Pneumatic actuator OMAL AGO SRN spring return

OMAL AGO SRN series spring-return pneumatic actuators are suitable for automating ball and butterfly valves in applications where the valve must move to a defined safety position on loss of air or control signal. Compressed air opens the actuator and loads the springs; when pressure is released the springs return it to its initial position.

Features

• Mode of operation: single acting, spring return (SRN). Fail close as standard — the spring closes the valve
• Torque range: 15–480 Nm (air at 5.6 bar)
• Rotation angle: 92° (-1°, +91°), adjustable with stroke screws
• Operating pressure: 5.6 bar nominal, maximum 8.4 bar
• Temperature: -20…+80 °C (special versions -50…+60 °C and -20…+150 °C)
• Media: filtered dry compressed air, lubrication not required
• Functional safety: SIL certified to EN 61508, up to SIL 3

Reading the torque values — use the spring column

The valve is sized on the spring torque, not the air torque. The spring provides the force that closes the valve in an emergency, and it is lower than the air torque.

The two torques behave in opposite directions across travel: air torque falls as the spring is loaded, while spring torque rises towards the closed position. For example the SRN120 delivers 120 → 80 Nm on air and 80 → 120 Nm on spring. The spring therefore develops its maximum torque at the moment of closing, where the valve needs it most.

Raising the pressure does not improve the safety-position force. The 6 bar column applies to air torque only; spring torque is determined by the spring pack and does not change with supply pressure. If the application requires a higher closing torque, select a larger size — not a higher pressure.

The spring pack is selected according to the working pressure. The table values correspond to the 5.6 bar nominal configuration. Air/spring pairs for other working pressures and the full torque curves are given in the catalogue.

Connections

• Valve connection: ISO 5211 flange F03–F12, compliant with EN 15714-3
• NAMUR: NAMUR solenoid valve interface integrated into the body — no separate adapter plate needed
• Pneumatic connection: G1/8" or G1/4" depending on size

Construction

• Cylinder, piston and end caps: aluminium alloy
• Shaft: stainless steel
• Scotch yoke, bushes, sleeves and springs: steel alloy
• Dynamic seals: polyurethane; O-rings NBR; shaft seals FKM
• Piston bearing surfaces: PTFE carbo-graphite filled

Explosion protection

ATEX version according to directive 2014/34/EU. Order the ATEX version by adding YX to the end of the code.

A double-acting version of the same series is available as the DAN model. Note that the SRN480 has a 36 mm shaft whereas the double-acting DAN480 has 27 mm — the spring pack requires a heavier shaft, so the mounting kit is not the same.