Pre-filtering fluid

[5030tinkerer]

Anyone have any tips on how to pre-filter hydraulic fluid? I've got an old Koehring excavator that requires fresh fluid going into the tank to be filtered through a 10 micron filter. They particularly go out of their way to indicate that brand new fluid is not clean enough. Any ideas on how to go about pre-filtering like this? We're talking 60 gallons of fluid here...

 

[Scooby074]

old Koehring excavator

How old? I wouldnt sweat the pre filtration.

It certainly can be done though. Usually there is a filter cart, with a couple larger hyd filters and a pump. The pump sucks from a bucket of new oil and pushes it through the filters into the tank. You can buy or rig something up, but the carts I know of coast several hundred each.

Its one of those things that sounds good to engineers and manual writers, but in practice is more hassle than its worth. New, high quality oil from a clean bucket, with a clean funnel is fine. I used to dump $250/bucket synth hydraulic oil directly into $750,000 excavators without pre filtering. Cleanliness, particularly around the tank opening, buckets and funnels is more important that pre filtering IMHO. One chunk of dirt falling in the tank when you open the filler will undo $1000 worth of pre-filter cart every time.

 

[Bigfoot62]

Scooby's right. Just buy good fluid.

I get Mobilfluid 424 in 5 gallon buckets from the local Exxon/Mobil jobber.

 

[wdchyd]

I would only be worried about pre-filtration if it comes out of a 55 gal drum......5 gal pails usually are prefiltered and cleaner

 

[firemanmike69]

I absolutely wouldn't even bother with pre-filtering the new oil. Like others said make sure the funnels and cap are free of loose dirt and change the oil

 

[Gary Fowler]

Fluid from 50-70 years ago might not have been very clean, but todays fluids are cleaner than 10 micron filters right out of the can.
As others have said, make sure your equipment tank filler hole, funnels and other filling equipment is clean and don't worry about the oil itself.

 

[5030tinkerer]

The machine is circa 1988 - not THAT old, but old enough from a parts availability perspective, it seems.

A bit more info on the filtering - I just had had a hose burst on this machine a couple weeks ago and lost 50 gallons of fluid. It's a 100 gallon system. I kept the new containers knowing that this service was coming up and drained the main reservoir into the 5 gallon pails yesterday. This is *actually* the main reason for wanting to filter now. In fact, I'd like to run it through a 2 micron filter if at all possible. I may pick up a filter head and spin on 2 micron filter along with a few hoses and mock something up.

 

[Scooby074]

I assume the buckets were clean. The drain hole area was also clean. No Floor Dry in the area (floor dry = bad mojo)

Personally on a excavator that old, assuming you made sure everything was clean prior to dropping the fluid, Id just reuse it without filtering.

You can certainly rig something up to put your mind at ease. Here's a "cheap" cart for some "ideas" 1/2 HP Oil Filter/Transfer Cart | Princess Auto

 

[5030tinkerer]

The buckets and drain hole were clean, yes. Interesting cart! I may have to fab something up. If this were the only machine I had, I wouldn't bother. I have a small fleet, though.

 

[MHarryE]

At Caterpillar - our large cold planers (for milling the asphalt off roadways) had a pre-filter package. Pour the oil into a fill reservoir, then operate a hand pump to filter the oil fine enough to meet all the piston pump and motor requirements. Added expense but worth it on a machine with so many hydrostatic drives. We test cleanliness of every hydraulic system before shipping - if it fails it needs to be attached to a kidney loop machine for extra cleaning.

 

[oldnslo]

Companies like Parker, Hydac/Schroeder, etc. all make filter carts like the Scooby posted the picture of. And new fresh oil is not necessarily all that clean. A couple of years ago I worked with an oil supplier on a filter system for filtering from batch mixer into 55 gallon drums. Some oil manufacturers or distributors require certain ISO cleanliness on their oils and others don't.

