Again, it was the same long hot summer down south, same job as the last story. Here I wasn't on the side of the cheap man for a change.


As the project wound down, we came to the time for the punch list. I had invested a lot of time and sweat into this project and desperately wanted to see it run, but the cheap man (project manager) spoke: "There is no room in the budget to stay. Come home!"


So I did, but not before one last quick tour of the job. I took note of a stainless steel heat exchanger we had installed. When I had last seen it, the sliding end was bolted tight to its mount. It still wasn't corrected and I again brought it to the attention of the foreman.


Later, I saw a photo of this exchanger after it had failed. It had buckled in the middle and needed extensive repairs. I wondered why bolts weren't loosened, but could not do anything else. I was puzzled by this decision not to loosen the sliding end for a long time, and I believe I now know the answer.


This exchanger was built for high temperature operation, 600 degrees F. In order to compensate for the difference in expansion between the tubes and the shell, there was a bellows in the middle of the shell. This must have led someone to think that the exchanger was self-compensating and needed to be anchored on both ends like a pipe with an expansion joint. The difference was I had read the vendor drawing.


What's to be learned from this? A big lesson is things aren't always what they appear to be. Also, a design person should have been in on the punch list corrections. Would it have made a difference if I had explained why the sliding end needed to be free? That is something I'll never know.


Dennis Novotny

© 08 November 2000

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