شیرهای کرایوژنیک

Cryogenic valves operate in fluid service below -46°C (ASHRAE definition) and down to -196°C (liquid nitrogen, LNG boiling point). At these temperatures, three design problems that standard valves never face become critical: (1) packing failure — standard PTFE packing cracks and graphite packing loses resilience below -100°C, so the packing chamber must be kept at ambient temperature through an extended bonnet that adds enough stem length to move the packing gland above the frost line. (2) trapped liquid pressure lock — when a valve closes with cryogenic liquid trapped inside the body cavity, that liquid warms slowly through heat conduction, expands from liquid to gas, and the pressure spike can lock the closing element against the seats; vent holes through the ball (ball valves) or body cavity gas vents (gate valves) prevent this pressure lock. (3) seat material embrittlement — standard PTFE becomes brittle below -100°C and cracks under seating stress; PCTFE (Kel-F) and TFM retain flexibility and sealing integrity down to -196°C. FLOWKS manufactures eight cryogenic valve configurations covering ball, globe, butterfly, gate, and control valve types. Top entry cryogenic ball valves provide in-line service access through a top cover without pipeline removal. Two-piece cryogenic ball valves offer compact bodies at 1/2"-4" sizes where in-line serviceability is less critical. Butt weld cryogenic globe valves eliminate all flanged connections for zero flange leak risk on small-bore permanent installations. Cryogenic butterfly valves with inspection ports combine isolation and process monitoring in one body through a sealed access port for temperature/pressure sensing. Cryogenic control valves regulate flow with extended bonnets keeping actuators at ambient temperature and multi-stage trim preventing flash flow during cryogenic pressure letdown. Flanged forged steel cryogenic gate valves provide forged-body integrity at 2"-12" with flanged access for periodic maintenance. Cast-body cryogenic gate valves cover the full range 1/2"-24" at cost-effective cast pricing for general cryogenic isolation. Small-bore forged steel cryogenic gate valves deliver zero-porosity forged integrity at 1/2"-2" with socket weld/threaded connections for critical permanent isolation points.