Check Valves for LNG & Cryogenic

Check valves in LNG and cryogenic service prevent liquid reverse flow in LNG pump discharge lines, boil-off gas (BOG) compressor suction and discharge, LNG loading arms, and cryogenic transfer piping. Operating temperatures range from −101°C (propane refrigerant) to −196°C (liquid nitrogen, LNG). At cryogenic temperatures, body materials must be impact-tested and notch-tough - A352 LCC (−46°C min) for most LNG service; SS 316L/CF8M (−196°C) for liquid nitrogen and deepest LNG cold box service. Spring and disc materials must retain elasticity at cryogenic temperatures.

Get a Quote Browse Check Valves

What check valves does the LNG & Cryogenic industry use?

Key Applications - Check Valves in LNG & Cryogenic

LNG Pump Discharge - Non-Return Protection

Swing check or dual-plate check valves on LNG submerged pump discharge lines in storage tanks and regasification send-out pumps. Rapid closure required to prevent liquid hammering on pump trip. A352 LCC body, SS 316 disc and hinge pin, Inconel 718 spring for −160°C LNG service.

DN50–DN300, Class 150–300, A352 LCC body, SS 316 trim, dual-plate design

BOG (Boil-Off Gas) Compressor Protection

Piston check valves on BOG compressor discharge lines prevent reversal during shutdown and surge events. Tight shutoff required - Class VI leakage for cryogenic gas. A351 CF8M (SS 316 cast) for −196°C BOG service. Metal-seated for bubble-tight closure in critical BOG re-liquefaction trains.

DN25–DN150, Class 300–600, A351 CF8M, piston check, Class VI shutoff

LNG Loading Arms and Marine Berth

Check valves on LNG marine loading arm circuits prevent reverse flow during emergency disconnection. Extended bonnet design required to maintain valve operability when body is at −160°C while stem area approaches ambient. API 6D and BS 6364 fire tested.

DN100–DN400, Class 150–300, A352 LCC + extended bonnet, BS 6364, API 6D

Liquid Nitrogen and Oxygen Service

Check valves for liquid nitrogen (LN₂, −196°C) and liquid oxygen (LOX, −183°C) service in air separation units and industrial gas supply. SS 316L (CF8M or CF3M) body and trim for all cryogenic liquid gas service. Oxygen service requires rigorous degreasing - no hydrocarbon contamination.

DN15–DN100, Class 150–300, A351 CF3M, degreased for O₂, piston check

Cryogenic Cold Box Piping

Check valves inside LNG cold box (brazed aluminium heat exchangers) for refrigerant circuit separation. Compact wafer-pattern check valves with A351 CF8M body for −160°C mixed refrigerant service. Lightweight, low-pressure-drop design for process efficiency.

DN25–DN150, Class 150, A351 CF8M, wafer pattern, low-ΔP piston check

Required Certifications

BS 6364 cryogenic testing - body and seat leakage test at operating cryogenic temperatureAPI 6D for pipeline check valves at LNG terminals and marine berthsAPI 607 fire-safe test certification for all hydrocarbon-service LNG check valvesASME B16.34 rated for the applicable pressure classCharpy V-notch impact testing of A352 LCC at −60°C (minimum) or at design temperatureEN 10204 3.1 MTCs (heat number traceability) for all cryogenic-service componentsPMI (Positive Material Identification) to confirm alloy on all cryogenic valves

Recommended Materials

A352 LCC (Low-temperature carbon steel) - LNG service to −46°C; most LNG storage tank and loading line check valves

A351 CF8M (cast SS 316) - down to −196°C; liquid nitrogen, deep cryogenic service

A351 CF3M (cast SS 316L) - −196°C, preferred for long-term cryogenic service due to lower carbon content

A350 LF2 - forged low-temp carbon steel, −46°C, for forged piston check valves

Inconel 718 spring material - retains elasticity at −196°C for spring-loaded check valves

