Case Study – Around 18 years old tank which is required to be inspected is offered by owner (The Exterior Only). The tank inspections documents are missing including project specification
Points To Consider-
Case Study – Prior to maintenance, thorough tank inspection shall be carried out and complete case study report shall be prepared and submitted for approval.
The assessment and the accuracy depends on the experience of the coating Inspector, hence the inspection data can vary from Inspector to Inspector based on their findings.
You as a Coating Inspector herein shall inspect and provide your inspection survey report.
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Herein Are Some Main Guidelines – Case Study – Around 18 years old tank
Case Study – Pre-Assessment
Gather all the information on physical characteristics of the tank such as operating temperature by referring to project drawings etc.
Case Study – Observation
Overall Tank Rating – POOR
Paint peeling off observed, paint defects found due to aging. Some locations chalking also observed. Greasy/oily kind dust accumulation found at tank surroundings. Rust stains dripping down from exterior of the tanks observed. Contamination of oil and grease is visible mainly at the valve operating areas. Pin point and spot rusting is also observed on few locations.
All paints have different drying /curing mechanism and the use of solvent is a simple way to determine the generic type of coating. Hence, solvents (xylene, white spirit, MEK or acetone) different reactions will occur when testing the paint system.
Tests to Be Carried Out – Direct Inspections
- Check the paint system – The use of solvent is a simple way to determine the generic type of coating
- Rusting evaluations as per ASTM D 610-01 to decide the rectification process
- Cross cut adhesion test as per ASTM D – 3359 A
- MEK rub test
Tests Carried Out and Findings Observed
- DFT was checked and the average thickness measured were between 150 – 260 microns
- 3 coat system – Zinc Rich Epoxy + Polyamide Epoxy + Polyurethane
- As per ASTM D 610-01 – > 16.0% and ≤ 33.0% – The rusting is randomly distributed in sizes and in areas throughout the painted surface (General rusting)
- Most of the portion has good adhesion of primer when done as per cross cut adhesion test ASTM D 3359 method A.
- While top coat showed very poor adhesion in some locations
Cause of Failure
- Regular maintenance was not carried out
- Thorough Surface preparation & with high pressure water washing with degreasing shall be carried out.
- The damaged areas shall be blasted and existing paint system shall be applied – Repair procedure shall be submitted for approval.
- The repair works shall be carried out as per the safety standards – shall comply with HSE requirements
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