Knife Gate vs Gate Valve — Isolation for Slurry, Pulp, and Clean Service
A standard wedge gate is for clean liquid/gas isolation. A knife gate uses a sharp blade for solids-laden media (slurry, pulp, powders). They are not drop-in substitutes.
Quick selection
Clean process / water / hydrocarbons: wedge gate. Slurry, ash, pulp: knife gate. State uni- vs bi-directional seat.
Comparison table
| Factor | Wedge gate | Knife gate |
|---|---|---|
| Media | Clean liquids / gases | Slurry, pulp, powders, solids |
| Closure | Wedge into seats | Blade shears through media |
| Standards | API 600 / 602 common | MSS / manufacturer / project specs |
| Pressure | Class 150–2500 range | Often lower PN/Class; confirm rating |
| Bi-directional | Typically yes when specified | Often uni-directional unless stated |
| Buyer action | Size, Class, MOC, ends | Size, rating, seat, uni/bi |
Common specification mistakes
Ordering “gate valve” on a slurry line often yields the wrong product. Name knife gate explicitly.
- Hard-faced seats for abrasive slurry.
- Pneumatic actuation common on large knife gates.
RFQ wording that works
- “Knife gate, WCB body, SS316 blade, DN150, uni-directional, PN10.”
- Clean service: “API 600 gate, Class 150, RF, WCB.”
FAQ
Can a knife gate replace a wedge gate on water?
Sometimes on low-pressure water with solids — confirm with process engineering.
Is knife gate good for steam?
Generally no.
Bi-directional knife gate?
Available; must be specified.
Metal seat vs soft seat knife?
Abrasive slurry often metal / hard-faced.
Related RFQs and hubs
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