September 21, 2016

Navigating Your Hydraulic Cylinder Components

If you’ve been working with Hydraulics for any length of time, you’re probably familiar with all of the components involved and what their purpose is. However, if you’ve never had the experience of tearing one down, you may be missing out on how complex the engineering in these components has become to ensure precision, reliability, and structural integrity.

A hydraulic cylinder is primarily built inside a barrel. The barrel is the main body of the hydraulic cylinder and holds the pressure of the cylinder inside. The barrel houses the other components that make up the hydraulic cylinder and is fabricated from a seamless steel tube.

The base of the cylinder encloses the barrel at one end. It can be connected to the barrel through welding, threading, bolts or tie rods. The base holds the mounting solution at one end of the cylinder and seals it tight to prevent fluid from escaping and maintain pressure. The base secures the hydraulic cylinder to the equipment that the body of the equipment doing the work.

On the other end of the barrel is the head. The head of the cylinder helps maintain hydraulic pressure by closing off the other end of the barrel and allows the piston to extend and retract while under pressure. The head contains the seals and bearings that both seal the barrel and head, as well as seal the opening and align the piston rod.

Inside the barrel, the piston is the component attached to the rod that bears the force of the hydraulic fluid, allowing it to extend or retract. A piston is often machined with several grooves to allow seals to fit around it and maintain hydraulic pressure inside the barrel. The piston transfers its power to the piston rod and is attached by threads, bolts, or nuts.

The piston rod is typically a hard chrome-plated piece of cold-rolled steel attached to the piston and extends from the cylinder through the head. The piston rod connects the hydraulic cylinder to the machine component doing the work, such as a plow, or a dump body. The mounting attachment will connect directly to the piston rod.

In many build styles, the cylinder head contains a seal gland, that houses seals to prevent the pressurized oil inside the barrel from leaking past the interface between the rod and the head. The advantage of a seal gland is easy removal for seal replacement. The seal gland typically contains a primary seal, a secondary seal / buffer seal, bearing elements, wiper / scraper and static seal. In some cases, especially in small hydraulic cylinders, the rod gland and the bearing elements are made from a single integral machined part.

Hydraulic seals, like the hydraulic cylinder itself, are spec’d based on cylinder working pressure, cylinder speed, operating temperature, and application. Seals used on hydraulic cylinders are dynamic, and must be able to stand up to the wear of the piston rod extending and retracting. In general, seals are made from nitrile rubber, Polyurethane or Teflon, and are best in lower temperature environments, while seals made of Fluorocarbon are better for higher temperatures. Metallic seals are also available and commonly use bronze for the seal material. Wipers are often made from polyurethane and are used to eliminate contaminants such as moisture, dirt, and dust, which can cause extensive damage to cylinder walls, rods, seals and other internal components.

If you find your equipment in need of replacement components and seals, reach out to one of our hydraulic cylinder experts at 888-771-1894 and we’ll help you determine the best route to take to eliminate your downtime.