Tube-End Coating

 Discussion

 Copper based alloys may erode within the first foot or so of the inlet end. Other tube materials may deteriorate because of galvanic or microbiological issues.

Inlet-end erosion is generally due to turbulence present at the tube inlet before laminar flow is established.  The degree of erosion depends on the nature and amount of entrained solids in the cooling water and flow velocities. Micro and macrofouling of tube surfaces may also contribute to selective tube deterioration.

 Oulet-end erosion may also occur due to outlet flow induced turbulences such as cavitation.

The Plastocor® Tube-End Coating is precisely applied in three coats of alternating colors. The 100% solids, high performance epoxy coating can be installed to any depth and is performed in conjunction with the Tubesheet Cladding so as to confer maximum protection.  Each coat is approximately 2 to 3 mils thick and is applied further down the tube than the previous coat.

 Our three coat method creates a feathered termination, eliminating the chance of step-erosion, a problem that can exist with plastic or metal inserts.  This  method can also bridge small perforations of the tube wall.

 The joining of the tubesheet cladding with the inlet coating creates a uniform and smooth transition from waterbox to tube. This reduces fouling and turbulence which raises flow efficiencies.  The tube ID is not significantly reduced which permits the unrestricted use of eddy current testing and most tube cleaning methods. The Plastocor® Tube-End Coating can indefinitely protect condenser tubes against inlet end erosion.

In those cases when the tube-end has eroded to the point where structural integrity has been lost or is threatened, a metal insert can be incorporated into the coating to bridge between the tube and the tubesheet and restore integrity.