Hydraulic Cylinder Guide: Identifying Parts of Hydraulic Cylinders

By Alexa Yates |

When one hydraulic cylinder part fails, it will usually impact the performance of other parts. That’s why all hydraulic cylinder repairs require a full disassembly and reassembly of the cylinder itself. During the disassembly process, each part is thoroughly examined for general wear and tear and signs of failure.

If your hydraulic cylinder is underperforming, or has failed altogether, keep reading this article. In it, we’ll break down the major parts of a hydraulic cylinder, the function of each part, and how they work together as a unit. Knowing this information can help guide you during repairs, identify potential problems, and potentially save you time and money.

hydraulic cylinder cross-section diagram

Barrel

The first major part of a hydraulic cylinder is the barrel, which is a smooth cylinder that keeps pressure inside the cylinder. Designed internally to reach the correct diameter, most cylinder barrels have exterior finishes between four and 16 micrometers.

Additionally, there are two major types of barrels: single-acting and double-acting. The main difference between the two is that single-acting barrels have welded ports on the end of the base, while double-acting barrels have welded ports at both bases.

Cylinder Head/End Caps

Hydraulic cylinder heads are the endpoints where an extended piston rod delivers productive force. The primary purpose of the cylinder heads is to prevent leakage of pressure from the pressure chamber at both ends of the cylinder.

Heads can either be attached to barrels via a screw connection, spring ring, or, less commonly, by welding. Head interiors are finely grooved to coordinate with glands, rod wipers, and piston rod seals.

Hydraulic Cylinder Base/Gland

Also called the rod end, the hydraulic cylinder base is the visible opening that a cylinder rod connects to. The gland is attached with tie rods, bolts, welding, or threading. Hydraulic cylinders incorporating a tie rod utilize high-strength steel rods that are threaded for holding end caps to the barrel. Welded body cylinders do not have tie rods. Instead, the barrel is directly welded to end caps while ports are welded to the cylinder barrel.

Hydraulic Cylinder Piston

Inside hydraulic cylinders is the piston that functions to isolate pressure zones within the barrel. Pistons are manufactured to fit metallic or rubber seals that can be double-acting or single-acting. To facilitate the transference of linear motion, piston rods are attached using nuts, bolts, or thread. Hydraulic cylinders retract or extend depending on the location of applied pressure relative to the piston. For example, pressure exerted on the cap end results in the extension of the rod outside the cylinder barrel.

Piston Rod

Typically made from cold-rolled steel fortified with hard chrome plating, the piston (cylinder) rod is attached to the cylinder head and the piston. Hard chrome is essential for giving piston rods the ability to last a long time. The piston rod also enhances the seal, which helps prevent leaks.

Seal Gland

Hydraulic cylinders also have a seal gland, which typically have a number of seals within them, including primary, secondary, wear, wiper, scrapper, and static.

Seals

As previously mentioned, there are many seals inside a seal gland. The purpose of each seal is to prevent leaks from occurring beyond the interface of the head and rod. Seals are also exclusively designed to accommodate a cylinder’s speed, working pressure, and operating temperature.

When hydraulic cylinders are used in low environmental temperatures, it’s recommended that the seals be made from nitrile rubber materials. On the other hand, hydraulic cylinders operating in high-temperature conditions should be made from fluoroelastomer, a rubber compound providing a strong fluorine-hydrogen bond that makes it resistant to extremely hot (and cold) temperatures.

Lastly, seals should be replaced if they are damaged (broken, ripped, worn edges, etc.,). While they are easy to remove and replace, it’s vital that you purchase the right type of seal replacements for your cylinder. Please visit our blog to learn more about replacing seals.

Repair Your Cylinder With Help from Yates

Hydraulic cylinders are complex. Although every hydraulic cylinder has similar components, there are a wide variety of classifications, designs, and configurations. Even if you know how to identify each component, it’s always recommended to have a professional help you perform evaluations.

If you have general questions about the various parts of a hydraulic cylinder, or need help performing repairs, turn to Yates Cylinders. In business for nearly 50 years, we’re a globally recognized and ISO- certified manufacturer and rebuilder of pneumatic and hydraulic cylinders. We also sell hydraulic cylinder accessories and seal kits. You can view our complete line of cylinders and cylinder accessories here. To schedule a consultation with one of our specialists or to request repair services, please fill out our online form.