Hydraulic Cylinders

Hydraulic Cylinders

Seaway Fluid Power (SFP) Hydraulic cylinders are actuators which provide mechanical assistance to drive movement in machinery. These cylinders generate power in a linear or straight line direction. The type of power created by hydraulic cylinders is hydrostatic pressure which is the power created by a combination of the compression of hydraulic fluid within the cylinder and the rate at which the hydraulic fluid is flowing.

The basic design of a hydraulic cylinder consists of a cylinder that has a steel rod inside it. Hydraulic fluid is injected into the cylinder. Typically, a piston is attached to the bottom of the steel rod and serves as the means to apply pressure to the hydraulic fluid. A unique aspect of the piston construction is that it allows the steel rod to be a smaller diameter than the cylinder itself. It is this basic design that allows for the hydraulic cylinder to operate in both directions by either pushing or pulling on the hydraulic fluid. A time tested solution to creating movement hydraulic cylinders can deliver upwards of 3,000 psi or higher.

A simple ram-type cylinder consists of a cylindrical tube (hence, “cylinder,”) and a steel rod inserted and sealed in that tube. Pressurized fluid is pumped into the cylinder, where pressure upwards of 3000 psi or more acts upon the circular bottom of the tube. The force of the pressurized fluid will push the rod out of the cylinder as long as the mass on the rod is less than the force created against the rod by the fluid. It should be noted that force, not flow creates motion; the creation of movement due to flow is a popular misconception requiring explanation another day.

As a result of their simple design and highly efficient operation, hydraulic cylinders are currently in use I a wide variety of applications. Applications that take advantage of the linear force generated by hydraulic cylinders include:


  • Agricultural
  • Construction
  • Heavy Industry
  • Material Handling
  • Metal Fabrication
  • Mining
  • OEM Manufacturing
  • Oil & Gas
  • Transportation
  • Waste & Recycling

It should be noted that part of the reason for the use of hydraulic cylinders in so many industries is their common use for mobile applications like excavating machines, dump trucks, front end loaders, grading machinery and bulldozers.

Types of Cylinders

Welded Cylinders

Welded cylinders are typically more compact and lighter than tie-rod cylinders. As a result of this compressed footprint welded cylinders are frequently found in mobile applications where space is at a premium.

In terms of construction, these cylinders have the end flanges welded directly to the cylinder barrel. End caps are attached to each end flanges and held in place by bolts that are inserted through holes in the end cap and flange.The ability to increase the number of rods associated with the cylinder.

Tie-rod Cylinders

Typically have end caps that are attached to the end of the cylinder barrel via a rod that is inserted through holes in the end caps. Once through the hole, the rods are secured in place by nuts threaded onto the end of the rod.

Tie-rod cylinders tend to be used in heavy industrial/manufacturing operations due to their robust nature. Tie-rod cylinders come in various configurations. One of the main variations associated with tie-rod cylinders is the number of rods associated with the cylinder which can vary from four to twenty rods. The addition of rods to the cylinder increases the pressure capacity of the cylinder.

Telescoping Cylinders

Telescoping cylinders are comprised of multiple tubular sections that fit together. The tube-based sections function independently as small cylinders. By adopting this design, it is possible to vary the size of the individual tubing sections to create long overall cylinders. At the same time, the ability to telescope down into a small footprint makes this type of cylinder desirable for mobile applications in which the cylinder mounting area is restricted.

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