 

[CJONE]

Any machine that has hydrostats or high pressure piston pumps needs oil to be prefiltered if they don't have filtration on the suction side. Even if they do it is good practice. A easy way to do this is add a filter head on the discharge side of your pump. It can be done for about $40 to $50 dollars. I don't worry about gear systems as much but if my customers do not prefilter oil, their warranty is void. I will gladly let them use my pump systems to avoid this. CJ

 

[CJONE]

At Caterpillar - our large cold planers (for milling the asphalt off roadways) had a pre-filter package. Pour the oil into a fill reservoir, then operate a hand pump to filter the oil fine enough to meet all the piston pump and motor requirements. Added expense but worth it on a machine with so many hydrostatic drives. We test cleanliness of every hydraulic system before shipping - if it fails it needs to be attached to a kidney loop machine for extra cleaning.

+1 Schramm and a few other manufactures have prefilter systems or some way of cleaning any oil added just for this reason that you stated. A lot of the harvesters we have around here are now running 3 micron off line filtration with great results. The old thinking with gear pumps a 2000psi and no filters is long gone on a lot of modern equipment, now the ones who know have to help change this way of thinking with the new equipment. CJ

 

[5030tinkerer]

Any machine that has hydrostats or high pressure piston pumps needs oil to be prefiltered if they don't have filtration on the suction side. Even if they do it is good practice. A easy way to do this is add a filter head on the discharge side of your pump. It can be done for about $40 to $50 dollars. I don't worry about gear systems as much but if my customers do not prefilter oil, their warranty is void. I will gladly let them use my pump systems to avoid this. CJ

Awesome idea! $40-$50, heh? Can you tell me what filter assemblies you are referring to? I guess I don't know what I am looking for as the ones I find in that range are only rated for the suction side.

Filters on my machine are getting increasingly hard to find. If I can add one or more currently available filter head(s), I prolong the life of the existing really hard to find and expensive filters, especially if I put a gauge on them to determine when they are clogging up.

How can I determine the GPM capabilities of the current pump so that I can get a properly-sized solution?

Also, there appear to be multiple outputs on the pump - or maybe even sub-pumps (I don't actually know what I am looking at, but see multiple hoses leaving the pump area with varying diameters - three 3/8" lines, one 3/4" line, and one 1" that I recall - going either to different filter assemblies or, in the case of the 1" line, out to the valves directly).

I have what sure looks like a canister pilot filter, a canister swing filter, a spin on filter that attaches to the outside of the hydraulic reservoir, and an in-reservoir filter that I have found thus far. While I have filtration on the suction side via the in-tank filter, it would be incredible to at least filter the line leading to the valves with a 10 micron filter. If the filter head had a separated port, I could then add in a much finer maybe 2-3 micron filter as a bypass type as well.

 

[CJONE]

Awesome idea! $40-$50, heh? Can you tell me what filter assemblies you are referring to? I guess I don't know what I am looking for as the ones I find in that range are only rated for the suction side.

Filters on my machine are getting increasingly hard to find. If I can add one or more currently available filter head(s), I prolong the life of the existing really hard to find and expensive filters, especially if I put a gauge on them to determine when they are clogging up.

How can I determine the GPM capabilities of the current pump so that I can get a properly-sized solution?

Also, there appear to be multiple outputs on the pump - or maybe even sub-pumps (I don't actually know what I am looking at, but see multiple hoses leaving the pump area with varying diameters - three 3/8" lines, one 3/4" line, and one 1" that I recall - going either to different filter assemblies or, in the case of the 1" line, out to the valves directly).

I have what sure looks like a canister pilot filter, a canister swing filter, a spin on filter that attaches to the outside of the hydraulic reservoir, and an in-reservoir filter that I have found thus far. While I have filtration on the suction side via the in-tank filter, it would be incredible to at least filter the line leading to the valves with a 10 micron filter. If the filter head had a separated port, I could then add in a much finer maybe 2-3 micron filter as a bypass type as well.

