Backhoe pressure relief valve test

[Jaylegger]

I have a Woods BH6000 backhoe installed on my Massey GC2600 and would like to test the backhoes PRV setting at some point. The hoe is working fine but I'm thinking the valve may be set lower than the 2,000 psi spec (same as the tractors output pressure rating) due to its max digging forces being reached when the tractor RPM is around 1500. Raising RPM above this does not equate to any additional pressure in the cylinders and my experience with the tractors loader pressure does increase as RPM's rise above 1500 RPM, plus I was expecting a little more power at the bucket and dipperstick.

The backhoes manual outlines the test and adjustment procedure for the valve which is below. My question is regarding the hookup of the gauge. I presume it goes into the main supply line connecting the pump and backhoe which indicates a T fitting is required. Is that correct?

Also where are these value oriented testing kits I keep reading about, I've can't seem find them anywhere.

Thanks.

Pressure Setting Adjustment

NOTE: Before changing the pressure setting on the valve, determine tractor hydraulic system pressure. Many tractors do not create 2000 psi. If your tractor does not create 2000 psi, changing the relief valve setting will not improve the backhoe performance. To adjust relief valve setting, place a 3000 psi pressure gauge in the line attached to the valve inlet (IN) port. Remove cap from top of main relief (1, Figure 17). Turn adjusting screw clockwise to increase pressure and counter clockwise to decrease pressure. Start tractor and set throttle for full engine speed. Move right stabilizer control lever to raise stabilizer to transport position and hold the lever so full pressure builds. Adjust screw to attain 2000 psi. Shut off tractor and replace cap.

 

[AKKAMAAN]

The hoe is working fine but I'm thinking the valve may be set lower than the 2,000 psi spec (same as the tractors output pressure rating) due to its max digging forces being reached when the tractor RPM is around 1500.

So the tractors output pressure setting is 2000psi RIGHT??!!
If so, just set backhoe to the same setting....If you need more pressure to backhoe, first need to increase tractor pressure....check recommendations for your tractor...

Raising RPM above this does not equate to any additional pressure in the cylinders and my experience with the tractors loader pressure does increase as RPM's rise above 1500 RPM, plus I was expecting a little more power at the bucket and dipperstick.

Modern PRV's do not increase pressure when increasing rpm's (flow), some valves even drop the pressure a little when by pass flow increases.

The backhoes manual outlines the test and adjustment procedure for the valve which is below. My question is regarding the hookup of the gauge. I presume it goes into the main supply line connecting the pump and backhoe which indicates a T fitting is required. Is that correct?

YES

Also where are these value oriented testing kits I keep reading about, I've can't seem find them anywhere.

Best value for the money is IMO just a proper gauge, some 1/4" hose and some fittings....
Valley Instrument 2 1/2in. Stainless Steel Glycerin Gauge — 0-3000 PSI | Filled Gauges | Northern Tool + Equipment

Thanks.

You are welcome

Pressure Setting Adjustment

NOTE: Before changing the pressure setting on the valve, determine tractor hydraulic system pressure. Many tractors do not create 2000 psi. If your tractor does not create 2000 psi, changing the relief valve setting will not improve the backhoe performance. To adjust relief valve setting, place a 3000 psi pressure gauge in the line attached to the valve inlet (IN) port. Remove cap from top of main relief (1, Figure 17). Turn adjusting screw clockwise to increase pressure and counter clockwise to decrease pressure. Start tractor and set throttle for full engine speed. Move right stabilizer control lever to raise stabilizer to transport position and hold the lever so full pressure builds. Adjust screw to attain 2000 psi. Shut off tractor and replace cap.

Instruction good!!

 

[Jaylegger]

So the tractors output pressure setting is 2000psi RIGHT??!!

The tractor manual states the relief valve setting is 1920 psi. I would guess the entire system can be safely governed by the tractors relief valve making the backhoes valve redundant. With that in mind and without measuring the pressure perhaps a half turn or so on the backhoes valve will ensure it's not prematurely relieving pressure and using all the tractor can supply.?

Best value for the money is IMO just a proper gauge, some 1/4" hose and some fittings....
Valley Instrument 2 1/2in. Stainless Steel Glycerin Gauge 0-3000 PSI | Filled Gauges | Northern Tool + Equipment

Great, thanks.

 

[AKKAMAAN]

The tractor manual states the relief valve setting is 1920 psi. I would guess the entire system can be safely governed by the tractors relief valve making the backhoes valve redundant. With that in mind and without measuring the pressure perhaps a half turn or so on the backhoes valve will ensure it's not prematurely relieving pressure and using all the tractor can supply.?

Manual states 1920psi.....what would a gauge state?? Spring fatigue happens in PRV's.....tractor pressure could be 1700psi by now....I think you still should check the tractor PRV and the BH PRV.....

 

[Jaylegger]

Manual states 1920psi.....what would a gauge state?? Spring fatigue happens in PRV's.....tractor pressure could be 1700psi by now....I think you still should check the tractor PRV and the BH PRV.....

Picked up a gauge and necessary 1/4" and 3/8" fittings and quick disconnects at Princessauto. Hooked up the 1/4" fittings and measured the tractors pressure at the fel and it is perfect with a high of 2050 psi at 3000 rpm and a low of 1750 at idle (1100 rpm). Hooked up the 3/8" quick disconnects to measure the backhoe and the #$@% things won't fit. The 3/8 sizing is correct but the length of the shaft at the business end of the couplings is shorter than required. There's always something.

To be continued....

 

[daman1]

Keep i mind also allot of manuals recommend oil being at a certain temp(130-160 deg) before setting pressure relief,check that out.

 

[Gale Hawkins]

If your max source pressure of 2050 PSI was taken when hot (like after working for a while) it seems to me you are correct to assume the backhoe PRV setting wide open would be fine because the tractor top PSI is not greater than the hoe can handle. I would still try to get the fittings to test the hoe.

If PSI was taken cold then the 2050 reading would be expected to drop when hot but there could be other factors to consider.

I need to this for both the transmission pump and hydraulic pump on our old JD backhoe but I have to get the new filters and fluid installed before any readings are consided valid per John Deere.

 

[Jaylegger]

All right, I'm back after spending far more money and time than anticipated but at least I have the proper quick couplers (not cheap) to match those on the hoe. A rather anti-climatic ending however, the stone cold pressure reads between 1800 (idle) and 2200 psi@3000 rpm at the hoe. Yesterday the tractor was slightly warm after mowing. (daman1, thanks for the reminder)

I was hoping to tweak a little extra out of the system but it's reassuring to know the hydraulic pressures appear to be in spec so will leave everything as is. I now can only wonder if removing the hoe's, redundant and likely flow restricting, primary pressure relief valve and capping it would increase gpm flow therefore increase speed. Kidding.... it's plenty fast as is.

 

[Gale Hawkins]

Knowing the facts is a good thing. Now you have a base line for future checks on each.

 

[Jaylegger]

Knowing the facts is a good thing. Now you have a base line for future checks on each.

Just knowing the pressures are as they should be puts my mind at ease and as you point out will also aid in any future troubleshooting, but now there's no excuses I just have to concentrate on learning how to use the thing.