How to Choose Cryogenic Valves for LNG

If you are responsible for sourcing valves for an LNG terminal, a liquefaction facility, or an LNG bunkering project, the valves on your cryogenic lines carry more risk than almost any other component in your piping system. LNG is handled at approximately −162 °C, and at that temperature a valve that would perform perfectly in steam, oil, or water service can seize, leak, or fail its seat entirely. Choosing correctly is not only about avoiding downtime; it protects the people working around your storage tanks and keeps your operation compliant with the standards your customers and insurers expect you to meet.

This guide walks you through cryogenic valve selection in the order your procurement team should actually follow: what makes a valve truly cryogenic, the four valve types you will most often choose between, a five-step selection process you can reuse across projects, and the standards and tests—especially BS 6364—that prove a valve is fit for LNG duty before it ever reaches your site.

What Is a Cryogenic Valve?

A cryogenic valve is a valve engineered to seal and operate reliably at very low service temperatures—commonly defined as below −50 °C, with LNG service demanding continuous performance down to −162 °C and test verification at −196 °C in liquid nitrogen. The challenge at these temperatures is physical, not theoretical: metal bodies contract, polymer seats harden and lose resilience, and any moisture trapped in a component turns to ice. A standard industrial valve dropped into LNG service will usually leak past its seat, bind at the stem, or destroy its soft parts within the first thermal cycles.

Cryogenic valve design answers those problems with three signature features you should look for on every datasheet you review. First, an extended bonnet: a long bonnet and stem column that positions the stem packing and actuator 150–250 mm above the cold source, so the packing stays above freezing and does not fail, while the column also acts as a thermal barrier that limits heat input into the line. Second, materials with verified low-temperature toughness, typically austenitic stainless steels for the body and closure members, paired with seat materials such as PCTFE that keep their shape at cryogenic temperature. Third, meticulous cleanliness: every cryogenic valve must be fully degreased and moisture-free before shipment, because a single trace of oil or water becomes a hazard or a blockage at −162 °C.

When you compare suppliers, treat these three features as pass/fail criteria rather than marketing points. A manufacturer who can explain exactly how long its extended bonnet is, which seat polymer it uses and why, and how it documents cleanliness is showing you the evidence base you need for your own file.

What Are the 4 Common Cryogenic Valve Types?

Most LNG valve packages are built from four families, and each earns its place by doing a different job on your line. Understanding the split between them is the fastest way to narrow your shortlist before you ever request a quotation, because the costliest selection mistakes usually come from specifying a shutoff valve where the duty actually needs throttling, or the reverse.

The cryogenic ball valve is your workhorse for tight, fast isolation. Quarter-turn operation makes it easy to automate, and in larger sizes or higher pressure classes it is almost always trunnion mounted, so the seat seals carry the load instead of the ball. The cryogenic globe valve is the type you choose when your process needs controlled throttling, reliable vent and bleed duty, or a valve your maintenance team can reseat in the field. The cryogenic gate valve offers a full, unobstructed bore for lines where pressure drop must stay minimal and pigging is required, which is why it appears on transfer and loading lines, though it is strictly an open-shut valve and should never be used for throttling. Finally, the cryogenic check valve protects your pumps and compressors by preventing reverse flow when a line shuts down—unglamorous, but without it a single trip event can send product and surge pressure back into equipment that was never designed for it.

How to Choose a Cryogenic Valve in 5 Steps

Use the sequence below as a repeatable checklist for every LNG line you specify. Working in this order keeps the commercial conversation with your supplier efficient, because by the time you request a quote you already know the duty, the type, the materials and the tests you will accept.

