Double or Single Acting Hydraulic Cylinder – Which is Best?

Hydraulic cylinders perform many different functions in business today. They make it possible to greatly amplify the work effort and energy it takes to lift and move things. Two of the most basic types of cylinders are the single and double action hydraulic cylinder. Both are very important but each one has its own advantages. Let’s compare these two to help you decide which one is best for your needs.

Single Action Cylinders

A single acting cylinder has only one port for fluid. This is how a reciprocating engine works. The piston applies pressure in one direction only and it is returned to position by use of some kind of force on the other side of the piston head. The working hydraulic fluid only acts on the piston side, it can be returned by a spring, air pressure, another cylinder or a flywheel mechanism on the rod side.

The forward stroke is created by hydraulic fluid entering the cylinder and as the pressure increases, it moves the piston back. A control valve then releases pressure on the fluid and opposing pressure on the piston (from a spring for example) returns the piston back to its original position, in a single acting hydraulic cylinder. You will find these types of cylinders in hydraulic pumps and rams.

Double Action Cylinders

A double acting hydraulic cylinder has a fluid port on both sides of the piston. This allows the cylinder to exert force or pressure in two different directions. When fluid enters one port, it is forced out the opposite port by the action of the piston.

Benefits of Double Action

Because most cylinders today are double action, they are widely available and provide many different options. A double acting cylinder also has its own fluid reservoir (so smaller reservoirs are needed). In fact, the cylinder itself holds a great deal of the hydraulic fluid in the system. This is ideal where space is at a premium.

Double acting cylinders are used where both pushing and pulling are needed. Excavating machines, log splitters or any action where you need to lift and replace objects, are just a few examples of uses.

Benefits of Single Action

If you have low force requirements, a single acting hydraulic cylinder may be a good choice. They are very durable and can take a great deal of use. Plus, no additional electrical components are needed in many single action applications. They are commonly used in ejection equipment and door operations.

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