PDA

View Full Version : Do you wrap the tev before brazing ?







kengineering
11-03-2006, 03:56 AM
The instructions that come with expansion valves tell you to wrap the valve with a wet rag before brazing. It seems to me the smaller valves braze up so quick the wrap isn't nessary until you finish the joint. I keep the tip away from the power head and cap tube, angle the direction of the flame away from the body of the valve, then apply lots of water to cool it when done. When I wrap the valve as the instructions state it takes much longer to heat and get the job done. It sometimes needs to be done again because the wrap is sucking up the heat and the braze didn't flow well leaving a void.

What do you guys do?

Ken

Dan
11-03-2006, 04:38 AM
I see your point, Ken, knowing that you are working with small valves. Sporlan offers extended tube valves to simplify operational problems resulting from overheating.

If you get in and get out quickly, your risk to the powerhead and body are lessened. But it is not an "all" or "nothing" proposition. I recommend that you try a less damp rag, or a top or bottom wrap, or just common sense.... meaning that if you watch how you are heating things, you should have a pretty good feel how to not heat the things that could be damaged. I wish Professor Sporlan were still around, because I think that the brass body warping is what causes push rods to not function well, and that overheating the brass body is the culprit.

US Iceman
11-03-2006, 04:38 AM
I would wrap the wet rag around the valve body. Use a large enough torch tip (oxygen/acetylene)to heat the sockets quickly, fill the joint, and cool the valve off as quickly as possible.

The longer it takes to heat up the sockets, the more potential you have for overheating the inside of the valve.


It sometimes needs to be done again because the wrap is sucking up the heat and the braze didn't flow well

That is a good indication that the torch tip is too small. The insufficient heat source is not providing a uniform heating of the sockets and the brazing material is cooling off before a complete joint is made.

What type of torch are you using Ken?

adam
12-03-2006, 03:31 AM
we usually use sporlan tev's, so i take them apart so there's no need to wrap. you have to be careful not to lose the bits though :D

kengineering
12-03-2006, 03:43 AM
I use a "Turbo Torch" acetylene with a #11 or 14 tip.

we usually use sporlan tev's, so i take them apart so there's no need to wrap. you have to be careful not to lose the bits though
If Dan is correct , that the brass body warps affecting the push rod operation, I'm not sure dismantling the valve would be helpful.
Ken

dogma
12-03-2006, 08:59 AM
We use danfoss TXV with stainless/copper conections. There is no need to wrap nor take apart. But you have to be very quik and use a good % brasing rod.

US Iceman
13-03-2006, 12:25 AM
...so i take them apart...

You might want to be careful with this. If you remove the power element, you may have problems with leaks on the power element joint. This is a knife edge joint, that may be difficult to reseal.

Dan
13-03-2006, 05:06 AM
This is a knife edge joint, that may be difficult to reseal.

Iceman, I have heard this phrase and read it without really thinking about it.

How would you better describe what a "knife edge joint" is?

US Iceman
13-03-2006, 11:47 PM
Hi Dan,

It has been some time since I had one of these apart.

What I remember is the top of the valve body (where the power element screws on) has a small flat area around the perimeter on top of the threads. If you take one of these apart you should find a slight circular impression on this flat area.

A couple of times when I had to replace a power element I always had a leak at this joint. I did not want to over-torque the threads, so I used some leak-lock (the blue stuff) on the threads.

Somewhere I saw a mention that this threaded joint had a knife-edge that provided a seal to the top of the valve.

After all of that messing around, I changed the valves completely (with a new TXV). Fix it once and forget it as call backs are too expensive and frustrating.

NoNickName
20-03-2006, 03:31 PM
Danfoss TUBE type are made in stainless steel with copper film. Instructions say that warming the TEV is not necessary, just warm the pipe, and to use a high % silver alloy brazing stick.

puddleboy3
20-03-2006, 09:50 PM
When i used to fit expansion valves i used to spray the vales with this stuff called cool gel it came in a spray bottle, dont know what its called in the US. All you would do is cover the valve in this gel then braze up your connections job done!

US Iceman
20-03-2006, 10:39 PM
I have seen something similar. This was a gel that came in a squeeze tube. It felt like silicone. It did work though.

Kiwifrig
06-06-2007, 02:45 AM
Hi Ken, we use Sporlan Q series valves which have changeable orifaces. By having 1 valve body for most different type cases you can just change to the oriface that suits your application best. I look for the oriface size that gives me the lowest stable super heat. I'm not sure if you are using a test room to justify your results but if you are a massflow meter should give you your refrigeration duty. I don't quite understand why from a manufacturing point of view you are using a TX valve on your smaller units as the cost of a cappillary system is far cheaper and lowers your production costs.

The MG Pony
06-06-2007, 07:22 PM
Thats quality, cost be damned so long as it does its job in perfect order, that's what makes my blood boil about producers, if I wanted garbage I'd go to the dump (Sadly thats what I DO end up doing as I can make it my self with far superior quality for most things <_<) TXV may cost more but it will be a far superior unit in its abilities and thus a true high quality peice of kit!

If I could I'd use a tev on my bar fridge!



BTY What's with all the Necrothreading lately with every one? Is it realy that slow around here as of late???

gas_n_go
26-06-2007, 08:03 AM
To be perfectly honest for me it`s a matter of experience on the call of how to proceed. If I feel I can get away with it, I use oxy actelyne torch, nice fast heat hit it and get off then cool her down. If I feel I might be in danger of damaging the valve, I might pull it apart so the heat will disapiate faster, I might wrap it also, but I dont normally wrap it the typical way others do. It dosnt take a big rag ontop of your valve holding a pint of water you can simply use a thin piece of cloth tie it nice and tight around the stub between the joint and the body but as far away from the joint as possible. keep that rag wet, it creates a barrier between the valve and the joint and the valve will not hit temps above aprox 212 farenhieght. typically you should be ok I try to adhere to manufactors recomendations as much as possible remember they are always going to give you conservative instructions thats in thier best intrests.