What is the difference between soft-sealed and hard-sealed flanged butterfly valves?
Release time:
2025-09-23
Differences in Sealing Materials
Soft-sealed butterfly valves use elastic non-metallic materials such as rubber and polytetrafluoroethylene (PTFE) to achieve high sealing performance through compression and deformation, but they have relatively poor temperature resistance (typically ≤80°C, though PTFE can withstand up to 200°C). Hard-sealed butterfly valves employ metal materials like stainless steel and alloy steel, or hard alloy materials, offering excellent resistance to high temperatures (up to 400°C or higher) and high pressures (PN25/40/64 and above), though their initial sealing performance is relatively weaker.
Structural Design Features
Soft sealing: Mostly adopts a centerline design, relying on the deformation of elastic materials to compensate for irregularities on the sealing surfaces, with a simple structure.
Hard sealing: Typically employs single-eccentric, double-eccentric, or triple-eccentric designs to enhance sealing through a metal wedge effect, with high precision requirements for machining.
Performance Comparison
Features Soft-sealed butterfly valve Hard-sealed butterfly valve
Sealing Performance ★★★★★ (Zero Leakage) ★★★☆ (Requires High‑Precision Machining)
Temperature resistance: ≤200℃ (PTFE), up to 850℃
Pressure resistance: ≤1.6 MPa, can reach over 10 MPa
Applicable Media: Water, Air, Clean Fluids; Particulates, Corrosive Media
Lifespan: Below 50,000 cycles (requires replacement) – Over 100,000 cycles
Application Scenarios
Soft sealing: Low-pressure, ambient-temperature applications such as municipal water supply, food and pharmaceuticals, and air conditioning systems.
Hard sealing: Applications involving high temperature and high pressure, or media containing particulates, such as in the petrochemical, power, and metallurgical industries.
Maintenance and Costs
Soft-sealed valves have low maintenance costs but require regular replacement of sealing rings; hard-sealed valves have high initial costs but long service lives and more complex maintenance.
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