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catmastertech
catmastertech, Technician
Category: Heavy Equipment
Satisfied Customers: 1894
Experience:  19 years Cat, 3 years Case
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Flow on a cat 320c excavator auxiliary circuit..electronic..tool..cab

Resolved Question:

Hello there,
I need to reduce the no-load flow on a cat 320c excavator auxiliary circuit. The machine is NOT equipped with the integrated electronic tool control. It has the monitor in the cab, but doesn't have supporting hardware. I need 40 gpm and 3200 psi max on the aux. circuit. We have adjusted the relief valve on the aux. spool to accomplish the max pressure setting, but don't know how to reduce the flow from 59 gpm to 35-40 gpm. Can this be done?
Submitted: 3 years ago.
Category: Heavy Equipment
Expert:  catmastertech replied 3 years ago.

Donnie :

Without the proper pump control system, you cannot limit flow to one circuit. Any adjustment to the pump flow would limit it to all its circuits.

Donnie :

The valve does not have any flow limiting controls either. Only pressure relief.

Donnie :

If you have a hydraulic supply company you can contact, they could offer an add-on valve to limit the flow and dump excess back to tank.

Donnie :

I am assuming you are running a motor constantly and restricting the lines is not an option.

Customer:

That's correct. The control valve is the variable valve foot pedal as opposed to the thumb buttons. I was hoping that there may be an adjustment somewhere in either the pilot system or the main valve itself. I wonder if I could set an adjustable stopper on the foot pedal?

Donnie :

I haven't seen that done but, I don't know of any reason it won't work.

Donnie :

It would be extremely sensitive though and the minimum pump flow is 41 gpm anyway.

Donnie :

What are you adding to the machine?

Donnie :

The pump has an option to add an extra drive to it. If flow is critical, another pump would be the best option.

Customer:

My local dealer claims to have the flow set when the circuit is under load, however, it appears to me like nothing has changed other than the relief pressure. The flow does drop to 40 gpm at 3200psi, but i believe that only tells me that it pumps 40 gpm over the relief valve. I think they are just trying to cover up the fact thet they don't know what they are doing.

Customer:

I am putting on a hydraulic anchor driving attachment and it is an auto-shift model. The high flow seems to be creating excess back pressure and since the pressure build-up is what causes the unit to down-shift, I think that I am experiencing shifting issues due to the excess flow.

Donnie :

If back pressure is an issue, could it be resolved by plumping the return flow directly to the return lines instead of the valve. This may cause flow to increase.

Donnie :

Did they test flow with an inline tester?

Customer:

Yeah they used an inline flow meter, but the attachment wasn't on the machine. Just hooked it up from one aux line to the other. I was hoping there might be some spool travel stoppers that could be adjusted to control the flow, but maybe I'll have to try a stopper on the pilot pedal or just run the machine at lower rpm when using the attachment. I kinda need to run both lines to the valve as unit is bidirectional.

Donnie :

The valve does not have an adjustment but, you could install washers to prevent spool travel in each cap.

Donnie :

This could be tricky to find the right thickness. Each end is different.

Customer:

perfect. I'll try that. Is there 867 pieces and springs that are gonna fly out if I take the caps off?

Donnie :

Don't use anything plated, it could flake off and cause trouble if it stick in the pilot valve.

Donnie :

No, only an o ring on each end that will be a pain to get back into place.

Donnie :

Order a new set just in case you cut one.

Donnie :

The centering spring is on the top side. Nothing on the bottom.

Customer:

Ok. Do you know where I can get an exploded view of the valve or is it pretty straight forward.

Donnie :

Do not tamper with the spring or its washers.

Donnie :

I can get you a picture, hold on a second.

Donnie :

6V-5597 is the o-ring

Donnie :

for the caps

Customer:

I think that should be all I need. I guess I should have tried this first. Could've saved myself a lot of grief. You've been a tremendous help.

Customer:

Will adding washers or spacers under the caps screw up the neutral position?

Donnie :

It is possible the washer would get jammed in between the spring and the cap when it shifts the other way. It may be better to make a spacer the thickness of the washers that will limit the travel once you find the sweet spot. That way you don't need to worry about a washer turning side ways and jamming the spool down. The spool only moves 3/8" normally, You can block most of that travel and it should limit the flow correctly. Maybe leave 1/8" travel in each direction.

Customer:

Sounds good. Thank-you very much.

Donnie :

Your welcome. Thanks for using JustAnswer.

catmastertech, Technician
Category: Heavy Equipment
Satisfied Customers: 1894
Experience: 19 years Cat, 3 years Case
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