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 ****skies 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

 

[oldnslo]

MX
The adjustment is for the shift point pressure and turning screw clockwise will increase shift point pressure. Set to high this will stall your engine.
I don’t remember where the check is located but suspect under a different hex cap or plug.

 

[mx842]

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

I may have wrote that wrong. When I first hit the lever to send the cylinder out the needle hardly moves until it hits the piece of wood then the pressure builds to around 600 lbs and sits there for what seems like an eternity, 7 to 10 seconds +/- depending on the rpm I'm running. then all of a sudden the pressure shoots up until it starts to split the log then it will drop back down and stay there unless it hits a hard spot then it will pop back up to what is needed to finish the splitting the log. Once the log has started to split the pressure up and down is normal operation while the log is being split. Most wood starts to split at around 1000 psi and with clean wood with no knots it will drop back to hi mode and finish the split. It's just that initial hesitation just before the shift to low that is the deal breaker.

 

[mx842]

MX
The adjustment is for the shift point pressure and turning screw clockwise will increase shift point pressure. Set to high this will stall your engine.
I don’t remember where the check is located but suspect under a different hex cap or plug.

That's kind of what I was thinking so I guess I might try turning it CCW a little to lower the shift point and see what happens. I can't remember now but I don't think there is but one plug cap on the pump. That may be wrong and when I go out I'll look at it again.

 

[s219]

Make sure you don't have an air leak on the suction side, as it will pull in air and foam up the fluid. That causes exactly the symptoms you describe. If you have a clear suction line you can spot this easily, otherwise look in the reservoir tank and see if the fluid has a lot of bubbles or foam.

When this happened to me, it was a leaky shaft seal on the pump that was allowing air to get sucked in. Very small leak but boy did it suck in a lot of air.

 

[mx842]

Make sure you don't have an air leak on the suction side, as it will pull in air and foam up the fluid. That causes exactly the symptoms you describe. If you have a clear suction line you can spot this easily, otherwise look in the reservoir tank and see if the fluid has a lot of bubbles or foam.

When this happened to me, it was a leaky shaft seal on the pump that was allowing air to get sucked in. Very small leak but boy did it suck in a lot of air.

I have suspected air from the start and there is a possibility that my suction line may be the problem. It doesn't seem to show any leakage on the outside but it is an old piece of hose. I was going to put a new one on when I pipped it in but when I went to the hydraulic shop to buy one they wanted $47 a foot and I just couldn't see me paying that much for a piece of hose. I just ordered a 5' section from surplus center and it should be here next week so I'll try that and see what happens. That 5' piece with shipping was $43 and some change.

 

[mx842]

I have suspected air from the start and there is a possibility that my suction line may be the problem. It doesn't seem to show any leakage on the outside but it is an old piece of hose. I was going to put a new one on when I pipped it in but when I went to the hydraulic shop to buy one they wanted $47 a foot and I just couldn't see me paying that much for a piece of hose. I just ordered a 5' section from surplus center and it should be here next week so I'll try that and see what happens. That 5' piece with shipping was $43 and some change.

Well I finally got the 1" hose from surplus center and put it on the spliter but it does the same thing as when I had the 3/4" hoes on it. I also had a strainer in the line that I removed also so I'm pretty sure it's not starving for oil. I also checked to see how many caps were on the pump and there are two caps, one on the intake side and one on the output side. I was going to try an adjust the pressures but can't find out which one to adjust. I would think that the one on the intake side would be the one but didn't want to blow anything up in doing so. I know how dangerous hydraulics can be if all is not well in the system.

 

[CADplans]

Where is the oil return back into the tank, relative to the top of the oil level?

In other words, does the oil return into the air space above the oil?
or
Does the return oil go into the submerged area below the top of the oil level?

If the return is into air,, you get splashing, and foaming,,
and air compression that takes, OH,, a guess,, 7 to 10 seconds,,,

The suction and return need to be FULLY submerged ALL the time.

How deep is the tank?

One of the functions of a suction strainer is to stop the type of air suction that you see when a bath tub is being emptied.

A bath tub is only emptying at 2 to 5 gallons per minute,, that is enough to suck air.
Your pump is trying to suck 16 gpm,, if air is the easiest thing to grab, the pump sucks in air.

 

[triptester]

Well I finally got the 1" hose from surplus center and put it on the spliter but it does the same thing as when I had the 3/4" hoes on it. I also had a strainer in the line that I removed also so I'm pretty sure it's not starving for oil. I also checked to see how many caps were on the pump and there are two caps, one on the intake side and one on the output side. I was going to try an adjust the pressures but can't find out which one to adjust. I would think that the one on the intake side would be the one but didn't want to blow anything up in doing so. I know how dangerous hydraulics can be if all is not well in the system.

 

[mx842]

Where is the oil return back into the tank, relative to the top of the oil level?

In other words, does the oil return into the air space above the oil?
or
Does the return oil go into the submerged area below the top of the oil level?

If the return is into air,, you get splashing, and foaming,,
and air compression that takes, OH,, a guess,, 7 to 10 seconds,,,

The suction and return need to be FULLY submerged ALL the time.

How deep is the tank?

One of the functions of a suction strainer is to stop the type of air suction that you see when a bath tub is being emptied.

A bath tub is only emptying at 2 to 5 gallons per minute,, that is enough to suck air.
Your pump is trying to suck 16 gpm,, if air is the easiest thing to grab, the pump sucks in air.

I built the tank out of a piece of 10" schedule 40 iron pipe that is roughly 5' long. The oil level is higher than the pump inlet. The in/ out/ vent is all on one end of the pipe. The inlet pipe goes through the cover and extends 3/4 of the way to the back of the tank. I have a 45* fitting on the end that is turned downward and toward the back. I have a diverter plate about 6" from the end of the inlet pipe so as to keep the full force of the oil from just spraying into the tank. The oil exits the inlet tube at about the half way point of the tank and like I said it is somewhat turned down on a angle.

I have the suction line coming out of the tank as low as I could get it and there is probably about 1" off of the very bottom. There is about an inch air space at the top at the vent. I put right at 20 gal of oil in the tank and let it purge excess out of the vent to level it out. It may have spit out 1/2 gal or less and that's where it's been since I have been using it.

I know that this tank is probably a little small gal wise but my old splitter had only a 4 1/2 gal tank with a 11 gpm pump and I used that one for over 35 years with no problem. The oil never get's much over 100* even in the summer with hard use. I had thought about maybe adding another pipe tank over top of this one to get a little more volume because I was worried about the oil overheating but it never did in the time I have used it.

I had been worried about air in the oil so I put a section of clear line on the suction side to see what was going on but the oil always looked clear with no bubbles. You may be on to something with the bath tub thingy but it was doing the same thing with it in the line as it's doing now.

 

[WranglerX]

Interesting video....