Contamination is the largest problem associated with EHC systems.
Maintaining a clean EHC
system is an on going
problem.
The on-board fluid
conditioning system is
not capable of
maintaining the fluid
within OEM
specifications. Over a
period of time dirt,
water and acids
accumulate in the fluid
causing problems with
the components of the
high pressure fluid
system. Component wear
and servo valve failures
are the most common
problems of fluid
contamination.
Servo Strainer
The servo valve contains a 90 mesh strainer which is located downstream
of the 3 to 5 micron pump discharge filter. With this arrangement it
appears that the servo strainer should never get plugged. After careful
evaluation of many plugged servo strainers, gelled EHC fluid was found
to be the major source of this contamination. In addition, varnish build
up on the inner walls of the Fluid Supply pipes occur over a period of
time due to the low flow of the fluid through these pipes and elevated
temperatures surrounding the lines. The cause of both the gel and
varnish is actually a combination of Fullers Earth mixed with EHC fluid
that has migrated past the polishing filters.
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