LNG Valves: 8 Selection Factors for Cryogenic Service
LNG Valves are critical flow-control components used throughout liquefied natural gas production, storage, transportation, loading, unloading, and regasification systems. Their primary functions include isolating LNG pipelines, regulating flow and pressure, preventing reverse flow, controlling emergency shutdown sequences, and protecting equipment from unsafe operating conditions.
Liquefied natural gas is natural gas that has been cooled to approximately −162°C, or −260°F, so that it can be stored and transported as a liquid. At this temperature, ordinary industrial valves may experience material embrittlement, seal shrinkage, excessive leakage, increased operating torque, or damage caused by thermal contraction.
Reliable LNG Valves must therefore be engineered as complete cryogenic assemblies. Valve body materials, seats, stem packing, bonnet extensions, cavity-pressure-relief arrangements, actuators, testing procedures, and installation orientation must all be evaluated against the actual LNG process conditions.
Fujian JST Valve Manufacturing Co., Ltd. has nearly 33 years of experience in industrial valve engineering. JST Valve provides customized valve solutions for low-temperature, corrosive, high-pressure, abrasive, and other demanding industrial applications. Valve structures, materials, sealing systems, actuators, and testing requirements can be configured according to customer datasheets and project specifications.
Typical Temperature
LNG is normally handled at approximately −162°C, although temperatures vary across different parts of an LNG facility.
Main Valve Functions
Isolation, throttling, pressure control, reverse-flow prevention, emergency shutdown, loading, and unloading.
Common Valve Types
Cryogenic ball valves, gate valves, globe and control valves, check valves, butterfly valves, and emergency shutdown valves.
What Are LNG Valves?
LNG Valves are valves designed or selected for liquefied natural gas and associated cryogenic or low-temperature process systems. Depending on their location, they may come into direct contact with LNG, cold natural gas vapour, boil-off gas, refrigerants, utility fluids, or natural gas at temperatures above the main cryogenic process temperature.
Not every valve in an LNG terminal operates at −162°C. Upstream gas-treatment lines, compressor systems, boil-off-gas units, utilities, and regasified-gas pipelines may operate at significantly different temperatures and pressures. The design temperature shown on the valve datasheet must therefore reflect the actual process location rather than the general temperature associated with LNG.
A properly selected LNG valve should maintain pressure integrity, seat tightness, acceptable operating torque, stem-seal performance, and reliable actuation during normal operation, cooldown, startup, shutdown, and emergency conditions.
Where LNG Valves Are Used
LNG facilities contain many process stages, each with different valve duties. Typical applications include:
- Natural-gas pretreatment and contaminant-removal systems
- Liquefaction trains and refrigerant circuits
- Cryogenic LNG storage tanks and associated piping
- LNG loading arms and marine loading systems
- LNG carrier loading and unloading manifolds
- Truck, rail, container, and bunkering stations
- Boil-off-gas collection and compressor systems
- LNG pumps, vaporizers, and regasification equipment
- Fuel-gas supply and gas-send-out pipelines
- Emergency shutdown and process-isolation systems
Why Cryogenic LNG Service Is Challenging
At cryogenic temperatures, valve materials contract. Different components may contract at different rates, changing clearances between the ball, disc, seat, stem, body, bonnet, packing, and bearings. A valve that seals correctly at ambient temperature may behave differently after cooldown.
The low temperature may also reduce the toughness or flexibility of unsuitable materials. Soft seats and elastomeric seals must be carefully selected because not every polymer or elastomer retains adequate properties at LNG temperatures.
Another concern is trapped liquid. If LNG is isolated inside a closed body cavity and later absorbs heat, it can vaporize and generate a rapid increase in cavity pressure. Cryogenic ball valves may therefore require a project-approved cavity-pressure-relief arrangement, such as a self-relieving seat design or another engineered pressure-relief method.
Engineering Note
The required cavity-relief direction, seat arrangement, valve orientation, and flow direction must be identified on the valve documentation. These details should not be assumed from the valve type alone.
8 Selection Factors for LNG Valves
1. Minimum Design Temperature
The minimum design temperature is one of the first parameters required when selecting LNG Valves. It determines the acceptable body, bonnet, stem, bolting, seat, packing, gasket, and actuator materials.
The valve specification should distinguish among normal operating temperature, minimum operating temperature, minimum design metal temperature, cooldown conditions, and potential exposure to cold vapour. Specifying only “LNG service” is not sufficient for an accurate valve selection.
2. Valve Body and Trim Materials
Austenitic stainless steels are commonly considered for direct cryogenic LNG service because they can retain useful toughness at very low temperatures. Depending on the application, selected nickel alloys and other low-temperature-qualified materials may also be specified.
Low-temperature carbon steels may be used in warmer sections of an LNG facility when their certified temperature limits are appropriate, but they should not automatically be applied to piping that may reach full LNG temperature.
Final material selection should be based on design temperature, pressure class, process composition, corrosion requirements, impact-test requirements, applicable standards, and the customer-approved material specification.
