Technical requirements for cryogenic valves according to the BS 6364 standard
The BS 6364 standard regulates comprehensive engineering requirements for the design, manufacturing methods, and testing protocols of isolation and control valves intended for operation in deep-cooling conditions. The use of these valves requires strict adherence to specialized British standards, ensuring equipment reliability:
- Steel wedge gate valves: BS 1414;
- Steel check valves: BS 1868;
- Steel globe valves, stop-check valves, and check valves: BS 1873;
- Steel ball valves: BS 5351;
- Steel wedge gate, globe, and check valves (DN 50 and smaller): BS 5352;
- Brass globe, gate, and check valves: BS 5154;
- Testing of valves: BS 6755;
- General-purpose butterfly valves: BS 5155.
The standard covers sizes from DN 15 up to the maximum values stipulated by the base standards. The operating temperature range is from -50 °C to -196 °C, accounting for startup, shutdown, and continuous operation cycles under extreme conditions.
Note 1: When designing equipment for offshore platforms with operating temperatures below -165 °C, it is necessary to additionally consider specialized regulations for cryogenic systems.
Note 2: Appendix C contains a list of critical data provided by the customer when placing an order specification with EV Group China.
Materials science and design features
The selection of materials for seals and gland packing falls outside the scope of this standard due to the wide range of polymers and alloys used. However, Appendix B provides recommendations for the use of austenitic steels and non-ferrous metals that possess the necessary toughness at ultra-low temperatures.
Fasteners (bolts) must comply with the requirements of BS 4882.
Technical recommendation: During the initial cooldown of the system to -196 °C, minor changes in geometric parameters may occur in austenitic steels due to phase transformations. This can lead to a reduction in the preload force of bolted connections. EV Group China engineers recommend accounting for this factor when calculating tightening torques.
Seat design can be either metal-to-metal or combined (soft seal with a metal core). When using pure PTFE, the design must eliminate the risk of material cold flow.
To prevent the seizing (galling) of moving parts at cryogenic temperatures, the selection of trim materials must be carried out taking into account linear expansion coefficients and tribological properties.
Casting repair technology
Any repair work on casting body parts performed by welding must fully comply with the quality acceptance criteria according to the BS 5998 standard.
Product marking
Each unit of products supplied by EV Group China undergoes mandatory marking in accordance with the base standard for the specific type of valve. Additionally, the designation of the BS 6364:1984 standard and the minimum permissible operating temperature (e.g., -196 °C) are marked, which ensures traceability and operational safety of the equipment.