Selection according to the sealing mechanism
- Soft Seal Valve Seat
Material: commonly used rubber (e.g. EPDM, NBR), polytetrafluoroethylene (PTFE), etc.
Applicable scenarios: normal temperature and pressure, clean media (such as water, gas), requiring zero leakage (leakage level up to VI).
Limitations: poor temperature resistance (EPDM ≤ 135 ℃, PTFE ≤ 180 ℃), not resistant to particle scouring and strong corrosive media.
- Hard seal valve seat
Material: metal (such as stainless steel, alloy steel) or metal + wear-resistant coating (such as tungsten carbide).
Applicable scenes: high temperature (up to 800 ℃), high pressure, containing particles or corrosive media (such as steam, acid and alkali, slurry).
Characteristics: wear-resistant, but high leakage (usually IV ~ V).
According to the media characteristics of matching
- Corrosive media (such as hydrochloric acid, strong alkali)
Priority to corrosion-resistant materials: PTFE lining, Hastelloy, duplex stainless steel (such as 2205).
Case: coking plant in the high temperature corrosive media suitable for duplex steel valve seat (such as Z41Y-150LB-DN100-2205).
medium containing suspended particles (such as slurry, sewage)
Choose wear-resistant hard seal or flat plate gate valve seat with scraping function to avoid particle jamming.
- High temperature/high pressure media
Steam system: metal seal + alloy steel (such as WCB cast steel, forged alloy steel).
High pressure differential applications: hardened metal seats (e.g., surfaced Stellite alloy) for sleeve or double-seated valves.
Combined with the valve structure and working conditions
|
Valve Type |
Recommended Seat Type |
Advantages |
|---|---|---|
| Ball/Globe Valves |
PTFE soft seal or metal hard seal |
Reliable sealing, adaptable to regulation or cut-off |
| Gate Valves |
Metal wedge seals or resilient seats |
Resistant to particle scouring, low opening and closing forces |
| Butterfly Valve |
EPDM/NBR soft seal or stainless steel hard seal |
Lightweight and economical for large calibres |
|
Regulating valve |
Single-seat valves (precision control) or sleeve valves (high differential pressure) |
Stable flow characteristics and high resistance to differential pressure |
Key Performance Parameters Calibration
Temperature and Pressure: Seat material needs to be higher than the medium working temperature/pressure (Example: Steam pipeline ≥150℃ select metal seal 710.
Seal Grade:
Soft Seal: ANSI Class VI (Zero Leakage)
Hard Seal: ANSI IV~V.
Life requirements: frequent opening and closing conditions choose wear-resistant materials (such as carbon graphite + alloy) or self-compensating structure of the valve seat.
Optimisation of Special Requirements
Fire Safety: Select API 607/6FA certified fire safety valve seat (remains sealed in case of fire).
Hygienic requirements: PTFE or electropolished stainless steel seats for food/pharmaceutical industry to avoid media residue.
Economy: low pressure water system can choose ductile iron + EPDM valve seat, reduce costs.