Quick answer
Do not specify a butterfly valve only by DN, PN and actuator type. First define whether the valve will remain fully open or closed, modulate through a controlled range, or perform both duties. Then confirm the medium, temperature, pressure differential, required flow range, operating frequency, shut-off expectation, fail position and available power or air supply. These inputs determine whether the proposed valve and actuator can be reviewed for the actual duty.
Why the duty definition changes the selection
An isolation valve is normally selected around reliable opening and closing under the stated differential pressure. A throttling valve must also hold intermediate positions and respond predictably to a control signal. The disc is then exposed to changing velocity, torque and pressure conditions over its travel. A mixed-duty valve must satisfy both the required control behavior and the closed-position sealing expectation.
“Flow regulation” on a product page does not by itself confirm every control application. The usable opening range, control accuracy, allowable velocity, cavitation or flashing risk, noise, vibration and actuator response must be reviewed for the specific system.
Conditions to confirm before selection
| Input | Why it matters |
|---|---|
| Medium, composition and solids | Changes material compatibility, seat choice, erosion risk and the likelihood of deposits around the disc or seat. |
| Operating and design temperature | Affects seat limits, material selection, thermal movement and actuator sizing conditions. |
| Upstream and downstream pressure | The maximum differential pressure can govern valve torque and actuator output. |
| Normal, minimum and maximum flow | Defines the control range that must be evaluated rather than relying on line size alone. |
| Shut-off expectation | Clarifies the required closed-position performance and the test or acceptance basis to be agreed. |
| Operating frequency | Frequent cycling changes the review of actuator duty, controls and wear-sensitive components. |
| Fail position and utilities | Determines the pneumatic or electric actuator arrangement, accessories and control philosophy. |
| Pipework and installation | Disc clearance, alignment, straight-run conditions and nearby fittings can affect operation. |
Common specification mistakes
- Using line size as the only basis for a modulating valve.
- Stating “control duty” without minimum and maximum flow or pressure conditions.
- Assuming an on/off actuator is automatically suitable for modulating service.
- Requesting a fail-open or fail-closed action without describing the process safety objective.
- Choosing a seat material from the fluid name alone, without concentration and temperature.
- Ignoring disc clearance, alignment and the effect of adjacent elbows, reducers or pumps.
- Treating a model designation as proof of a particular shut-off or control performance.
Step-by-step decision logic
- Define the normal position. State whether the valve is normally open, normally closed or continuously modulating.
- Describe every operating case. Include normal, start-up, shutdown, upset and maximum differential-pressure conditions.
- Set the control objective. Identify whether the valve controls flow, pressure, level or temperature and provide the required operating range.
- Define the closed-position requirement. State the acceptance basis required by the project instead of using an unqualified leakage claim.
- Review materials and seat construction. Confirm the medium, concentration, temperature, solids and cleaning conditions.
- Size the actuator from the valve duty. Provide the maximum differential pressure, cycling rate, speed, fail position, control signal and available utility.
- Check installation conditions. Confirm the mating standard, pipe orientation, clearance and upstream/downstream disturbances.
- Approve the final configuration. Use the project data sheet and approved order documents for the supplied valve.
This guide explains the information needed for review; it does not size a valve or actuator. Final selection depends on the complete operating envelope and the approved product configuration.
Related real butterfly valve products
The following existing models illustrate two different actuation and seat families. Their inclusion is not a universal recommendation; use the model pages as reference and submit the actual duty for confirmation.
Inquiry checklist
- Medium, composition, concentration, solids and temperature
- DN, pressure class, connection and mating standard
- Upstream/downstream pressure for each operating case
- Normal, minimum and maximum flow
- Isolation, throttling or mixed duty
- Operating frequency and required opening/closing time
- Shut-off acceptance requirement
- Actuator type, power or air supply, control signal and fail position
- Required documentation, quantity and destination
TAI TONG VALVE can review the stated duty, product configuration, actuator requirements and OEM documentation needs after these conditions are provided.