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Watch out for contaminated fluid in hydraulic cylinders

Author : Andrew Delaney, marketing communications manager, Parker Cylinder Division Europe

01 October 2012

Andrew Delaney kicks off our new hydraulics blog with this short tutorial on the deleterious effects of contaminated fluids in hydraulic cylinders.

Contaminated fluid can cause premature rod seal failure.  Abrasive particles suspended in the fluid can damage the seal and the piston rod surface, while airborne contamination can be drawn into a cylinder via a faulty wiper seal.

Water is a common contaminant in mineral oil systems, affecting the lubricity of the fluid and causing some of the most widely used seal materials to ‘age harden’ at temperatures above 65°C. 

Polyurethane seals are subject to hydrolysis effects in high water based fluids at temperatures above 50°C, leading to a loss of hardness and tensile strength, which allows fluid leakage from the rod seal.

Air is often overlooked as a fluid contaminant, but aerated oil can cause physical damage to piston rod seals.  Pressure shocks in systems with high cycling speed can cause air bubbles to become highly charged with heat energy, a condition often referred to as ‘dieseling’.

This condition is particularly pronounced in vertical, rod up applications where a rapid increase in hydraulic pressure can cause intense localised heating of the bubbles at the lip of the primary seal.  The presence of air in the fluid can also intensify the transmission of vibration, which, in turn can lead to other forms of system failure.


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