Pneumatic Actuator Stroke Time Calculator
Estimate how fast a pneumatic actuator can stroke: the time to fill and to exhaust its volume through the positioner, booster or solenoid valve air capacity.
- Free air = V × (p₁ − p₀) ÷ patm = 6 × 0.8 ÷ 1.013 = 4.737 L
- Fill time = free air ÷ fill capacity = 1.89 s
- Exhaust time = free air ÷ exhaust capacity = 2.37 s
Stroke Time Estimate
t = free air ÷ air capacity
Vact is the actuator volume swept between the start and end of stroke plus tubing, p₀ and p₁ the gauge pressures at the start and end of stroke, and air capacity the average free air flow of the positioner, booster, quick exhaust or solenoid valve. For spring diaphragm actuators p₀ and p₁ are roughly the bench set range.
Worked example
A 6 L diaphragm actuator stroked from 0.2 to 1.0 barg needs about 4.7 L of free air. With 150 L/min fill capacity it strokes in about 1.9 s, and returns in about 2.4 s at 120 L/min exhaust.
Frequently Asked Questions
How do I speed up a slow actuator?
Fit a volume booster, a larger solenoid valve or a quick exhaust valve, and use larger tubing.
Why is the real stroke time longer?
Flow through valves falls as the pressure difference reduces near the end of stroke, and friction and inertia add delay.
What stroke time do ESD valves need?
It is set by the process safety requirement, often a few seconds, and verified by testing.
Learn more on the blog
Diaphragm actuator vs piston actuator
A practical, field focused guide on instrumentationblog.in that explains the theory behind this calculator and how engineers apply it on real plants.
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