Valve Actuators

Valve actuators convert an electric, pneumatic or hydraulic power source into the thrust or torque that moves a valve stem or shaft. Seven Star LLC supplies actuators and actuator spare parts to plants in Oman, with more than 200 listed items from AUMA, Masoneilan, ABB, Biffi and Rotork, among others.

The category covers spring-diaphragm actuators for globe control valves, electric multi-turn, part-turn and linear actuators, and pneumatic and hydraulic fail-safe units for shutdown valves, together with AUMA gearboxes and linear thrust units.

Electric, pneumatic and hydraulic actuator types in this category

Pneumatic spring-diaphragm actuators, such as the Masoneilan Type 37/38 and 87/88 and the Samson Type 3271, are the usual drive for sliding-stem control valves. Air acts on a diaphragm against a spring, so the valve moves to a defined position when the air supply is lost. AUMA electric actuators cover multi-turn duty (SAEx and SAREx) and part-turn duty (SQR), with separate versions for open-close and modulating work. ABB Contrac and the Rotork CVA are electric actuators built for continuous modulating control. Biffi pneumatic and hydraulic actuators, including fail-safe versions, are typically used on pipeline and shutdown valves. Fisher, Bettis, Limitorque, Flowserve, Festo and pFlow models are also listed.

How to select an actuator for a valve

Start from the valve: linear or rotary motion, the thrust or torque it needs at the worst-case differential pressure, and the stroke or angle of travel. Then define the duty. On-off, inching and modulating duties place very different loads on an electric motor, and the duty class has to match. Decide what the valve must do on loss of power or signal: fail open, fail closed or stay put. Finally check the environment: hazardous-area classification, ingress protection, ambient temperature and the coating required for coastal or desert sites. Actuators for classified areas are ordered with ATEX or IECEx certification that matches the zone, gas group and temperature class.

What to send for an actuator quotation

• Valve type, size, pressure class and required torque or thrust
• Power supply: air pressure, or voltage, phase and frequency
• Duty (on-off or modulating) and fail position
• Control signal and feedback, for example 4-20 mA, HART or a fieldbus
• Area classification and ambient temperature range

For a replacement, the nameplate data and serial number of the existing actuator are usually enough. We check the configuration against the manufacturer documentation before quoting, for projects across the GCC.