Shell-and-Tube Channel Cover and Tubesheet Repair

The challenge

On this shell-and-tube exchanger the channel cover and the tubesheet face had grooved and pitted around the pass partition and the gasket land. With the pass-partition rib worn down and the gasket land no longer flat, the unit weeped between passes and the cover would not seal on reassembly. Process fluid bypassing the partition robs the exchanger of duty, and a cover that will not pull up tight keeps the unit out of service. Left as it was, the corrosion would keep cutting into the sealing surfaces and the leak between passes would only widen.

Our approach

We took the cover and the tubesheet face down to clean, profiled metal by grit-blasting, so we could see the true extent of the grooving and give the repair a sound surface to bond to. We rebuilt the eroded pass-partition rib and the gasket land with a metal-repair composite and reformed the sealing surfaces back flat, working cold so the cover saw no heat distortion. Once the metal was back to profile, we laid down a barrier coat over the cover and the tubesheet face keyed to the process side, so the rebuilt areas and the surrounding bare metal sit under one continuous film. With the rib, the land, and the faces reformed, the cover pulls up tight on reassembly and the passes stay separated.

1. Assess and mapWe inspect the channel cover and tubesheet face, map the grooving and pitting at the pass partition and gasket land, and confirm the process side so the barrier coat is keyed correctly.
2. Grit-blast prepWe grit-blast the cover and the tubesheet face to clean, profiled metal so both the composite and the coating bond to bare steel.
3. Rebuild rib and landWe rebuild the eroded pass-partition rib and the gasket land with a metal-repair composite, working cold with no hot work and no replacement.
4. Reform the sealing facesWe reform the gasket land and partition rib flat so the sealing surfaces meet true on reassembly.
5. Barrier-coat and return to serviceWe apply a continuous barrier coat over the cover and tubesheet face, then hand the unit back for reassembly with the cover pulling up tight.