The Basic Parts of Hydraulic Cylinders You Need to Know

Every hydraulic machine relies on the pressure from a hydraulic fluid for its operation, the basic common component used in these machines that converts fluid pressure into linear actuated motion is the hydraulic cylinder. Today, we will explore the basic hydraulic cylinders parts and understand their functional mechanisms.

Hydraulic Cylinder Barrel

Cylinder barrel is the main component of the hydraulic cylinder. It forms a closed cavity with the cylinder head, piston and other parts to push the piston to move. The quality of its processing will directly affect the life and reliability of the entire hydraulic cylinder. The material is generally required to have sufficient strength and impact toughness, as well as good welding performance. Cylinder barrel blanks are mostly cold drawn or hot rolled seamless steel pipes, and large-sized cylinder barrels are usually made of forgings.

Hydraulic Cylinder Head

Hydraulic cylinder head is also called cylinder gland or gland or guide sleeve. It plays a guiding role when the piston rod reciprocates, and is used to support and ensure the coaxiality of the piston rod and the cylinder barrel. It requires high matching precision, fast movement, good wear resistance, and can withstand the pressure, bending, impact, vibration and self-gravity of the piston rod caused by external forces. At the same time, it also provides a support for the oil seal of the cylinder port. Some hydraulic cylinders don’t have cylinder head and are directly guided by the cylinder head holes, which reduces the number of components and makes assembly simple, but the cylinder head is easily damaged, resulting in waste.

End Cap

End cap is also called cylinder base or cylinder cap. It is a component that is threaded to the bottom of the hydraulic cylinder and used to enclose the pressure chamber at one end.

Piston Rod

A piston rod extends from inside the hydraulic cylinder through the head cap. It transfers the force from the hydraulic cylinder to the equipment on which the cylinder system is used. Same as the cylinder barrel, the quality of the piston rod also directly affects the life and reliability of the hydraulic cylinder. The basic requirements for the piston rod are sufficient strength, stiffness, stability, good wear resistance, high machining accuracy and surface roughness. It is necessary to structurally minimize the effects of stress concentrations and to ensure reliable connection and prevent loosening. Furthermore, the design of the piston rod structure should facilitate the disassembly and assembly of the piston.


A piston is attached to the piston rod. It separates the cylinder barrel into two compartments and reciprocates back and forth when the pressureis developed on any side of the cylinder chamber.


A set of circular sealing rings are used in the interface of metals. These rings are assembled by making groups in the metals.

The seals used between the surface of metals in relative motion are dynamic seals and those acting between two surfaces at rest with respect to each other are static seals.

A piston seal acts as a pressure barrier between two chambers separated by piston. 

The guide rings prevent metal to metal contact and resists radio forces acting in the hydraulic cylinder. 

A wiper seal is used to wipe dirt from the piston rod while entering through the cylinder head and prevent contamination of oil. 

A piston rod guide ring is used to absorb transferred forces acting on the system and also prevents metal to metal contact of piston rod and hydraulic cylinder head. 

A rod seal prevents the fluid from escaping the chamber.

A buffer seal protects the main seal during peak pressures.

A head static seal is used to seal the interface between hydraulic cylinder head and cylinder barrel.

Other Hydraulic Cylinders Parts

There are other hydraulic cylinder parts or components, such as clevis, mounting flange, mid trunnion, buffer device, exhaust device, and so on.

parts of hydraulic cylinders

Now let’s understand the working of a hydraulic cylinder, the picture above is a double acting hydraulic cylinder which means the system can extend or retract by using hydraulic fluid on both conditions. A fluid pumping unit creates flow of hydraulic fluid into chamber CA.

Since the chamber is confined the fluid exerts pressure on all sides and the boundary of chamber. But in this case the piston is the only movable portion of chamber boundary. So when a sufficient amount of force is developed, it is forced towards the chamber of low pressure, this also pushes the fluid back to the reservoir from chamber CA, the effective pressure that can be used to generate forces, the difference of pressure exerted on the high pressure chamber CA, and that on the low pressure chamber CB.

Put the pressure on the chamber CB is almost zero compared to that in the chamber CA. Then force applied on the piston is pressure at chamber CA multiplied by area of piston, this is the force by which the piston and piston rod is pushed outwards. Similar principle is followed by fluid flows and the chamber CB, but in this case the effective or useful area is the difference of cross section area of the piston to that of piston rod’s fluid cannot exert pressure on the cross section area of rod. This means the effect of area in this case is less than the previous case. This is why the retracting force of hydraulic cylinder is always less than the force during extensions.

We trust that you learned something today about the basic hydraulic cylinders parts and components. JW HYDRAULIC is dedicated to not only manufacturing and supplying hydraulic cylinder component parts and bespoke hydraulic cylinders, but also provide cylinder repair, replacement and refurbishment services.

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