Step 1: Define Your Operating Conditions Precisely

Start with the numbers, because every downstream decision depends on them. Confirm your minimum design temperature—remember that cooldown transients can briefly take a line below normal LNG temperature—along with operating and design pressure, line size, flow rate and allowable pressure drop. Also note where the valve sits: a valve on a tank internal line faces different thermal conditions from one on a loading arm. As a benchmark, established cryogenic valve suppliers commonly cover 1/2" to 24" nominal bore and Class 150 to Class 2500; if your duty falls inside that envelope, a standard cryogenic design will usually be available, while extremes of size or pressure call for early engineering discussion with the manufacturer.

Step 2: Match the Valve Type to the Duty

Now map each function on your line to one valve type from the table above. For pure isolation your default choice is a trunnion mounted cryogenic ball valve, and if you are weighing design options it helps to understand how floating vs trunnion mounted ball valves behave as pressure and bore increase—floating designs suit smaller, lower-pressure lines, while trunnion designs take the seat load off the ball and are the norm in LNG service. Where the process needs modulation, venting or frequent operation, choose a cryogenic globe valve, and reserve cryogenic gate valves for the full-bore, open-shut lines where pigging or minimal pressure drop matters. Getting this mapping right at the drawing stage prevents the classic retrofit problem: a gate valve installed where operators keep trying to throttle, wearing seats and leaking long before their design life.

Step 3: Specify Materials and the Extended Bonnet

Materials decide whether the valve survives its first thermal cycle. For LNG, insist on an austenitic stainless steel body and closure members with documented impact toughness at service temperature, and pay particular attention to the soft parts: PTFE seats that work perfectly at ambient temperature lose resilience as temperatures fall, so for −162 °C service you should expect PCTFE or an equivalent cryogenic polymer in the seats and seals. The extended bonnet deserves equal attention—ask each supplier for the actual bonnet extension and confirm it keeps the packing above the frost line for your insulation thickness and orientation, because a bonnet that is buried in insulation or installed horizontally defeats the design. This is also the stage to agree on cleanliness and leakage containment requirements, and if your specification demands near-zero stem leakage, it is worth reading how bellow seal valve designs achieve zero-leakage sealing before you finalize that clause.

Step 4: Demand Evidence — Testing and Certification

A cryogenic valve is only as good as the tests it has passed, so make test evidence a contractual requirement rather than a brochure claim. At minimum, require ambient shell and seat testing to a recognized leakage standard, plus cryogenic testing to BS 6364 or an equivalent procedure, performed in liquid nitrogen at −196 °C with measured operating torques and seat leakage rates. Ask each shortlisted supplier for the actual test reports, not just certificates of conformity, and check that the certificate references match the valve marks on the nameplate. When you evaluate a cryogenic valve manufacturer or supplier, the ability to produce complete, traceable test documentation at −196 °C is one of the clearest signals that the product will behave in your plant the way the datasheet promises.

Step 5: Plan Installation, Operation and Maintenance Before You Buy

The best valve will still underperform if installation realities are left out of the specification. Decide early how each valve will be operated—manual wrench or handwheel for accessible points, and electric, pneumatic or hydraulic actuation for valves on tank roofs, elevated lines or emergency shutdown duties—and confirm the actuator and its accessories are also rated for cryogenic exposure. Plan the insulation and cold box details around the extended bonnet, specify installation orientation (globe and gate bonnets upright, within the angle the manufacturer permits), and make sure your team keeps post-weld cooldown procedures in mind when welding the valve into the line. Finally, think about the day after commissioning: spare seat and seal sets, documented re-torque values and a maintenance plan will decide your cost of ownership, and a good starting point is this guide to maintaining a cryogenic globe valve for long-term reliability.

Which Standards and Tests Prove Cryogenic Performance?

Standards exist to take guesswork out of your procurement file, and for LNG valves a small set covers most of what you need. BS 6364 is the reference most buyers reach for first: it defines how a valve is cooled down in liquid nitrogen to −196 °C, the operating and leakage checks performed at that temperature, and the acceptance criteria the valve must meet before it can be called fit for cryogenic service. Complementary standards fill in the rest of the picture—covering extended bonnet requirements, seat leakage classes, fugitive emissions and, where your project demands it, fire-safe design. The table below summarizes the set you are most likely to reference in an LNG valve specification.

