Low-Temperature Butterfly Valve Leakage: Causes, Solutions, and Optimization Best Practices
Industrial facilities relying on cryogenic processes such as LNG production, air separation, and petrochemical processing face persistent challenges with valve performance. Among the most critical issues are internal and external leakage in low-temperature butterfly valves, which compromise safety, increase maintenance costs, and reduce operational efficiency.The main Butterfly Valve product names of China Butterfly Valve Network include:Three Eccentric Multi-level Metal Hard-sealed Wafer Butterfly Valve,Flange Metal Sealed Swing Butterfly Valve,High Temperature Butterfly Valve,Butt Welded Hard-sealed Butterfly Valve,Extended Hard-sealed Flange Butterfly Valve,Electric Metal Hard-sealed Wafer Butterfly Valve,Pneumatic Metal Hard-sealed Wafer Butterfly Valve,Sanitary Butterfly Valve.
Understanding Internal Leakage in Cryogenic Service
Internal leakage occurs when sealing components undergo dimensional changes due to phase transformation at extreme temperatures. For example, testing of a DN250 butterfly valve in liquid nitrogen (-196°C) revealed that the 1Cr18Ni9Ti disc developed sealing surface warping up to 0.12 mm—sufficient to cause significant leakage.
To address this, advanced triple-eccentric metal-seated butterfly valves now incorporate a tapered conical sealing design. The valve seat features an elliptical sealing surface that interfaces with a flexible metallic sealing ring mounted on the disc. During closure, the elastic ring gradually deforms, compensating for any thermal distortion in the valve body or disc. This design not only ensures bubble-tight sealing at cryogenic temperatures but also eliminates friction during operation, significantly extending service life.
External Leakage: Root Causes and Engineering Solutions
External leakage typically occurs at two critical points: flange connections and valve stem packing.
Flange joints are susceptible to leakage due to differential thermal contraction between bolting and flange materials. Converting flange connections to welded end configurations eliminates this failure mode entirely.
Stem packing presents another challenge. While PTFE (F4) offers excellent chemical resistance and low friction, its high thermal expansion coefficient causes shrinkage at low temperatures, leading to leakage paths. Advanced solutions employ self-compensating packing designs that leverage PTFE's expansion characteristics, maintaining effective sealing across both ambient and cryogenic temperature ranges.
Material Selection and Design Considerations
Successful low-temperature valve performance depends on three critical factors:
Body Materials: Austenitic stainless steels (such as 1Cr18Ni9Ti) with face-centered cubic crystal structures maintain ductility at cryogenic temperatures and resist embrittlement.
Bearing Surfaces: SF-1 composite bearings provide low friction and self-lubrication, preventing galling and seizure during operation at extreme temperatures.
Geometric Design: Symmetrical body configurations minimize thermal stress and reduce cool-down energy requirements.
Industry Applications and Future Trends
Triple-eccentric butterfly valves offer distinct advantages over traditional gate and globe valves in cryogenic service, including lower flow resistance, faster actuation, reduced weight (40-50% lighter than equivalent gate valves), and bidirectional sealing capability.
As global demand for LNG and industrial gases continues expanding, properly engineered low-temperature butterfly valves represent a critical technology for safe, efficient plant operations.
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