Splitter Hydraulics

[niemeyjt]

I have a Bell Pickpine log splitter - purchased used. It uses a hydraulic pump connected to the tractor's PTO and has a hydraulic oil tank of its own. The splitter works in what I imagine is normal way with a two way lever on a control valve - one to extend hydraulic ram, one to retract. Obviously, there are four pipes connected to the control valve - one to each end of the ram, one from pump and one to the tank.

OK - the problem was that on reaching full extent of stroke, the hydraulic pump laboured for a few seconds progressively slowing and stalling the tractor.

I reasoned (rightly or wrongly) it was the relief valve in the control block not activating to release the pressure when the ram was extended, the pump was pumping, and the oil had nowhere to go. So, I removed the relief valve assuming it was faulty with a view to getting a replacement. No replacement was available, so I refitted it, broke the seal on the valve and backed it off two turns so it released at a lower pressure.

It worked - on reaching end of stroke there was a wierd sort of squealing noise, but tractor carried on at same revs! However, the splitter did not have quite the power on knotty wood it had before - the splitter would stop part way through making the same sort of squealing noise. I have therefore started to wind the valve back in - so far 1 1/4 of the two turns, and the situation has improved.

This is where I would welcome comments from the experts on here!

My thinking:

1) the factory set relief valve was not releasing below the max pressure being delivered by the pump (supposedly 3200 psi / 220 bar)

2) this is either due to pump not delivering max pressure or some problem with the valve

3) the oil feed to the pump may be partly obstructed so I need to clean out filter and see if it improves (although as valve now adjusted, it will be hard to tell)

4) possibly there was some crud in valve that prevented it working that got dislodged when I removed it

5) I need to progressively wind the screw back in the full two turns in quarter turn increments and test each time.

I am not able to fit a gauge easily - there are not obvious places and it will foul the safety cover - although I guess I could.

Have I missed anything - does anyone have better suggestions?

Regards,

Julian

 

[J_J]

Why can you not install a tee with gage in the system. You need it to set relief.
If the pump is squealing, then the pump is working close to the relief setting, and the relief is there to protect the pump. If you lower the relief pressure, then you will lose power. For every 100 psi, you will lose about 1,257 lbs of push force. For every 500 psi change, you will lose or increase about 6,000 lbs.

 

[niemeyjt]

Thanks for advice - it is not easy as many of pipes are shaped metal - however the output from the pump is flexible so I may be able to T off there immediately after the filter on the output of the pump.

I am about to clean filters to get pump running at max efficiency - then will set valve until pump squeals then back off a quarter turn until I get a gauge in place.

I need the manufacturer to confirm the 3,200psi / 220 bar figure. It is what they printed on the product label.

According to specs, it delivers 12T = 12,000Kg = 26,400 lbs.

Using JJ's figure of 100 psi,for 1,257 lbs of push force, this works out at 2,100psi.

Thanks,

Julian

 

[J_J]

Well, not exactly, I used a pressure of 3000 psi, and computed the push force, and then computed the push force using 2900 psi. The difference is the lose or gain.

You should set your relief at 3100 or 3150 psi for max force.

 

[glastron23]

good day... please install a pressure gauge and set the pressure regulator to the required factory setting, you MUST/MUST/MUST find out what it is, the machine you have is european?? contact Bell with your model and they will get you the proper hydraulic settings
3200 psi is REALLY high for most small equipment, most of the hydraulic equipment industry is running about 2250 psi, the pump MAY be rated for 3200 but that would be the MAX it can produce, the rest of the parts may not be rated for this and could/will fail if it continues to run at a higher pressure. Setting a systems pressure be SOUND is just asking for BIG problems.... stand back because you have a really big bomb next to you.... Jim

 

[glastron23]

JJ.. you haven't gone far enough with the calculations ... What size of cylinder does the splitter have... 3 inch, 3.5, 4, 4.5, 5 or bigger?????
3 inch at 2250psi=15904# 3 inch at 3100 psi= 21913#
3.5 inch at 2250 psi=21648# 3.5 inch at 3100 psi= 29825#
4 inch at 2250 psi=28274# 4 inch at 3100 psi= 38956#

PLEASE find out from the MANUFACTURE what pressure it is DESIGNED to run at....GUESSING what pressure to set it at is asking for trouble.... Jim

Hydraulic Cylinder Calculator here is a link for easy cylinder calculations....

 

[J_J]

The PTO pumps are usually about 2200 psi. and although the manufacture may state that the cylinder has been tested to 3200 psi, the 2200 psi pump will not achieve that rating. However. they sometimes use the max pressure to state the capability of the system. and they are fudging the figures. So if you take a 4 in cyl with a 2 in shaft, and the pump can produce a pressure of 2200 psi, then that cyl can push with a force of 27,646 lbs. That is equal to 13.82 ton. I really don't think he can hurt that cyl at PTO pump pressure. In that case, the pressure relief should be set at around 2100 psi.

Some of the two stage pumps used on U. S. A. log splitters usually work at 2500 psi, in the high pressure mode.

 

[J_J]

I assumed a 4 in cyl and 2 in shaft, using various pressures.

 

[niemeyjt]

Thanks Jim and JJ.

I have now cleaned the filter - there were small metal shards - what I would think is manufacturing swarf - so I guess this was its first clean. Given the difficulty separating the pieces to get at the filter I understand why! Having said that, there is no apparent increase in output after cleaning.

The relief valve was factory set and sealed. I broke seal to reduce the pressue it relieved at. At the factory setting, I am guessing, it was too high that the pump never reached that pressure to trigger the pressure relief and the pump ended up stalling the tractor engine. Now, I have unwound it sufficiently that I guess pressure is being relieved by the valve as the tractor engine labours, but does not stall.

Having looked at plumbing and safety covers, I recon I can put a T piece in immediately after the filter and before flexible pipe on output side of the pump. I imagine the critical setting will be when the ram has reached its full extent and the valve should be relieving.

I will try and contact Bell - Easter holidays may mean it wont be until Tuesday. I must admit I was expecting something around 2200psi - similar to tractor's own hydraulics - as one variant of splitter uses tractor's hydraulics as opposed to the separate pump and it uses the same RAM and nominally delivers same splitting force.

I may try and persuade the supplying dealer to get me another relief valve, as well!

J

 

[glastron23]

I assumed a 4 in cyl and 2 in shaft, using various pressures.

you said the proper word here "ASSUMED" NEVER assume anything in hydraulics... what if they built the machine in the cheap and used single wire hose???? what if the they used a valve bank rated at 2500 psi??? what if they built the ram/beam to handle 13 ton???? NEVER ASSUME ANYTHING, get the FACTS then proceed.
just because SOME build them to 2500psi doesn't mean that ALL build to this