Sourced and supplied across Saudi Arabia
Two families share this name. A linear cylinder is specified like any cylinder — bore, stroke, mounting — with the caveat that air is compressible, so a pneumatic cylinder is poor at holding a position mid-stroke and good at moving between end stops. A quarter-turn actuator on a valve is a different specification, and the question that governs it is what should happen when the air fails. A double-acting actuator stays where it is; a spring-return actuator drives to a defined position, and choosing fail-open or fail-closed is a process safety decision rather than a preference. That choice also sizes the unit, because a spring-return actuator must produce the required valve torque on the spring stroke alone, against the lowest air pressure the plant will actually deliver rather than the nominal one. Give the valve torque with a safety margin, the real air pressure, and state whether the mounting must suit an ISO 5211 flange and a NAMUR accessory interface.
The more of this you send, the closer the first quotation lands.
| Actuator type | Linear cylinder, or quarter-turn rack and pinion or scotch yoke |
|---|---|
| Fail position | Double-acting stays put; spring-return fails open or closed |
| Valve torque required | Break, run and seating torque, with a safety margin |
| Air supply pressure | The lowest pressure actually available at the valve |
| Valve mounting | ISO 5211 flange size and the stem dimensions |
| Accessory interface | State if a NAMUR interface is required for solenoid and switches |
| Bore and stroke | For linear cylinders, with the mounting arrangement |
| Cycle rate | Operations per hour, and whether it modulates or is on-off |
| Accessories | Solenoid valve, limit switch box, positioner, speed controls |
| Hazardous area | State the zone if any electrical accessory is fitted |
| Ambient and process temperature | Both, since heat travels up the valve stem |
| Materials and coating | Coastal or offshore exposure decides the body finish |
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