Myth #1. Hydraulic pump inlet lines must have a strainer.
A pump inlet or suction strainer is a 140 micron, mesh screen
which is screwed onto the pump intake penetration inside the
hydraulic reservoir.
These stainers increase the chances of cavitation occurring
in the intake line and subsequent damage to, and failure of
the hydraulic pump. Piston-type pumps are particularly vulnerable.
If the reservoir starts out clean and all fluid returning to the reservoir is filtered, inlet strainers are not required since the hydraulic fluid will not contain particles large enough to be captured by a coarse mesh screen.
The main argument for installing suction strainers is to protect
the pump from debris that enter the reservoir as a result of
careless maintenance practices.
Fact is, nuts, bolts, tools and similar debris pose minimal threat
to the pump in a properly designed reservoir, where the pump intake
is located a minimum of four inches off the bottom.
When you consider the damage that vacuum-induced cavitation can
cause to a hydraulic pump, NOT installing a suction strainer is
definitely the lesser of two evils.
I generally recommend removing and discarding all filters fitted
to pump intake lines.
The one possible exception to this rule is charge pump intakes on hydrostatic transmissions.
If in doubt, consult the hydraulic pump manufacturer.
On the last paragraph...YMMV...
