Pressure relief valve to ease quick couplings

[MossRoad]

The world of digital thermometers is sapping knowledge from our yungins

Ken

See my comments on "board swappers".

 

[SPYDERLK]

I have mentioned this many times before. You only need one QD fitting. a short hose, and a plug in the end of the hose.

When you remove the attachment from the PT, plug the adapter in to the matching QD. This will let any fluid that may expanded, seep into the adapter hose. This may cause only a few psi of air in the adapter. If the hot attachment ever cools down, it will suck in a little air. No biggie.

Could also use a needle valve on a tee before the QD to release pressure.

:thumbsup: Anybody listening?
... larry

 

[oldnslo]

Larry,
I agree JJ's idea is great. Only concern would be if you have multiple implements at different locations or worse yet multiple operators that go care about your equipment or the next guy. Then the possibility of using "connect under pressure" QD's would make more sense.

Roy

 

[PTWannaHave]

:thumbsup: Anybody listening?
... larry

My apologies to JJ, I somehow missed that simple solution when reading various forum threads. It would work great for the homeowner (where only 1-3 people use the machinery), provided that the adapter can indeed be connected with little force, to relieve the pressure. (I like this idea more than a 'pressure relief screw fitting'.)

I.e. my wife could use this home-made adapter that is kept on the tractor, relieve the pressure in the implement and/or tractor, and then make the QD connection between tractor and implement.

Heck, I would even ask Power-Trac to make me one and throw it in when taking delivery of a new machine...

Thanks for the feedback,

 

[jeffinsgf]

Well here's one less thing to worry about: sitting in the sun won't increase the pressure in your hydraulic system. Unlike gases, fluids don't expand or contract with temperature.

Oh, boy, do you need to go back to class. Everything expands and contracts with changes in temperature...liquids, solids and gasses. Why do bridges have expansion joints? Why does concrete crack? Why do ice cube trays overflow?

You're confusing expansion and contraction with compression. Gasses can be compressed. Liquids cannot. That's what makes a hydraulic cylinder work differently from an air compressor.

 

[MossRoad]

Oh, boy, do you need to go back to class. Everything expands and contracts with changes in temperature...liquids, solids and gasses. Why do bridges have expansion joints? Why does concrete crack? Why do ice cube trays overflow?

You're confusing expansion and contraction with compression. Gasses can be compressed. Liquids cannot. That's what makes a hydraulic cylinder work differently from an air compressor.

Liquids can be compressed.

 

[jeffinsgf]

Liquids can be compressed.

Liquids and solids can be compressed, but the pressure needed to affect a significant change is enormous. This is a quick quote from a wiki page:

The effect of pressure and temperature on the densities of liquids and solids is small. The compressibility for a typical liquid or solid is 10−6 bar−1 (1 bar=0.1 MPa) and a typical thermal expansivity is 10−5 K−1. This roughly translates into needing around ten thousand times atmospheric pressure to reduce the volume of a substance by one percent. (Although the pressures needed may be around a thousand times smaller for sandy soil and some clays.)

 

[oldnslo]

My apologies to JJ, I somehow missed that simple solution when reading various forum threads. It would work great for the homeowner (where only 1-3 people use the machinery), provided that the adapter can indeed be connected with little force, to relieve the pressure. (I like this idea more than a 'pressure relief screw fitting'.)

I.e. my wife could use this home-made adapter that is kept on the tractor, relieve the pressure in the implement and/or tractor, and then make the QD connection between tractor and implement.

Heck, I would even ask Power-Trac to make me one and throw it in when taking delivery of a new machine...

Thanks for the feedback,

PT,
for this to work you have to connect the length of hose when there is no pressure on the system. I.e. when you are removing an implement. If you don't the pressure will build do to heat and you will not be able to connect the hose the same as it won't connect to your tractor.

Does this make sense?

Roy

 

[MossRoad]

Liquids and solids can be compressed, but the pressure needed to affect a significant change is enormous.

I believe we discussed this much earlier in the thread.

 

[PTWannaHave]

PT,
for this to work you have to connect the length of hose when there is no pressure on the system. I.e. when you are removing an implement. If you don't the pressure will build do to heat and you will not be able to connect the hose the same as it won't connect to your tractor.

Does this make sense?

Roy

Ah, yes, thanks Roy! One 'dongle' per implement then, and perhaps an additional one on/for the tractor.

Cheers,

 

[BobRip]

I used to do that, too, and also use chiller spray to cool components. However, today's electronics are becoming less and less able to troubleshoot on a component level. We have become board swappers.

Yeah, used the cold spray to. With the IPAD, I suspect the whole computer is swapped out.

 

[SPYDERLK]

I have mentioned this many times before. You only need one QD fitting. a short hose, and a plug in the end of the hose.

When you remove the attachment from the PT, plug the adapter in to the matching QD. This will let any fluid that may expanded, seep into the adapter hose. This may cause only a few psi of air in the adapter. If the hot attachment ever cools down, it will suck in a little air. No biggie.
Could also use a needle valve on a tee before the QD to release pressure.