SS 316L disc and hinge pin - impact tough at cryogenic temperatures, compatible with LNG

Selection Factors

Check valve type: Dual-plate (wafer) check valves have fast closure due to spring-assisted closure - preferred for BOG compressor protection; swing check valves have lower pressure drop but slower closure (water hammer risk in LNG pump lines if not spring-assisted)

Extended bonnet: Required for all cryogenic check valves where the bonnet/hinge assembly must remain above the cold box insulation line - prevents frost build-up seizing the hinge mechanism

Spring material: Standard carbon steel springs lose elasticity below −40°C - specify Inconel 718 or SS 304 springs for LNG and LN₂ service

Leakage class: LNG service typically requires Class VI (bubble-tight) shutoff for check valves on pump suction lines and BOG compressor inlet - prevents vapour bypass causing compressor surge

Cryogenic test: BS 6364 requires body and seat leakage tests at the lowest design temperature with liquid nitrogen as test medium; API 6D Annex F is a similar cryogenic test protocol - both are acceptable

Technical FAQs

What check valve design is best for LNG pump discharge service?

For LNG submerged pump discharge lines (−160°C, Class 150–300, typically DN50–DN200), dual-plate check valves (wafer pattern) with spring-assisted closure are the preferred design. The spring assists rapid disc closure on pump trip, limiting liquid reverse velocity and water hammer. Dual-plate check valves are more compact and lighter than swing check valves - important for cryogenic piping where pipe support loads are already increased by thermal contraction. Materials: A352 LCC body (minimum design temperature −46°C, impact tested at −60°C); SS 316 disc and disc pin; Inconel 718 or SS 316 spring. BS 6364 cryogenic testing at −196°C (nitrogen test medium) is standard for LNG terminal check valves - confirms body integrity and seat leakage at operating temperature. For LNG loading arm check valves (DN150–DN400), API 6D-rated swing check valves with spring-assisted closure are common - the larger bore makes dual-plate less compact.

How does extended bonnet design help check valves in cryogenic service?

An extended bonnet (also called extended stem or cold box extension) on a cryogenic check valve keeps the mechanical components (hinge pin, spring, disc actuating mechanism) above the insulation boundary - at or near ambient temperature - while the valve body (and the fluid contact surfaces) are at the cryogenic operating temperature (−160°C to −196°C). This prevents three problems: (1) Icing and frost seizure - if the hinge pin assembly is at −160°C, condensation and frost from atmospheric moisture can ice up the moving parts, preventing the check disc from seating properly. The extended bonnet keeps these parts above the dew point. (2) Packing degradation - PTFE packing loses flexibility at cryogenic temperatures; keeping the packing area warm prevents packing stiffening. (3) Metal embrittlement - while LCC and SS 316L bodies are rated for cryogenic temperature, the extension keeps non-cryogenic-rated components (springs, pins, bonnets) at ambient temperature. BS 6364 check valve designs specify minimum extension lengths based on insulation thickness.

Does LNG service require BS 6364 or API 6D cryogenic certification?

Both BS 6364 (British Standard - Testing of Valves) and API 6D (Annex F - Cryogenic Testing) are accepted cryogenic certifications for LNG service, and both are widely specified. The choice depends on the project specification and the operating company's standards: Shell, BP, and European IOCs commonly specify BS 6364; ExxonMobil and US-based operators more often cite API 6D Annex F. The test requirements are broadly similar: both require shell pressure test and seat leakage test at the actual operating cryogenic temperature (using liquid nitrogen, −196°C, as the test medium) and at ambient temperature (to confirm no permanent deformation occurred from thermal cycling). Key difference: BS 6364 specifies leakage in drops/minute (Class A = 0 drops, Class B = 5 drops/minute); API 6D Annex F specifies leakage in drops/minute for liquid and bubbles/minute for gas. If the project specification requires both, simply state 'cryogenic tested per BS 6364 and API 6D Annex F' - most major LNG valve manufacturers can provide both.