Repeating Chiller Condenser Tube Failure

[dogbertcountry2]

I have a set of chillers that require at least one to be layed up for the winter months. Three years ago we laid Machine 1 up from December-April. On start-up we found more than half of the tubes had burst. We attribute the failures to poor layup practice and installed low point drains in every place imaginable. The next year we laid Machine 2 up with the new pradctices and drain spots. When we started it up we had similar results to the year before (hundreds of tube failures). Every evidence appeared as if it had been drained and the drains left open (and tagged) all winter. Local metellurgists examined the failed tubes and found no signs of corrosion and claimed that the failures were caused by confined waterfreezing and expanding.

When we laid up Machine 3 this past winter, we physically removed the heads, blew the tubes out with air and wrapped the ends with plastic. Upon startup, we found one tube had failed. We ran a camera back through the tube and found a similar burst in it as we had in the years before.

In all years, we could not find any evidence of sagging tubes. We did find a small amount of whitish buildup in a couple of tubes that had not burst. (We believe that this is some kind of carbonate from cooling water residual.)

My trouble is that I don't know if this is the same problem happening over and over again or if we have a different problem.

Help!?

 

[metengr]

I don't believe you have a current problem. From what you have stated below...

When we laid up Machine 3 this past winter, we physically removed the heads, blew the tubes out with air and wrapped the ends with plastic. Upon startup, we found one tube had failed. We ran a camera back through the tube and found a similar burst in it as we had in the years before.

...



you had poor lay-up practices. I believe the one off tube failure above could have been a tube that suffered from prior freeze damage, and did not rupture until some time later. I have seen this before. Follow your improved lay-up practices.

 

[dogbertcountry2]

I had thought of that, but I am having trouble rationalizing what the driving force during the layup would have been to have the failure burst. Before we laid the machine up, we had no problems. There was no water in the refrigerant, so the burst must have heppened during the layup period.

Any ideas of the driving force? You said that you have seen this before. Did you see tubes that had bulged, but not failed, and then these same tubes failed?

 

[metengr]

Yes, I have seen tubes on boilers and heat exchangers where we locally bulged and partially induced cracking in the tube material (carbon and nonferrous materials)during a prolonged outage during winter.

 

[blacksmith37]

Old guy story: northern refinery with a 100+/- years of working on steel and brass exchangers. They took their first aluminum exchanger (shell and all) out for service; when it was opened some tubes were burst between every baffle.
Like Rust, "cold" never sleeps.