Hi all, Wondering if anyone has ever done a hydraulic pressure adjustment on the thumb circuit on the above mentioned. I've picked up a used NPK-2 hoe pack and hammer a while back. The hoe pack works great but can't get the hammer to move. Nitrogen is good, chisel point down etc. Last thing to try before tear down is hydraulic pressure adjustment which runs off the thumb circuit. The gauge plugged in at the quick connect reads approx. 1950 psi. To the best of my knowledge the hammer should have about 2700. Wondering if the 700 or so PSI could be a cause of the hammer not working and if so, any tips as to the adjustment.
Just went through this on my new VIO80-1A. Since it was intended for a thumb, auxiliary reliefs were set at 1950psi. Hopac sounded good in free air, but, wasn't effective at, well, compaction. As a rule, hammer/ compactor circuits should have their relief set 500psi above attachment operating pressure. Set my relief @ 2800 (only on one side of aux circuits) and hopac now works correctly. Haven't brought the hammer over yet, but, that's how all my Takeuchi TB180FR are set, and hammer works great on there.
I'm working on my Vio70, I haven't got the service manual yet, how involved is changing the relief pressure, handy gauge port someplace? does the valve provide overload relief?
Put gauge on hose coupling instead of hammer/ hopac/ thumb. Loosen 17mm jamb nut on relief. Turn Allen stem inward, 60°, and retry. Keep adjusting in until relief is 400~500 psi over tool operating pressure. On vio80, main valve bank is under floor, reliefs were different color than rest, as most left factory with dummy plug instead of relief cartridges, 5th row in. On same section of valve as the auxiliary hoses exit from. On mine, it was the cartridge pointing forward for the cab side line (pressure when in 1way flow).
Sweet info. Thank you everyone for your input. Hoping to make these adjustments on the weekend and they'll make the hammer shake....
Remember hammer needs return to tank...
Right, but does the return side of the thumb circuit not provide that? Left side is pressure side/right side is return side.?? My hoe pack runs great and that also needs a return to tank?
Not near enough....plus the backpressure and heat created would be bad. Most excavators have a 3 way ball valve that allows you to use boom lines but sends B port straight back to tank without going through B port valve.
Your hoe pack will run...so will hammer...but the heat and backpressure can and will cause problems....also on a hoe the 3 way ball valve sends return oil straight through the oil cooler at a higher flow rate and no extra heat from return spool....this is excellent for best cooling performance. It also has the extra bonus of only allowing one way flow to the attachments as B port will only be a return.
I run mine in 1 way mode. And I agree, to a point, but, looking at my takeuchis, it just returns to tank, not thru cooler. That would make too much sense.
It still cools better in one way...straight to tank is ok cause your gear pump will circ oil through cooler. I guess that is why kubota, deere and the likes are more expensive...my kubota goes through cooler and return filter first...
Well today was a good day. The NPK came to life. The relief on the valve bank was red/rest were all green; set the pressure to 1750. Couple of gentle taps with the tip to the floor and she came to life. Now try to figure out this heat/back pressure thing. The return to tank I'm assuming you're thinking case drain? I understand that for things like mulchers etc. with gear pumps etc. but don't think my NPK even has a port for a case drain.
Case drain? Your confusing me. For auxiliary hydraulics, let's call the plumbing lines A & B. In 1 way setting, oil goes out A to the tool, and returns in the B line to either cooler then tank, or just to tank. In 2 way setting (on a 1way tool like hopac or hammer), oil goes out the A line, and returns in the B line, through the main control valve, then cooler, then tank. It's the restriction of coming back through the main control valve that cause poor performance or attachment seal failure.
Yes a hoe pack or hammer does not like back pressure...when A Spool opens and goes through circuit at high pressure/volume B spool is open the same amount to return...but pressure is reduced ....this is called pressure differential.. pressure diff is referred to as ^p.(delta p). So picture a load of cattle in a trailer with a door opening of 36 inches....now picture a chute(hallway) that is 30 ft long and 60 inches wide...then a gate that is 36 inches wide at the end of chute with a pasture on the other side.....guy scares cattle out of trailer....they run through small door....down the chute...and because chute is wider...they slow down ...till more cattle come behind them....then they are forced through the little gate into wide open pasture....well all the strain is on the gate posts...if the pressure is not more than posts can handle the gate (shaft seal) holds...if not it breaks....going straight to tank makes the gate way wider....therefore reducing the stress on the gate...aka heat and shaft seal pressure... but when operating a cylinder you want A=B or you will have issues...just like when branding...you want on calf at a time going through the chute....so you dont over pressurize the traffic in....A=B...hope this helps...clear as mud if you have never ranched lol...
With hammer there is no case drain...with hoe packs most case drains are internally plumbed into B Line...that is why it is important to have B line to tank and min back pressure....mulchers have piston motors and need separate case drain line.
Sounds good rondig. That's a lot to absorb but starting to make sense. Thank you for sharing your wealth of knowledge.....