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A Quick Guide to API 653 Certified Storage Tank Inspector Syllabus: Example Questions and Worked Answers

Clifford Matthews
Clifford Matthews
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Co-published by ASME Press and Woodhead Publishing (UK)
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Overall, a lot of the storage tanks in the world are in a bit of a mess. Here are the reasons why:

Poor maintenance. Tanks are easily forgotten when allocating maintenance budgets to higher priority parts of a plant. They are often seen as being less process-critical. Access is also difficult — external inspection/maintenance requires scaffolding or mobile cranes.

Long lifetimes. It is not unusual for tanks to be 50 or more years old.

Multiproduct use. Changing process conditions leads to unpredictable (frequently unknown) corrosion rates.

Construction standards. Although tank construction codes (particularly recent ones) are technically consistent in themselves, tanks are hardly high technology items. Most are made from corrosion-prone low carbon steel. They are simple utilitarian fabrications, rather than cutting-edge engineering structures, which is reflected in their low price.

Environmental conditions. A lot of tanks are situated in dirty or marine environments. Once the external painting starts to break down, corrosion occurs quickly. It is worse if the external surfaces are lagged.

The result of all this is that most storage tanks end up needing a lot of repairs during their lifetime. These can range from small patches or replacement plate inserts through to replacing complete tank bottoms, shell courses (or ‘strakes’) or roofs. Some of these do little for the cosmetic appearance of the tank, but are perfectly technically viable — and cheaper than buying a new tank.

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