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Compare complete valve-and-actuator configurations against the same duty. Write down the required response to each failure condition instead of relying on the words “pneumatic,” “electric” or “fail-safe.”
Begin with what the valve must do
For equipment packages and process plants, actuator selection starts with the valve function: on/off isolation or continuous modulation. State the expected operating pattern, travel requirements and process conditions before comparing pneumatic and electric options.
The actuator must also be reviewed with the selected valve. Identify the required torque or thrust information, the mounting arrangement and the operating differential pressure. Existing motor power or a similar external appearance is not a complete replacement specification.
Compare the same requirements for both options
| Requirement | Pneumatic actuation | Electric actuation |
|---|---|---|
| Site supply | Specify the available air supply and its operating range, plus any electrical supply needed by the accessories. | Specify voltage, frequency and phase where applicable, together with the site power requirements. |
| Valve duty | State on/off or modulating duty, required travel time and operating pattern. | State on/off or modulating duty, required travel time and operating pattern. |
| Control and feedback | Identify the command signal, positioner or solenoid interface and required position feedback. | Identify the command signal, remote/local controls and required position feedback or communication. |
| Failure response | Define the required valve position on loss of air, electrical supply or command signal, as applicable. | Define the required valve position on loss of power or command signal, and request the proposed means of achieving it. |
| Mechanical interface | Provide the valve load information, mounting arrangement and installation space. | Provide the valve load information, mounting arrangement and installation space. |
| Environment | State ambient conditions, enclosure requirements and any project-specified hazardous-area requirements. | State ambient conditions, enclosure requirements and any project-specified hazardous-area requirements. |
Separate normal control from failure response
List the relevant loss-of-supply and loss-of-signal conditions individually, then state whether the process requires the valve to open, close or remain in position. The required behavior comes from the process and site requirements.
Ask how the proposed actuator, accessories and valve arrangement achieve that behavior. The response depends on the complete configuration; it cannot be established from the power-source label alone. Review the applicable product documents and the required functional checks.
For an actuator replacement, keep the interface records
These records allow a supplier to identify interface differences in the proposal. Any unconfirmed dimension, load or control requirement should remain visible as an open item until it is resolved.
- Existing valve and actuator nameplates and available load information.
- Mounting, stem or shaft dimensions and the available installation drawing.
- Wiring or pneumatic interface information, with available control and feedback details.
- Required normal operation, failure response and local operating access.
Questions for the quotation review
Does an electrical control signal require an electric actuator?
Specify both the command signal and the actuation supply. A pneumatic valve package can include an electrical control interface, depending on its positioner and accessories.
What should be included in the proposed package?
Ask the quotation to identify the valve, actuator, control accessories, mounting, applicable drawings and agreed checks. Certificate requirements should be tied to the relevant item and configuration.
Use this brief for your inquiry
Send the information already available and mark unknown items. You can also include your existing data sheet or project requirements when you write to us.
Hello Leo, Please review an actuated valve package. Valve family / size / quantity: Process conditions / differential pressure: On-off or modulating duty: Required travel time / operating pattern: Torque or thrust information available: Air supply / electrical supply: Command signal / feedback / communication: Required position on each supply or signal failure: Mounting and installation drawings available: Environment / required documents: Unknown items:Send the available process data
Opens your email app. You review and send the message.
Further technical reading
Spirax Sarco: control valve actuators and positioners
Background on actuator operation, positioners, differential pressure and the importance of the valve-and-actuator combination.
Use this guide to prepare an inquiry. Final materials, ratings and configuration are confirmed against the specific duty and applicable product documents.