Oil Well Casing
From Cargo Handbook - the world's largest cargo transport guidelines website
Threads on ends are particularly liable to damage by rough handling, even though thread protectors are fitted. Threaded ends so damaged may be cut and re-threaded in the oil-fields, where special machinery is usually available. Bends and dents, if not too severe, may also be straightened by special machinery in the larger oilfield centres, but, as oilwell casing is subject to high pressure, such repairs must be tested and inspected by technical processes, which are expensive.