What a relief! Not really...

[Jay4200]

I've posted a bunch of times regarding my squealing valve on my snowblower rig. The 2-spool DA valve appeared to go to relief just about every time I pulled a lever, almost regardless of load. I never did find resolution - the chute controls did function, so I've just been living with the noise. Odd that the 3pt didn't trigger the relief valve - still don't understand that part.

Anyway, as I was just about finishing up using the blower Saturday, I realized that the chute controls weren't squealing. How cool - it fixed itself, I thought. Then I dropped my tractor to idle, and quickly found that my 3pt hitch wasn't working. It worked OK when I revved the tractor up though. Then I heard the hissing coming from the 'blower valve. So, it now appears that the relief valve is stuck/broken open and bypassing to tank, such that there remains insufficient pressure to operate the 3pt hitch (next function downstream) while at idle. The relief remains in bypass regardless of valve position, but (at least when I stopped working) allows enough pressure to build downstream for 3pt operation with the tractor revved up.

So, it looks now like the valve was probably defective all along - but now what to do? What do you think? Is there anything to be gained by taking the relief valve out and taking it apart? Can I get a replacement relief valve, or do I need to change out the entire valve assy.? I'm at a bit of a loss. Are the reliefs simply springed plungers, or shim-valved like motorcycle suspension?

Figures - this was my first hydraulic system project. While everything should've worked, with zero experience, as simple as the system is, there is still always that thought that I did something fundamentally wrong. Defective part - infuriating. My industry 100% tests components, billions of them per year - I just don't get defective parts.

JayC

 

[kjung17]

Jay,
As long as there are no warranty issues, I would disassemble the valve and take a look. It may be easily repaired. Debris or a small burr?

 

[oldnslo]

What it ever set for the proper pressure? To get jammed open far enough tha tit will build little or no pressure now would suggest it may have never been set to the correct pressure. Take it apart and then reste using a gauge. Should be a simple spring and ball or poppet design.

Roy

 

[J_J]

If you install a 3000 lb hyd gage in the system, you can readily see the results of your snow plow operation, and 3pt operation. If it is not set correctly, then do so . Remove it and check, repair or replace. It could have shims or spring. Might have parts missing.

It does not take a lot of force to move the plow, or chute.

Is there any difference in the sound if you max out the lever on the valve?

 

[Jay4200]

What it ever set for the proper pressure?

No, it was not - at least not by me. It is SUPPOSED to be factory set to 2000PSI (according to the literature), which implies a live test, which they obviously didn't do. Sauer-Danfoss 1627 valve, BTW.

I called the shop where I got the valve, and they seemed willing to give me another relief valve, BUT I need the specific part number on the valve, since the valve series evidently supports two different reliefs. Naturally, my tractor is at my camp, and I only go there on weekends...blah. Hope it doesn't snow this week. Of course, I find when someone offers a deal over the phone, when I show up and mention the call, they always seem to get short-term memory loss - can't imagine the confusion I am going to create when I waltz in a week from now...

I'm hoping that I will be able to simply unscrew the old relief and screw in a new one and *poof* all of my previous and current problems will magically be gone.

Assuming I remember, I'd also like to pick up a 3000# gauge and stick in on the valve while I'm at it.

JayC

 

[Jay4200]

Well - the plot thickens...but I think I figured everything out.

I contacted the hydro shop on Friday and explained my relief-valve problems. Talked to a different guy this time - he is sending me a new relief valve.

Turns out I have a 'direct-acting' relief, vs. a 'pilot-operated' relief. The difference being that the direct-acting valve comes in pieces and is built into the valve body, vs. the pilot doo-dad that is a self-contained cartridge that screws in all at once. Fine.

Props to the guys level of service as TST Hydraulics in Merrimack, incidentally - they have always been exceedingly helpful on the phone, and this time the guy at the shop even offered to bring the relief-valve pieces to my house on Saturday (he was going to be in the area for something else). I declined the offer...

At any rate, after I got off the phone, I did a little research on the direct vs. pilot thing. Direct acting is basically a big spring that holds off the pressure, and has a relatively large region between crack pressure and full-blast relief. The pilot-operated uses some kind of more complex setup that basically blows wide open at crack pressure. The pilot-operated is better for a blow-off relief like us tractor guys use.

I then looked into the specific valve literature and found out that the direct-acting valve is factory set to 1200PSI, and the pilot-operated valve is set to 2000PSI. AHA!! That helps explain some of the problems.

So, bottom line is they gave me the wrong valve in the first place - I should've gotten a valve setup with the pilot-operated relief since I requested a 2000PSI system valve. Learn something new every day - mental note: request pilot-operated relief valves from now on...

I was able to get my hydraulic system working correctly (or at least looked correct) this past weekend by increasing the relief setting. I decided I wanted it up as high as it could go, so I ended up cranking it in until I hit a stop (full in - completely closed maybe?), then backed it off 1/4 turn just in case full in was closed. With the adjuster cranked in, the controls all worked, nothing made nasty noises, and my 3pt hitch went up while at idle.

So, now that the system is working, I don't know if I should go to the trouble of replacing the valve (I'm reasonably sure the hydro shop would swap out mine with the pilot-relieved valve), or if I should leave well-enough alone. I'd bet that the relief is still operating below 2000PSI (adjustment ranges on direct-acting valves are small) - even if it is completely disabled, the remote system is still protected by the loader relief (which is upstream). OTOH, it would be nice for my first hydraulic project to contain all of the correct components. Any comments or suggestions?

Thanks - JayC

 

[J_J]

Here is one.

Where is you snow blower valve in relation to the other valves? If you want full pressure to the 3pt, then the snow blower valve should be equal or higher than the PRV. If you reduce the pressure for the snow blower, the 3pt will see the same pressure relief. What will happen is this. The FEL valve PRV being first will set the highest pressure for the circuit. , and then the fluid will go to the snow blower valve, and be relieved at a lower pressure, and then the 3pt will see snow blower relief pressure if the load is sufficient.

Therefore, is you crank it down, the snow blower relief will be non functional, and the 3pt will have all the available potential to build up max circuit pressure.

 

[Jay4200]

Here is one.

Where is you snow blower valve in relation to the other valves? If you want full pressure to the 3pt, then the snow blower valve should be equal or higher than the PRV. If you reduce the pressure for the snow blower, the 3pt will see the same pressure relief. What will happen is this. The FEL valve PRV being first will set the highest pressure for the circuit. , and then the fluid will go to the snow blower valve, and be relieved at a lower pressure, and then the 3pt will see snow blower relief pressure if the load is sufficient.

Therefore, is you crank it down, the snow blower relief will be non functional, and the 3pt will have all the available potential to build up max circuit pressure.

The blower valves are between the loader and the 3pt hitch.

As luck would have it, I don't need full pressure on my 3pt. My blower weighs 650-700 pounds or so, which is child's play for my 3pt hitch, which can lift over 3000 pounds at full pressure.

The only functional problem that I had when the remote relief valve malfunctioned and stuck open is that the 3pt wouldn't raise while I was at idle. I could still operate it with the tractor revved up, however. With the relief cranked in, even though I'm sure the crack pressure is still well lower than the desired 2000PSI, everything operates just fine - both functions on the chute move w/o noise or issues, and I can raise the blower on the 3pt w/o issues and at any RPM. Hence my dilemma - leave well enough alone, or go through the effort of swapping valves just so it would be "correct". I also don't know if there are any potential issues with running the direct-acting relief cranked almost all the way (or all the way) in - I don't think there would be, primarily because the remotes are protected by the loader relief, but I don't have any previous experience with these kinds of systems.

JayC