AMMONIA CONDESER

[picasa]

An ammonia condenser has well water as cooling media on the tubeside. Condensing Ammonia on the shell side. After just ~6 years in service, tube leaks developED. Obvious first hand solution was to plug the leaking tubes with tapered plugs. Now during retubing, if you try to drill out the plug, existing pressure is noticed behind the plug! why is that? what is the mechanism for this to happen? Theoretically, leaking tubes should release to atmosphere when the exchanger is depressurized.

 

[TGS4]

You're correct that "theoretically" there should be no pressure. However, it could be the internal pressure on the tubes that was causing the leak through a small leak path. Circumferential thermal expansion which _might_ open a crack could also be an explanation. Finally, the leak path could also have sealed itself with corrosion products to the extent that it might retain a small amount of pressure. That certainly is troublesome though. I hope no one was hurt!