Articles
Condenser Tube Repairs Using Tube Inserts
June 18, 2004
By Peter M. Tallman
CTI Industries
It is common knowledge that many heat exchanger (HX) tube failures occur within the first 6 in. (150mm) of the bundle. Inlet-end erosion, stress corrosion cracking, and crevice corrosion are different types of failure mechanisms that are common in shell-and-tube HX.
In the past, the accepted repair for heat exchanger (HX) tube damage localized close to the inlet was full tube replacement or shortening of the tube buncle - despite the fact that more than 95% of its length usually remains undamaged. Either type of repair has proven extremely expensive and time consuming.
Accordingly, alternatives to full retubing repair long have been sought, including:
- Protecting damaged tube inlets.
- Restoring plugged leaking tubes to active service.
- Restoring original compressive strength to weakened tube-to-tube-sheet joints.
Tube Shields/Thin-Walled Inserts
Metallic, thin-walled inserts or shields were introduced in 1976. They are inserted and then expanded - either mechanically, hydraulically, or by a combination of the two - into the existing tube ends.
Previous attempts to correct tube end erosion/corrosion have included the use of conventional ferrules made of plastic or ceramics. Such conventional ferrules typically are loose-fitting, and normally are cemented or glued in place.
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