BS ISO 21159:2018,Ships and marine technology — Butterfly valves for use in low temperature applications — Design and testing requirements.
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BS ISO 21159:2018 specifies requirements for design, manufacture, and test methods of cryogenic butterfly valves in order to have an excellent quality leakage stability in a very low temperature service (−196 °C to 80 °C).
Butterfly valves can be divided into two types, with maintenance holes and without maintenance holes. For butterfly valves with maintenance holes, the disc or seat sealing shall be removable from the maintenance hole without removing the valve from the pipe. The butterfly valve is extended bonnettype. The end connection of the body is welding ends type or flanged ends type, a wheel or levers is used to apply the turning torque or thrust to open or close the valve. The butterfly valve may be either soft-seated or metal-seated. Configuration and functions of the butterfly valve are shown in this document. If there are some differences from this document the manufacturers can make a decision after reaching an agreement with the purchasers. General examples of the structure of the valve areshown in Annex A.
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