Suction filter killing performance, need better options.

[grayw0lf1]

On my old Kubota L355SS the suction filter assembly was badly damaged when I bought it. I replaced it with a 10 micron suction line filter with 3/4" ports that is rated to flow well beyond my tractor's hydraulic flow output. That being said, I'm tired of slow & weak hydraulics, so I timed how long it takes to lift 600lbs of concrete bags from ground to fully raised. The results very much confirmed my theory of the filter restricting flow. (No, a new filter didn't help.)

Results with 600lbs of concrete in the bucket:
Engine Speed Time to max lift with filter Time to max lift with filter assembly removed
idle - 600rpm no lift very slow, but moving
1500rpm 25 seconds 13.6-14 seconds
1800rpm 30+ seconds 9.0 seconds

Background on the filter setup:
The straight 1" pipe comes from the tractor case, flex hose to 90 bend while reducing to 3/4", filter with 3/4" ports, to hosebarb with flex hose to the pump.

Concerns / Possible Fixes:
1. Is the filter assembly just too close to the pump?
2. Will a 150 mesh spin-on filter make enough of a difference?
3. Or should I find another simple 150 mesh screen solution?
4. Should I move the filter to a return line? If so, where? What line would be under low enough pressure?
5. Throw 1-4 out the windows & go with your much more knowledgeable suggestions.

Thanks for the help. All suggestions are much appreciated.

 

[grayw0lf1]

The chart I tried to make above didn't turn out well...
Oh yeah, I'm also trying to avoid that whole "cavitation ruining the hydraulic pump" thing.

 

[grayw0lf1]

& this is what I was considering for the 150 mes spin-on filter in #2.
Nortrac Suction Filter Assembly | Hydraulic Accessories| Northern Tool + Equipment

 

[kthompson]

Have you verified with Kubota dealership you are using correct filter? Doubt you are using too heavy an oil.

 

[grayw0lf1]

Its definitely aftermarket. The original screen & housing assembly was pretty much trashed. I have a hard time paying... I think it was around $325+ for an OEM replacement.

 

[KyleH]

Can you post a picture of what you have setup? It would help to see how you have it setup.

Is the filter you have on the same flow rating as the oem style filter? Maybe swapping to a different filter may be the solution.

If it is cavitating, it could damage the pump, if changing the filter doesn't help it may be cheaper in the long run to just buy the proper filter housing and filter setup. Hopefully you can make your setup work and save some money though.

 

[Leejohn]

Are you getting good free flow from the sump?

PS, One thing I just though of, make sure the sump vent isn't stopped up.

 

[grayw0lf1]

I assume I'm getting good flow. I'm not even sure where the vent is, but I'll look into it.

 

[KyleH]

Was just looking at the parts diagram and think I know what you are talking about now.

I would figure out what your thread size is on your filter head, then get a spin on filter with wire mesh to match.

Donaldson, Fleetguard, and Baldwin should all make them.

 

[SPYDERLK]

On my old Kubota L355SS the suction filter assembly was badly damaged when I bought it. I replaced it with a 10 micron suction line filter with 3/4" ports that is rated to flow well beyond my tractor's hydraulic flow output. That being said, I'm tired of slow & weak hydraulics, so I timed how long it takes to lift 600lbs of concrete bags from ground to fully raised. The results very much confirmed my theory of the filter restricting flow. (No, a new filter didn't help.)

Results with 600lbs of concrete in the bucket:
Engine Speed Time to max lift with filter Time to max lift with filter assembly removed
idle - 600rpm no lift very slow, but moving
1500rpm 25 seconds 13.6-14 seconds
1800rpm 30+ seconds 9.0 seconds

Background on the filter setup:
The straight 1" pipe comes from the tractor case, flex hose to 90 bend while reducing to 3/4", filter with 3/4" ports, to hosebarb with flex hose to the pump.

Concerns / Possible Fixes:
1. Is the filter assembly just too close to the pump?
2. Will a 150 mesh spin-on filter make enough of a difference?
3. Or should I find another simple 150 mesh screen solution?
4. Should I move the filter to a return line? If so, where? What line would be under low enough pressure?
5. Throw 1-4 out the windows & go with your much more knowledgeable suggestions.

Thanks for the help. All suggestions are much appreciated.

10 micron is too tight for a suction line filter. Can you get a 25 micron element for that assembly? What hyd fluid are you using?

 

[Farmerford]

Spyderlk is right on; 10 microns is way too tight. You did not give the rate of flow, but I suspect you have a pressure drop of several psi across that filter; since the flow into the filter is not the typical forced return line flow, that means a vacuum at the pump. I don't know if 25 micron would solve the problem. I would get a 150 mesh screen.

 

[SPYDERLK]

Spyderlk is right on; 10 microns is way too tight. You did not give the rate of flow, but I suspect you have a pressure drop of several psi across that filter; since the flow into the filter is not the typical forced return line flow, that means a vacuum at the pump. I don't know if 25 micron would solve the problem. I would get a 150 mesh screen.

Thanks! ... It isnt intuitive on the screen issue, but they are often more restrictive than one would think. It seems you cant convolute the screen enuf to get anywhere near the filter area of a paper filter. -- So a screen has to be pretty coarse before it flows freely.

 

[grayw0lf1]

I think I have to agree that 10 micron is too fine for a suction line. I do have a 25 micron sitting around somewhere. I am using a spin-on type filter setup & using a generic Kubota UDT equivalent hyd fluid.

I just ordered a 149micron steel mesh filter that will fit the spin-on type filter head. I'll have to do testing after I receive the filter.

 

[oldnslo]

Graywolf,
Does the pump sound noisy when operating? I.e. growling or grating type noise. Does this change with RPM?

 

[grayw0lf1]

I've not noticed any noises coming from the pump.

 

[dfkrug]

I would get a 150 mesh screen.

That's the approach I took for this McCormick. I took apart the inlet filter and saw how it was
made. McCormick wanted crazy money to replace it AND some hydraulics experts think
that any inlet filtration is not advised.

So I bought some 150u stainless steel mesh and made up my own filter (2nd photo).

 

[grayw0lf1]

That's the approach I took for this McCormick. I took apart the inlet filter and saw how it was
made. McCormick wanted crazy money to replace it AND some hydraulics experts think
that any inlet filtration is not advised.

So I bought some 150u stainless steel mesh and made up my own filter (2nd photo).

Nice work! Were you able to use the stock housing?

 

[dfkrug]

Nice work! Were you able to use the stock housing?

Thanks. Fits right into the inside of the tranny housing. I epoxied the mesh into the steel
end pieces. A spring holds it under pressure against the end seals. This tractor was an
'05, made by Landini, and parts availability was quite poor.

 

[IceStationZebra]

Suction filters for off-road hydraulic systems are usually 100-150 mesh. They are only meant to be trash screens. ISZ

 

[grayw0lf1]

Thanks everyone for all the info. I should have a 100 mesh screen coming in the next few days. I'll let you know how it turns out.