inline hydraulic pressure reduction

Ron Snyder · Dec 17, 2009

Can anyone recommend how to reduce 17 gpm hydraulic volume (max 2000 pressure) (inline) to 11-12 gpm hydraulic (max 2000 pressure)?

I need to drive a REVERSIBLE 3pt snowblower that requires 11-12 gpm using 3/4" hose. Manufacturer (Loftness) says that current over pressure is the reason that snowblower doesn't spin properly (and a new hydraulic pump (rated at 17-20) costs over $1000.

I have read about inline control valves that may provide a solution, but I would like any advice from experienced experts (I really rely on you guys, you're great!!).

thanks,
Ron

mkirsch · Dec 17, 2009

You're using "pressure" and "flow" interchangeably. They are two different things.

I take it the snowblower is rated for 11-12GPM and 2000PSI?

I also take it the tractor is rated for 17GPM and 2000PSI?

2000PSI is 2000PSI, regardless of flow. Your hydraulic system is providing the correct PRESSURE.

If they are telling you that you have too much pressure, ask to speak with someone else. The person you are talking to does not know what he is talking about.

The only thing you can do inline is reduce flow. They make flow-limiting valves that are fairly inexpensive.

I doubt that "too much flow" is your problem.

What is the problem, anyway?

450D · Dec 17, 2009

Back off the throttle. Reducing engine rpms will reduce flow.
Dave

Ron Snyder · Dec 17, 2009

manufacturer Loftness says that 2nd stage chute does not spin fast enough to throw the snow.

And overflow of hydraulic is the cause. (17 gpm)

Ron Snyder · Dec 17, 2009

Does the flow limiting control need a relief valve.

I don't understand how these would be incorporated. Currently I have two 3/4" quick connect that drives the pump on the blower.

Do I add a flow control valve on each line? (the snowblower pump is reversible); What happens to the excess flow (4-5 gpm that is in the portion of the line prior to the flow control valve?

Thanks for being patient with someone that knows very little about hydraulics.

charles todd · Dec 17, 2009

If you are really putting out 17 gpm and its rated for 11-12 gpm, then the blower should be kicking it. Volume at pressure is what makes it happen, displacement of oil. I think maybe your total system flow may be 17 gpm, but after steering and other sources of consumption and valving you may have half that. This is if you are using tractor hydraulics. If this is a PTO pump with an externat reservoir, I'd look for restrictions.

As for control, a motor spool valve or a motor speed control would do nicely. I do not know why you would want to install flow controls, because if its not fast enough its because of lack of flow not too much.

CT

teddy52food · Dec 17, 2009

If it doesn't spin fast enough it is because of lack of pressure and or flow.

mkirsch · Dec 17, 2009

Overflow? Sounds hokey to me.

What kind of tractor are you using to power this?

Handyman · Dec 17, 2009

First thing I would do is put a pressure gauge on the return side of the motor and see how much back pressure there is there. it should be less than 500psi, if more you have too much restriction in the return line and that is robbing you of your flow.

bc · Dec 17, 2009

Ron, go to the loftness website and then tell us which model you have.

The lowest flow one I see is 15 gpm and they go up to 60 gpm. They only use one hydraulic motor and a chain drive to run the main impeller and the diverter spout.

Sounds like hooey to me too. You need more gpm meaning a higher gpm pump.

try this:
loftness

PaulW_NJ · Dec 17, 2009

I don't know much about hydraulics, but working in oil refineries for 25 years, if we had a pump that put out more flow than we needed, we simply installed a bypass, or kick-back loop. That is, installing a line from the pump discharge back to the low pressure side, with a needle valve in between. That way you could control whatever flow you wanted: the more you kicked-back, the lower the net output. Easier to correct too big a flow, than not enough.

Maybe you could try that . . . .

IH fan · Dec 17, 2009

(quoted from post at 19:18:36 12/17/09) I don't know much about hydraulics, but working in oil refineries for 25 years, if we had a pump that put out more flow than we needed, we simply installed a bypass, or kick-back loop. That is, installing a line from the pump discharge back to the low pressure side, with a needle valve in between. That way you could control whatever flow you wanted: the more you kicked-back, the lower the net output. Easier to correct too big a flow, than not enough.

Maybe you could try that . . . .

This will work to a certain extent.... as pressure in the system increases due to load on the snow blower, the by-pass flow will also increase... higher load= higher pressure (up to the 2000psi relief valve pressure)= more flow by-passed= less flow to the blower= slower blower speed... not what you need. If you have more flow than you need (not what I believe to be the case here, but don't know enough about the system to say for sure) there are pressure compensated flow controls available, but at higher cost. Been retired 7 years and don't remember the companies that made them, but should be several. We made them at one time (Cessna), but a lot of the good stuff went down the tubes when Eaton bought us in the late '80s.

David G · Dec 20, 2009

I do not believe that the manufacturer is telling you anything worthwhile. Most of the folks here are telling you the same thing. Make sure you have adequate pressure and the flow will take care of itself. It is quite evident that you do not have enough flow if you cannot maintain the required pressure.

inline hydraulic pressure reduction

Ron Snyder

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450D

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Ron Snyder

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Ron Snyder

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charles todd

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