Important factors that must be considered when selecting hydraulic seals
Dec 08, 2022
When we select hydraulic seals, we must consider a number of important factors (e.g. pressure, temperature, friction) to ensure that the seal maintains good sealing performance over its life cycle, while having low friction and wear, and hopefully also good performance in harsh operating environments.
The following is a brief description of the impact of each factor on seals.
Pressure
The level of pressure in a hydraulic cylinder, and the length of the pressure cycle change, has a significant impact on hydraulic seal damage (e.g. extrusion). The higher the pressure, the greater the effect on the performance of the hydraulic seal of other factors such as temperature, speed, seal material, clearance between the piston and cylinder barrel, and clearance between the piston and cylinder head.
Temperature
It is difficult to describe the maximum and minimum operating temperatures of a seal material as this is the result of a combination of factors. For both pistons and rods the operating temperatures are different and they have to be selected differently.
Friction
The friction between hydraulic seals and sealing surfaces depends on a number of factors: surface roughness, surface characteristics, pressure, media, temperature, seal material, seal type and speed of movement.
Surface finish
Experience has shown that the surface characteristics of cylinder pistons and rods have a very significant impact on the seal life. Surface characteristics are often defined by the value of surface roughness Ra, which is the arithmetic mean of the absolute value of the deviation of the surface shape from the centre line. However, these values do not give a complete indication of the effect of surface condition on the seal, as different surface shape characteristics can lead to different levels of seal wear on the seal, even at the same roughness.
A more scientific selection of seals, taking into account the above factors when choosing hydraulic seals, can play a vital role in the overall hydraulic system.
