Options for dealing with pressure build up in disconnected hydraulic lines

[namesray]

well, last winter i was using my snow plow up to the time i disconnected it and hooked up the blower. a few hours later i went to re-hook up the plow and the lines wouldn't engage without using a piece of wood to relieve the pressure. this does get old. In the summer i generally leave the implement or the loader under a shaded area so there isn't as much of a problem..... yet sometimes there is. Its never as cut and dry for me.

did you shut the engine off and then move all hydraulic lever functions before you disconnect to make sure there was no cylinders under pressure that could gravity bleed off over time because that can add pressure to lines no matter what the temperature gets. EXAMPLE: i could leave my loader bucket pushing down slightly lifting the loader and disconnect the couplers to unhook my loader. the couplers would probably come apart easy but as gravity takes ahold, the bucket cylinders will drift down until gravity bleed off can no longer occur. this can build pressure and give me a hard time when i would go to recouple. wouldn't matter then if hydraulic fluid was cold, hot, went from cold to hot. the bleed off would then be the problem causing pressure, not temps. you have to prepare for both is all i am saying or it will all be for nothing.

i am not against the bleed off valves ideas, i have even thought about it for myself as much as i use the qd's. however when i was told the idea of heating up the fluid right before you disconnect, i thought it would save me some time modifying things and some money. the idea i mention is more for the common "joe" to use to help out i guess. this idea has worked so far everytime for me.

 

[grsthegreat]

did you shut the engine off and then move all hydraulic lever functions before you disconnect to make sure there was no cylinders under pressure that could gravity bleed off over time because that can add pressure to lines no matter what the temperature gets. EXAMPLE: i could leave my loader bucket pushing down slightly lifting the loader and disconnect the couplers to unhook my loader. the couplers would probably come apart easy but as gravity takes ahold, the bucket cylinders will drift down until gravity bleed off can no longer occur. this can build pressure and give me a hard time when i would go to recouple. wouldn't matter then if hydraulic fluid was cold, hot, went from cold to hot. the bleed off would then be the problem causing pressure, not temps. you have to prepare for both is all i am saying or it will all be for nothing.

i am not against the bleed off valves ideas, i have even thought about it for myself as much as i use the qd's. however when i was told the idea of heating up the fluid right before you disconnect, i thought it would save me some time modifying things and some money. the idea i mention is more for the common "joe" to use to help out i guess. this idea has worked so far everytime for me.

yup, all shut down and i relieved all pressure. didnt help me.

 

[SPYDERLK]

i guess i am not understanding you guys. call me crazy, but seems o me everyone is over engineering this thing. the op stated having problems with heat expansion in uncoupled hydraulic lines and reconnecting was hard due to the expansion putting more pressure on the qc's then what is easily pushed together by hand force. you all lean towards buying valves and time consuming modifications. if you just work the function of the hoses repeatitly you are going to dissconnect right before you dissconnect them, you HEAT up the fluid. that hot fluid is already expanded when you dissconnect. cools off then super easy to reconnect later. even if the outside temps warm up, there is room for the expansion and still easy to reconnect. this has worked for me 100% of the time since i started doing it lately. i see jj reason of drawing in air=can be purged through normal operation or an easy procedure. as for water getting in, just don't let the couplers near water or expose it to it. wrap a plastic bag around it. i am not saying the valve ideas are silly to releave pressure, just seems like it would be easier to work the fluid until warm, and then shut the engine/pump off, move valve in all directions to releave all pressure or potential gravity leak down that can lead to pressure build up and then dissconnect. doesn't cost anything either. just my 2 cents.

... or see post#9

 

[CurlyDave]

I was always able to deal with pressure build up in disconnected hydraulic lines due to warmer temperatures when reconnecting. But it was different last week when I reconnected the loader lines. The curl lines went on fairly easily. But there was no way I could release pressure on the arm lines. I finally resolved it by using a plastic dead blow hammer which gave me a hydraulic oil shower. Now I know next time to cover it with a rag! But I was surprised at how much pressure was built up and the amount of oil released.

I'm thinking one way around this would be to place a female quick connector on one hose of each disconnected pair to prevent pressure build up, and wrap a rag around the ends to catch the oil and keep out dirt.

Is this a good idea or are there other suggestions?

I use a very similar technique. I put a coupler on both hoses and instead of a rag, I loosely thread a plastic pipe plug into the end of the dummy coupler. This is much better at keeping dirt out than a rag.

 

[Gary Fowler]

I would advocate that if you are going to buy female couplings to put on the disconnected hose end, just buy the connect under pressure QD couplings and install them on your tractor. I havent priced them but would bet that they are not more than a few bucks more than a standard female coupling but that would solve your problem forever.

 

[banjodunn]

I would advocate that if you are going to buy female couplings to put on the disconnected hose end, just buy the connect under pressure QD couplings and install them on your tractor. I havent priced them but would bet that they are not more than a few bucks more than a standard female coupling but that would solve your problem forever.

G'day just had a quick look at one of our suppliers and it is around $39au for standard d/a coupler and $69au for the same thing but connect under pressure. This is prob the reason we don't stock the connect under press ones as we would have a hard time selling them


Jon

 

[CJONE]

yup, all shut down and i relieved all pressure. didnt help me.

It won't, the only wat to avoid that in a sealed system is to have some type of space for the expanding fluid to go. That is what the air in the lines does. it does not take alot, just about a teaspoon full out of the lines does it. That is why everbody is saying to push the poppet in on one of the couplers for a few seconds then hook the lines together. With the air space the pressure will not build up too much that you cannot hook up the lines. That is basically what a jumper line does is introduce air. CJ

 

[Scooby074]

Seems there is a bunch of overthinking here.

A screwdriver does the job fine for relieving any built up pressure. Takes but a few seconds.

 

[J_J]

The most simple thing one can do to relieve the pressure, is to push the ball or poppet in on a male QD with a rag over the QD.

 

[SPYDERLK]

The most simple thing one can do to relieve the pressure, is to push the ball or poppet in on a male QD with a rag over the QD.

Preventing the possibility of significant pressure build up is actually the most simple and least wasteful. Bleed a teaspoon or so from each line immediately after disconnect into a catch container or onto anyplace needing lubrication. No tool needed. Dont even need to then plug the lines together.
larry