hydraulic cylinder component parts

hydraulic cylinder component parts

A hydraulic cylinder is an executive element in a hydraulic transmission system. It is an energy conversion device that converts hydraulic energy into mechanical energy. Basically, it is composed of cylinder barrel and cylinder head, piston and piston rod, sealing device, buffer device, exhaust device, and other hydraulic cylinder component parts.

hydraulic cylinder barrels

Hydraulic Cyinder Barrel

It is the main body of the hydraulic cylinder, and its inner hole is generally manufactured by precision processing techniques such as boring, reaming, rolling or honing. The surface roughness is required to be 0.1-0.4μm, so that the piston and its seals and supports can be smooth Sliding, so as to ensure the sealing effect and reduce wear. The cylinder barrel has to withstand a lot of hydraulic pressure, so it should have sufficient strength and rigidity.

cylinder piston rod

Piston Rod

The hydraulic cylinder piston rod is a connecting part that supports the piston to do work, as well as a moving part with frequent movement and high technical requirements. The quality of its processing directly affects the life and reliability of the hydraulic cylinder, which has high processing requirements and strict requirements on coaxiality and wear resistance. 

hydraulic cylinder end cap

End Cap

The hydraulic cylinder end cap is installed at both ends of the cylinder barrel to form a closed oil cavity with the cylinder barrel, which also bears great hydraulic pressure. Therefore, the end cap and its connecting parts should have sufficient strength. When designing, it is necessary to consider the strength and choose the structural form with better manufacturability.

Cylinder Component - Head Cap

Hydraulic Cylinder Head

The hydraulic cylinder head guides and suppoarts the piston rod or plunger. Some hydraulic cylinders do not have a cylinder head and are directly guided by the end cover hole. This structure is simple, but the end cover must be replaced after wear.

Cylinder piston


The most commonly used connection between piston and piston rod is threaded connection and half-ring connection. In addition, there are integral structures, welded structures, taper pin structures, and so on.

cylinder flange


The installation methods of hydraulic cylinders are: earring type, flange type, hinge type, tie rod type, and foot type. Among them, flange-type hydraulic cylinders can be divided into two types of installation: front flange type and rear flange type.

Seal Kits

The piston device is another one of the important hydraulic cylinder component parts that is mainly used to prevent the leakage of hydraulic oil. A good seal is a guarantee for the transmission of power and normal operation of the hydraulic cylinder. According to whether there is relative movement between the two coupling surfaces that need to be sealed, the seal can be divided into the dynamic seal and static seal. The basic requirement for the design or selection of the sealing is to have good sealing performance and automatically improve the sealing performance with the increase of pressure. In addition, the friction resistance should be small, oil resistance, corrosion resistance, wear resistance, long life, simple manufacturing, easy disassembly, and easy to install are also necessary. Common sealing methods are gap seal, piston ring seal, O-ring seal, Y-ring seal.

Buffer Device

When the hydraulic cylinder load is large and the speed is fast, the hydraulic cylinder should generally be equipped with a buffer device. If necessary, a buffer circuit should be provided in the hydraulic transmission system to avoid excessive mechanical collision at the end of the stroke and damage to the hydraulic cylinder. The principle of buffering is to increase the oil return resistance in the oil discharge chamber when the piston or cylinder is close to the end of the stroke, thereby reducing the movement speed of the hydraulic cylinder and avoiding the collision between the piston and the cylinder head.

Exhaust Device

Air is often mixed into the hydraulic transmission system, making the system unstable, causing vibration, crawling, or forward rushing. In severe cases, the system cannot work normally. Therefore, when designing hydraulic cylinders, the removal of air must be considered. For hydraulic cylinders that are not demanding, special exhaust devices are often not designed, but the oil ports are arranged at the highest point at both ends of the cylinder so that the air follows the oil to the tank and spills out of it. For hydraulic cylinders that require high-speed stability, special exhaust devices, such as exhaust plugs, exhaust valves, etc. are often installed at the highest point of the hydraulic cylinder.