Hot hydraulic fluid

[SolarAndWood]

This is a splitter my recently passed father in law made 15 years ago. Yesterday, I replaced the 4 cylinder Wisconsin out of a Bobcat with a 5 hp electric motor off of a compressor. It works amazingly well. So, today I split the ceremonial first cord with it. After about 1/2 a cord, maybe 1/2 an hour running, the pump was making some noise and all hydraulic components were hot. I let it sit and 20 minutes later it had cooled and I split another 1/2 cord with the same result. I am wondering if this is just a change the 15 year old filter and fluid thing or more like it needs a bigger tank? The tank is somewhere between 4 and 5 gallons. Or something else my uneducated self wouldn't know to ask?

 

[SolarAndWood]

other side

 

[SolarAndWood]

and for the curious

 

[Gooserider]

If the fluid & filter is that old, I would say that changing it out is a good idea just on general principles... While you have the tank empty, check to see if there is any sort of suction strainer between the pump and tank; if so it may need cleaning / replacing (if it was mine I would just get rid of it, as suction side filtration can cause problems in general.)

Hydraulic systems generate heat when the fluid pressure drops without doing useful work, so you might want to make sure that you have minimized the number of flow restrictions in the system.


Just out of curiosity, what is that behind the splitter - looks like some sort of boom crane that is burried in the wood pile?

Gooserider

 

[f3cbboy]

the only change is the prime mover? no other change to anything with the hydraulics? does the electric motor have a much higher rpm?

 

[crazy_dan]

I would change the fluid and filter for just because it has been that long.
If it were mine and it would only do a 1/2 a cord at a time then have to take a 15-20 min break I would just run with it, and enjoy the frequent breaks.

 

[Billster]

I agree with changing the fluid & filter.

 

[SolarAndWood]

If the fluid & filter is that old, I would say that changing it out is a good idea just on general principles... While you have the tank empty, check to see if there is any sort of suction strainer between the pump and tank; if so it may need cleaning / replacing (if it was mine I would just get rid of it, as suction side filtration can cause problems in general.)

Hydraulic systems generate heat when the fluid pressure drops without doing useful work, so you might want to make sure that you have minimized the number of flow restrictions in the system.


Just out of curiosity, what is that behind the splitter - looks like some sort of boom crane that is burried in the wood pile?

Gooserider

Thanks, just wanted to make sure I wasn't missing some basic design thing. That is a 3 pt backhoe behind it. It won't get used again until I am done with the excavator. And then I will likely just get rid of it after being spoiled by the excavator.

 

[SolarAndWood]

the only change is the prime mover? no other change to anything with the hydraulics? does the electric motor have a much higher rpm?

The only change was replacing the gas engine/fuel tank/battery box with the electric and topping off the hydraulic tank. The electric spins at 3400 rpm. My guess is that the Wisconsin was never run that high.

 

[SolarAndWood]

I agree with changing the fluid & filter.

I used to do it before I did anything else with a new to me piece of equipment...with fluid at $60/pail, I tend to make sure everything is basically OK before I even put cheap fluid in it.

 

[SolarAndWood]

If it were mine and it would only do a 1/2 a cord at a time then have to take a 15-20 min break I would just run with it, and enjoy the frequent breaks.

An IPA every 1/2 hour might work while sitting with a vertical splitter, but it would catch up with you on a horizontal.

 

[JustWood]

Agree on chamging oil and filter and check for blockage.
Heat rises . Maybe repositioning filter off to side of tank wood help keep oil cooler.
I don't think the RPM of electric motor wood make any dif .

 

[SolarAndWood]

Maybe repositioning filter off to side of tank wood help keep oil cooler.

Do you mean rotate it down as opposed to horizontal? Or, move it further from the tank?

 

[JustWood]

Maybe repositioning filter off to side of tank wood help keep oil cooler.

Do you mean rotate it down as opposed to horizontal? Or, move it further from the tank?

Down wood be ideal butnot necessary. Off to the side of tank wood be best. Not sayin its going to cure the problem but wood help keep oil cooler. Use a sawzall to cut a chunk of old tire to wedge between the tank and pipe fitting to keep the vibrations at a minimum.

 

[Billster]

I agree with changing the fluid & filter.

I used to do it before I did anything else with a new to me piece of equipment...with fluid at $60/pail, I tend to make sure everything is basically OK before I even put cheap fluid in it.

I use John Deere hydraulic fluid and its not cheap... I dread when the time comes around to change the fluid in my tractors.... A couple years ago it was $100 for 6-gallon.

 

[SolarAndWood]

Maybe repositioning filter off to side of tank wood help keep oil cooler.

Do you mean rotate it down as opposed to horizontal? Or, move it further from the tank?

Cool thanks. There is a little stub of pipe between the elbow on the top of the tank and the filter housing. I'll replace it with a longer piece so that I can rotate the filter down next to the tank.

 

[SolarAndWood]

I use John Deere hydraulic fluid and its not cheap... I dread when the time comes around to change the fluid in my tractors.... A couple years ago it was $100 for 6-gallon.

I feel your pain. I revived a 12 ton excavator over the winter and need to change the fluid/filters. Even worse though is the upcoming task of emptying the diesel tank and cleaning it to put an end to the fuel issues.

 

[LLigetfa]

I would inspect that intake hose really close. Sometimes it can look good on the outside but the inside could be delaminating and constricted. Maybe replace most of it with larger bore hard line and just have a short rubber section to decouple for vibrations. A hard line might also act as an oil cooler.

