Gate Valves Β· Knife Gate Valves
Bi-Directional Knife Gate Valves
A bi-directional knife gate execution to MSS SP-81: the gate seals in both flow directions, so it can be installed without regard to flow orientation - the practical difference from standard uni-directional knife gates on process skids and distribution headers. DN50 to DN400 in wafer or lug bodies, PTFE packing with polyurethane/EPDM/NBR/Viton seal rings, handwheel or actuated operation.
Part of the Knife Gate Valves family
Last updated: 2026-11
Specifications
| size range | DN50 to DN400 |
|---|---|
| pressure class | Class 150 to Class 30, PN10 |
| body materials | Carbon Steel, Ductile Iron, SS316 |
| disc materials | SS304, SS316L |
| operation | Handwheel, Electric Actuated, Pneumatic Actuated |
| design standards | MSS SP-81 |
| testing standards | API 598 |
| knife materials | SS304, SS316 |
| wedge materials | SS304, SS316, SS316L |
| packing | PTFE |
| seal ring materials | Polyurethane, EPDM, NBR, VITON |
| yoke materials | SS304, SS316 |
| packing gland materials | CF8, WCB |
| end types | Wafer Type, Lug Type |
| face to face standard | MSS SP-81 |
| flanged end standards | DIN, JIS |
| seat design | Bi-Directional Resilient Seated, patented perimeter seat design, bubble-tight shutoff in either direction, even on dead end service |
| body construction | One piece cast body |
| applications | isolation and on/off applications, paper, chemical, mining, power, waste water industries |
| media | clean, dirty, viscous and corrosive liquids, sludge, fibrous slurries, clean and corrosive gases |
| design standard options | MSS SP-81, ANSI, API, ISO, DIN, EN, JIS |
| end flange standard | ASME B16.5, ASME B16.47, DIN2533 |
| flange rating options | EN1092 PN10,PN16,PN25, ANSI B16.5 (class 125,150) |
| operation options | Handwheel, Gear, Pneumatic, Hydrau-Pneumatic, Electric |
| body material options | Ductile Iron, Cast Steel, Stainless Steel, Duplex and Special Alloys |
| gate material options | Stainless Steel, Duplex and Special Alloys |
Pressure class is shown as collected: "Class 150 to Class 30, PN10". The source text's "Class 30" is retained verbatim as a recorded source difference β it is commonly read as a typographical variant of Class 300, but that reading is not asserted here; the governing class is confirmed at quotation.
Application & selection guidance
Specify bi-directional sealing where installation orientation is a real constraint - pump suction headers, manifolds and retrofits where flow direction may reverse or was never fixed. End type decides maintenance philosophy: wafer needs the line drained on both sides, lug allows one side to stay pressurised while the downstream spool is removed.
Frequently asked questions
What does bi-directional sealing change in practice?
A standard knife gate seats on one side only and must be installed with flow against that seat; the bi-directional execution seals either way, so orientation errors and flow-reversal scenarios stop being a risk. The benchmark page covers DN50-DN400 at Class 150 / PN10 in wafer and lug bodies.
Which materials are offered?
Body in carbon steel, ductile iron or SS316; knife and wedge in SS304/SS316; PTFE packing with seal-ring options in polyurethane, EPDM, NBR and Viton - the elastomer pick should follow the medium and temperature.
Which standard governs the valve?
Design, manufacture and face-to-face dimensions to MSS SP-81, flanged ends to DIN and JIS, inspection and test to API 598, with a full DN50-DN400 dimension and weight table on the page.
Ordering & documentation
Documents
Ask for the documentation set you need with the inquiry β typical items for this execution (material certificates, test reports to the listed inspection standard, dimensional drawings) are confirmed and supplied with the quotation.
Quotation
A quotation-ready inquiry states: nominal size and pressure rating, body and seat material preference, end connection, operation, and the service medium with temperature. Typical values on this page are benchmark reference ranges; the binding values are confirmed at quotation.
Sample & supply
Supply terms, order quantities and lead time are agreed per order β state the destination country and required schedule with the inquiry.
Storage & shipping
Store valves with seats and seals protected from UV, ozone and deformation, keep end-face protectors on until installation, and for elastomer- or PTFE-seated executions avoid prolonged outdoor storage β seat compounds age fastest in direct sunlight and freezing conditions.
Knowledge: selection guides
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