Butterfly Check Valve (Wafer Style Check)
Valves / Check Valve / Non-Return ValveA butterfly check valve uses two half-discs (butterfly plates) hinged on a central shaft that swing open with forward flow and close on reverse flow, combining the compact wafer design with low pressure drop for efficient backflow prevention in water and process systems.
Working Principle
The butterfly check valve body is a thin wafer design that fits between pipeline flanges. Inside, two semicircular plates (butterfly plates) are mounted on a central hinge pin. Forward flow pushes both plates open, creating a nearly full-bore flow passage with low pressure drop. When flow stops or reverses, the plates swing shut under their own weight and the reverse flow pressure, seating against the body bore. Springs on the hinge pin assist closure and reduce the slam. The dual-plate design distributes the closing impact across two smaller plates rather than one large disc, reducing vibration and noise. This is the same basic design as the dual-plate wafer check valve, widely used as a cost-effective alternative to swing check valves.
Key Components
Wafer body, two butterfly plates (half-discs), central hinge pin, torsion springs, seat (metal or resilient), body bore seal.
Types & Variants
| Type | Key Feature | Typical Use |
|---|---|---|
| Standard dual-plate wafer | Two plates + torsion springs | Oil/gas, petrochemical, water |
| Resilient-seat dual-plate | Buna-N or PTFE seat inserts | Zero-leakage water/chemical service |
| Full-bore dual-plate | Full-port plates for pigging | Pipeline service |
| High-pressure dual-plate | Heavy-duty for Class 600+ | High-pressure pump discharge |
Common Materials
Body: ASTM A395 ductile iron, A216 WCB carbon steel, A351 CF8M stainless steel. Plates: same as body or higher alloy (316SS common). Springs: 316SS or Inconel X-750. Seat: metal (integral) or resilient 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 across all industries
- Compressor station discharge
- Cooling water systems
- Boiler feedwater backflow prevention
- Fire protection systems
- Oil and gas pipeline check protection
Advantages & Disadvantages
Advantages
- Most widely used check valve design worldwide for NPS 4-24
- Compact wafer design — shortest face-to-face
- Low pressure drop — nearly full-bore when open
- Springs assist closure for reduced slam and water hammer
- Lower cost than swing or tilting disc check valves for most sizes
Disadvantages
- Not for dead-end service — wafer body requires both flanges
- Spring-assisted closure is not as fast as axial flow/nozzle check
- Resilient seat inserts can degrade in high-temperature service
- Plates can vibrate (flutter) at low flow rates if spring force is too low
- Not suitable for very high differential pressure service without heavy-duty design
Selection Guide
- Dual-plate wafer check valves have largely replaced swing check valves for NPS 4-24 — they are lighter, cheaper, and have lower pressure drop
- For pump discharge, install the check valve as close to the pump as possible to minimize the volume of fluid that can reverse on pump trip
- Specify resilient seat inserts for water treatment applications where zero leakage is required
- On gas service, ensure the spring is sized for the actual gas density — liquid-service springs may be too heavy, causing the valve to not fully open
Practical Tips
- The dual-plate wafer check valve is the industry workhorse — it accounts for more check valve installations than all other types combined in the NPS 4-24 range
- Flutter at low flow is the most common field complaint — it means the spring is too strong for the operating condition. A lighter spring or a soft-seat design that dampens plate motion can help
FAQ
What is the difference between a butterfly check and a dual-plate wafer check?
They are the same design. Both terms refer to a wafer-body check valve with two half-discs on a central hinge pin with torsion springs. The term 'butterfly check' emphasizes the plate shape; 'dual-plate wafer check' is the API 594 standard terminology.
When should I use a dual-plate wafer check instead of a swing check?
Use dual-plate wafer check for NPS 4-24 in general process and utility service where compact installation, low cost, and low pressure drop are priorities. Use swing check for very large sizes (NPS 30+), high-viscosity service, or when the pipeline cannot support the wafer between flanges.