Corrosion Under Insulation (CUI) API 571 Asset Integrity

Corrosion Under Insulation (CUI) API 571 Asset Integrity

Corrosion Under Insulation (CUI) API 571 Asset Integrity

CUI is one of the most important subjects and can be understood easily we go through following scenarios and understand the knowledge level on the subject and likely problems faced.

 
Scene One

Project Manager – Why the insulation job is getting delayed?
Construction Engineer – Sir we are not getting the front for work.
PM - What do you mean?
CE – Sir hydro test of many piping not completed.
PM – So what ??
CE – Sir I am having the problem organizing manpower – it is either idle or short as sometimes I do not get any work front as Hydro tests are not complete and then suddenly many HT get completed simultaneously and a lot of work front released??

Scene Two

CE – Sir I am on the job of providing TSA (Thermal Spray Aluminium) and after 2 days I will be short of machines to keep up with jobs released so request you to organize one more machine with the crew to take up the job so that project schedule can be met.

PM – Yes day after tomorrow you will have 1 more TSA machine with the crew.

Above 2 scenarios may be common in a huge project. When scenario 1 exists there is all the chance that compromises may be made on insulation application quality and such plant may be susceptible to problems due to CUI (corrosion under insulation). The scenario 2 gives the confidence that CUI problem is given utmost attention and the plant constructed will be immune to the threat of CUI.

When CE in scenario-1 was asked what is done for combating CUI  in his new project he replied  I understand that painting of piping has to be as per specification, the insulation material is carefully chosen so also even the Aluminium (Al) cladding for insulation etc. When asked what is so special about Al cladding he replied that the Aluminium Sheet used will be of thickness  0-016 into 0-032 in  3105 alloys having the H14 temper and 3 mil of polysurlin moisture barrier (factory heat laminated). Also, I understand that apart from cladding application it is equally important to have right sealants on lap joints as well on self-tapping screws to prevent ingress of water/moisture.

So no doubt the CE was knowledgeable and wanted to enforce the specification in totality but possibly the time pressure was coming in the way ??
When CE in scenario – 2 was asked what is done in combating CUI in his new project he replied  That I understand  that the basic solution to prevent Corrosion under insulation is the use of the high quality coating which can be considered as one of the lines in defense to combat CUI eg when the outer jacketing, the insulation material fail to prevent ingress of water the final defense eg the coating should work – hence I am so particular about TSA application to be done properly.
Both the CE’s were asked how their knowledge level on CUI was so high and they answered they attended a Course on CUI and also read through the two important recommended practices by NACE (RP 198) and API  (581) on the subject.
 
Writer – Prakash Shende

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