Thread: Hydraulic oil foaming in a pressbrake

I have a Scale and Engineering hydraulic pressbrake.
When I use it the oil foams/aerates very quickly.
I don’t think this is a new problem as, when I bought it, it had a fair bit of oil around the hydraulic bay, but I thought this was just an accumulation from years of use.
I cleaned it up and added oil to the full level.
Next time I used it I found that it was overflowing through the breather after only about 10 minutes use.
The oil is an off white colour and clearly has small bubbles of air in it. This settles out and reverts to normal looking oil over night.
The only things I can think of are contaminated oil, or a leak in the hydraulic circuit spraying into the oil in the tank.
Has any one got any suggestions.

Originally Posted by pcx

I have a Scale and Engineering hydraulic pressbrake.
When I use it the oil foams/aerates very quickly.
I don’t think this is a new problem as, when I bought it, ithad a fair bit of oil around the hydraulic bay, but I thought this was just anaccumulation from years of use.
I cleaned it up and added oil to the full level.
Next time I used it I found that it was overflowing throughthe breather after only about 10 minutes use.
The oil is an off white colour and clearly has small bubblesof air in it. This settles out and reverts to normal looking oil over night.
The only things I can think of are contaminated oil, or aleak in the hydraulic circuit spraying into the oil in the tank.
Has any one got any suggestions.

id try some new oil

Thanks for the suggestion.
I don't have a problem with that but it holds 200 litres so I would like to be fairly sure that is the problem.

Originally Posted by pcx

Thanks for the suggestion.
I don't have a problem with that but it holds 200 litres so I would like to be fairly sure that is the problem.

yea i didnt think of that.I've notice in the description of some of the better hydraulic oils that they have anti foaming properties.

It may have a leak on the suction or inlet side of the hydraulic pump. The inlet side of the pump will produce a pressure slightly less than atmospheric and any leaks will tend to draw air into the system and aerate the oil.

Edit: I can't see any other reason or place where air would be introduced into the oil.

Just a thought

Simon

Is the pump in the tank?

A long shot that likely isnt the problem(but hey you never know), is the return below the oil level?.....If not this can aerate the oil.......but I've only ever seem it do that.... not foam. Then if the system pressure gets high enough it diesels in the pump and the oil goes blackish.

Stuart

Thanks guys,
Both good suggestions.
The pump is in the tank. Suction directly into the pump at the pump inlet and this is at the bottom of the tank.
The return line is a pipe welded into the tank so unless it has broken off it should be original.
I think I need to pull the tank apart and remove the pump for examination. Pretty big job I am not looking forward to.
Any other suggestions welcome.

same thing happens to old english tractors when used in australia.
they have a large gearbox and diff , large in volume of air in the cases (just the design of the castings ) in europe this is not a problem but here it is what happens is there is a lot of air space above the oil and because of our tropical air this forms condensation in the gearbox ( same as fuel tanks that are left with not much fuel in them often ) then at night when the air cools the condensation drips into the oil water and oil equals white oil equals foamy oil .so i am wondering if the sun shines on your tank at all through the course of the day cos i rekon this would make it even worse . i have an old nuffield tractor and it is a problem for me with the gear oil , i drained it all out flushed inside and replaced the oil with new stuff ( 60ltrs ) and within a few months back to square one with white crappy oil again , so it is what it is i just put up with it .
i did think of trying to simmer the oil and boil the water off but never tried it .
if your tank has a lot of air space maybe you could fix the problem by reducing the unused airspace in the tank , just my thoughts on it and i could be wrong .
also you are in brissy and the humidity would not be helping at all .

Originally Posted by texx

same thing happens to old english tractors when used in australia.
they have a large gearbox and diff , large in volume of air in the cases (just the design of the castings ) in europe this is not a problem but here it is what happens is there is a lot of air space above the oil and because of our tropical air this forms condensation in the gearbox ( same as fuel tanks that are left with not much fuel in them often ) then at night when the air cools the condensation drips into the oil water and oil equals white oil equals foamy oil .so i am wondering if the sun shines on your tank at all through the course of the day cos i rekon this would make it even worse . i have an old nuffield tractor and it is a problem for me with the gear oil , i drained it all out flushed inside and replaced the oil with new stuff ( 60ltrs ) and within a few months back to square one with white crappy oil again , so it is what it is i just put up with it .
i did think of trying to simmer the oil and boil the water off but never tried it .
if your tank has a lot of air space maybe you could fix the problem by reducing the unused airspace in the tank , just my thoughts on it and i could be wrong .
also you are in brissy and the humidity would not be helping at all .

Agree with Texx about it being contaminated with water. If it runs hot the water starts to boil and foam up the oil pushing it out the breather. I don't think it's possible to boil off the water and restore the original qualities of the oil. If your pump develops high pressure I'd be wary of using emulsified oil for to long.

