Direct answer · Updated July 2026
What is the difference between uni and bi-directional knife gates?
Uni-directional valves seal in one flow direction only (lower cost). Bi-directional valves seal from either direction — required when backflow isolation or unknown flow direction is possible.
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Applications
Mining & Tailings
Isolation and line breaking on abrasive slurry, concentrate, and tailings pipelines.
Pulp & Paper
Black liquor, stock, and fibre slurry shut-off with minimal clogging.
Wastewater & Sewage
Raw sewage, grit, and biosolids handling in municipal and industrial plants.
Ash Handling & Power
Fly ash, bottom ash, and FGD slurry isolation in power and cement plants.
Cement & Bulk Solids
Powder, clinker, and pneumatic conveying line isolation.
Chemical Slurry
Viscous, solids-laden, and corrosive process media with SS316 or alloy options.
Complete Knife Edge Gate Valve Range
Flow in one direction — wafer/lug, slurry & pulp service
Shut-off from either direction — self-sealing option
Stellite / SS seat for abrasive ash, dry solids & high temp
EPDM, PTFE, Viton — bubble-tight Class VI closure
Double-acting cylinder, solenoid, limit switches, FRL
Technical Standards
Special Features & Options
- Shut-off from either flow direction
- Self-sealing gate with deflection seat
- Suitable for pump isolation and dual-header lines
- Soft seated (EPDM/PTFE) or metal-to-metal
- Pneumatic double-acting cylinder packages
- Mining tailings and wastewater reverse-flow lines
- Bevel gear and chain wheel for buried service
Material of Construction
| Part No. | Part Name | Material / Standard |
|---|---|---|
| 01 | Body / Chest | WCB / CF8 / CF8M / GGG40 |
| 02 | Gate / Blade | SS304 / SS316 knife edge |
| 03 | Seat Ring | Integral SS or replaceable liner |
| 04 | Stem | SS304 / SS316 |
| 05 | Gland Follower | SS304 / WCB with epoxy coating |
| 06 | Packing | PTFE / Graphite braided |
| 07 | Handwheel / Yoke | Ductile iron / SS option |
| 08 | Bolting | SS304 / B7 as specified |
Face-to-Face Dimensions — MSS SP-81 Short Pattern
Typical face-to-face (F-F) dimensions for wafer/lug knife edge gate valves per MSS SP-81 short pattern. Flange drilling per ASME B16.5 Class 150#. Confirm at enquiry for your exact bore and end type.
| DN (mm) | NPS | F-F (mm) | ØD Flange | N Bolts | PCD |
|---|---|---|---|---|---|
| 50 | 2 | 51 | 108 | 4 | 60.3 |
| 80 | 3 | 57 | 190 | 4 | 152.4 |
| 100 | 4 | 57 | 229 | 8 | 190.5 |
| 150 | 6 | 76 | 279 | 8 | 241.3 |
| 200 | 8 | 89 | 343 | 8 | 298.5 |
| 250 | 10 | 114 | 406 | 12 | 362.0 |
| 300 | 12 | 127 | 483 | 12 | 431.8 |
| 350 | 14 | 140 | 533 | 12 | 476.3 |
| 400 | 16 | 152 | 597 | 16 | 539.8 |
| 450 | 18 | 171 | 635 | 16 | 577.9 |
| 500 | 20 | 190 | 699 | 20 | 635.0 |
| 600 | 24 | 222 | 813 | 20 | 749.3 |
Lug type with tapped holes; wafer type with through-holes. DN650–900 and PN16/Class 300 on request.
Also available: Self-sealing bi-directional variant; hydraulic actuation for Class 300/600 mining service.
Request Knife Edge Gate Valve Quote
Send valve type (uni/bi-directional, seat type), size DN, end connection, actuation (manual/pneumatic), quantity, and application. Engineering response within 24 hours.
Or call +91 97732 78770 · info@supremevalves.in
Frequently Asked Questions
What is the difference between uni and bi-directional knife gates?
Uni-directional valves seal in one flow direction only (lower cost). Bi-directional valves seal from either direction — required when backflow isolation or unknown flow direction is possible.
Is bi-directional suitable for slurry?
Yes. Bi-directional knife gates with EPDM or polyurethane liners are used on mining tailings, wastewater, and pulp lines where reverse flow shut-off is needed.
Can bi-directional valves be pneumatically actuated?
Yes. Double-acting pneumatic cylinders are standard for remote on-off control. We supply solenoid valve, limit switches, and FRL as a complete package.