VALVE TYPE
Gate Valves
Zero obstruction when open — the classic full-bore isolation valve.
Multi-turn valve whose gate retracts fully out of the flow path — zero obstruction and negligible pressure drop when open. The classic full-bore isolation valve for pipelines and plant utilities, built to stay fully open or fully closed.
The envelope
| Size range | DN50–DN1200 in the screened envelope |
|---|---|
| Functions | isolation |
| Seat options | METAL |
| Shut-off | Metal-seated — tightness class decides |
| Standards | API 600 (cast steel, ≥DN50); API 602 (forged, ≤DN50); ASME B16.34 |
Never throttle with a gate valve — partial opening wire-draws the seat and destroys it. On steam above 250 °C the wedge can seize from differential expansion: parallel-slide or globe is the documented practice (dispute steam_wedge). Size×class envelope follows Neway E-GGC-2025 published matrix (bolted; pressure-seal extends the high classes).
Where it is used
- Large-bore or high-pressure lines that stay open or closed
- Pipeline and plant-utility isolation
- Lowest flow resistance of the five types
Where it stops
- Never throttle — partial opening wire-draws the seating surfaces
- On steam above 250 °C a wedge gate can seize from thermal binding — parallel-slide or globe is the documented answer
- Multi-turn and slow — not for frequent or automated operation
Related reading
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