Frozen Busted McQuay Chiller Tubes.....
I'm posting this in hopes that i can get some good insight on the precarious situation I'm in right now and possibly prevent this from happening to someone else. So here goes..
I have a McQuay Chiller M/N: PEH087, S/N: 57B0076200 holding roughly 911 lbs of R-134a. We were taking the machine down to perform some mundane leak repairs, nothing serious. We contracted an independent refrigerant recovery service to pull the gas due to the amount of gas. The day before the recovery service shows up, I isolate and drain the evap and condenser barrels. When the recovery service arrives they hook their machine up and begin to suck harder than a crackhead hooker. They end up recovering roughly 930 lbs out of the machine, not surprising considering that amount of work that has been performed on this machine previously. Once they left we broke the 15"wc vacuum with nitrogen to 15psi. We then used the pressure on the machine to push the oil out of the sump. When we come back the next day we are surprised to see there is no pressure on the machine. We re-pressurize and find nitrogen blowing out of the condenser water pressure gauge ports, OH SH*T! There are tubes busted.....
We drop the heads and found the entire bottom row of tubes in the condenser which is technically the subcooler are blowing out nitrogen. I am having an Eddy Current test done tomorrow to check the rest of the tubes for damage. I am hoping it is just the seven tubes on the bottom row that ruptured. Here are a couple of questions i have, any input is appreciated!
1) In speaking with McQuay, they say i can plug up to 12 tubes in the subcooler but do not recommend plugging them. They would rather see them replaced. There are a total of 161 tubes in the subcooler and 450 total in the condenser. What should i do?
2) How hard is it to replace a tube that has swollen and ruptured? Any company's in the MD/DC/VA area that anyone recommends for retubes?
3) What are the chances that the refrigerant he pulled out has moisture in it? I assume it does, just not sure what to do with it.
4) I also have to assume there is a negligible amount of moisture in the machine now, shouldn't be a lot since the tubes were drained just the water laying in the sag of the tube. Do i just plan on an infinite amount of vacuum pump oil changes? Or maybe a dry ice trap?
In hind sight , I should have just run water through the barrels while the refrigerant was being transferred but due to other system repairs i was unable to..... Thanks for any comments!
Did you happen to find the bottom row of tubes blocked?
No, not blocked. Apparently just enough water sitting in the bottom of the tube to freeze.
Yeah that is a tough one there. I always like running water myself but I know it can't always be done. I say plug then and run it. From what I recall you are allowed to plug up to 10% of the tubes before you see Amy real effects.
Originally Posted by jon98tt
I always run the water when pulling gas, this is the second story I have heard like this.
You can have the machine re-tubed, there are specialty companies that can do it and they will travel. Prepare your anus though.
With the POE oil and H20 you are going to have a nightmare of a time getting that machine dried out. Pull all the oil, build a house around the machine and heat it up, cold trap it, and invest in a ton of vac pump oil and filter driers.
the company you hired to pull the freon out needs to pay for it. if they removed all the liquid freon first before the vapor this probably would not have happen. I agree with everone else run water through it when you can. I would replace the tubes, you may have alot more tubes damaged which you will find with a eddy current. the customer did not cause the damage.
I'm not familiar with McQuay chillers, but I gather from this that it is possible to have condenser tubes below the liquid level when the chiller is off?
Yes it is. On a McQuay the condenser barrel is lower on the machine than the evaporator.
Originally Posted by Nuclrchiller
There are so many things here that were done wrong, I don't know where to start. The onus is on the recovery company. They did not recover the refrigerant properly.
I will guarantee there are many people (me included) who could remove every last pound of refrigerant out of that machine without any damage to the tubes. Running water through the tubes will help, but what if one or more of the tubes is blocked or has a restriction? If the proper recovery procedure isn't followed then you can still freeze a tube in a condenser.
What happened was the recovery company did not stop the recovery when the pressure in the machine dropped to 29 PSIG. If they had stopped and waited for 15-20 minutes the pressure would have increased indicating there was still liquid refrigerant in the shell(s). So now you have a hell of a mess and if I owned that chiller I would be one pissed off hombre. Water inside a chiller can have long term deleterious effects.
If you have access to a refrigerated cold pot I would start with that after plugging the tubes. Trying to pull a dozen tubes that have freeze bulges is impossible. I have seen instances where dozens of good tubes had to be removed (along with windows cut into the shell) to get the bulged tubes out. Cutting windows on that shell are out of the question unless you have a certified welder and someone to ASME certify it after the repair.
There's probably a good chance the refrigerant has moisture in it. I would take a sample from the last cylinder and send it to National Refrigerants or Hudson Technologies and have it analyzed. If it's wet it'll need to be cleaned up.
I hope that helps.
Wow, going to have to take all into consideration. The valve of your Customer and their maintenance practices, the machine and it's load. Etc etc. I personally wouldn't have a problem with plugging seven tubes, as long as all history with that chiller is good. ( pass Eddie current testing and no problems with water treatment , chiller load isn't already maxed out and customer hasn't flipped out and trusts you) clean up ........ I would weigh in the option of a flush job done/ also reclaim refrigerant at the same time
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So it seems like the general consensus is that the recovery procedure was improperly performed. Then i will pursue the recovery company for some answers and see what they will do. The customer is very important to us and we are willing to do whatever it takes to get the machine in proper operation again. It just sucks that we called this company in to save us some recovery time and look what we ended up with..... Thanks for the input guys!
I think the saying goes something like this ..... "If you want a job doing properly ...Do it yourself " ..
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Be prepared... It's common practice to run water through both barrels while recovering. That is your mistake and they will pin it right back on you.
Originally Posted by jon98tt
They absolutely screwed up in their recovery but I promise they will fight tooth and nail after they see the repair/replacement costs.