The return line looks to be going into the top of the tank. It would be better if it had a dip tube or went in the side, below the oil level so that the oil cannot get aerated. How does the oil look after it gets hot? Is it clear or milky?

 

[f3cbboy]

that was my thougth too that it was was getting aerated by teh pump (cavatating) due to rpm, but there was never problems before right? maybe the setting of the relief off the block valve has moved. pressure could be gettin too high due to that valve and causing excessive heat.

 

[SolarAndWood]

Does the dip tube turn into the same hole that the elbow is in? Then, screw the elbow into it? Something I get from Grainger?

Not sure if the fluid is milky when hot, but it is pretty cruddy period. I wanted to make sure there weren't any obvious problems with the basic design, implementation and condition before I went too far.

The pump runs very smooth with the ram in both directions both free and under load until it gets hot. I assume I would know if it is cavatating?

 

[SolarAndWood]

I haven't heard anyone say the 4 or 5 gallon tank isn't enough? As a reference, I saw that the Timberwolf TW5 has a 15 gallon tank. It has a similar cylinder and cycle time. I also assume not having a 2 stage pump will generate more heat?

 

[SolarAndWood]

but there was never problems before right?

I don't think it ever saw much use as this was one of my father in law's last projects as his health was deteriorating. The cord and a half it split yesterday may very well be more than it has done previously.

 

[Gooserider]

That it is running smoothly is a good thing, and suggests that the design is reasonably sound. However the fact that you say the fluid looks cruddy is a strong indicator that you need to do a fluid, and especially a filter change sooner rather than later... It might even be reasonable to just change the filter a couple of times. Cavitation could definitely be a part of your problem, either from a clogged suction line strainer, or a partially collapsed suction line as mentioned.

The fluid capacity issue is a good question - most of the "how to design hydraulic systems" stuff I've seen suggest that the tank size should be about equal to, or a bit more than, the pump GPM rating, which would suggest that most splitters should have a 10-20 gallon tank. However in practice, nearly all the splitters I've ever encountered looked to be more on the order of about 5 gallons, including the fluid filling the pump, hoses, cylinder, etc... They seem to get away with it - my splitter gets to the point where it's uncomfortable to touch the plumbing, but not where it would cause burns, so I don't see why it would be a problem in your machine.

Gooserider

 

[SolarAndWood]

Thanks all. So, it would seem I need to:

1. drain the fluid
2. look for/remove suction line strainer
3. inspect suction line/replace if necessary
4. install dip tube on return line into tank
5. replace pipe between tank and filter housing so that it can be turned down
6. replace the filter/replace twice more after some use
7. new fluid
8. split another cord and see where I am

I think I found the pump. Is it possible that Northern has the same part number on it after 15 years? If so, it is cool that it actually is a 2 stage...might save some electricity.

http://www2.northerntool.com/hydraulics/pumps/item-1056.htm

So, the only real reference for too hot is when the pump starts to complain? Until then, it isn't hurting anything? I also assume that my plan of a foot switch to turn the motor on and off is a non-starter because it needs to be running to cool the fluid?

 

[Gooserider]

Thanks all. So, it would seem I need to:

1. drain the fluid
2. look for/remove suction line strainer
3. inspect suction line/replace if necessary
4. install dip tube on return line into tank
5. replace pipe between tank and filter housing so that it can be turned down
6. replace the filter/replace twice more after some use
7. new fluid
8. split another cord and see where I am

I think I found the pump. Is it possible that Northern has the same part number on it after 15 years? If so, it is cool that it actually is a 2 stage...might save some electricity.

http://www2.northerntool.com/hydraulics/pumps/item-1056.htm

So, the only real reference for too hot is when the pump starts to complain? Until then, it isn't hurting anything? I also assume that my plan of a foot switch to turn the motor on and off is a non-starter because it needs to be running to cool the fluid?

IMHO all of these are good things to do, but I would put 1, 2, 3, 6, and 7 as the highest priorities. The dip tube may be difficult, and while getting the filter away from the tank will help the cooling a little bit, I don't think it's that big of a factor.

Northern may well be using the same part number, seeing as how they are getting the pump from Haldex, who probably hasn't changed the number either... The big advantage of a two-stage pump isn't so much saving electricity as it is allowing the use of a higher volume pump under low load conditions.

For fluid temperature, I would say that if the pump is complaining, you are either WAY to hot, or you have a different problem that is being agravated by the fluid warming up... I believe I've seen some stuff that suggests hydraulic fluid starts to be damaged by temps in the 180*F range. I haven't put a thermometer on my splitter, but the general rule I've seen is that metal parts get uncomfortable to touch around 110* or so, and start causing burns around 130-140*F, so I figure if it isn't hot enough to burn, it isn't overheating - but I could be wrong.

As far as the foot switch idea, I'd be hesitant, not so much because of the fluid cooling question (The fluid actually will cool BETTER when it's not circulating unless you are running it through a cooler of some sort. as simply pumping it will cause it to get hot) but because electric motors generally pull a lot more current when starting than when running. Thus you won't necessarily save any electricity, and you could overheat the motor - larger electric motors, especially capacitor start units really don't like being short cycled... I would say that you probably want to have the motor running all the time while you are actually splitting, just possibly turning it off when you go to restack more rounds or some such.

Gooserider