More than 15 Years of Experience in Hydraulic Repairs
Get in touch below
Fields marked with an * are required

Everything You Need To Know About Hydraulic Cylinder Parts

Hydraulic cylinders are some of the most important components in modern machinery. Used within multiple systems across construction, manufacturing, automotive and agricultural sectors, these cylinders facilitate movement and lifting with precision and strength. 

All hydraulic cylinders follow the same principle – a pump pushes pressure into the cylinder. Inside the cylinder is a piston, pushed and activated by the fluid to facilitate what would look like simple movements to us on the outside. For example, when you watch a bulldozer lift its arms, the cylinder’s pistons are doing the pushing. 

Here we outline the components that make up hydraulic cylinders, ensuring all those who work with hydraulics will have some understanding of the machines they may operate. 

Main Components of a Hydraulic Cylinder

The following is a breakdown of the hydraulic cylinder by component: 

Cylinder Barrel 

The barrel of the cylinder is the body that holds all the components inside of it. It acts as the chamber in which the piston rod moves in and out. This facilitation of movement ultimately is converted into mechanical energy that is transferred to the parts of the machine that require the energy. The barrel must be made up of strong materials to avoid deforming, as compressing the chamber within will reduce the amount of pressure that can be converted, or even hinder the movement of the piston rod. 

Cylinder Barrels are usually made up of materials that are strong and durable. The material it’s made of typically depends on the intended application of the system. Steel is preferred for heavy-duty work due to its ability to withstand high pressure, whereas aluminium is chosen for work where portability is key. 

Cylinder Base/Cap 

Found at one end of the cylinder, the cap is crucial for containing the pressure within. Without it being tightly sealed, it would lose pressure and machine functionality. Aside from that, its presence also supports the structure of the barrel. 

They are attached in different ways, but the predominant methods are through welding or threading. Welded caps are permanently fused to the barrel, ensuring a strong, leak-proof connection. Alternatively, threaded caps are screwed onto the barrel. This less-secure method is preferred by those who have the interest and/or capacity to disassemble and/or maintain the component. 

Cylinder Head 

The head of the cylinder contains the rod sealing and bearing components, allowing the piston rod to extend and retract from the cylinder during movement. It has components on the rod that ensure that it keeps the cylinder sealed whilst moving, preventing leaks and infiltration. 

Cylinder heads are made from steel and/or cast iron, due to their need to withstand high pressure. 


The piston sits inside the cylinder barrel, which is split into two. It moves back and forth from the force of the hydraulic fluid entering one of the two chambers. As one half of the chamber fills, the other moves, and thereby functions the rod.

Typically, they are made from steel and aluminium. In terms of design, they can sometimes come with grooves to facilitate seals.

Piston Rod

The piston rod extends from the piston, through the cylinder head and to the outside. It is a transmitter of force, generated by the movement of pressurised hydraulic oil inside the cylinder, to different parts of the machine to command motion. Whenever you operate hydraulic machinery and command it to move/lift, this is what’s happening inside the machine. 

Pistons are made from the highest strength quality steel can offer due to the constant repeated movement. On top of this, they’re usually coated in some sort of material such as chrome to resist corrosion and wear. 


Seals come modified for each component within and without the cylinder, including piston seals, rod seals, wiper seals and O-rings. Seals can be modified to serve several purposes, the most important being preventing leakage and keeping contaminants out. 

Rod Gland

The rod gland is the part of the cylinder head and serves several purposes. It ensures that the rod piston is aligned, ensuring the most efficient movement. It also is another component that requires seals. 

Hydraulic Cylinder

Types of Hydraulic Cylinders

Though each component of a hydraulic cylinder is more or less the same in terms of function, there are several different types of cylinders with different operational characteristics. 

Single Acting Cylinder

Single acting cylinders are the simplest hydraulic cylinders. The way it works is simple – hydraulic fluid enters one end of the cylinder. The force pushes the piston, which is within the cylinder. This pushes out the piston rod, which then activates motion in the machine. In order to reset the piston to its original position, a spring or force from the outside is required. 

These cylinders are used in applications where work is only required in one direction, since this is all the cylinder is capable of – a single action. Examples of these applications are automotive jacks and simple press machines. 

Double Acting Cylinders

Double acting cylinders are much like their single acting cousins. Instead of having one entry point for hydraulic fluid, there are two. This is so that the hydraulic fluid can make it so that the piston, and the rod by extension, can be moved in both directions. 

Double acting cylinders allow movement in both ways, giving them power and control that single acting cylinders can’t provide. They are often used in heavy machinery, such as excavators, loaders and bulldozers. The possibility of extension and retraction allows for complex movements within these machines, such as in the forks, arms and buckets. 

Telescopic Cylinders

These cylinders, aka multi-stage cylinders, have several cylinders within one another. They get their name from their compact nature, and how they can roll out much like a telescope. Sequentially, they can extend and retract, allowing for a much longer extension. 

They are ideal in situations that require long strokes, but cannot remain in the extended formation for long. Typically used in applications such as dump trucks and refuse collection vehicles,  the body of the truck can extend, pushing out the refuse, before returning to its retracted position. 

SMART Technology in Hydraulic Cylinders

Technological advancements with hydraulic cylinders in recent years have included the application of smart systems. Smart systems typically consist of sensors, data gathering, and data display. 

In hydraulic cylinders, smart equipment can measure parameters such as pressure, temperature, positions and speed of the piston.It allows for users to monitor the overall performance of their hydraulics. This is useful, as previously the only way to detect faults in your cylinder was witnessing its loss of functionality. With this, you’re able to detect issues before they become too problematic or more expensive to repair or replace. 

IoT Technology 

IoT technology revolves around the ability to display SMART information on various devices, such as smartphones, computers etc. Without this tech, the SMART technology will either have to display on an embedded system, make autonomous decisions or alerts, etc. 


Overall, hydraulic cylinders are irreplaceable parts of the hydraulic system, responsible for the movement of these complex machines. Understanding their inner workings and having effective performance monitoring systems is the best way of detecting when a cylinder is not working properly and could be in need of repair or maintenance. 

CJ Plant can help you with all your hydraulic cylinder maintenance needs, including replacement parts. As hydraulic repair and maintenance specialists, we ensure that when your plant and machinery has a problem, we can diagnose and repair it fast to minimise your downtime.

On This Page