HOLD ON NOW. I was referring to your transfer pump, we were talking about prefiltering oil, not the pumps/hydrostats on the machine. That as you know has to be sized to the pumps. With the hydrostats having suction filters and the open loop pumps having return line filters. I have been building return filters into the tops of my reservoirs also lately. IMHO over filtration is better than under. I have also been putting pressure filters inline with the hydrostatic loops, this has been quite effective in stopping the loss of the hydrostat when the motor fails. CJ

 

[jaydee325]

I've got some experience with the old Koehring excavators from the late 70's. They had cutting edge hydraulic technology for the time. They were very sensitive to hydraulic oil cleanliness. I would follow the recommendations of the manual. At this point, failures due to contaminated oil could result in expensive issues since these excavators are no longer in production.

Also, I've seen some recommend modifications that add additional filtration to the unit. This should only be considered by those very experienced in hydraulics as a mistake could be very costly.

 

[5030tinkerer]

I've got some experience with the old Koehring excavators from the late 70's. They had cutting edge hydraulic technology for the time. They were very sensitive to hydraulic oil cleanliness. I would follow the recommendations of the manual. At this point, failures due to contaminated oil could result in expensive issues since these excavators are no longer in production.

Also, I've seen some recommend modifications that add additional filtration to the unit. This should only be considered by those very experienced in hydraulics as a mistake could be very costly.

I hear you loud and clear. Trouble is, finding filters for this machine is getting impossible. I figure that my adding auxiliary filtration, I lengthen the life of my impossible to find filters. Of course, I need to ensure that I use the proper filter assembly and filter - I can't be starving the valves. Current thinking is a duplex filter like this 50gpm-rated one with 8" filters: http://www.donaldson.com/en/ih/support/datalibrary/063509.pdf

 

[CJONE]

I hear you loud and clear. Trouble is, finding filters for this machine is getting impossible. I figure that my adding auxiliary filtration, I lengthen the life of my impossible to find filters. Of course, I need to ensure that I use the proper filter assembly and filter - I can't be starving the valves. Current thinking is a duplex filter like this 50gpm-rated one with 8" filters: http://www.donaldson.com/en/ih/support/datalibrary/063509.pdf

Get you filter ###'s and call this place 800 285 5364. I am almost 100% sure they can help you. You may have to send them a sample but they can do just about anything when it comes to filters. You would be talking some major $$$ to refit equipment on filtration. I do it quite a bit and it usually is more cost effective to find or build different elements. CJ

 

[J_J]

Seems to me that if you can find the return line to tank you could do almost anything to filter, from adding a double filter to adding a by pass filter using a filter element of 1 micron.

The particles greater than 10 micron may cause problems, but people forget that the smaller particles less than 10 microms are what causes the wear, rubbing, polishing on hyd parts causing loss of pressure capability.

Inline filter for that kind of flow would be very expensive.

So some good return line filters from each hyd circuit returning to tank would be ideal.

 

[IceStationZebra]

I can tell you from personal experience that "we engineers" are not making this stuff up. I have personnaly added 5-6 barrels of a major brand high-end hydraulic oil to a brand new system. As I was getting to the bottom of the barrels I was looking in with a flashlight to see how much was left and was startled by how much crud was floating in there! If I can see it from 5ft away with a poor flashlight there is no way in **** that it is even filtered to 100 micron. It made a total believer out of me. (I think buckets are cleaner, but I have no personnal experience to say for sure)

I agree with JJ about fine particles being a major contributor to wear. I would caution about going much below 7-10 micron filtration for fear of stripping out some of the additives (especially with gear lube). You also would need much larger filters to keep the backpressure reasonable and prevent bypassing when cold.

As far as the filter carts go I have bought one and I've made one, both work the same. My ideal filter layout would be a mesh screen to catch the big chunks, then a ~25 micron feeding a parallel set of 7-10 micron filters. One thing to watch out for is keeping the outlet side clean. It doesn't make much sense to scrub the oil to then use a dirty wand/connection to put it into your system.

ISZ