Relief valve or packing?

James Sorochan · Jun 6, 2022

Hi everyone. When I’m digging my bucket relieves noticeably. I raised the attachment up overnight and this morning the bucket cylinder dropped around 8” of stroke. Is that to much? If so I guess we need to re-seal then? I will go over relief and check to see if she heats up. How long should it take? Thanks

uffex · Jun 6, 2022

Good day James
Bucket cylinders normally have a much higher creep rate than that of arm & boom, as there are no additional valves other than the spool to prevent creep. To advise you precisely, we would need to know the make and model you are operating. Tall buckets and quick couplers make the cylinder more prone to lifting the relief valves.
Kind regards
Uffex

fastline · Jun 6, 2022

Bucket should be the strongest component. But for a cylinder to bypass bad enough to act like it is on relief, I would think the bucket would damn near fall instantly. Put some load on the bucket such as a full load of dirt, curl all the way and see what it does.

As for heating, 20-30sec on relief should cause something to warm up noticeably.

pumkinhead · Jun 6, 2022

if you can cap the lines on cylinder with the bucket on the ground and then raise it and see if it drifts will help eliminate the cylinder as cause

fastline · Jun 6, 2022

pumkinhead said:
if you can cap the lines on cylinder with the bucket on the ground and then raise it and see if it drifts will help eliminate the cylinder as cause

Not really. There is a volumetric lock that occurs in a cylinder that is truly capped. However, if piston seals fail, forces are no longer acting on on the piston, they are acting on the rod, which increases line pressures significantly, and can easily push to relief.

Another method would be to install pressure gauges on both sides of the cylinder circuit.

heymccall · Jun 6, 2022

Since the carry (curl) relief is suspect, put the bucket nearly open (dump), and with the teeth on the ground, raise the machine. Does it drift the cylinder the other way?

James Sorochan · Jun 6, 2022

Scooped up a bucket of died and curled up. Dropped about 10” in 1 or 2 seconds then continues creeping but only say 1” a minute.

James Sorochan · Jun 6, 2022

Ok heymccal. Got it in position. I took a measurement and will check it in a say 1 hour. Thanks

Bluox · Jun 6, 2022

This is a surefire way to check a cylinder,
Set the boom down with the bucket like your picture,
Take the hose off that goes to the bucket end of the cylinder and cap it,
start the machine and on idle close the bucket,
a lot of oil coming out of cylinder and it not holding means a trip to the hyd shop.
Bob

James Sorochan · Jun 6, 2022

Thanks Bob. I'll try it right after lunch and report back. The bucket stretched out in dump position dropped 1/8' of stroke in 1 hour.

fastline · Jun 6, 2022

James Sorochan said:
Scooped up a bucket of died and curled up. Dropped about 10” in 1 or 2 seconds then continues creeping but only say 1” a minute.

Sounds like piston seals so far. Personally I would dig a bit and check for cylinder heating. If you have that, that is two failed tests, which is usually enough for me to confirm.

Look at what I mentioned above about pressures. This is where you can be fooled. With bucket curled, and a normally functioning piston, we might say you have 3000lb pushing on that piston, say the cylinder is 4" ID, that is 238psi line pressure. Now remove the piston seals from the equation and all forces effectively push on the rod alone. Say that rod is 2", that is now 954psi line pressure. You can see how you can get to a line pressure that WILL open a relief.

James Sorochan · Jun 6, 2022

Just a thought. The hydraulic quick release is tied into the bucket circuit. Can this come into play here?

uffex · Jun 6, 2022

Good day
Normal standards are to time creep over a five-minute period from the measurements do not seem so bad.
Kind regards
Uffex

James Sorochan · Jun 6, 2022

Turned the compost pile for 10 - 15 minutes. Upper part of cylinder is hot to the touch. Lower part just warm. I’ll see what I got for capping off bucket hose as Bob suggested to see for sure.

James Sorochan · Jun 6, 2022

Started the machine and curled bucket at idle with line to bottom of cylinder capped off and orifice of cylinder plugged with plastic plug. Bucket was moving and I couldn’t see any oil spraying out. I jumped off machine and pulled plastic plug and got a steady stream of oil. I then shut it down and put the plug back in. What’s everyone verdict?

Bluox · Jun 6, 2022

James Sorochan said:
Started the machine and curled bucket at idle with line to bottom of cylinder capped off and orifice of cylinder plugged with plastic plug. Bucket was moving and I couldn’t see any oil spraying out. I jumped off machine and pulled plastic plug and got a steady stream of oil. I then shut it down and put the plug back in. What’s everyone verdict?

The bucket teeth have to be on the ground so the cylinder has something to push against for this test to work.
Bob

fastline · Jun 6, 2022

If you are going to continue on this path, just curl the bucket all the way, smack the relief and watch her spray!

James Sorochan · Jun 6, 2022

The bucket was on the ground with arm extended. By the way it’s a 2008 Doosan Solar 340LCV. Serial no. DKHELW50001703. I stuck a clear hose in the orifice and put it in bucket and tried curling again. The flow seemed to increase a bit but I’m not sure. Might have to wait to see if the barrel actually empties out up to the gland. If it does I could start it and try again? Thanks for the help so far.

James Sorochan · Jun 6, 2022

OK fastline. I was trying to not make to big of mess in front of shop but at least we’ll know for sure. Thanks

Bluox · Jun 6, 2022

James Sorochan said:
The bucket was on the ground with arm extended. By the way it’s a 2008 Doosan Solar 340LCV. Serial no. DKHELW50001703. I stuck a clear hose in the orifice and put it in bucket and tried curling again. The flow seemed to increase a bit but I’m not sure. Might have to wait to see if the barrel actually empties out up to the gland. If it does I could start it and try again? Thanks for the help so far.

Yes let the cylinder empty out then start the test.
Bob

Relief valve or packing?

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