Help hydraulic problem with splitter

[AKKAMAAN]

To start over again, we need to visulize the pump system.

Pump A, is the low volume pump, produces about 1/4 (0.194 cui/rev) of the total 11 gpm (0.711 cui/rev). Pump B is the high volume pump, that produces the other 3/4 (0.517 cui/rev) of the total 11 gpm.
The pressure unload valve on the right can be set between 400psi and 900 psi. When pressure on the output get higher than pressure unload valve setting, unload valve opens and bypasses the flow from the high volume pump B, back to suction port. Pump A will then be the only flow into the splitter control valve, and its max pressure is controlled by the PRV, built into the splitter control valve. Max allowed pressure for the pump is 3600psi. Other components, like cylinder and/or control valve etc, might require lower pressure.

So if presssure gauge is reaching 2000 psi, we know this is the setting on PRV.
If engine is bogging down/getting killed, at that pressure, can either be caused by low power output from engine, or that pressure unload valve, fail to unload pump B.

By checking the flow under pressure, we can determine if unload valve is working or not. That means that we need to create something to control the load (out put pressure), with out forcing PRV to open. That can be done with a variable flow restrictor (0-11+gpm) on the line between control valve and and cylinder (capped side). By cycling cylinder and monitoring speed (flow) and pressure, you can determine if unload valve operates properly at set pressure.
Of course a 300$ inline flow meter can work also.

With dimension numbers on cylinder and a clock, we can calculate actaul flow. By increasing pressure with the restrictor, we shall be able to see cylinder speed drop, when reaching 400-900 psi. If no speed drop, unload valve in pump is failing.

What power does the 11 gpm pump require?
That depends on pressure settings on unload valve and PRV.
At high volume and 900psi, about 5.8hp, and at 2000psi 12.9hp (stall/kill)
At low volume and 2000psi, about 3.5hp, at 3000psi, about 5.3hp.

So if your engine is OK, there is now reason for boggin/kill, unless unload valve is stuck.

Here is a link to spread sheet showing "all the numbers", read the "11 gpm" line...

I assumed a 4"x2"x24" cylinder.

Spread sheet can be down loaded to your own computer as Excel or OpenOffice file. Then you can edit numbers as you want...keep this link for recovery, if formulas get lost....

Only numbers in the Green cells are subject to change.

Play with pressure setting numbers to see how horse power requirement changes

Pump displacements and max allowed pump speed and pressure, is copied from Haldex-Barnes info PDF file

Note that all flow numbers are based on a 3600rpm pump speed.


Have fun!

 

[jags]

Good info, and this info here is very telling:

At high volume and 900psi, about 5.8hp, and at 2000psi 12.9hp (stall/kill)
At low volume and 2000psi, about 3.5hp, at 3000psi, about 5.3hp.

If the pump WAS kicking in to low volume/high pressure the engine would have no problem with maintaining 2000+ psi. If it IS staying in the high volume mode (and I believe it is) it would take all the HP of the engine to maintain about 1000 psi (6.5 hp) and surely stall after that. The 2000 psi that you saw was probably a momentary thing. The inertia of the engine spinning at 3600 rpm could have caused that.

Good info - thanks again for posting.

 

[kevin j]

thanks per. Excellent post as usual.

Arlen: You are reading pressure and adjusting the high pressure relief valve at the handle valve. If it was set at at 2500 and you turned it out to say 2200, it won't matter, the engine stalls at 1200 or 2000 due to inertia and flywheel.

You need to adjust the pump unloading point, to something under 1200 psi. Adjust that at the pump, not at the main relief.

Then once the unloading is set, you may find it relieves on low volume, high pressure at something well under where it should be. Then you use the gauge to reset the main relief back up to where it was. 6.5 hp is plenty of engine, but I would not go above 3000. I would set it at 2500 psi main relief. On low volume, about 3 gpm, 2500 psi is under 5 hp. Plenty of power.

On high volume, 11 gpm, at 2000 psi is 13 hp. So it is inertia like per and jags described. 11 gpm at 1200 psi is still 8 hp, too much. 11 gpm at 900 psi is 6 hp, so I expect you will end up unloading at about 700-800 psi and the engine will handle it fine. But adjust the pump unloading, not the main relief, first. Then the main relief.

In SAE units, pump HP required = (GPM x PSI)/1714
Easier to remember, and accounting for pump mechanical and volumetric losses, is
HP = (GPM x PSI)/1500

 

[arlen]

Akkamaan thanks

OK I installed a gage on my husky 27 ton horizontal vertical splitter it has a 5" cylinder. I extended the cylinder to the end and watched the gage it went up to 3500 lbs and the engine did not stall I let off on it tried it a few times same results.

I went to my challenge splitter with the 4" cylinder and noticed a screw on the side of the pump. I got a flat tip screwdriver and noticed it was screwed all the way in so I screwed it out a few times when I extended the cylinder the pressure went up to over 3000 lbs and the engine did not stall. I split wood for about an hour and nothing stopped the splitter I watched the gage go up to 2000 sometimes before the round split. I guess the adjustment screw on the pump help the pump to unload and go into high pressure low volume. Thanks everyone for all of the help and input. Splitter is working correctly now. David

 

[mizzou]

Way to go!

