TXV overhaul

[coldkeeper1]

Recently I´ve noticed that temperatures in a freezing room are not going down as usual. The TXVs that came installed with the evaporators are SPORLAN SBFVE size B. They all have inlet mesh screens that I from time to time remove and clean. This time I´ve decided not to just clean the filtes but rather to overhaul them all since they are about 9 years old and don´t look very nice. Our supplies clerk indicates that SBFVE-B valves are not currently available but has about a dozen SBFVE-A. My question is: could I just simply retain the same valve body and size B internal rod, and overhaul the power head, plate, spring and cap with the size A valve components without altering the performance of the valves?

[US Iceman]

Why were you cleaning the inlet filter screens on the TXV's on a regular basis? I have never had to do this in the past and have never heard of anyone else doing this?

TXV's do not loose capacity or especially with "*****" valves wear out in only 9 years.

You have some other problems that I believe are making you think you have to do the above. This is NOT normal.

[monkey spanners]

I can only remember having to clean two tev inlet filters in fifteen years, but maybe i've been lucky.
I've seen many more tev's that have lost thier charge from the power head/phial, either in part or fully. This would reduce the duty the system is able to do or bring it to a stop in the case of complete charge loss.
Are these the steel power heads and are they rusty?

If your system has a lot of particles/dirt circulating round and blocking the tev on a regular basis i'd be looking at changing the filter/driers, installing a suction drier if there is not one fitted and changing the compressor oil and the refrigerant.
If left in the system it will lead to the premature failure of the compressor.

Jon

[coldkeeper1]

Thank you USIceman for your interest in this topic. First of all, the type of valve that I´m working with allows the removal of the mesh screen by using just a 5/8 open wrench. No need to untight or desolder any connections. Such a tech-friendly feature indicates to me that it was designed with serviceability in mind. If you have never pumped down a system and checked the inlet screen of a TXV, specially right after the installation and fire-up of the system, I think you are missing a very rewarding experience. Even after start up, you might have debris flying around the system, specially if your system has suffered, like many others, compressor failure or normal mechanical and oil wear. Some even say that the dissecant contained in the filter driers eventually become loose, and that the UV dyes for leak seeking purposes might decompose after a while inside the system. For this reasons I try to check on these filters from time to time. I understand your point when you say that ***** doesn´t loose capacity and that a typical TXV valve might work troublefree for 9 years, but the TXVs I´m referring to have the power heads very rusty and the copper capilars look dull and fragile. That´s why I would like to change them

[coldkeeper1]

Hi monkey spanner. As you pointed out, the power heads are indeed make of steel and all rusty, with capilars looking very fragile too. I thought that both are evidence of possible leakage.
This system suffered a compressor burnout a few years ago, but that´s about all the trouble I´ve had. Nevertheless, as it is so easy to pump down and untight the plug/mesh, I like to peform this operation at least annually. It´s easy, it´s cheap and it doesn´t offend anyone, besides allowing you a quick visual check of what´s inside the pipes.

[monkey spanners]

Those power elements are quite cheap, i keep a couple on the van just in case as they are used on a make of milk tank i service and they don't last too long in a dairy with all the chemical fumes from the milking plant wash cycles.
If you check out the sporlan/parker site there will be a technical bulletin for how to select and fit a replacement.
I've wondered about drier cores breaking up and filling a system with dust.

Jon

[US Iceman]

If you have never pumped down a system and checked the inlet screen of a TXV, specially right after the installation and fire-up of the system, I think you are missing a very rewarding experience.


Ohhh, I've done more than my share of start-ups and installations. To have these problems on start-up are even afterward are a sign of the installation techniques used.

The most I have ever had to do was to change the filter driers after a few months.

I have seen some of the grit from the drier cores in the strainers, so yes it does happen....although the only time I have seen a drier drastically breakdown was when some genius put the filter drier in the discharge line.:rolleyes:

Before I replaced the drier cores I would always rub them with my hand to remove some of the loose particles, then put the cores into the shell. This helped to remove the loose stuff that would eventually come off anyway.

My experience with power heads is... they either work or don't. So, you might see some capacity loss when one completely fails and it might be a good idea to replace any suspect element.

But again... it's pretty rare for a power element to fail too. However, if they are rusty then it's a good indication that you should be thinking the way you are right now.

[SteinarN]

I have seen some of the grit from the drier cores in the strainers, so yes it does happen....although the only time I have seen a drier drastically breakdown was when some genius put the filter drier in the discharge line.:rolleyes:

LOL :D

Regarding powerheads, I have replaced some smal numbers of Sporlan heads due to lost charge, a couple of them only a few years old. This has mostly been MOP heads which has less charge than ordinary heads. The superheat increases and it is not possible to adjust it. Rusty heads may be an indication. I agree with you US Iceman, generally TEV's is very reliable