Tube Troubles

Your May 1999 issue contains a startling article about the unsuccessful efforts at solving condenser tube problems at the William C. Gorgas Electric Generating Plant.

We’re told that after 17 years of service, the 90/10 Cu-Ni tubes had excessive leaks and lost 0.12 inch of wall thickness, which must have been about all the wall thickness they had. How was the metal lost? From the inside? From the outside? Over the full length of the tubes or just from local areas? Just on the inlet end? Always on the bottom of the tube? We’re not told.

We’re told that three other condensers at the plant also are tubed with 90/10 Cu-Ni or Admiralty, which will have to be replaced. Do all the 90/10 condensers have the same problems, and does the condenser with Admiralty tubes have similar problems? We’re left to guess.

Past favorable experience at another unit at the same plant with stainless steel condenser tubes led to the selection of stainless as the replacement for the 90/10 Cu-Ni. The stainless steel tubed condenser with the favorable experience also was equipped with a sponge-ball cleaning system. The cleaning system is rather expensive to install. Although past experience was important in deciding to go with stainless steel, the economics played a major role, and the cleaning system was omitted. As a result, the experience with the new stainless steel tubes has been one problem after another.

The team is still looking for an acceptable solution. But they have not thought to engage a metallurgist to look into why the Cu-Ni tubes developed problems and how those problems could be eliminated.

Harry E. Lunt, P.E., FASM, FASTM Mendham, N.J.

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