Currently researching LNG cryogenic service valve...
Metal-seat Triple-offset Butterfly Valves (TOBV) are well-suited to LNG service.
They are very inexpensive for inch of diameter.(Small mass, simple construction)
It is easy to fit them with an extension bonnet so that they can be used on cryo services and the stuffing box (stem seal) is outside the ice-ball.
The metal seat makes them inherently fire-safe while providing tight shutoff.

At 3 inches (75mm)  and below, the ball valves work better.  Small TOBVs have very limited capacity because even with the disk in the full open position there is still a lot of metal hanging in the flow stream. Remember, disk and stem are in the flow path with a TOBV. ANd in the higher pressure classes the shaft diameter increases to handle the additional torque, firther restricting flow.  You can barely see daylight thru a small, opened TOBV.Ball valves have virtually unobstructed flow paths, and in these sizes there is not that much more metal to have to pay for.  Firesafe/Cryogenic seats are available as are cryo stem seals and/or extended bonnets.

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