Pneumatic Proportional Control Valves
Pneumatic proportional control valves adjust the valve stroke steplessly according to the control signal by means of a diaphragm actuator driven by compressed air and a positioner, holding temperature and pressure precisely on steam and hot water lines. When the air supply fails, the actuator spring takes the valve to a predetermined safe position.
For globe-bodied types, a PN16 grey cast iron body is used in DN15–DN100; for larger flows, stainless globe bodies in DN80–DN150 and segmented ball valves in DN50–DN80 are offered as options. Actuators have effective diaphragm areas from 250 cm² to 2400 cm² and generally operate with up to 6 bar supply air. On types with positioners, a 4–20 mA signal is converted into stroke position; on types without, a separate I/P converter turns the signal into air pressure.
Main Applications
- Temperature control of steam heat exchangers and calorifiers
- Flow control on hot water and thermal oil circuits
- Steam pressure reducing stations
- Temperature and level control on process tanks
- Lines requiring a safe position on air failure
Technical Data
| Actuator type | Diaphragm, reversible, bellows-protected stem |
|---|---|
| Actuator sizes | 250 · 400 · 800 · 1600 · 2400 cm² effective area |
| Supply air | Generally max. 6 bar; 2.5–5 bar limit on some spring/pressure combinations |
| Spring ranges (example) | 0.4–1.2 · 0.8–2.4 · 1.5–2.9 · 2.0–3.8 bar (250 cm²) |
| Safe position | Spring-to-close or spring-to-open on air failure |
| Control signal | 4–20 mA on positioner types |
| Cast iron body, PN16 | DN15–DN100 (globe) |
| Pressure–temperature (cast iron PN16) | 16 bar up to 120 °C · 12.8 bar at 200 °C · 9.6 bar at 300 °C |
| Stainless globe | DN80–DN150, PN16 (from product names) |
| Segmented ball | DN50–DN80, PN16 (from product names) |
| Manual operation | Optional top-mounted handwheel |
| Accessory | I/P converter 1/4″ (4–20 mA) |
Material Options
| Part | PN16 · cast iron globe | PN16 · stainless globe | PN16 · segmented ball |
|---|---|---|---|
| Body | EN-GJL-250 (EN-JL1040) | Cast stainless, depending on model | Depending on model |
| Plug / segment | Stainless steel, depending on model | Stainless steel, depending on model | Depending on model |
| Stem sealing | PTFE V-ring, EPDM or graphite | PTFE V-ring or graphite | Depending on model |
| Actuator housing | Depending on model | Depending on model | Depending on model |
| Actuator diaphragm | Depending on model | Depending on model | Depending on model |
| Actuator stem protection | Bellows | Bellows | Depending on model |
Air preparation note: The actuator and positioner need oil-free, dry and filtered air; an air preparation unit should be fitted on the supply line. Grey cast iron bodies are not used in steam boiler plants covered by TRD 110.
Advantages
Stepless Control
- Stroke changes in proportion to the signal.
- Narrow temperature deviation band.
Safe Position
- On air failure the spring closes or opens the valve.
- A safe state in case of failure.
High Force
- Diaphragm areas up to 2400 cm².
- Shut-off at high differential pressure.
Fast Response
- Short stroke time with air.
- Adapts to rapidly changing loads.
Wide Body Choice
- Globe and segmented ball types.
- From fine control to high flow.
Construction and Design Features
- Globe or segmented ball valve body
- Diaphragm actuator on the yoke
- Actuator stem protected by bellows
- Mounting face for positioner and feedback
- Optional top-mounted handwheel
Send the fluid, flow, inlet and outlet pressure, temperature and safe position through the Request a Quote form; we will calculate Kvs, body and actuator size and prepare the valve.
How to Choose?
- Define flow and pressure dropCalculate Kvs from full-load flow and the differential pressure across the valve.
- Choose the safe positionDecide whether the valve must close or open when air fails.
- Choose actuator sizeSelect the diaphragm area and spring range that meet the shut-off differential pressure.
- Confirm the signal typeChoose a positioner type or an I/P converter type according to the controller output.
- Match body to temperatureOn a cast iron body, check the allowable pressure that falls with temperature.
Complementary Products
Why ORFA?
Other Proportional Control Valves
Our Pneumatic Proportional Control Valves
ORFA supplies pneumatic proportional control 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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