This chapter covers the failure modes and mechanisms of concern in hydroprocessing reactor vessels and the methods used to assess lifetime and performance. It begins with a review of the materials used in the construction of pressure-vessel shells, the challenges they face, and the factors that determine shell integrity. The discussion addresses key properties and design parameters including allowable stress, fracture toughness, the effect of microstructure and composition on embrittlement, high-temperature creep, and subcritical crack growth. The chapter also provides information on the factors that affect cladding integrity and ends with a section on life-assessment techniques.

The necessity of developing the lightest-weight structures with sufficient strength was the driving factor for the development of filament-wound composite pressure vessels. This chapter presents a brief history of the development of rocket motor cases (RMCs), followed by a comparison of the advantages of composites over metals for RMCs. A discussion on a typical design, analysis, and manufacturing operation follows. The chapter introduces the basic design approach and shows some sizing techniques along with example calculations. It discusses the processes involved in the testing of the composite pressure vessel.