Dual Plate Check Valve Installation Between Flanges
Installation guide · Supreme Valves India · 2026
API 594 dual plate wafer check valves install between existing pipe flanges—no integral valve flanges on the body. Correct orientation, bolt length, and flange preparation are critical for non-slam performance and leak-free service. This guide applies to Supreme Valves wafer (H) and lug (L) dual plate checks.
1. Pre-installation checks
- Verify NPS, pressure class, and L (face-to-face) against the datasheet for your flange standard (ASME B16.5 or B16.47).
- Confirm flow arrow on body matches pump discharge → system direction.
- Inspect seating faces for damage; flat seat requires clean, parallel flange faces.
- Match gasket type to service (RF soft gasket, spiral wound, or RTJ ring for high pressure).
2. Wafer (model H) installation sequence
- Isolate and depressurize the line; support adjacent piping if required.
- Spread flanges or remove spool piece to create gap ≥ face-to-face L.
- Insert valve centrally between flanges with arrow oriented correctly.
- Install studs or bolts through one flange + valve + opposite flange using the bolt circle from B16.5 (count and diameter per datasheet table).
- Tighten in a star pattern to avoid cocking the wafer body; do not over-torque elastomer seats.
- Perform commissioning: slow fill, verify discs open fully, no chatter at low flow.
3. Stud length calculation
Approximate stud length (RF, raised face):
Lstud = Tupstream + Lvalve + Tdownstream + 2× nut height + gasket crush
Example: 6" Class 150 wafer, L = 98 mm, 25 mm flanges each side → ~98 + 50 + nuts ≈ use datasheet L1 column (e.g. 205 mm RF stud for 6" Class 150).
| NPS | Class 150 L (mm) | Typical stud L1 RF (mm) |
|---|---|---|
| 4 | 73 | 170 |
| 8 | 127 | 240 |
| 12 | 181 | 310 |
Full tables: dual plate datasheet.
4. Lug (model L) installation
Lug valves bolt to the upstream flange through threaded lugs on the valve body; downstream flange bolts only to the downstream pipe, not through the full wafer stack.
- Allows dead-end removal of downstream spool for maintenance.
- Upstream lug bolts must engage full thread depth in lugs—do not use short bolts.
- Still observe flow direction; lug pattern is scalloped to save weight but must align with flange bolt holes.
5. Vertical and special orientations
Spring-assisted dual plates can work in vertical runs (flow up or down) on many sizes because discs are spring-returned, not gravity-dependent. For NPS ≥ 24 or dirty media, request written confirmation from Supreme Valves engineering. Avoid installing swing checks in vertical down-flow—dual plate is often the correct choice there.
6. Common installation errors
| Error | Consequence |
|---|---|
| Reversed flow arrow | No flow or immediate closure |
| Studs too short | Insufficient engagement, flange leak |
| Wafer used for dead-end | Cannot isolate downstream safely — use lug (L) |
| Over-torque on soft seat | Seat damage, leak after hydrotest |
| No straight run upstream | Disc flutter, premature wear |
7. Testing after installation
Line test per project ITP—typically shell/seat hydrotest per API 598. For check valves installed in pump discharge, functional check: run pump, stop, verify no backflow and minimal water hammer. Compare to non-slam check guidance for critical pump stations.