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Cylinder sizing · Pneumatic glossary

SA — Single acting

Single acting

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Term
SA
Full form
Single acting
Selection effect
Check spring force, fail position, and usable stroke.

01

SA: definition and engineering context

Single acting. Air powers one direction and a spring or external load returns the actuator.

The term belongs to the cylinder sizing context. Its exact limits can depend on the cited standard, catalog convention, unit system, reference state, and component configuration.

02

Why SA affects pneumatic selection

Check spring force, fail position, and usable stroke.

  • Cushioning: Match kinetic energy and cycle speed; cushioning does not replace external stopping when limits are exceeded.
  • A: Use the rod-side annular area for retract force, not the full bore area.
  • Bore: Force rises with the square of bore diameter.
  • Stroke: Confirm usable motion, overall length, and allowance for cushioning.

03

How to evaluate SA in a catalog or replacement project

Read the value together with its unit, test basis, operating pressure, temperature, circuit state, and manufacturer definition.

For replacement work, compare the complete datasheet and drawing. A matching abbreviation or nominal size does not by itself prove functional or dimensional interchangeability.

  • End-of-stroke cushioning: A method of reducing piston speed near an end cap.
  • Effective piston area: Pressurized piston area used in the theoretical force calculation.
  • Cylinder bore diameter: Inside diameter associated with piston area.
  • Cylinder travel: Distance between the retracted and extended end positions.

Selection checklist

What to verify before selection

  1. 01

    Check spring force, fail position, and usable stroke.

  2. 02

    Match kinetic energy and cycle speed; cushioning does not replace external stopping when limits are exceeded.

  3. 03

    Use the rod-side annular area for retract force, not the full bore area.

  4. 04

    Force rises with the square of bore diameter.

Application caution

Common mistakes

  • Treating SA as a universal definition without checking the manufacturer or standard context
  • Mixing gauge and absolute values, incompatible units, or different reference conditions in one comparison
  • Selecting a component from the term or nominal value alone without checking the complete operating point and drawing

FAQ

Questions engineers often ask

01Terminology checkWhat does SA mean in pneumatics?

Single acting. Air powers one direction and a spring or external load returns the actuator.

02Terminology checkWhy does SA matter when selecting a component?

Check spring force, fail position, and usable stroke.

03Terminology checkCan SA values be compared directly between catalogs?

Only after the unit, reference condition, test method, operating point, and manufacturer definition have been reconciled.

Source notes

Technical references

This lookup table explains practical usage. Definitions, reference conditions, symbols, and abbreviations may differ by standard or manufacturer. Treat the applicable datasheet and standard as authoritative.

  1. ISO 5598:2020

    Provides the international fluid-power vocabulary used to interpret pneumatic terminology.

  2. ISO 3320:2013

    Specifies cylinder bore and piston-rod diameter conventions used in fluid-power data.