 

[arlen]

thanks for the advice

Kevin I really appreciate you following the post and giving such helpful info. Tomorrow with the gage I can re adjust the pump and the splitter spool valve.

 

[CJ1]

Kevin I really appreciate you following the post and giving such helpful info. Tomorrow with the gage I can re adjust the pump and the splitter spool valve.

I would strongly suggest you keep the main relief below about 2700psi these pumps are rated at 3000 but they don't last very long at that pressure. You can adjust the transfer screw in until the motor loads down before it shifts to the high side, this will allow you to have faster split times. [I am not kevin but I hope this helps!] CJ

 

[jags]

WHOOO HOOO! I love a happy ending.

 

[AKKAMAAN]

I would strongly suggest you keep the main relief below about 2700psi these pumps are rated at 3000 but they don't last very long at that pressure. You can adjust the transfer screw in until the motor loads down before it shifts to the high side, this will allow you to have faster split times. [I am not kevin but I hope this helps!] CJ

The max psi setting do not matter that much, as you only reach that max pressure if you stall the cylinder at the end of stroke. 99.99% of all logs are cracked and split before the end of stroke. If you stall at 2700psi for a tough log, you will ask for another 300 psi anyway....

There might be a short pressure spike at end of retract before detent kicks out, can be minimized if detent pressure is set as low as possible, at 1000psi, spike should not reach 2000psi???

Under sized suction design, air vent and poor filter management, will have more impact on pump life time, than reducing pressure setting to 2700psi....

 

[CJ1]

The max psi setting do not matter that much, as you only reach that max pressure if you stall the cylinder at the end of stroke. 99.99% of all logs are cracked and split before the end of stroke. If you stall at 2700psi for a tough log, you will ask for another 300 psi anyway....

There might be a short pressure spike at end of retract before detent kicks out, can be minimized if detent pressure is set as low as possible, at 1000psi, spike should not reach 2000psi???

Under sized suction design, air vent and poor filter management, will have more impact on pump life time, than reducing pressure setting to 2700psi....

I agree 100% on the inlet and filtration, with out a doubt both of them are usually poor at best. Most reliefs set a 2700 or so will creep up a few hundred pounds. One customer stuck a log and kept beating on it until it puked. Of course he also had happy fingers and turned the relief in a little :msp_thumbdn:. that cost him a pump. Anyway glad the o/p is up and running. CJ

 

[AKKAMAAN]

I agree 100% on the inlet and filtration, with out a doubt both of them are usually poor at best. Most reliefs set a 2700 or so will creep up a few hundred pounds. One customer stuck a log and kept beating on it until it puked. Of course he also had happy fingers and turned the relief in a little :msp_thumbdn:. that cost him a pump. Anyway glad the o/p is up and running. CJ

Thats way it is best to have it, PRV, set at max allowed, and then do not mess with it any more.....btw, if stuck , a little hit on the log with back side of +an axe/maul, together with with some pressure from the cylinder, can do wonder....might need a helping hand with that though....

Always use a gauge when setting PRV....

Also, remember that a PRV spring is very progressive, which means that increasing pressure 300psi from 1000psi to 1300psi, can take a full turn on the screw, but increasing pressure 300 psi, from 2700psi to 3000 psi, might only need 1/8 of a turn on the screw.

Actually this "progressivity" also applies on a variable orifice....

 

[arlen]

Thats way it is best to have it, PRV, set at max allowed, and then do not mess with it any more.....btw, if stuck , a little hit on the log with back side of +an axe/maul, together with with some pressure from the cylinder, can do wonder....might need a helping hand with that though....

Always use a gauge when setting PRV....

Also, remember that a PRV spring is very progressive, which means that increasing pressure 300psi from 1000psi to 1300psi, can take a full turn on the screw, but increasing pressure 300 psi, from 2700psi to 3000 psi, might only need 1/8 of a turn on the screw.

Actually this "progressivity" also applies on a variable orifice....

I will follow your suggestion and leave the PRV valve in the max setting. When the pressure creeps up to 3000 psi I back off on pressure by releasing the handle. My other splitter which has the 5" cylinder gets stopped by a round occasionally. Sometimes I need to look for a crack and try it again, and sometimes the round blows apart sending both halves 10 feet in either direction one towards me and the other away. A few months ago one hit me in the forehead and knocked me loopy :msp_ohmy: I needed a break from splitting and a few stitches in the forehead. David

 

[arlen]

I would strongly suggest you keep the main relief below about 2700psi these pumps are rated at 3000 but they don't last very long at that pressure. You can adjust the transfer screw in until the motor loads down before it shifts to the high side, this will allow you to have faster split times. [I am not kevin but I hope this helps!] CJ

Hey I'm not Judy my name is Lisa:msp_tongue: Just kidding do not know if you remember the song? I am also grateful for your advice David