LNG & Cryogenic×Butterfly Valves

Butterfly Valves for LNG & Cryogenic

Triple-offset butterfly valves for LNG and cryogenic service combine the cost and weight advantage of a butterfly valve at large bore with metal-seated bubble-tight shut-off and fire-safe performance. Vajra Industrial Solutions supplies cryogenic triple-offset butterfly valves with SS 316L bodies, extended stems, and BS 6364-compliant cryogenic testing for LNG terminal vapour headers, boil-off gas (BOG) systems, and large-bore low-pressure cryogenic service — complementing cryogenic ball valves for smaller bore and high-pressure applications.

Key Applications — Butterfly Valves in LNG & Cryogenic

LNG Boil-Off Gas (BOG) Headers

Triple-offset butterfly valves for large bore LNG boil-off gas headers at LNG terminals and satellite stations. BOG is methane vapour generated from LNG warming — it must be routed to compressors or flare. Large-bore butterfly valves (DN300–DN900) provide cost-effective isolation for BOG headers at Class 150 pressure. Cryogenic extended stem (not full extended bonnet needed for vapour service as process temperature is −80°C to −120°C, not −162°C liquid).

DN300–DN900, Class 150, SS 316L, triple-offset metal seat, cryogenic extended stem

LNG Terminal Vapour Return Lines

Butterfly valves for LNG carrier vapour return lines from ship to shore. During LNG unloading, the displaced vapour from the ship's tanks must be returned to the terminal — typically large bore (DN300–DN600) at low pressure (Class 150). Triple-offset butterfly valves provide bubble-tight shut-off and fire-safe performance at reduced weight and cost compared to equivalent ball valves. Extended stem standard for vapour return headers.

DN300–DN600, Class 150, SS 316L, triple-offset, API 607 fire-safe, extended stem

Industrial Gas Plant — Large Bore Cryogenic Isolation

Cryogenic butterfly valves for air separation units (ASU) — large bore liquid oxygen, liquid nitrogen, and liquid argon streams. At DN300 and above, butterfly valves offer a significant weight and cost advantage over ball valves for low-pressure (Class 150/300) cryogenic service. Oxygen cleaning mandatory for LOX service. Cryogenic functional test per BS 6364.

DN200–DN900, Class 150–300, SS 316L, oxygen-cleaned option, BS 6364 cryogenic test

Required Certifications

BS 6364 — Cryogenic functional testing at design temperatureAPI 607 — Fire-safe design (LNG hydrocarbon service)API 609 — Butterfly Valve Standard (Category B for flanged LNG service)EN 10204 3.2 MTCs — third-party material certificationATEX (actuated valves in LNG hazardous area Zone 1)

Recommended Materials

A351 CF8M (SS 316 cast) — standard large bore cryogenic butterfly valve body
A182 F316L (SS 316L forged) — disc and trim for aggressive cryogenic environments
INCONEL 625 (N06625) — seat ring overlay for long service life
A350 LF2 — limited to −46°C minimum; not suitable for full LNG liquid temperature

Selection Factors

Triple-offset design mandatory for metal-to-metal shut-off at cryogenic temperature — elastomeric seats become brittle
Extended stem (not full extended bonnet for vapour service) — keeps packing above −29°C in BOG and vapour return service
Full extended bonnet required if valve sees liquid LNG (−162°C) rather than BOG vapour (−80°C to −120°C)
Fire-safe API 607 mandatory for all LNG service — specify Category B flanged design per API 609
Size range: butterfly valves competitive vs ball valves at DN300+ for Class 150 BOG and vapour service

Technical FAQs

When should I choose a butterfly valve over a ball valve for LNG service?
Choose a cryogenic butterfly valve for large bore (DN300+) low-pressure (Class 150) LNG vapour and BOG service where the weight and cost advantage of a butterfly valve outweigh the need for full-bore capability. Ball valves are the standard for liquid LNG service (−162°C), high-pressure Class 300+ service, and any service requiring full-bore pigging capability. For LNG terminal block valves on liquid headers, ball valves (API 6D) are the standard. For BOG compressor suction isolation and vapour return at DN600+, butterfly valves can reduce weight and cost by 60–70%.
Why can't elastomeric-seated butterfly valves be used for LNG service?
Elastomeric seats (EPDM, NBR, natural rubber) become brittle at temperatures below approximately −30°C to −50°C. At LNG temperatures (−162°C), elastomeric seats would shatter on valve operation, resulting in loss of seating integrity. Triple-offset butterfly valves with metal-to-metal seats (SS 316L disc against Inconel 625 seat ring, or stellite hard-faced seat ring) maintain seating integrity at cryogenic temperatures because metals do not become brittle in the same way. All cryogenic butterfly valves for LNG and industrial gas service must be triple-offset metal-seated.

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Butterfly Valves for LNG & Cryogenic

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