacuum-Insulated Tank) is used for low-pressure liquid storage, while a VIE (Vacuum-Insulated Evaporator) integrates vaporisation to supply gas directly. VIE systems operate at higher pressures and are designed for continuous gas delivery.
Boil-off gas is reduced through high vacuum insulation, low thermal conductivity materials, and pressure control systems. In LNG systems, BOG can be recovered, recondensed, or reused to improve efficiency.
Inner vessels are typically made from austenitic stainless steel (304/316) for cryogenic toughness, while outer shells use carbon steel. Insulation includes perlite or multilayer systems under vacuum.
Key standards include ASME Section VIII for pressure vessels, API 620 and API 625 for LNG tanks, ISO 13458 for cryogenic vessels, and NFPA 55 for gas safety.
Pressure is managed using pressure-building systems, economisers, and relief valves. These components maintain stable operating pressure and ensure safety under varying load conditions.
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