TABLE OF CONTENTS Two new vessels built for equal pressures and temperatures and the same type of service can fare very differently in different locations. In one plant, capable maintenance personnel will keep the vessel in top shape by means of a systematic schedule of inspection and maintenance. In another, an equal number of personnel, through ignorance, incompetence, or neglect, can bring about the failure of the vessel in a comparatively short time. Competent personnel are obviously a key factor in the longevity and safety of a pressure vessel.
Most pressure vessels are subject to deterioration by corrosion or erosion, or both. The effect of corrosion may be pitting or grooving over either localized or large areas. Corrosion over large areas can bring about a general reduction of the plate thickness.
Some of the many causes of corrosion are inherent in the process being used, but others are preventable. Vessels containing corrosive substances, for example, deteriorate more rapidly if the contents are kept in motion by stirring paddles or by the circulation of steam or air. If the corrosion is local, it may not appear serious at first; as the metal thickness is reduced, however, the metal becomes more highly stressed, even under normal pressures. The more stressed the metal becomes, the faster it corrodes, at last reaching the point of sudden rupture. Corrosion in unstressed metal is less likely to cause such sudden failure.
Many plate materials are not at all suitable...