PT,
for this to work you have to connect the length of hose when there is no pressure on the system. I.e. when you are removing an implement. If you don't the pressure will build do to heat and you will not be able to connect the hose the same as it won't connect to your tractor.
Roy

Ah, yes, thanks Roy! One 'dongle' per implement then, and perhaps an additional one on/for the tractor.
Cheers,

:thumbsup: Right -- For this to work and continue doing so the user will need to fully realize and correctly sort and apply the principles brought out in the thread. Some maintenance will probably be required unless youre both smart and lucky. The dongle may become oil logged. Orienting it upward in use will help average out -- but youll probably still have use situations that tend to cause it incrementally. Detecting this and bleeding the dongle into a catch container will ensure its ready when you are.
larry

 

[Gravy]

I misunderstood JJ's solution until SPYDERLYK brought it back to my attention. It's an expansion tank. A nice thing about it is that it only requires the plug part of the coupler, which is a lot cheaper than the other half, and the hose can be pretty much anything that won't disintegrate from oil contact. It could even be a short piece of pipe and a cap. Might be able to make the whole thing up for $10.

 

[RoyJackson]

I have mentioned this many times before. You only need one QD fitting. a short hose, and a plug in the end of the hose.

When you remove the attachment from the PT, plug the adapter in to the matching QD. This will let any fluid that may expanded, seep into the adapter hose. This may cause only a few psi of air in the adapter. If the hot attachment ever cools down, it will suck in a little air. No biggie.

Could also use a needle valve on a tee before the QD to release pressure.

And this is an excellent idea!!

 

[toy]

I know some have used the hammer and flat ended punch method to relieve the pressure, and it has worked. I have used this method also successfully by using a large flat ended air chisel punch and hammer. I mentioned large as in respect to what you are working on because if you use something that could slide and damage the fitting plunger it may cause you to have to buy a new fitting and we don't want to spend money needlessly or at least I don't. I don't seem to have that much trouble hooking and unhooking, but my question is why not just get two wrenches that fit the hose fittings and just crack loose the hose just a little to let the pressure off and then tightening it back up. The machine is turned off so there isn't a pump running supplying pressure, there shouldn't be any pressure from a suspended load like would be if you cracked a hose on the loader arms with the arms raised and I would hope that nobody would do something like that. If there has been anybody that has loosened a hose under load hopefully they didn't get hurt, maybe just sprayed with oil, but if there has been anybody that has done that I bet it left a lesson of lasting impression on them. If any one doesn't understand what I am talking about or don't feel comfortable doing it this way then don't.

 

[J_J]

It is not a good idea to keep loosening NPT type fittings once sealed. If you use the QD plug and capped tube, the pressure will never build up on a hyd motor circuit. On a QD attachment with cylinder, the weight of the metal can produce pressure on the cyl and therefore the QD. In that case, you might need a QD adapter for the male and female QD. As we get older, our hands do not have the strength for certain things, and we need all the help we can get.

 

[jbooth]

And Now here is the solution you have all been waiting for!!! I have used it all my life.

Just buy old machinery. It will leak and not build up pressure.

 

[toy]

It is not a good idea to keep loosening NPT type fittings once sealed. If you use the QD plug and capped tube, the pressure will never build up on a hyd motor circuit. On a QD attachment with cylinder, the weight of the metal can produce pressure on the cyl and therefore the QD. In that case, you might need a QD adapter for the male and female QD. As we get older, our hands do not have the strength for certain things, and we need all the help we can get.

I have not had my hoses off on that particular fitting, but are you sure that the hose ends have male pipe threads or are they hose ends with a male and a female taper inside of them? If they have hose ends I have never had a problem with taking them apart and reconnecting them and in this case you are only going to crack it a little to let a drop or two of oil out. On everything that I have had to work on so far has had hose ends and the fittings had a mating hose end on one end and on the other had a pipe end on the fitting [swivel lock with o'ring], I have cracked that fitting before and got the feel that it was a hose end, but never took it all the way off to see for sure. I wasn't talking about cracking it on the quick coupling itself but the hose end. I'll have to give it a look see next time I'm around it. The attachments that I have with mine and the way I handle them wouldn't leave pressure from holding part of the attachment up, but on say a grapple bucket if you left the grapple open then I could see where it would have pressure with the grapple arms leaking down when you cracked the hose, but like I said if you don't feel comfortable doing it this way or don't know what to look for that might cause a problem then don't do it the way I said, but it is easy for me don't have to do it that often.

 

[toy]

And Now here is the solution you have all been waiting for!!! I have used it all my life.

Just buy old machinery. It will leak and not build up pressure.

Hey that will work.

 

[J_J]

toy,

I believe just about all the QD's hose end have a NPTF thread. The other hose end could have a number of different fitting with tapered or straight threads.