Quck-Connect vs. Residual Pressure

[DaveK OR]

OK, I'm guessing there is an easy answer to this, but I haven't figured it out for myself. I'm connecting my backhoe hydraulics to the tractor through quick-connect fittings. Residual pressure in the system is preventing the poppets in the quick-connects from opening as I press the fittings together, and it keeps them from seating properly. I can manage the tractor-side fittings, simply by flipping the control valve to make the port a "return" line. The backhoe side doesn't have any similar capability that I've found, and I need to relieve pressure on both sides of the connection.

Any suggestions, other than a modified c-clamp to force the poppet to release, resulting in a squirt of hydraulic oil when it opens? Trying to do it force the connections together by hand is really difficult, unless there's a simple trick I don't know.

 

[Dave M7040]

My experience has to do with what you do before you start trying to connect. In fact when you disconnect.

Further, my experience is with FEL's not backhoes.

I find if I shut the machine down, and then move the control levers back and forth several times, the amount of residual pressure when I come to reconnect is minimal.
I look forward to seeing other members advice to you.

Dav e M7040

 

[davrow]

On my Kioti (basically same) I have a rear valve control. I always assumed toggling it with tractor off was same as moving joystick for the FEL... relieves pressure on all lines.

Do you not have the valve control, or does it not work as I have described?

 

[DaveK OR]

Cycling the rear control valve works fine to relieve the tractor-side pressure. I'll try cycling it with the backhoe connected (and engine off) to see if that gets rid of the problem. I thought I'd done that before I disconnected the hoe, but I may be mistaken about that. The other problem might be gravity working on one or more cylinders while the hoe is in its storage position.

If I do need to force the poppet open to relieve pressure, is the modified c-clamp the best way to do it?

 

[Tractor Seabee]

When you disconnect hook the P and T hoses together (mine are set up with matching QCs). Cycle the valves before hooking up and that equalizes the pressure through the BH system. I assume you tractor is shut off when doing all this.

Ron

 

[Dave M7040]

Cycling the rear control valve works fine to relieve the tractor-side pressure. I'll try cycling it with the backhoe connected (and engine off) to see if that gets rid of the problem. I thought I'd done that before I disconnected the hoe, but I may be mistaken about that. The other problem might be gravity working on one or more cylinders while the hoe is in its storage position.

If I do need to force the poppet open to relieve pressure, is the modified c-clamp the best way to do it?

DaveK
I had a brass hammer and a brass punch about 1/2" flat face. In my quick connects, the male had a ball at the end which was completely exposed. I would wack it with the hammer, and a tiny amount of fluid would come out, but that was all it took. On the female quick connects, the ball was deep inside and i would use the brass punch with the flat face. Brass, because it is soft compared to any steel and wont damage the ball.

The mount of fluid to drop the pressure, since the fluid is incomprehensible, is very small.

Others may have a better way but this one worked for me.

Dave M7040

 

[DaveK OR]

My connectors are a little different (a little truncated cone instead of a ball), but the principle is the same that it seats under pressure to prevent leakage. My only brass hammer is probably too small, but I do have an old copper bus bar I could use on the male-side poppet, I suppose. I've used it as a drift before when I didn't want to mar a steel part, so it ought to work to whack the poppet without damaging it. I'd do the hose connection thing, but I'd need a female-female quick connect adapter to do it. Tractor side has both female, backhoe side both male.

 

[Dave M7040]

My connectors are a little different (a little truncated cone instead of a ball), but the principle is the same that it seats under pressure to prevent leakage. My only brass hammer is probably too small, but I do have an old copper bus bar I could use on the male-side poppet, I suppose. I've used it as a drift before when I didn't want to mar a steel part, so it ought to work to whack the poppet without damaging it. I'd do the hose connection thing, but I'd need a female-female quick connect adapter to do it. Tractor side has both female, backhoe side both male.

I removed the hose connection option but you read it too soon.

I think upon reflection it would make things worse.

The volume of oil on one side of the cylinder is less than the other. The volume of the push rod is the reason.

You can inadvertently created a hydraulic amplifier because one side of the cylinder piston has more area than the other. It was a bad idea.

Dave M7040

 

[rfc143]

Here's two additional possibilities:
1. if the equipment is not at it's zero energy state...that is, the bucket is not hanging, continuing to push oil against the disconnect even after bleeding, bleeding will not help.
2. I had one Female QC that would not go all the way home no matter how hard I pushed...built a clamping tool and everything. I discovered one of the teflon O rings had gotten pinched way down inside, preventing the shell from sliding, completing the connection. Replaced the QC and all was good.