When you collect bids, ask every supplier to state explicitly which standards each valve is tested to and to attach the corresponding reports. If a quote for cryogenic service does not mention BS 6364 or an equivalent cryogenic test, treat the valve as unproven for LNG duty no matter how attractive the price is—retesting or replacing a valve after installation costs far more than the premium you pay for documented performance.

FAQs

What temperature counts as “cryogenic” for valve selection?

For valve engineering, cryogenic service generally begins at around −50 °C and certainly by −100 °C, while LNG service demands continuous operation at approximately −162 °C and verification testing at −196 °C. The distinction matters because material behavior changes progressively: carbon steels lose toughness well before LNG temperatures, and standard soft seals lose resilience as you approach −100 °C. If any part of your duty can drop below −50 °C—including cooldown transients—you should be specifying cryogenic construction for that valve.

Why do cryogenic valves have extended bonnets?

The extended bonnet creates a gas column between the cold media and the stem packing, keeping the packing, gland and actuator above freezing where they can function normally. Without that column, packing freezes, loses its seal and allows cold gas to escape, and the actuator or handle becomes unusable with ice. The bonnet also serves as thermal insulation between the atmosphere and the cryogenic line, and standards such as MSS SP-134 define the design details so the extension matches the insulation and installation orientation of your line.

Ball valve or globe valve for LNG service — which should you choose?

Choose by function, not by habit. If the line needs fast, tight, full-bore isolation—tank inlet and outlet, manifolds, loading arms—a cryogenic ball valve is normally the right answer because it closes in a quarter turn and seals tightly with low pressure drop. If the line needs throttling, frequent operation, vent or bleed duty, a cryogenic globe valve gives you precise control and seats your maintenance team can reseat in the field. Many LNG packages use both: ball valves for isolation and globe valves where control and containment matter most.

What seat material should you specify for −162 °C LNG?

For LNG duty, PCTFE is the seat material most engineers specify because it retains its shape, hardness and sealing performance at cryogenic temperature far better than PTFE, which becomes progressively less resilient as temperature falls. That said, PTFE-based compounds remain valid in less extreme cryogenic ranges, and some designs combine materials across seat, body and stem seals. The right question for your supplier is which polymer they use at your exact minimum design temperature and what test evidence backs that choice—reputable manufacturers will answer with a temperature rating and a BS 6364 report, not a general datasheet.

What is BS 6364, and do you really need it for LNG valves?

BS 6364 is the British Standard for cryogenic valve testing, and it defines the whole proof sequence: cooling the valve in liquid nitrogen to −196 °C, verifying that it operates and seals at that temperature, and recording the torques and leakage rates observed. For LNG service it is effectively the industry benchmark, and most project specifications require it or an equivalent such as GB/T 24925. If you skip it, you are buying a valve whose low-temperature performance is a claim rather than a measurement—rarely a risk worth taking on a line that handles methane at −162 °C.

Can you install a standard valve for LNG if you derate it?

No—derating pressure does not fix the problems that disable a standard valve at cryogenic temperature. At −162 °C the body material must have verified low-temperature toughness, the seat and stem seals must remain elastic, and the bonnet must be extended so the packing survives; a standard valve has none of these features, so it will leak or seize regardless of its pressure rating. The only acceptable route is a valve designed and tested for cryogenic service, with the documentation to prove it.

Conclusion

Choosing cryogenic valves for LNG comes down to a disciplined five-step process: define your operating conditions precisely, match each valve type to its duty, specify materials and an extended bonnet that survive −162 °C, demand BS 6364 or equivalent test evidence, and plan installation, operation and maintenance before the purchase order is signed. Apply that sequence line by line and you will end up with a valve package that passes commissioning the first time and stays tight for its design life.