Steps to Follow During Rubber Lining Inspection Procedure
Proper inspection and maintenance of a rubber lining are critical for its prolonged life and to avoid costly procedural shutdowns due to damage. In most cases, damage can be mitigated with regular inspections and a proactive approach to repairing failures at their earliest stages.
Adhering to the following steps during a rubber lining inspection procedure can help to reduce damage to the vessel, the downtime necessary for repairs, and the safety of those involved in the process.
1. Chemical Mitigation and Prior Testing
To inspect a rubber-lined tank, first, you must empty the vessel, neutralizing and rinsing it thoroughly. It should be aired out for 24 hours or overnight to remove fumes. Before entering the tank, test oxygen levels to be sure that toxic fumes have escaped.
2. Necessary Equipment
For a complete and thorough inspection, an experienced tank lining inspector will need a general drawing of the equipment to help locate and mark areas needing repair. He or she will require a reliable light source, chalk, a clipboard for the drawing, durometer (rubber measuring tool), and a spark tester for proper inspection.
For safety purposes, an inspector should wear disposal coveralls, hard hat, goggles, disposable gloves and a respirator.
Lining inspection is a difficult task, and every situation is different. Everything from minor to major failures should be assessed during an examination. Due to complexity, a cursory look around the entire lining should help determine the overall conditions.
General appearance may indicate the lining to be in good condition if the rubber surface shows either the polyethylene embossing pattern or liner use to roll up the rubber. In these spots, the durometer should measure the hardness expected, revealing the lining is in good condition and not in need of repairs. Additional testing with a spark tester can help verify no leaks are present.
Small areas less than 18” in width, can be fixed with a fill and overlay. It is recommended repairs are completed with a 45° skive. The procedure for minor repairs is to fill in the area using the same gauge rubber as the original lining then overlay the repair area with the same lining extending 2” beyond the perimeter of the fill-in patch.
If multiple repairs need to be made within a small area, the spots should be filled and then covered with one larger section of rubber to maintain a clean appearance. This method will help reduce the chance of leakage due to a lifted corner, which is common with rubber.
For larger repairs, a single sheet rubber layer can be employed as the laps will be less stressed compared to that of a much smaller area. If a good wide angle skive can be achieved, it is acceptable to have a single sheet patch repair, even in areas that are several square feet.
5. Continued Maintenance and Monitoring
A proactive strategy for inspection and maintenance should be followed for the prolonged survival of rubber-lined equipment. Monitor for green or yellow stains as it can be a sign of deteriorating steel from acid seepage. Chemical deposits are another sign of leakage and can foretell an imminent failure.
Metal repairs can often be mitigated if timely repairs occur at the first signs of a rubber lining failure.
Exposure to excessive heat is the most prominent culprit of premature aging of a rubber tank lining. Temperatures exceeding 200°F(93°C) have a definitive role in the deterioration of a rubber lining. Rubber linings should never be exposed to direct sunlight although some exceptions exist including Chlorobutyl, Hypalon, and Neoprene linings.
With a proactive and detailed approach to inspection and repair of your rubber-lined equipment, costly and time-consuming lining failures can often be prevented.