Jul 18, 2010

The management of pressure equipment operating in a cyclic service can be difficult as little guidance is provided in the codes of construction or in any of the post construction guidance documents. In terms of design, the ASME Section VIII, Division 2 Code does provide guidance for the design and fabrication of vessels that will be in a fatigue service. Of specific interest are those vessels that were designed to ASME Section VIII, Division 1 with varying levels of attention paid to the cyclic nature of the operation. This becomes a problem when operating facilities must determine the long term strategy for a piece of equipment where fatigue is the only (or dominant) method of degradation. With the variation in design methods, methods of addressing fatigue crack growth, material properties, and the desire to minimize inspection expenditures for this type of equipment; practical guidance for long term inspection considerations is presented in this paper. A case history for a Pressure Swing Adsorbtion (PSA) vessel that is subject to cyclic pressure only is discussed to illustrate design considerations, inspection strategies, and determination of remaining life. This provides a fairly simple and approachable example for determination of remaining life and inspection strategies, as well as highlighting regions of interest in these types of vessels. The same approach can then be applied to equipment where more complex (mechanical, thermal) cycling occurs.

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