1. Introduction

Profitability of modern high investment process industry depends on maintaining the operation of plant without unscheduled breakdowns, the primary responsibility of which depends on plant personnel. However, indirectly it largely depends on how the plant has been built with respect to material selection, engineering design and proper supervision during fabrication and construction activities. The plant personal has to ensure the reliability of these equipments by maintaining proper operating parameters and conducting periodic inspection and maintenance. This chapter introduces the basic considerations like (i) degradation under operating environment (ii) mechanical and physical properties (iii) type of equipment (iv) fabrication procedure and quality (v) plant inspection, maintenance, corrosion control and (vi) capital available which determine selection of material. Higher capital investment with better material would cost less in maintenance against high maintenance cost in a low investment plant. A step-by-step approach in final selection of material is also described. Finally six cases of catastrophic failures have been cited to emphasize the importance of strictly adhering to specified steps during all stages of a project implementation and operation.