Centrifugal compressors materials used

Materials of Construction. The principal materials of construction are ferrous throughout, but different grades are used for the different components. Casings usually are in cast iron or cast steel, and impellers may be in the same materials or in fabricated steel. Early designs of centrifugal compressors used riveted assembly for impellers castings or welded construetions are preferred today. Shafts usually are of carbon steel with hardened or stainless steel sleeves at points where erosion is likely. The selection of materials for smaller components that may be subject to friction is particularly important because of the danger of comlnistion. 

In order to improve compressor reliability it is critical to choose the correct materials when operating in harsh environments. Using the proper materials, centrifugal compressors can be designed to handle corrosive and erosive gases. In order to choose the correct materials, all possible operating conditions must be accurately defined. 

Positive-displacement compressors are most often used for low-flow applications and for slightly higher compression ratios than are centrifugal types. Single-stage positive displacement compressors would appear to be better suited to compression evaporation than centrifugal machines because of lower cost and their characteristic fixed capacity. However, they are not available In a wide range of materials of construction and are limited in capacity and efficiency. Consequently, their application is limited. 

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