Products & Services: Tube-End Coating
Examples
of Deteriorated Tube-ends
Cross-section of tube with Tubesheet Cladding and three coats
protecting the tube-end
The Tubesheet Cladding can be applied
to any tube-to-tubesheet configuration experiencing any level of
deterioration providing structural integrity
is not threatened. The diagrams below show the cross-section
of three examples. Each configuration is shown as it would appear
with a new or slightly corroded tubesheet (upper half) as well
as with a more severely corroded tubesheet (lower half).
Tube-End Coating
Copper based tube alloys can be subject to selective
erosion within the first foot of the inlet tube-end.
Other tube materials can deteriorate because of galvanic or microbiological
issues.
Inlet-end erosion is due to turbulence present at the initial section
of tube before laminar flow is
established. The degree of erosion depends on the nature and amount
of entrained solids in the
cooling water, the type of tube alloy and its susceptibility to corrosion,
water velocities,
micro/macrofouling of tube surfaces, and other design/operating factors.
Oulet-end erosion may also occur due to outlet flow induced turbulences.
The Plastocor® Tube-End Coating is precisely
applied in three coats of alternating colors to provide
complete protection. 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.
This three stage method creates a feathered termination, eliminating
the chance of step-erosion,
a common problem with the use of plastic or metal inserts. This method
can actually bridge small
perforations of the tube wall thereby repairing the tube and returning
it to service. The need to retube is
therefore postponed or eliminated. The joining of the tubesheet cladding
with the inlet coating creates
a uniform and smooth transition from waterbox chamber to tube interior.
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.
