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Double-acting air cylinders. The workhorse of industrial pneumatics.


Double-acting air cylinders! These are the work horses of the compressed air circuit, so named, because compressed air is used to both extend and retract the rod - a double action.

Single acting air cylinders use an internal spring to either extend or retract the cylinder rod.

The first graphic depicts a double-acting air cylinder in which compressed air has entered the cylinder port at the rod-end of the cylinder.

The piston and rod combination are shaded in purple, and the compressed air is shown in blue, for ease of identification.

’Air

Air has pressurized the inside of the cylinder barrel, and in so doing, has driven the cylinder piston to the rear. In so doing, the rod, which is attached to the piston, is retracted, and whatever tooling is attached to the rod end, does some work.

The air that was in the rear of the cylinder has exited from the rear-cap cylinder port, through the exhaust port in the air valve, and out to atmosphere.

’Air

The second graphic shows that the reverse has occurred. Air has entered the rear cylinder cap port, driven the piston to the rod end, and the rod has extended, allowing it to do some sort of work.

Double-acting air cylinders can be manufactured in a repairable or non-repairable format.

They are usually manufactured to industrial standards, including those of the National Fluid Power Association or to the European standards of ISO-6431 or ISO 6432 .

When selecting a double-acting air cylinder for your application, here are the details you will need to clarify:

  • How big a diameter? Force = pressure x area, so the bigger the diameter, the greater force available from a given air pressure.
  • What is the rod length, which translates into how far you wish to move the object.







  • Does the application require a larger than standard rod and rod bearings?
  • What size and type of thread is required, and does the application require a male or female thread?
  • Will your logic device need an input signal showing rod end positioning? If so, you may need a magnet on the cylinder piston and a proximity switch .
  • How will the cylinder be mounted?
  • How will the cylinder rod be connected to the tooling?
  • Ensure that you have the correct fittings for the cylinder ports.
  • Do you need to control the cylinder speed? If so, what type of flow controls will you need?
  • How will you stop the piston travel inside the cylinder barrel? Will you need cushions ?
  • Will the application require a lubricator, Will the application require a lubricator, or will the factory lubrication suffice? (Check with the cylinder vendor if yours is a high speed application.)

    There are a huge number of manufacturers of double-acting cylinders in the world, most of whom are represented by stocking industrial distributors making this style of air cylinder among the most readily available for original purchase, and for MRO (maintenance, repair & overhaul) replacement.

    Need some sources for air cylinders? Feel free to use the search box below:


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