Squealing control valve

   / Squealing control valve #21  
I will get a pressure gage but at this time I feel there is a restriction problem and the Prince relief valve should not require adjustment. It would seem the problem has to be in the new 1/4" lines going to the SA PA cylinders, the QD couplers attached to the Prince valve or the valve itself. Unfortunately I used none swivel type NPT F couplers to add the new lines back to the control so disassembly will be cumbersome and I don't have spare mating parts for the QD's at the valve. But I will disasemble the suspected components and test them in my shop with air. I will also double check to make sure there is no mechanical hangup producing an excessive load but I think that is doubtful.
bar

May be a stupid question...But have you tried to unhook and then reconnect the QD's? Frequently they "look" connected but are not pushed together all the way.
 
   / Squealing control valve #22  
If no one blew out the hoses before installation, there might be some trash behind one of those QD's. The hoseman is supposed to do that before he gives it to the customer. However, if the QD's were installed later, a bug or trash could have entered the hose. I would unscrew one of the QD's off the hose leaving the QD's connected and let some fluid flow through on each hose.
 
   / Squealing control valve
  • Thread Starter
#23  
Update on squealing control valve:
I disassembled my system and checked for proper functioning of QD's, hoses & valves with 25lbs of air. All worked well. Also checked for mechanical binding and could angle the blade by hand very easily with the cylinders connected and short hoses open. I then reassembled and..... no surprise... still had the squealing but I noticed if I feathered the spool no squeal. So I then did a no no.. I checked the relief valve and found there were two full turns of adjustment available for increasing pressure so i increased pressure by 1/2 turn. Now the blade angles crisply, not to fast or slow and no squeal.

Question:
I know, I know get a pressure gage but how do I know what pressure to set the relief valve to? Is it possible/probable that the 30 feet of 1/4 in hose coupled with the capacity of the tractor pump could cause the pressure to rise that much?
bar
 
   / Squealing control valve #24  
Update on squealing control valve:
I disassembled my system and checked for proper functioning of QD's, hoses & valves with 25lbs of air. All worked well. Also checked for mechanical binding and could angle the blade by hand very easily with the cylinders connected and short hoses open. I then reassembled and..... no surprise... still had the squealing but I noticed if I feathered the spool no squeal. So I then did a no no.. I checked the relief valve and found there were two full turns of adjustment available for increasing pressure so i increased pressure by 1/2 turn. Now the blade angles crisply, not to fast or slow and no squeal.

Question:
I know, I know get a pressure gage but how do I know what pressure to set the relief valve to? Is it possible/probable that the 30 feet of 1/4 in hose coupled with the capacity of the tractor pump could cause the pressure to rise that much?
bar

Gotta say it so get ready: I told you so;)


To set the pressure, first-find the rated pressure spec for your machine, then check your FEL valve and see if it's up to spec, then finally set your new valve at the same or just below the rated pressure for the system.

If you don't know or can find that spec, then set it for whatever the FEL valve is set for.
 
   / Squealing control valve #25  
Kennyd is correct that a pressure gauge would have located your problem, but you would have to have made several measurements.

Here is why (I think).

According to my handbook, using ISO 32 fluid at 104 deg F, 8.5gpm through 30' of 1/4" ID hose with three right angle fittings has a pressure loss of 1215 psi. Add in a quick disconnect and a couple more fittings and you might get to 1250 psi. At 50 or 60 deg , or with heavier fluid than ISO 32, the pressure loss would be much more.

And that is for the one-way trip of 30'. The return hose from the other cylinder will have the same loss, for a total loss of 2500 psi if there were no resistance in the cylinders. So when you shifted the spool completely, so that 8.5gpm was directed to the 1/4" lines, the pressure in the relief valve rose quickly to 1500psi and the relief valve opened to limit the pressure. Therefore, the flow through the pressure line, cylinders, and return line was limited to a rate that produced a total pressure loss of 1500 psi.

The pressure loss was great because the fluid was moving so fast through the lines that its flow became turbulent rather than laminar, and the losses increase greatly when the flow changes from laminar to turbulent.

But a guage at the valve would have shown 1500psi since it would be measuring before the fluid entered the hoses. If you moved the guage to the cylinder end of the hose and deadheaded the cylinder supply hose into the gauge, you would also measure 1500psi because with the hose deadheaded into the gauge, no fluid would be flowing and there would be no pressure loss between the relief valve and the gauge. I think you would have to tee the gauge into the cylinder port so that the fluid could flow. Then the gauge would read much less than 1500psi because fluid would be flowing through the hose and suffering the pressure losses.

Glad it turned out to be an easy problem to fix.
 
   / Squealing control valve #26  
Kennyd is correct that a pressure gauge would have located your problem, but you would have to have made several measurements.

Here is why (I think).

According to my handbook, using ISO 32 fluid at 104 deg F, 8.5gpm through 30' of 1/4" ID hose with three right angle fittings has a pressure loss of 1215 psi. Add in a quick disconnect and a couple more fittings and you might get to 1250 psi. At 50 or 60 deg , or with heavier fluid than ISO 32, the pressure loss would be much more.

And that is for the one-way trip of 30'. The return hose from the other cylinder will have the same loss, for a total loss of 2500 psi if there were no resistance in the cylinders. So when you shifted the spool completely, so that 8.5gpm was directed to the 1/4" lines, the pressure in the relief valve rose quickly to 1500psi and the relief valve opened to limit the pressure. Therefore, the flow through the pressure line, cylinders, and return line was limited to a rate that produced a total pressure loss of 1500 psi.

The pressure loss was great because the fluid was moving so fast through the lines that its flow became turbulent rather than laminar, and the losses increase greatly when the flow changes from laminar to turbulent.

But a guage at the valve would have shown 1500psi since it would be measuring before the fluid entered the hoses. If you moved the guage to the cylinder end of the hose and deadheaded the cylinder supply hose into the gauge, you would also measure 1500psi because with the hose deadheaded into the gauge, no fluid would be flowing and there would be no pressure loss between the relief valve and the gauge. I think you would have to tee the gauge into the cylinder port so that the fluid could flow. Then the gauge would read much less than 1500psi because fluid would be flowing through the hose and suffering the pressure losses.

Glad it turned out to be an easy problem to fix.

There you go bar, FarmerFord's facts from a book and my gut instinct...How could you go wrong:D
 

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