Turning a high flow pump down

[cat 297c]

I have a Rayco c140 Would like to turn my high Flow Pump Down, Right now She's Flowin round 67gpm @ 6000 psi. Wanting to know if it's possible to turn her down to round 55 gpm @ 5000 to 5500 psi? Right now if you stall the cutter head it kills the engine some other guys said they turned their's down an it helped out but they didn't know how much the dealer turned it down to.

 

[AKKAMAAN]

I have a Rayco c140 Would like to turn my high Flow Pump Down, Right now She's Flowin round 67gpm @ 6000 psi. Wanting to know if it's possible to turn her down to round 55 gpm @ 5000 to 5500 psi? Right now if you stall the cutter head it kills the engine some other guys said they turned their's down an it helped out but they didn't know how much the dealer turned it down to.

This crawler has some impressive numbers....here is a spec sheet pdf
67GPM and 6250PSI makes 182kW or 244hp....

So this 140hp John Deere engine is going to have a tough time to keep up with tough flow-pressure demands....lol...

I think there must be some kind of a torque/power limiter in the system....which might need an update resetting...Is there any info in owners manual about this??

Lowering the rpm's will just lower the flow, and you also will need to lower the max pressure to survive the stall....

I would start with lowering the max pressure and keep the rpm's as high as possible....high speed is high inertia on the cutter, and it will better overcome cutting resistance...

 

[mikehaugen]

If it is a fixed displacement pump you won't be able to alter flow, unless like AKKAMAAN said, you change the RPM's. You can however look for a relief valve that will allow the fluid to bypass back to tank if implement stalls, while still allowing engine to run. I would assume that it has one, though I am not familiar with your machine, but that is probably what the "other guy" was referring to. If it doesn't have one, you should consider adding one. If you are actually killing your engine you sure aren't doing your pump any favors, or the rest of your hydraulic system for that matter. Again though, I don't know your machine to know what type of pump or valving it has, I am just speaking from my experience with general hydraulic equipment (mostly in an industrial setting).

 

[Taylortractornut]

Our roll off trucks have 30 GPM pumpsand the little tarp lines are cutdown to 15 gpm thetrucks use a flow divider valve to cut itdown. Also we have one on our AC D grader at work with a power steering box added.

 

[J_J]

Maybe one of these.

https://www.surpluscenter.com/item.asp?item=9-2280&catname=hydraulic

 

[dynasim]

One caution about lowering the relief pressure:

The designers may have designed the system such that the engine stops, instead of the pump going into bypass. All of the power generated by the engine is turned into heat as it passes through the relief valve. Normally that power(heat) is dissipated into the brush you are destroying.

If you put the system into bypass for a relatively short period of time, it will overheat the oil, and likely destroy any seals in your system. If the engine doesn't have the power to put the system into bypass, the relief valve only needs to relief impulse flows, which are very small.

Also, lowering the engine RPM probably won't help your problem. The shutdown is caused by the pump requiring more torque than the the engine can produce. The required torque for a given pump is only related to the differential(discharge) pressure. Since the torque curve for a diesel engine is relatively flat, changing he rpm should not have much effect.

I guess what I am saying is be careful. If you are the one driving the machine, and know the issues, it may not be a problem, but if you are hiring someone to run it, and they constantly are putting the thing in bypass, it will likely break.

Chris

 

[Bikewanderer]

I have a Rayco c140 Would like to turn my high Flow Pump Down, Right now She's Flowin round 67gpm @ 6000 psi. Wanting to know if it's possible to turn her down to round 55 gpm @ 5000 to 5500 psi? Right now if you stall the cutter head it kills the engine some other guys said they turned their's down an it helped out but they didn't know how much the dealer turned it down to.

That sounds like a closed loop hydrostat type system. If so there will be a way to adjust the swash plate and reduce maximum displacement. It doesn't affect pressure, but will allow you to "downsize" the pump to not stall your engine. I would consider turning down farther than required and working your way up until the engine is nearly stalled or struggling when the cutter is stalled.

This will affect cutter speed though.

Your other option would be a relief valve to limit pressure.