New wood splitter hydraulic problem

[mx842]

I built a new splitter last fall that works pretty good but I have a small problem. I put a 16 gpm pump on this one and one of those newer two spool 5200 series Prince valves. One of the spools operates the log lift table and the other works the splitting cylinder. The problem I'm having is that when I go to split a log the cylinder moves out like it should but when it hit's the piece of wood that is tough enough to make it shift to the low speed it hesitates for sometimes 10 seconds or more before it builds up pressure enough to push on through. Once it shifts it works like it should but it's really annoying to have to sit there a wait for the cylinder to start to move again.

The problem is I had to get the pump from one place and the valve from another because neither place had both in stock at that time. I called and talked to both places and got the ol blame the other guy story. The place I got the pump from is saying the valve is bad and the people that I got the valve from says the pump is bad. both say send the part back to prince or MTE and they will check it out but I'll have to ship it to and from them on my dime. On top of that they say it could take 3 to 4 months before they would probably look at it.

I decided to just use it like it is because it does work, just slow as heck.

 

[mrmikey]

IMHO I'd say it was the pump, the valve should have no bearing on when the pump kicks down to low flow/high pressure. Only way I can think it would be the valve is if the pressure relief is opening before it should or it's set too low.
Put a pressure gauge in the system right off the pump and see what you get..............MIke

 

[WranglerX]

From all my reading and experience while rebuilding a old abandon DUERR 20 ton splitter I would say its a pump issue... There is a slight pause when the ram meets to much resistance then motor grunts and changes pitch as valving changes in pump and ram moves again, certainly not 10 seconds but there is a small time lag.... And 3-4 months to evaluate a warranty issue is unreal.... Local hydraulic shop can do it in a couple of days.... Sure its cost out of pocket but then problem solved...

https://mentoredengineer.com/how-a-two-stage-hydraulic-pump-works/

 

[mx842]

Thanks......I have a gauge in the system and from what I see as far as the gauge goes everything looks ok. Rod out the reading is 500/600 lbs when it finally kicks in the low speed it reads what ever it takes to split the wood up to 3000 lbs if needed. When I first got everything together and tested it the pressure was set at 4000+ so I adjusted it back down to 3000 lbs. So I know the pump can build up pressure and hold it once it goes into low. Once it finally shifts the pressure builds up right now with no hesitation. Also it doesn't appear that the valve pressure relief is set too low because the pressure sits right at 600 psi and stays there until it finally decides to move past the resistance then it will climb to the pressure needed.

 

[mx842]

Yeah my old splitter I built 35 years ago worked great still I just wanted something faster and a lift table. That one had the 3000 series valve an a 8 gpm pump and it would switch with hardly any hesitation at all just a smooth transition like an automatic transmission in your truck. Even with this problem it is a lot faster ......maybe to fast because I split for 15 minutes and I have to stop for 20 minutes to move the wood out of the way so I can split more. I really need some kind of conveyor to keep the wood out of the way. I had thought about putting that old pump on it to see what would happen but I didn't want to go through the trouble of re-piping the whole thing.

 

[srhotz]

Could it be air in the system? That would take time to compress.

 

[oldnslo]

On the MTE pump there is a check valve that isolates the low flow hi pressure from returning to pump inlet and a sequence valve that shifts from low pressure hi flow to low flow hi pressure.

those are the only two components in the shifting of the pump. If you are mechanically inclined I believe both of these components can be removed for inspection without dismantling the pump.

 

[mx842]

I had thought about air in the system somewhere but I don't see how that could be. I have run the thing enough to split probably 10 or 12 cords of wood and it seems like any air would have been evacuated by now. The only place I could see any air might be trapped would be in the cylinder itself. I did try to bleed the in line to the cylinder by extending the cylinder and then cracking the hose fitting right at the in port hose then running the cylinder back to the in position. When I did this I didn't notice any air escaping from the fitting only oil. I don't know of any other way to bleed the system.

 

[mx842]

oldnslo....... The guy at surplus center said those parts could be adjusted but he noted that if I removed them it might effect any warranty that might be left. At this point I don't give two shitskies about any warranty so I might just try that and see what I see. He also said that I could remove the cover cap and there was an adjustment screw that can be adjusted one way or the other to see if that helped. He didn't seem like he wanted to tell me much about which way did what he only would say turn the screw a little bit.

 

[mrmikey]

Rod out the reading is 500/600 lbs when it finally kicks in the low speed it reads what ever it takes to split the wood up to 3000 lbs if needed.

This statement is what makes me think:

The unloader valve is allowing the initial low volume/high pressure flow to leak past and return to tank along with the high volume/low pressure oil. It eventually seals and will eventually allow the pressure to build up.
You can have 3KPSI but it doesn't necessarily mean you have any flow or the flow is going where it's supposed to.
Just a shot in the dark on on my end tho ..............Mike