The pressure level affects the rod seal concerning sealing ability, friction and fatigue. Those factors which most determine the risk of damage by extrusion into the clearance between the rod and the cylinder head on the low-pressure side of the seal (normally the atmosphere side) are the bore diameter, the dimensional precision of the guide function, temperature, pressure, the strength of the seal materials and the duration of the pressure cycles.
A common characteristic of most types of seals is that the higher the pressure, the better they seal. The risk of the sealing properties being impaired at pressures of up to 40 MPa is small, provided that the surface of the rod is in good condition.
It is more difficult for the seal to maintain its sealing properties at low pressure or in zero-pressure conditions. This is especially applicable in extremely cold conditions, when the seal material is hard and less elastic, and the oil has a very high viscosity which makes it difficult to wipe off.