Myth #1. Hydraulic pump inlet lines must have a strainer. - Machine Underground -Tractor & Commercial Equipment Discussion Forum

**PaulChristenson** · 01-29-2008, 08:14 PM

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...

lincolnvt · 01-30-2008, 10:32 AM

Thanks Paul - very useful info and fun to read. Appreciate your time with this.

Cheers,
Brad

Mickey · 01-30-2008, 02:29 PM

Paul, you comments remind me of a few yrs back when I replaced the trans filter on the motorhome. Had to drop the pan and what do I see, a metal housing with window screen sized mesh for the filter. Like that was going to really help!

mighty mouse · 09-10-2008, 06:34 PM

Wow, I was absolutely crucified on another site for suggesting this. I was told by an engineer at the factory of a major equipment manufacturer that the only reason they install suction strainers is to cut down on warranty claims from stuff left in the hyd tank by the asemblers. I have also seen the window screen type get sucked shut when the pump ran. Turn the engine off, remove the strainer, it looks fine, run the pump, the strainer collapses. I have always removed these from my equipment on the first service and have never had a breakdown that a suction strainer would have prevented.

Dougster · 09-11-2008, 01:14 PM

Quote:

Originally Posted by PaulChristenson

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...

The old Dougster™ is a little confused.

What specifically are you folks saying or recommending as it relates to our equipment? That we should remove the hydraulic system suction filters and/or strainers on our tractors and other mobile equipment?

Not trying to start a debate or technical argument. To the contrary, I promise to be quiet for once and listen and not post again in this thread. Just trying to figure out specifically what you guys are recommending to us here.

Dougster™

mighty mouse · 09-11-2008, 01:25 PM

Doug,

Just saying that in a properly designed hydraulic system, the strainer poses more problems than it solves. When strainers get clogged, it is with gooey oil residue, not with nuts, bolts, and pieces of metal. All that stuff would go right thru the pump and components without causing any damage. The outlet from the tank to the pump should be up off the bottom anyway, so no steel should ever be picked up. When changing the hydraulic oil, the tank should be cleaned also, so anything in the bottom of the tank will be cleaned out anyway. Hope this clears it up for you.
Andy