Storage Tank | Case Study | High and Low Profile Observed

Case Study – High and Low Profile Observed During the Inspection of Chemical Storage Tank

The chemical storage tank was inspected by a certified coating inspector. In this assessment, high and low profile readings were taken in addition to finding salt levels on the surface borderline of the acceptable requirements, thus questioning the quality of surface preparation.

The inspector recommended sweep blasting to the crew of the contractor to bring the profile within acceptable criteria. However, after sweep blasting, the salt levels increased instead of decreasing and exceeded the specified requirements. This created a challenging situation because the job was in a running plant and required urgent completion.

Importance of testing chloride level Abrasive

Well, one would be checking how high the chlorine levels are at the abrasive for it to be acceptable to start on blasting. Abrasives can introduce salt contamination where they transfer in to the surfaces while blasting is done. Then testing the chlorides again for sweep blasting in SSPC SP 7 it will give greater detail of contaminated surface.

Project Specifications and Salt Content Requirements

Most project specifications require salt content on the surface to be less than 25 ppm, though it may vary from project to project. Adherence to these specifications ensures proper surface preparation and prevents failures in coating.

Ensuring Abrasive Material Quality

Abrasive material quality and grade are essential factors in achieving the desired surface profile. The abrasive used must be acceptable and of the required grade. Recycled garnet, which is usually applicable in some cases, is unacceptable for tank blasting. Tank blasting needs a clean steel surface that will meet the SA3 visual cleanliness criteria.

High-pressure water washing is an important step

The high-pressure water washing should be carried out prior to blasting, with the intention of removing the corrosive salts and other soluble contaminants from the surface. For storage tanks, it is also necessary because the presence of salt and corrosion residues would influence the coating performance. It ensures further contamination does not occur through the use of sweet water with a low salt content. It removes corrosive iron products, which settle at the bottom of pits, before the coating takes place.

Challenges in a Running Plant

In a running plant, time is always a constraint, and proper surface preparation becomes even more important. Any delay or repeated work can cause disruptions in operations and result in huge financial implications. Issues must be addressed the first time to avoid such disruptions.

Consultation of the Paint Manufacturer

The best course of action for the coating to be successful lies in consultation of the paint manufacturer if, through all necessary procedures, surface preparation fails to attain the minimum specifications. Most manufacturers have technical teams equipped with information or alternative ways that ensure the successful coating application by a slight alteration on the requirements.

Lessons Learned from This Case Study

This case study teaches the significance of proper surface preparation and observance of strict project specifications. Salt contamination and the surface profile problems are not addressed when they are noted during the initial inspection, hence repeated efforts are required, delaying the project schedule, and higher costs are involved. The inspectors have to be cautious, follow proper procedures, and take corrective action at the right time to avoid reoccurrence.

Conclusion on Storage Tank

The preparation and inspection of a storage tank’s surface need to be approached in an orderly procedure. Abrasives used must be checked for chloride content; high-pressure water cleaning should be undertaken, and only approved grades of abrasives must be used. Consultation with the paint manufacturer may also be helpful in difficult circumstances. Once prep is done the right way, the coating system performs as per its intent and requirements of the project. Addressing issues during the first inspection will ensure that everything runs smoothly without costly delays in the project.