Hydraulic Piston Cylinder

The diesel-effect appears -if it appears - on the oil side not on the gas side. But the presence of O2 is at higher pressure reducing due to oxidation the seal life expectancy. Even if you use a good seal on the wall there is a thin oil layer which will change its structure in the presence of O2, high pressure and high temperature in case of a rapid loading (near to adiabatic). this can lead to particles which will destroy the seal contact zone and lead to gas losses into the oil with the need to fill the accumulator at short intervals. Better use N2 and avoid all troubles. Do not consider that the guys who work on accumulator design and manufacturing are stupid there are reasons to respect prescribed conditions.

For sealing arrangement,use piston rings for greater reliability and long life.But the cylinder and piston must honed or grounded smoothly w/ tighter tolerance.

Secondly,use nitrogen with 95% or higher purity.Most hydraulic accumulators uses nitrogen for safety and consistency.

try research on pressure die casting machines,it will give you better insights.God bless. Arnold E.