What Are The Hydraulic Cylinder Parts-Cylinder Tube / Cylinder Barrel

What Are The Hydraulic Cylinder Parts-Cylinder Tube / Cylinder Barrel

The cylinder tube (or cylinder barrel) is made of steel; usually carbon steel. There are a range of different steels available in terms of strength, with higher pressures requiring stronger steels and thicker cylinder walls. In places where it cannot be painted (such as food preparation areas) it would be made of stainless steel to avoid it being prone to corrosion.  cylinder barrel can be coated in a variety of paint or coatings, with company logos often displayed here.

The internal diameter of the tube usually needs no protection with paint or chrome because the hydraulic fluid protects it from corrosion. However, if the hydraulic fluid is a corrosive material (such as water) the inside of the tube will be coated as well as the rod.


The cylinder rod is the only external part that can’t be painted. Because of this, it has to be protected in other ways. In order for the cylinder to work well the coating has to be completely smooth. The cylinder rod needs to be highly resistant to pitting, corrosion or wear. Any cracks can scrape on seals, causing contamination to enter the hydraulic fluid and leading to eventual hydraulic system breakdown. Therefore, the materials and coating of the hydraulic cylinder is of the utmost importance. Most commonly, the cylinder rod is made of steel or stainless steel and is then coated with Hard Chrome Plating (HCP).


The piston is attached to the piston rod and moves up and down the cylinder bore, pushed by the hydraulic fluid. It provides the area used to create the hydraulic force. It is vital that no hydraulic fluid can pass over the internal piston.


Most hydraulic fluids are oils, with a huge number of different types available. Different hydraulic systems, pumps and valves will require a different viscosity of fluid. Sometimes, in applications where any flammable liquid poses a risk, the hydraulic fluid may be water based.


Both ends of the hydraulic cylinder need a mounting interface; one at the base and one at the head. The mounting interface depends entirely on the customer requirements and application of the fabrication.
Different mountings include:

  • Pins
  • Threaded connections
  • Flanges
  • Trunnions
  • Spherical bearings
  • Foot mounted
  • Bolted


The hydraulic tube needs to be sealed at both ends to stop oil leaking and keep the pressure in. One end of the tube is sealed off with a base. However, the other end needs to be open to allow the rod to move in and out of the tube. At this end the tube is sealed with a neck gland that allows the rod to move in and out. The neck gland material would be chosen during design, with seals on both the rod and the tube.


Hydraulic fluid needs to enter and exit the cylinder via ports, with one port at either end of the cylinder tube and the hydraulic piston between the two ports. These must be secure, as a weak port can cause a dangerous leak of hydraulic fluid under intense pressure.


Seals are used throughout the hydraulic cylinder. They can be made of a wide variety of different materials, depending on the function and type of hydraulic cylinder. They need to be hard wearing, able to survive multiple repetitions of the rod moving in and out of the barrel, removing any contamination.

Posted in Honed Tubes.