Case Study – High and Low Profile Observed During the Inspection of Chemical Storage Tank
High and Low Profile – Salt level recorded just below or I should say at the border line of acceptance requirements. The Inspector suggested to the contractor (Crew) to sweep blast the area to bring the profile within acceptable criteria.
After sweep blasting the salt level increased further which is more than the specified requirement. The job is also very urgent.
As a professional inspector what will be the course of action in this situation.
Such case studies shall be solved within the first time as repeat performance does not occur again.
New Forum visitors are most welcome to add and raise any new questions in here for further discussion.
Case Study – For a certified inspector your course of action will be as under
– The chloride level of abrasive should have been checked prior to starting the blasting. It shall be checked again after sweep blasting (SSPC- SP-7) to get more information in this case.
Generally, as per the specification the salt content shall be less than 25 ppm, again depending from project to project specifications.
– The abrasive used is approved and which is as per the specified grade.
– Check if the Contractor has used recycled Garnet. Recycled Garnet is not acceptable for tank blasting since blast cleaning to visually clean steel is the requirement – SA3
– Did the contractor wash the surface prior to blasting? High pressure water washing is the requirement? The Contractor shall use sweet water for surface cleaning having low level of salt content.
Water washing will remove potentially destructive corrosive soluble iron corrosion products which form at the bottom of corrosion pits.
– When nothing is found acceptable then best remedy would be to consult the paint manufacturer.
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