3. Extended Bonnet and Stem-Seal Protection
Many cryogenic LNG Valves use an extended bonnet or extended stem arrangement. The extension helps position the packing and stem-sealing components farther away from the coldest process zone.
Bonnet-extension length and installation orientation must be selected carefully. The design should also consider insulation thickness, accessibility, frost formation, actuator mounting, thermal conduction, and the possibility of cold vapour reaching the packing area.
4. Seat Design and Leakage Performance
Seat design has a direct effect on shut-off performance, operating torque, wear, cavity pressure, and service life. Cryogenic seats must accommodate dimensional changes during cooldown while maintaining the required sealing load.
Depending on the valve type and project requirements, the sealing system may use cryogenic-compatible polymer seats, reinforced polymer seats, metal seats, resilient inserts, or composite arrangements. The required leakage acceptance criteria should be specified before quotation and manufacturing.
5. Pressure Class and Differential Pressure
Valve pressure class alone does not determine operating suitability. Maximum differential pressure influences seat loading, stem torque, disc or ball forces, actuator sizing, and the ability of the valve to open or close under emergency conditions.
Purchasers should provide design pressure, operating pressure, shut-off differential pressure, flow direction, pressure-relief requirements, and the maximum pressure that may occur during blocked-in or thermal-expansion conditions.
6. Fire Safety and Fugitive-Emission Requirements
LNG facilities handle flammable hydrocarbon fluids, so project specifications may include fire-test requirements, anti-static design, blowout-resistant stems, controlled external leakage, and fugitive-emission performance.
These requirements must be confirmed for the exact valve type, size, pressure rating, seat configuration, and selected standard. A general statement that a valve is “fire safe” should not replace project-specific documentation and test requirements.
7. Actuator and Emergency Shutdown Performance
Pneumatic, hydraulic, electric, or electro-hydraulic actuators may be used to operate LNG valves. The actuator must provide sufficient torque or thrust under the most demanding operating condition, including low ambient temperature, maximum differential pressure, extended-stem friction, and emergency shutdown duty.
Actuator specifications may include:
- Fail-open, fail-close, or fail-in-place action
- Required opening and closing time
- Minimum available air, hydraulic, or electrical supply
- Partial-stroke or full-stroke testing
- Local and remote position indication
- Hazardous-area electrical classification
- Fireproofing or environmental protection requirements
8. Cryogenic Testing and Documentation
Ambient-pressure and seat tests alone may not demonstrate valve performance at LNG temperature. Project requirements may therefore specify low-temperature production testing, cryogenic type testing, fugitive-emission testing, material traceability, impact-test reports, nondestructive examination, and functional actuator testing.
The testing scope should identify the test temperature, test medium, valve orientation, leakage limits, number of operating cycles, pressure levels, measuring method, witness requirements, and documentation to be submitted with the valve.
Common Valve Types Used in LNG Facilities
| Valve Type | Typical LNG Duty | Important Selection Considerations |
|---|---|---|
| Cryogenic Ball Valves | Pipeline isolation, loading systems, emergency shutdown, storage, and process-unit isolation. | Extended stem, cavity-pressure relief, seat direction, anti-static design, shut-off differential pressure, and cryogenic testing. |
| Cryogenic Gate Valves | Full-flow isolation in larger process, storage, transfer, and terminal pipelines. | Bonnet extension, wedge and seat alignment, body-cavity pressure, thermal contraction, stem sealing, and installation orientation. |
| Globe and Control Valves | Flow regulation, pressure control, bypass service, boil-off-gas control, and process stabilization. | Flow coefficient, control range, trim design, cavitation, flashing, noise, actuator response, and low-temperature packing performance. |
| Cryogenic Check Valves | Reverse-flow prevention around pumps, compressors, vaporizers, and transfer pipelines. | Minimum opening pressure, closing response, installation direction, pressure drop, disc stability, and low-temperature material compatibility. |
| Cryogenic Butterfly Valves | Large-diameter isolation and selected control duties where compact dimensions and lower weight are valuable. | Offset design, disc-to-seat movement, shaft sealing, leakage requirement, torque, differential pressure, and low-temperature seat behaviour. |
| Emergency Shutdown Valves | Rapid isolation of loading lines, storage systems, process units, and transfer equipment during abnormal conditions. | Fail-safe action, closing time, actuator sizing, position feedback, emergency power, fire exposure, and functional testing. |
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Material Considerations for LNG Valves
Material selection for LNG Valves must account for both low-temperature toughness and process compatibility. The selected materials must remain suitable for the specified design temperature and pressure while also meeting project requirements for corrosion resistance, welding, heat treatment, impact testing, traceability, and nondestructive examination.
| Material Group | Engineering Considerations |
|---|---|
| Austenitic Stainless Steel | Commonly considered for direct cryogenic service because selected grades can retain useful toughness at very low temperatures. Grade, casting or forging specification, welding requirements, and project-approved temperature limits must be confirmed. |
| Low-Temperature Carbon Steel | May be suitable for warmer gas, utility, or low-temperature sections when the certified material limit and impact-test requirements match the actual design temperature. It should not automatically be specified for full-temperature LNG service. |
| Nickel-Based Alloys | May be evaluated for specialized low-temperature, corrosion-resistant, high-strength, or demanding process applications. The exact alloy must be selected from complete service data. |
| Seats, Packing, and Gaskets | Polymeric, graphite, metallic, and composite sealing materials must be verified for the minimum design temperature, pressure, movement, leakage requirement, fire-safety requirement, and expected operating cycles. |
Material recommendations must be verified against the complete project datasheet and applicable standards.