 

[ovrszd]

I believe you have to find the cause for pressure? For example, is the hoe sitting on the stabilizers and the bucket?? If so, you have pressure on 3 circuits.

Doesn't sound like heat is the issue but I guess it could be?? Uncoupled during cold weather. Recoupling during warm weather.

 

[DaveK OR]

I believe you have to find the cause for pressure? For example, is the hoe sitting on the stabilizers and the bucket??

You may well be right about that being the source of the problem. In storage, the hoe rests on the bucket and two points of its frame, so it would most likely be the dipper cylinder. I use the thumb to constrain the bucket, so its cylinder shouldn't be an issue. The boom has a locking pin, so it is also restrained, and that leaves the dipper cylinder. I can temporarily address the dipper cylinder issue by positioning it for storage so the forces don't transfer to the cylinder. The problem is that I want a minimum footprint for storage, so I'll need to find a way to restrain the dipper to minimize forces on the cylinder. There's no weight on the stabilizers, but restraining them in the storage position will help a little.

I need to think on that for a bit, since it will affect how I configure a rolling base for the hoe when it's in storage.

 

[Luke'sScreenName]

If the pressure is just from temperature expansion and the hoe-side connector is male this is a simple solution:
Pioneer 1/2 in. Connect Under Pressure Tip, 1/2 in. NPTF - For Life Out Here

If the pressure is from unsupported weight acting on the cylinders then you either need to support the weight or install shut-off valves:
Pioneer 1/2 in. Connect Under Pressure Kit, Upgrade Your Tractor - For Life Out Here

:2cents:

 

[ovrszd]

Good idea Luke.

Quality shutoff valves in the main hoe to tractor hoses would allow the hoe to be parked with pressure on any of the cylinders and not cause reconnection problems.

 

[Luke'sScreenName]

Just to clarify, I doubt the shut-offs I linked are the appropriate ones but just a handy example. TSC won't have what he needs IMO.

 

[ericm979]

Pioneer makes connect under pressure female ISO 5675-A connectors, and TSC sells them: Pioneer 1/2 in. Connect Under Pressure Two Way Sleeve ISO Interchange - For Life Out Here

Might be able to get them cheaper elsewhere like 82 Series Quick Disconnect Couplings (Pioneer) - Hoses & Fittings - Mid-States Equipment

Info: 1/2” Connect Under Pressure Quick Couplings, Breakaway Sleeve, Push Connect, Pioneer ISO 5675, 3 psi - 82 Series Couplers | Parker NA

(sorry to nerd out on this but I was researching it earlier and still had the tabs up)

I may be missing something but I don't see how the shutoff valves would help. If you close them when there's residual pressure, wouldn't there still be pressure between the shutoff and the coupler? You'd have to close them after relieving pressure. At that point there's no need for them. With the typical ag coupler setup of females on the tractor (where you can relieve pressure) its the male side where the connect under pressure couplers would be the most use.

 

[ovrszd]

(sorry to nerd out on this but I was researching it earlier and still had the tabs up)

I may be missing something but I don't see how the shutoff valves would help. If you close them when there's residual pressure, wouldn't there still be pressure between the shutoff and the coupler? You'd have to close them after relieving pressure. At that point there's no need for them. With the typical ag coupler setup of females on the tractor (where you can relieve pressure) its the male side where the connect under pressure couplers would be the most use.

No problem on the "Nerding".

So you are preparing to disconnect the hoe.

Shut the valves.

Relieve the tractor side pressure by wiggling the controller sticks.

Disconnect.

No residual pressure is built up against the quick couplers because the shut off valves are preventing that.

Later come back to reconnect the hoe.

No pressure to deal with because the valves have contained it.

Clear as mud right??

 

[Luke'sScreenName]

You close the valve BEFORE disconnecting or combine with connect-under-pressure QDs.

You need the shut-off if the pressure is from unsupported weight because you're unlikely to relieve enough fluid to connect (with just CUP QDs).

Edit: Richard beat me to it.

 

[Luke'sScreenName]

And nerding out on hydraulic problems is good for both mind and spirit! :thumbsup:

 

[ovrszd]

)

Edit: Richard beat me to it.

Great minds think alike!!!!

 

[Luke'sScreenName]

Great minds think alike!!!!

Then I must have been thinking something else! :drink: