1. Core Performance Differences
Sealing Mechanism
Metal seat: metal-to-metal seal (e.g., stainless steel/alloy steel), relying on precision machining to achieve contact surface fit, requiring high differential pressure to activate the seal.
Soft seat: through the elastic material (EPDM, PTFE, etc.) deformation to fill the microscopic gap, low-pressure conditions can achieve zero leakage (ANSI Class VI standard).
Temperature and pressure resistance
Metal seat: applicable temperature range -196℃ to +600℃, withstand pressure up to PN100 or more, suitable for high temperature and high pressure steam and gas pipelines;
Soft seat: temperature resistance is limited by materials (such as EPDM resistance -40 ~ 120℃, PTFE resistance -200 ~ 200℃), conventional pressure is limited to PN10-PN16.
Medium adaptability
Metal seat: strong resistance to particle scouring, suitable for mineral slurry, corrosive fluids containing solid impurities, but need to avoid long-term erosion of strong acids/alkalis;
Soft seat: good compatibility with clean water, air, oil, EPDM resistance to weak acids and alkalis, but contact with mineral oil or hydrocarbons are prone to dissolution and failure.
2. Comparison of Typical Application Scenarios
|
Scene Characteristics |
Suitability of metal seats |
Suitability of soft seats |
|---|---|---|
|
high temperature and pressure (>200℃/PN25) |
✔️ (e.g. refinery steam pipes) |
❌(Material is prone to aging) |
|
Particulate/abrasive media |
✔️ (Wear-resistant alloy surfacing valve seats) |
❌(The seal is easy to wear) |
|
Food/Pharmaceutical Clean Lines |
❌ (Risk of metal contact contamination) | ✔️(FDA approved EPDM valve seat) |
|
Frequent opening and closing of low-pressure water systems |
❌ (High initial leakage rate of the sealing surface) | ✔️(Low torque, zero leakage) |
3. Life cycle cost analysis
Initial investment
Metal valve seats require high machining accuracy (Ra≤0.8μm), and the cost is 30%-50% higher than that of soft valve seats; soft valve seats have a simple structure, and standardized production reduces costs.
Maintenance cost
Metal valve seats: strong wear resistance, service life can reach 20 years, but the sealing surface needs to be regularly ground (about 5 years/time);
Soft valve seats: EPDM/PTFE valve seats need to be replaced every 5-10 years, but replacement takes only 1-2 hours (online maintenance design is available).
4. Selection decision tree
Conditions for giving priority to metal valve seats:
Medium temperature>150℃ or containing hard particles;
System pressure>PN25;
Long-term closed pipelines that do not require frequent maintenance.
Conditions for giving priority to soft valve seats:
Require zero leakage (such as pharmaceutical pure water system);
The medium is clean and the temperature is <120℃;
Requires fast maintenance or cost-sensitive projects.