Single Acting Pneumatic Wafer Butterfly Valves
In a single acting pneumatic wafer butterfly valve, the actuator uses compressed air for movement in one direction only; the return movement is made by preloaded springs fitted in the actuator end caps. When the supply air or solenoid power is cut, the valve returns by itself to its predefined safe position.
The rack-and-pinion actuator is mounted directly onto the stem of the wafer-bodied valve via an ISO 5211 flange. It works with 2.5–8 bar supply air, has ±5° end position adjustment in both opening and closing directions, and is used on butterfly valves from DN25 to DN300.
Main Applications
- Water supply lines that must close on air or power failure
- Automatic zone isolation in boiler rooms and heat stations
- Fail-safe isolation in cooling tower and process water circuits
- Filter backwash lines in treatment plants
- Level-controlled shut-off on tank filling lines
- Points to be closed by a fire or alarm signal
Technical Data
| Valve connection | Wafer; clamped between two flanges |
|---|---|
| Size range | DN25–DN300 |
| Valve pressure class | PN16 |
| Medium temperature | EPDM −10 / +130 °C · NBR −10 / +80 °C |
| Actuator type | Rack and pinion, single acting (spring return) |
| Supply pressure | Min. 2.5 bar · max. 8 bar |
| Ambient temperature (actuator) | Standard −20 / +80 °C · low temperature −35 / +80 °C · high temperature −15 / +150 °C |
| End position adjustment | ±5° in both directions; 0–90° adjustable limit stop optional |
| Shaft and interface | ISO 5211, DIN 3337, NAMUR |
| Air connection | 1/8″ … 1/2″, depending on actuator size |
| Safe position | Normally closed or normally open; set by piston orientation |
| Accessories | NAMUR solenoid valve (220 V / 24 V DC), limit switch box (IP67) |
Material Options
| Part | PN16 · GG25 body, stainless disc | PN16 · ductile iron body, bronze disc |
|---|---|---|
| Valve body | Grey cast iron EN-GJL-250 (GG25) | Ductile iron EN-GJS-400-18 |
| Disc | Stainless steel AISI 316 | Aluminium bronze |
| Valve seat | EPDM (−10 / +130 °C) | NBR (−10 / +80 °C) |
| Actuator body | Aluminium extrusion (ASTM 6005), hard anodised | Aluminium extrusion (ASTM 6005), hard anodised |
| Actuator end caps | Aluminium die-cast, epoxy or polyester powder coated | Aluminium die-cast, epoxy or polyester powder coated |
| Pistons | Aluminium die-cast, hard anodised | Aluminium die-cast, hard anodised |
| Springs | Preloaded cartridge springs, corrosion-protected | Preloaded cartridge springs, corrosion-protected |
| Actuator O-rings | NBR (Viton for high, silicone for low temperature optional) | NBR (Viton for high, silicone for low temperature optional) |
The spring-return actuator must be sized on the lowest supply pressure so that it covers the valve closing torque even at the end of stroke, where the spring is weakest. Nickel or PTFE coating is optional for actuator bodies and end caps in highly corrosive environments.
Advantages
Self-Acting Safe Position
- The spring turns the valve when air or power fails.
- The line is not left open during an outage.
Direct Mounting
- ISO 5211 and NAMUR interface.
- Solenoid and limit switch fit without adapters.
Precise End Position
- ±5° adjustment in both directions.
- The disc seats fully and correctly on the liner.
Compact Package
- Short length with the wafer body.
- Automation is possible in tight plant rooms.
Construction and Design Features
- Wafer butterfly valve with elastomer liner
- Rack-and-pinion single acting pneumatic actuator
- Preloaded cartridge springs fitted in the end caps
- Continuous three-dimensional position indicator
- Mounting face for NAMUR solenoid valve and limit switch box
Request a quote for single acting pneumatic wafer butterfly valves by stating size, medium, safe position (normally closed / open), supply air pressure and solenoid voltage.
How to Choose?
- Define the safe positionDecide from the process whether the valve must close or open when air is lost.
- Size on the lowest air pressureConfirm that spring and air torque cover the valve torque at the lowest plant supply pressure.
- Choose the pilotSpecify the NAMUR solenoid voltage (220 V AC or 24 V DC) and add a limit switch box if needed.
- Check ambient temperatureStandard seals cover −20 / +80 °C; choose the low or high temperature version for colder or hotter areas.
Complementary Products
Why ORFA?
Other Butterfly Valves
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Gear Operated Lug Type Butterfly Valves
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Gear Operated Wafer Butterfly Valves
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Single Acting Pneumatic Lug Butterfly Valves
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Wafer Type Butterfly Valves
Wafer type butterfly valves are lightweight, compact butterfly valves clamped between two flanges.
Details →Our Single Acting Pneumatic Wafer Butterfly Valves
ORFA supplies single acting pneumatic wafer butterfly valves in a range of pressure classes, sizes and connection types to suit your application. Descriptions, technical specifications, materials and dimension tables are available on each detail page.
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