Introduction

A core boiler, excluding the firing equipment, is mainly built with several high-tempera — ture materials, namely steels and refractories, with structural steels used for support and sheet materials for air and gas transport.

Refractories, heat-facing materials, are steadily being replaced by more steel for easier O&M. There is, however, a comeback of sorts for the refractory materials, with the rise of circulating fluidized bed combustion (CFBC) boilers where they are required in large quantities for furnace and cyclone lining.

Thus, the materials used in the construction of boilers comprise a variety of steels and refractories. Little nonferrous material is used for the outer surface, except aluminum sheet. A boiler is generally made of steel rounds in the form of tubes, pipes, and head­ers. Even the drums and reheater (RH) headers are rounds rolled from plates, as their diameters are large. Drums of up to 1100 mm OD are usually made of large seamless pipes.

In addition to tubes and headers, there are plates and strips, castings and forgings, and structural rolled and flat sections. The nonmetallic materials are mainly bricks, refracto­ries, insulation, and lagging (BRIL), most of which are used to cover the boiler.

This chapter covers almost all the materials used in boilers in a systematic and simple manner. The various tables present more data. For further details, the reader may refer to the appropriate standards.