Single- vs Double-acting Air Rams or Air Cylinders: Which One Should You Choose?

compressed air cylinder tanks
For air rams as well as pneumatic tools, call us at MasterMac 2000.

Pneumatic cylinders, also called air cylinders, air rams, and air actuators, are mechanical devices that use compressed air to move a load on a straight path. The most common type of pneumatic cylinder is a rod and piston moving inside a closed cylinder wherein the piston moves only in one direction. Pneumatic cylinders use compressed air as their source of energy to operate a given task. The compressed air causes the piston to extend and retract inside the cylinder.

Two types

Pneumatic cylinders come in two types: Single-acting and Double-acting. The main design difference between the two is the number of ports. Used as the port where pressurised air enters, single-acting cylinders have only a single port, while double-acting have two ports. When choosing which to use, it’s important to know the application of each device.

Single-acting cylinders

The thrust of force of a single-acting cylinder is only in one direction. The piston is returned by a fitted spring, weight, mechanical movement, gravity, or external spring. There is only one port for compressed air to enter, whether the cylinder action is for the ‘push’ or ‘pull’ type. 

Common applications for single-acting cylinders include clamping, positioning, marking, stroking, and light assembly operations wherein only one direction is needed.

  • Advantages:
    • Simple design.
    • Compact size.
    • Reduction in piping or valve costs.
    • Air consumption is reduced to half compared to double-acting cylinders.
  • Disadvantages:
    • Return spring is vented to the atmosphere that may allow entry of foreign matter, leading to malfunctioning.
    • Spring operation over an extended period may become inconsistent.
    • Bore size and cylinder stroke are limited because of the limited spring size and force.
    • A slight reduction in thrust due to the opposing spring force.

Double-acting cylinders

The thrust of this cylinder is in both extending and retracting directions since there is a port at each end to move the piston forward and back by alternating the port that receives the compressed air. Air pressure is applied alternately to the opposite ends of the piston. Double-acting cylinders account for almost 95% of all cylinders used in pneumatic control systems in manufacturing.

  • Advantages:
    • ISO standards are based on the design of double-acting cylinders.
    • This type of cylinder gives a more extensive range for more options on bore and stroke sizes.
    • Many variations are available from this design.
  • Disadvantages:
    • Cannot be held in a mid-position.
    • Compressed air being the energy source, the cylinder needs to be coupled to a hydraulic cylinder to have a constant feed.
    • Long-stroke cylinders need proper guidance for the piston rod.

MasterMac 2000

For your air rams and other process valves and pneumatic components, you can find all these and more of considerable quality from MasterMac2000. Since 1989, MasterMac2000 is the exclusive distributor of quality brands like Univer, Mack, Tolomatic, Piab, and more. Contact us today for more information on 07 3344 4711. You can also take a look at our product lines at

Leave a Comment