12-25-2010, 06:04 AM
Coating of the Fractonator column of Delayed Coker Unit(DCU) with TAFA 88T(SS316) coating.
We have just recently carried out coating of the Fractonator column of Delayed Coker Unit(DCU) with TAFA 88T(SS316) coating. The coating was carried out in replacement to Strip Cladding SS316 plates. We would like to know if anybody has carried out similar coating and the result (like enhancement).
We also like to know why during the Coating process we face difficulty in activating the surface. We carried out Chilled Grit Blasting. However, after Blasting we would observe Black Patches after a while. So we once again carried out Grit Blasting and immediately after carried out Coating using Bond Arc75B. But strangely we observed Black spots on the Bondarc75B within 15mins.
Since we were short of time(the job being carried out during Shutdown) we proceeded to heat the surface to a temp of 100/150 Deg C for an Hour and half and then proceeded to carry out BondArc 75B. The patches reduced substantially and then we proceeded with TAFA 88T.
Can anybody explain the reason.
We are intending to Carry out a similar process on CDU (Crude Distillation Unit). We would like to know if anybody is having experience about it.
12-28-2010, 04:44 AM (This post was last modified: 12-28-2010 04:46 AM by kschewe.)
|RE: DCU COATING
(12-25-2010 06:04 AM)ehasan Wrote: Dear Gordon,
Not sure if this may help but black spots with metallizing, seen to many times, is usually the substrate is contaminated with something like oil. We try and clean parts with a vapor degrease or pyro clean. Cast metals are bad
01-14-2011, 07:39 PM
|RE: DCU COATING
Agree with kschewe. This will be contaminants leeching out of the substrate and can be difficult to remove.
I understand the pressures bought to bear (Since we were short of time (the job being carried out during Shutdown), but it is vitally important to get the substrate preparation stage as near to perfect as possible or you will be building your coating on an unsecured footing. Impossible to correct without starting from scratch.
This is not usually a problem with new builds, but repairs to surfaces that have seen service often have suffered pitting corrosion, which can contain contaminants. After, typical cleaning and grit blasting, these contaminants leech out staining the the freshly prepared surface. Problem here is that this may not become evident until some time has passed or when preheat is applied.
Plan in a extra time/materials for cleaning, heating, grit blasting for the preparation stages, you will probably need it.
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