Standards Commonly Referenced for LNG Valves
The applicable standards depend on the valve type, installation, process system, customer specification, and jurisdiction. Project documents may reference standards covering low-temperature valve design, pipeline valves, pressure-temperature ratings, cryogenic testing, fire testing, emissions, and pressure equipment.
- ISO 28921-1: design, materials, manufacturing, and production testing for selected low-temperature isolation valves and check valves.
- ISO 28921-2: low-temperature type testing for isolation valves.
- ISO 21011: design, manufacturing, and testing requirements for valves used with cryogenic vessels.
- ASME B16.34: pressure-temperature ratings, materials, dimensions, testing, examination, and marking for applicable industrial valves.
- API Specification 6D: requirements for pipeline and piping valves where specified by the project.
Important
A reference to a standard does not mean that every valve automatically complies with every edition, option, annex, test, or certification requirement. The applicable edition and complete project requirements must be confirmed before quotation and manufacturing.
How JST Valve Supports LNG Projects
JST Valve works with customers to evaluate valve operating conditions and prepare project-specific solutions. Depending on the application and approved specification, the supply scope may include cryogenic ball valves, gate valves, globe valves, check valves, butterfly valves, actuated valve packages, and customized flow-control products.
JST Valve engineering support may include:
- Review of medium, temperature, pressure, and differential-pressure data
- Selection of body, trim, seat, packing, and gasket materials
- Extended-bonnet and extended-stem configurations
- Cavity-pressure-relief and seat-direction evaluation
- Pneumatic, electric, hydraulic, or fail-safe actuator packages
- Customized dimensions, connections, and operating arrangements
- Inspection, testing, traceability, and documentation according to purchase requirements
Explore the
JST Valve ball valve range
the
JST Valve butterfly valve range
or learn more about
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Information Required to Select LNG Valves
To obtain an accurate technical recommendation and quotation for LNG Valves, please provide:
- Process medium and complete fluid composition
- Minimum, normal, and maximum operating temperature
- Minimum design metal temperature
- Operating pressure and design pressure
- Maximum shut-off differential pressure
- Valve type, nominal size, and pressure class
- Required flow direction and installation orientation
- Required leakage acceptance criteria
- Body, trim, seat, packing, and gasket requirements
- End connection and face-to-face standard
- Actuator type, fail position, and required operating time
- Cryogenic, fire, emission, and functional test requirements
- Required certificates, inspection plans, drawings, and documentation
- Quantity, delivery schedule, and project destination
Frequently Asked Questions About LNG Valves
What temperature must LNG valves withstand?
Direct LNG service may approach approximately −162°C. However, the required valve design temperature depends on the exact location and process conditions. Some valves in an LNG facility operate in warmer low-temperature, vapour, utility, or regasified-gas service.
Why do cryogenic LNG valves use extended bonnets?
An extended bonnet or stem helps move the packing and stem-sealing area farther from the coldest process region. Its dimensions and orientation must account for insulation, thermal conduction, cold vapour, accessibility, and actuator installation.
Why is cavity-pressure relief important in LNG ball valves?
LNG trapped inside a closed valve cavity can absorb heat, vaporize, and generate increasing pressure. The ball-valve seat arrangement and pressure-relief direction must therefore be reviewed against the project piping and isolation philosophy.
Which valves are commonly used for LNG isolation?
Cryogenic ball valves and gate valves are commonly considered for isolation. Butterfly valves may be selected for certain large-diameter applications, while the final choice depends on leakage requirements, pressure drop, operating torque, space, weight, and project standards.
Can LNG valves also regulate flow and pressure?
Yes. Globe valves, control valves, segmented ball valves, and selected butterfly valves can be engineered for flow or pressure regulation. Control-valve sizing must evaluate flow coefficient, pressure drop, flashing, cavitation, noise, required range, and actuator response.
Can JST Valve manufacture customized LNG valves?
JST Valve can evaluate customized valve configurations based on the customer’s process data, drawings, material requirements, applicable standards, actuator specifications, inspection plan, testing scope, and documentation requirements.
Technical References
Additional technical information is available from the
U.S. Energy Information Administration LNG overview
the
ISO 28921-1 low-temperature valve standard
the
ISO 21011 cryogenic valve standard
and
ASME B16.34
Request an LNG Valve Recommendation
Need cryogenic valves for an LNG liquefaction plant, storage facility, loading terminal, regasification station, LNG carrier, bunkering system, or fuel-gas project? Send your process conditions and project specifications to the JST Valve engineering team.
We will review the temperature, pressure, medium, valve function, materials, sealing requirements, actuator configuration, testing scope, and documentation requirements before preparing a technical recommendation and quotation.
