Valve Stroke Time Calculator - Actuator Volume, Air Supply & Stroking Speed

How It Works

1. Select Actuator Mode

   Choose spring-return or double-acting. Double-acting uses the air-fill time for both directions; spring-return estimates the exhaust/spring stroke at 85 percent of the fill time (a simplified ratio, not a spring-force model).

2. Enter Actuator Volume

   Input the actuator effective volume in cubic inches. For diaphragm actuators, this is the effective area times the stroke. For piston actuators, it is the piston area times the stroke. Manufacturer datasheets provide these values, or measure the physical dimensions.

3. Enter Solenoid Cv and Supply Pressure

   Enter the supply pressure and the solenoid valve Cv from the manufacturer datasheet. The solenoid and tubing are combined as series restrictions; the smaller Cv dominates the system.

4. Pick Tubing Size and Length

   Select the tubing OD (1/4 inch to 1 inch) and run length. The tubing Cv is derated with length; long or undersized tubing runs add significant restriction that slows the stroke, especially on large actuators.

5. Review Stroke Times and Pass/Fail

   See the estimated fill stroke, return, and full-cycle times, the bottleneck component, and an optional pass/fail check against your entered required stroke time, plus a comparison table across all tubing sizes.

Built For

• Safety engineers screening assumptions before SIS/ESD stroke-time verification
• Instrument engineers checking whether solenoid Cv or tubing restriction deserves product-data review
• Maintenance techs comparing a rough fill-time estimate with measured stroke-time evidence
• Commissioning engineers documenting source gaps before baseline stroke tests
• Reliability engineers identifying when field stroke-time trends need qualified review
• Project engineers collecting inputs before evaluating boosters, quick-exhaust valves, or volume tanks outside this app

Features & Capabilities

ISA Gas-Flow Fill Model

Numerically integrates the standard ISA subcritical/choked gas-sizing pair (22.7 SCFM form, absolute pressures) over the actuator fill instead of using a single average-flow shortcut.

Series Cv Breakdown

Combines solenoid Cv with a length-derated tubing Cv in series (1/Cv2 = 1/Cv1 squared + 1/Cv2 squared) and identifies which component is the bottleneck, with an undersized-tubing warning below 50 percent of solenoid Cv.

Spring Return Estimate

Reports air-fill and return times separately. The spring-return exhaust stroke is estimated at 85 percent of the fill time - a simplified ratio, not a spring-force or exhaust-path model.

Required-Time Pass/Fail

Optional required stroke time input produces a pass/fail verdict with the time margin, plus a risk tier as the estimate approaches the requirement.

Tubing Size Comparison

Side-by-side stroke times for 1/4 inch through 1 inch tubing at the current conditions, showing which sizes meet the entered requirement.

Assumptions

• Supply air pressure is constant and adequate for the actuator throughout the full stroke.
• Actuator diaphragm or piston is in good condition with no air leaks.
• Packing friction is at a normal level consistent with properly adjusted packing.
• Solenoid valve is functioning correctly; quick-exhaust valves and boosters are not modeled.
• Tubing is modeled as a lumped Cv restriction derated with length; tubing internal volume itself is not added to the fill volume.

Limitations

• Tubing Cv-per-foot values are typical catalog-style estimates, not values from a specific manufacturer table (flagged as a source gap in the app).
• Spring return is a fixed 85 percent-of-fill-time ratio, not a spring-force or exhaust-path model; positioners, boosters, quick-exhaust valves, and volume tanks are not modeled.
• Partial stroke test (PST) timing and diagnostic calculations are not included.
• Does not account for actuator friction, spring pre-load, or process forces acting on the valve plug during stroking.
• Hydraulic actuator and electric actuator stroke time calculations are not covered.

References

• ISA-75.01.01 and IEC 60534-2-1 - gas-flow equation context for the fill model.
• Emerson Control Valve Handbook - valve/actuator pneumatic context.
• ANSI/ISA S7.0.01 - instrument-air quality context.
• Solenoid, tubing, booster, and actuator manufacturer datasheets govern real installed behavior.

Frequently Asked Questions