The Hydraulic Fight is Over - Hydraulic Coupling Pressure Relief Tool

[WinterDeere]

I don't think they'd have enough force to smack apart and whack me in the head.

This is correct. There is nearly zero stored energy in an incompressible fluid, like hydraulic fluid. You can build 1000 PSI or more, and still have very little stored energy.

It's compressible fluids, such as air, that store a lot of energy when compressed to high PSI. A 100 PSI air line rupture is far more exciting than a 3000 psi hydraulic line rupture, for this very reason. The larger the volume of compressed fluid, the more stored energy, and the more exciting the release. Think of those stories of failed air compressor reservoirs launching through shop walls, exploding tires, etc.

I know that the fluid within the implement and lines would still expand, even when lines form a closed loop, but for me, it has never prevented me from snapping them on the tractor fittings. I think the expanding fluid may be moving the hydraulic cylinder piston enough to not be overwhelming when connecting.

Yes, if you have a cylinder that can move to change the system volume, such as a hydraulic top link, this will usually prevent hydraulic lock-up. The two places where I need to use this tool are both cases where there is no cylinder or motor that can relieve the pressure:

1. There is a set of long (16 feet?) lines that run from the rear of my tractor to the wrist on the loader. These are made to carry the 3rd channel hydraulics, which are hard-plumbed to behind the seat, out to the end of the loader, for use with a grapple, plow, anything where you need 3rd function on the end of the loader. The lines both have male on the inlet end, and are dead-ended in smaller m/f fittings out on the end of the loader. If the temperature rises a good bit since the time I last used them, it will be nearly impossible to plug them back into the tractor for their next use, without using either this tool or the trick of slamming the male fitting nipple against something to relieve the pressure.

2. My snow plow has opposing cylinders, with a set of lines that terminate male/female. I keep them plugged together, which helps to some degree, but still doesn't always prevent lock-up if the temperature rises 80F from last use.

 

[Midniteoyl]

Not sure if that was directed at me, as you quoted my post and then asked if I read my own post. I've found that connecting the lines to each other helps reduce, but not entirely eliminate, this type of hydraulic lock-up. Moreover, some of my equipment has M/M for plugging into my factory rear 3rd channel (which is F/F on tractor), so I'd need to make up a F/F coupling for each one for storage.

This pressure relief tool is cheaper, easier, and more quickly at-hand than all of that. I keep it hanging from a nail on the door jamb of my shed, where I keep all of my equipment. If you don't ever need one, consider yourself lucky, but it's very handy for those of us who do.

Agreed.. I do the 'joystick wiggle' and connect both ends together as well, and it doesn't always work. Like this year when I had to loosen a connector on my grapple to relieve enough pressure to connect it up even after having both ends connected all winter.

 

[dstig1]

I do all the tricks and still can never get my grapple connected easily. I modified a clamp to be like the one shown before I had heard that such a thing existed (missed THAT market opportunity!) and I have to use the clamp to apply pressure and still do a couple more rounds of jiggling the valves to get the flat faced connectors together.

 

[Shenandoah MF1760]

There is nearly zero stored energy in an incompressible fluid, like hydraulic fluid. You can build 1000 PSI or more, and still have very little stored energy.

I agree. The stored energy is not coming from the hydraulic oil it's coming from the stress built up on the lines as the heat causes the fluid to expand.

 

[WinterDeere]

I agree. The stored energy is not coming from the hydraulic oil it's coming from the stress built up on the lines as the heat causes the fluid to expand.

It comes from change in volume. When the pressure is released by a hose failure, the fluid will immediately expand back to its volume at atmospheric pressure. With oil, this change in volume is extremely small, but with air it can be many times its compressed volume.

 

[Will S]

Unless your connectors are the kind that connect and disconnect under pressure, the pressure build up as the implement warm will lock the two connectors together.

Never happens, Pressure cannot build up, as the piston in the grapple cylinder would move as fluid expands, and never be high enough to matter.

 

[WinterDeere]

Never happens, Pressure cannot build up, as the piston in the grapple cylinder would move as fluid expands, and never be high enough to matter.

For a grapple, sure. Other than the weight of the thumb itself, there's nothing causing pressure.

But you're ignoring other cases, such as dead-ended lines, or snowplows with opposing cylinders for tilt.

 

[MossRoad]

For a grapple, sure. Other than the weight of the thumb itself, there's nothing causing pressure.

But you're ignoring other cases, such as dead-ended lines, or snowplows with opposing cylinders for tilt.

Are those single acting cylinders on the plow? One extending forces the other back? I think that's what I recall on my old truck snow plow.

The snow plow on my machine only has one double acting cylinder. So maybe that's why I haver no issues.

 

[WinterDeere]

Are those single acting cylinders on the plow? One extending forces the other back? I think that's what I recall on my old truck snow plow.

You know, I didn't plumb that one up myself, it came pre-assembled from dealership. It's still new enough that it hasn't needed any hydraulics repairs yet, so I've honestly never taken notice. I'm going to have to check next time I'm out in the shed where it's stored, and report back here.

 

[bnold]

My flat faced couplers are PITA for my grapple, connecting together hasn’t offered any help.

Same can be said for reconnecting loader, it isn’t the tractor side, it is the 150*F implement side that has increased pressure due to heating.