LNG Storage Tank Manufacturer in China: Capability, Codes and What to Verify

Liquefied natural gas is stored at around minus 162 degrees Celsius, and that single number changes everything about the vessel. Steel that is tough at ambient temperature can be brittle at that temperature, water in the wrong place turns into ice that jacks foundations apart, and heat leaking in from outside produces gas continuously whether the plant is running or not. An LNG tank is therefore less a storage container than a piece of process safety equipment that happens to hold liquid.

Sourcing it from China is now common, and the evaluation should be no different in principle from anywhere else - but it does require checking that the manufacturer holds the right pressure equipment qualification and can evidence it. Shijiazhuang Zhengzhong Technology Co., Ltd. (Center Enamel) manufactures pressure vessels and cryogenic tanks under a certified pressure equipment quality system, with design to ASME Section VIII or EN 13445 and to EN 14620 or NFPA 59A for refrigerated service.

1. What Types of LNG Storage Tank Are There?

The first decision is the containment philosophy, which sets how a credible failure is handled and how much land the installation needs. Three arrangements dominate large installations, with a fourth for small scale.

• Single Containment: One inner tank holds the liquid; a dike or impounding area sized to retain the inventory handles a release. Vapour from a release is not contained.
• Double Containment: An inner tank plus an outer wall designed to hold the liquid from an inner failure, but not necessarily to contain the vapour. Used where land is constrained.
• Full Containment: An inner metallic tank inside a vapour-tight outer tank - usually prestressed concrete - designed to contain both liquid and vapour. This is the modern base-load terminal standard.
• Shop-Built Vacuum Vessels: Factory-built inner vessel within an evacuated annulus with perlite or multi-layer insulation, delivered complete. Used for small and mid-scale plants.
• Pressurised Small-Scale Storage: Storage at elevated pressure rather than at full refrigeration, suited to satellite stations and vehicle fuelling where a refrigeration plant is not economic.

2. What Does Cryogenic Service Demand of Materials and Design?

The design temperature drives material selection, and thermal contraction drives the details. Both have to be right, and both are verifiable in the documentation rather than in a photograph.

• Design Temperature: Around minus 162 degrees Celsius at atmospheric pressure, with the design case set below that to cover the actual composition and any pressure effect.
• Inner Tank Materials: Nine percent nickel steel and austenitic stainless grades such as 304L or 316L retain toughness at cryogenic temperature. Ordinary carbon steel does not and is used only for the outer jacket.
• Thermal Contraction: Metals contract measurably between ambient and cryogenic temperature. Supports, anchorage and pipework have to accommodate the movement rather than resist it.
• Insulation System: Perlite fill with nitrogen purge, or an evacuated annulus, keeps heat ingress low enough to hold the boil-off rate within the design figure.
• Foundation Protection: The ground beneath a cryogenic tank must not freeze, or ice formation will heave the foundation. Heated foundations or a ventilated pedestal are the standard responses.

3. What Safety and Operational Systems Are Required?

The tank is one component in a system. Boil-off handling, over and under pressure protection, rollover prevention and the spacing and impoundment provisions are what make the installation acceptable to the authority and to the insurer.

• Boil-off Gas Handling: Heat ingress produces gas continuously - commonly in the region of 0.05 to 0.15 percent of inventory per day for large full-containment tanks. It is routed to a compressor, a recondenser, a user, or a flare.
• Rollover Prevention: Layers of different density can form and suddenly mix, releasing vapour far faster than normal. Density and temperature profiling, controlled circulation and correct top or bottom filling prevent it.
• Pressure and Vacuum Protection: Pressure safety valves with a vent or flare route protect against overpressure; vacuum protection prevents collapse during rapid draw-off or cool-down.
• Instrumentation and Shutdown: Level, temperature and density profile, gas detection, fire detection and an emergency shutdown system with remotely operated valves on the liquid lines.
• Spacing and Impoundment: Codes such as NFPA 59A set separation distances and impoundment requirements, including thermal exclusion zones, which constrain the plot layout as much as the tank does.

Engineering Assurance and Project Support

Every vessel delivered by Shijiazhuang Zhengzhong Technology Co., Ltd. (Center Enamel) is designed and manufactured under a certified pressure equipment quality system, with design to ASME Section VIII Division 1 or EN 13445 and to EN 14620 or NFPA 59A for cryogenic service, material certification with full traceability from heat to plate, weld procedures and welder qualifications documented before production starts, and non-destructive examination of the completed welds by radiography, ultrasonic or penetrant methods to the extent the code and the service require. Cryogenic vessels are supplied with material certification and traceability from heat to plate, nine percent nickel or austenitic stainless inner construction, perlite or vacuum insulation with the design boil-off rate stated, foundation protection against ground freezing, controlled cool-down procedures, boil-off connections, pressure and vacuum protection with a defined vent or flare route, instrumentation for level, temperature and density profiling, and a documentation package prepared for third-party and authority review.

"At minus 162 degrees the vessel is not the hard part. The hard part is everything that has to keep working while the metal is that cold."

Frequently Asked Questions (FAQ)

At what temperature is LNG stored?

Around minus 162 degrees Celsius at atmospheric pressure. The design temperature is set below that to cover the actual gas composition and any pressure effect, and it is what determines the material: nine percent nickel steel or austenitic stainless grades for the inner tank, with ordinary carbon steel used only for the outer jacket.

Which containment type should I choose?

Full containment - an inner metallic tank inside a vapour-tight outer concrete tank that contains both liquid and vapour - is the modern standard for base-load terminals with large inventories. Double containment suits constrained sites, and shop-built vacuum vessels or pressurised storage suit small-scale and satellite installations. The authority having jurisdiction often decides.

What happens to boil-off gas?

Heat ingress generates gas continuously, typically in the region of 0.05 to 0.15 percent of inventory per day for large full-containment tanks. It is routed to a boil-off compressor, recondensed, sent to a user such as a power plant or industrial offtaker, or flared. The design figure determines the capacity of that system.

Can an LNG storage tank be customized to our project?

Yes. Containment type, capacity, design pressure and temperature, inner tank material, insulation system, boil-off handling capacity, instrumentation, safety systems and the documentation route are all configured to the project specification and to the requirements of the authority and the third-party inspector.