I have heard a long pigs tail breather mounted horizontally can reduce condensation. That'd be the cheapest option otherwise look for the commercial moisture filters. They'll be cheap in comparison to the cost of a drum of oil.

Texx, we've got an old Nuffield too. Gearbox oil milky white within a week of changing! How do you go when it comes to buying oil filters for this rig?

Garry

Originally Posted by Garry 3

Agree with Texx about it being contaminated with water. If it runs hot the water starts to boil and foam up the oil pushing it out the breather. I don't think it's possible to boil off the water and restore the original qualities of the oil. If your pump develops high pressure I'd be wary of using emulsified oil for to long.

I have heard a long pigs tail breather mounted horizontally can reduce condensation. That'd be the cheapest option otherwise look for the commercial moisture filters. They'll be cheap in comparison to the cost of a drum of oil.

Texx, we've got an old Nuffield too. Gearbox oil milky white within a week of changing! How do you go when it comes to buying oil filters for this rig?

Garry

pretty sure last time i bought filters for it i bought them from express engineering in toowoomba . they should not be to hard to get though they are the same as some of the leylands tractors when leyland took over the nuffys all they did was paint them blue and call them leylands .i have manuals for a few of them if you ever need to know anything from them . my hydraulics are stuffed at the moment but i am not that worried about that cos i am not using it much and i have a dozer ( fiat50CI )that needs work doing to it more than the nuffy does.
the guy i worked for for quite a lot of years had 3 nuffys he just could not part with even though we had a fleet of about 15 tractors some worth over $250,000 still hung onto the old girls .
mine is a little 3/42 by the way . the others the mate has are 2x 10/45s and a 10/65 .

You could use a desiccant air breather to combat water contamination in the system.
All though if the problem is because of water continuation in the oil it maybe to late for this oil.
If your concerned about water in the oil preform a crackle test. Gently heat a small amount of
oil in a spoon. if bubbles appear in the oil sample you will know it contains water.
If you brought a second hand machine id change the oil i know it expensive but
you dont know condition of the oil.
aaron

I drained a sample of oil from the tank today.
No sign of water in the sample however the sample did have some contamination (dirty flakes) that I think has settled to the bottom of the tank.
I am thinking I need to drain and clean the tank then use new oil.
I will not get a chance to do this for a couple of weeks.
Will report back once the job is done.
Thanks for all the suggestions. If any one else has an ideas I would be happy to hear them.

When you drain the out I'd take a look inside the tank, the should/could be a wire screen type filter that is partially blocked which could make the pump struggle for oil, causing it to foam on the return. Does the bender work OK or does it struggle/sluggish when bending? There could be a small leak on the outlet side of the pump causing the oil to foam also. Just a couple of thoughts, may well be off the mark though!!!!
Kryn

Originally Posted by KBs PensNmore

When you drain the out I'd take a look inside the tank, the should/could be a wire screen type filter that is partially blocked which could make the pump struggle for oil, causing it to foam on the return. Does the bender work OK or does it struggle/sluggish when bending? There could be a small leak on the outlet side of the pump causing the oil to foam also. Just a couple of thoughts, may well be off the mark though!!!!
Kryn

good suggestion

Finally got back to the press brake.
After more research I think the oil foaming is caused by contaminated oil.
I have removed the pumps from the tank. They are fully submerged so suction leaks are impossible. The inlet screens are partly clogged but I don't think enough to cause cavitation of the pumps.
I am in the process of cleaning the tank and refitting the pumps. 200 liters of oil to refill the tank.

Since I have decided to do this job with the press I decided to also tackle the leaking rams at the same time. Big job.
The shafts of the cylinders are scored so I have decided to have them ground rechromed and ground.
Thee shafts are also the guides for the blade on the press so they run in brass bushes built into each cylinder cap. These bushes have some wear in them and are slightly oval by about .007 in.
The guys at the chroming shop have suggested adding about.003 to the shaft diameter which will take up some of the wear.
However I am thinking that I would like to hone/grind/machine the brass bushes to remove the ovality.
Although I have a lathe big enough to bore the bushes I am not game to try as I don’t want to risk destroying a bush.
I was wondering if anyone with cylinder honing experience thinks I might be able to take them to an engine reconditioner and have him hone them round. Or would the hone just follow the existing oval shape.
The required size finished would be 4.507 in but this is not critical as I can have the shafts ground to suit. The manufacturer specifies.004 - .006 clearance.
The bushes are about 1 in wide and the cylinder bore is 10.750 in.
Any other suggestions would be welcome
I have tried to attach a couple of pictures.
Also there does not appear to be any other problems with the tank or hoses return line etc.