Auger motor popping hoses

[memphismark]

Hi guy's.
I have a Bobcat 753 that I'm going to use the auxiliary hydro system to drive an auger motor which will drive a shop made 3 yard concrete mixer. I have a Prince RDRS 175-16 flow control valve from Surplus Center to slow the auger from about 50 rpm down to about 25 rpm. I'm new to hydraulics by the way. Anyway, on the motor side return to tank, the hose keeps blowing. I'm not sure what to do. I've heard a pressure spike may be occurring from the motor stopping too fast? Not sure. Maybe some of the smart guys here can give some good advise. Would really appreciate it. Thanks a bunch. Mark

 

[wdchyd]

add a four port cushion valve between the control-valve and the motor......what you are experiencing is an over-running load, when the control valve is shifted into neutral your motor momentarily turns into a pump ......or replace the hyd valve and get the motor spool option (open ports to tank when in neutral)

 

[memphismark]

Thanks for the comment. The Prince flow valve I have is "pressure compensated". I would assume this would take care of the 'feed' side? Maybe a 'cushion valve' on the return side from the motor only? I noticed the pressure relief valve I saw on Surplus website, Item #9-1556 has 3 ports. How would one plumb this into the system? The in and out ports I get, but the 'tank' port, I don't know what to do with because the return to tank line is where I would put the valve anyway! In other words, the motor return hose would go into the 'in' port and out the other side back to tank. Where does the tank port go? If you recommend the 4 port cushion valve even though the Prince flow control is pressure compensated, how would I plumb that one? As of now, the Bobcat auxiliary feed goes to the 'in' port on my present Prince flow control, than a hose from the "CF" or controlled flow port to the motor. From the return side of the motor a hose goes back to the Bobcat, but is also tee'd into the "EF" or excess flow port on my Prince flow control valve. This is correct, Yes?? Thanks so much for your thoughts. I'm not trying to talk too much here, but all the verbal 're-tracing' of my steps hooking this thing up may catch your attention to something I may have missed. I love this stuff, but I hate this stuff! Thanks.

 

[wdchyd]

The pressure compensated flow valve keeps the flow (speed) constant regardless of pressure........that way the speed doesn't change when introducing a load
It doesn't reduce the pressure achieved at the motor unless it has a built-in relief valve

With only putting the relief valve you mentioned it will return excess pressure to the tank but will do nothing for make up oil the motor is trying to pull from the inlet of the motor......so the motor in a sense will starve (maybe do damage in the long run)

installing the cushion valve (essentially a double relief valve) after the prince flow control and at the in and out on the motor will protect the motor in both directions and diminish the pressure (decelerate) when stopping motor .....some cushion valves can be adjusted (or shims removed) to reduce the pressure from the exhaust side of the motor if less back pressure is desired while maintaining the higher pressure on the inlet side of the motor

 

[memphismark]

I was thinking that since it always pops the same return hose, which is always the one directly out of the motor but just before or ahead of the tee that connects it to the EF (excess flow) and straight back to the Bobcat tank, that a cushion valve might just be needed there. However, I think after reading what you wrote, it sounds as if I wrongly assumed a "pressure compensator" flow valve was the doing the same work but I guess not. It made perfect sense what you said about compensating load and various pressures after it's introduced to the system. I will definitely heed your advice and put the double cushion valve as you noted, after the Prince valve and before the motor on the feed/supply side, and out from the return side of the motor but before the tee from the Prince valve EF (excess flow) which then goes on back to the tank. Yes? Would this valve at Surplus Center, Item# 9-4019-50-L be the one we are talking about? I don't no how to add this link to this e-mail or I would make it easier for you. Thanks so much for your time. Popping hydraulic hoses whipping around scare the B'Jesus out of me. I'll sleep better after your confirmation. Again, thanks so much. Mark

 

[J_J]

Is your aux hyd full on at 14 GPM or is it variable?

If your aux hyd is variable, you do not need the Prince valve.

If you need reverse on the auger, you need a motor spool valve, and don't need the Prince valve or the relief valve.

If your aux hyd is solenoid operated at full flow, then the motor spool valve would be the best way to operate the hyd motor in fwd and reverse.

You should be able to vary the GPM's by reducing the engine rpm.

If you are going to use a relief valve across the hyd motor, this is the relief valve that you need.

1/2" NPT 30 GPM 1500-3000 PSI RELIEF VALVE RV-H4

It depends on the year of the 753 as to the flow GPM's. 753f has 14.5 GPM, 753H is 22 GPM

http://www.princehyd.com/Portals/0/valves/valvesRd100.pdf

If you only need one direction, then run the hyd motor OUT port to tank as in the PDF.

 

[memphismark]

Thanks JJ. I don't have high flow so GPM is supposedly 14 on my 2001 year Bobcat. The auxiliary lines I'm using have no spool, just directly from Bobcat hydro outlets into the Prince flow control to slow the auger down a little bit from about 60 rpm to about 35 rpm. Also for a concrete mixer I only go in one direction, no reverse. The relief valve you suggested, would that go in the motor return to tank side? Here's a crude drawing of what I have. I'm not the most computer savvy person, so I hope it's not gigantic or upside down. Maybe this will help. Thanks again. Mark

 

[memphismark]

One more thing JJ. You mentioned in your reply and I forgot to answer, that "if I need to run in one direction, then run the hydraulic motor OUT port to tank as in the PDF". The Prince valve I have say's to block the EF (excess flow) port in a normally closed center system. My Bobcat is open center, and that's why I tee'd the motor return and Prince EF port together back to the tank per their PFD. It is always the hose out of the motor and before the tee that blows! Your thoughts. Mark.
'

 

[J_J]

If you ran the hyd motor out to tank, there would be no reason to blow the OUT hose, as it is low pressure expended fluid.

 

[memphismark]

What do you think would create such a high pressure return as in a blowout? Should I just plug the EF port on the Prince valve anyway? Is it possible that EF from the valve and motor return pressure and the tee where they collide/merge is getting out of control? I have no clue. Total novice. Your thoughts. Mark