Hydraulic cylinders fail by physical damage or by deterioration of their seals. Physical damage to a hydraulic cylinder is usually from an external source, such as another machine or a falling object. Physical damage can occur from excessive wear, especially as related to cylinder misalignment.

Clean all the seals so that they are free from any foreign matter. Install any backup rings needed behind O-ring seals. Pressure should toward the O-ring seal first, then the backup ring. Slide most piston seals on like an O-ring seal, But you may have to use special techniques to install some piston seals.

A positive seal prevents even a minute amount of oil from getting past. Positive seals do not allow any leakage whatsoever (external or internal). A non-positive seal allows a small amount of internal leakage, such as the clearance of the piston to provide a lubrication film.

With hydraulic cylinders, there is more than meets the eye. To contain the pressurized fluids in a hydraulic cylinder system and keep it in motion, a complex configuration of high-performance seals in two basic categories are required: (1) static seals and (2) dynamic seals (supported by guide rings).

Most seal manufacturers say that operation of the seal at one of these limits will result in a minimum life span of two years; three years with some seal types such as those specified in Standard API 682.

A type of dynamic hydraulic seal called a rod seal is exposed to movement on its inner diameter along the shaft or rod of a hydraulic cylinder. A type of dynamic hydraulic seal called a piston seal is exposed to movement on its outer diameter along the tube or bore of a hydraulic cylinder.

O-ring packings are used to prevent both internal and external leakage. This type of packing ring seals effectively in both directions and is the type most commonly used. In installations subject to pressures above 1,500 psi, backup rings are used with O-rings to prevent extrusion.

Is an O-ring seal a one-way or a two-way seal? A two-way seal. How can you be sure of getting an O-ring made of the correct material for a specific hydraulic component? The O-ring must have the correct part number and it must have been obtained from a reputable source.

Seals are used to prevent fluid from passing a certain point, and to keep air and dirt out of the system in which they are used. The type fluid used in the system. The metal finish and the clearance between adjacent parts.

An O-ring, also known as a packing or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a round cross-section, designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface.

O-rings are circular, ring-shaped pieces that sit in a groove between two (usually cylindrical) parts. Terminology note: Any o-ring can technically be called a gasket since they prevent the transfer of liquid and air, but while o-rings are a specific shape of gasket, any gasket cannot be called an o-ring.