Wafer Check Valve
Valves / Check Valve / Non-Return ValveA wafer check valve is a compact non-return valve designed to fit between pipeline flanges without its own flanges, using a spring-loaded disc or double-disc assembly that opens with forward flow and snaps shut on reverse flow to prevent backflow in pumping and process systems.
Working Principle
The wafer check valve body is a thin disc-shaped housing that sandwiches between two pipeline flanges, held in place by the through-bolts. Inside, a spring-loaded disc (or pair of half-discs in the dual-plate design) pivots on a hinge pin. When forward flow pressure exceeds the spring force, the disc swings open, allowing flow. When flow stops or reverses, the spring (often assisted by gravity and backpressure) snaps the disc shut against the seat, preventing reverse flow. The short stroke and spring assist mean the valve closes quickly, minimizing water hammer. The wafer design has the shortest face-to-face dimension of any check valve type, making it ideal for tight installations.
Key Components
Wafer body (cast iron, ductile iron, steel, or SS), spring-loaded disc or dual-plate assembly, hinge pin, seat (metal or resilient), springs, flange bolts from pipeline.
Types & Variants
| Type | Key Feature | Typical Use |
|---|---|---|
| Single-disc wafer check | Single swing disc + spring | Small-bore general service |
| Dual-plate wafer check | Two half-discs on center pin | Oil/gas, petrochemical, larger sizes |
| Wafer silent check | Spring-loaded disc, short stroke | Pump discharge, anti-water-hammer |
| Titanium wafer check | Titanium body + disc | Seawater, desalination |
Common Materials
Body: ASTM A395 ductile iron, A216 WCB carbon steel, A351 CF8M stainless steel. Disc/plates: same as body or higher alloy. Springs: 316SS or Inconel X-750. Seat: metal (integral) or Buna-N/PTFE insert. Hinge pin: 316SS or 17-4PH.
Applicable Standards
- API 594 (check valves)
- API 6D (pipeline valves, reference)
- ASME B16.34 (pressure ratings)
- MSS SP-71 (wafer check valves)
- BS 1868 (steel check valves)
Industrial Applications
- Pump discharge protection (prevent reverse flow on pump trip)
- Compressor station discharge isolation
- Boiler feedwater system backflow prevention
- Cooling water systems
- Process piping backflow prevention
- Fire protection pump discharge
Advantages & Disadvantages
Advantages
- Most compact check valve design — shortest face-to-face
- Lowest cost check valve for most applications
- Quick closure minimizes water hammer
- Easy installation between existing flanges
- Dual-plate design reduces slam and vibration
Disadvantages
- Not suitable for dead-end service — requires both flanges for support
- Spring-loaded designs create pressure drop even in full-open position
- Single-disc designs can slam and cause water hammer at low flow rates
- Wafer body cannot be used as a block valve — no manual isolation capability
- Disc/plate wear from frequent cycling requires periodic inspection
Selection Guide
- Dual-plate wafer check valves are preferred over single-disc for NPS 4 and above — lower pressure drop and reduced slam
- For pump discharge, specify a wafer silent check (spring-loaded, short stroke) to minimize water hammer on pump trip
- Match body material to pipeline material to avoid galvanic corrosion at the flange faces
- Install with the flow arrow pointing in the direction of normal flow — reversed installation causes immediate failure
Practical Tips
- Dual-plate wafer check valves have become the industry standard for NPS 4+ — they are lighter, have lower pressure drop, and close faster than swing check valves
- The most common wafer check failure mode is seat leakage from erosion by high-velocity flow through the partially open disc during low-flow conditions
FAQ
What is the difference between wafer and swing check?
A wafer check valve is a compact between-flange design with spring-loaded disc(s). A swing check valve has a flanged body with a hinged disc that swings open. Wafer is shorter, lighter, and less expensive. Swing check provides lower pressure drop and is available in larger sizes.
Can a wafer check valve be installed vertically?
Yes, if flow is upward. Spring-loaded wafer check valves work in any orientation because the spring provides the closing force. Gravity-assisted designs (no spring) only work in horizontal or upward-flow vertical installations.