GENERAL GUIDE FOR MATERIALS SELECTION

This guide covers the following materials and corrosion allowance (CA) for process equipment materials for low-temperature services and materials for wear and abrasion resistance. EQUIPMENT DESIGN UFE  

Materials selection is based on the following approximate design lives  

Materials selection should be based on design conditions, not operating conditions. 

Process flow diagrams, stream analyses, contaminant levels, upset conditions, and environmental conditions during shutdowns and start-ups should be evaluated in selecting materials. 

All materials for process equipment and piping should be identifiable and conform, where necessary, to the requirements of the ASTM(1) or other national standard specifications. Table A-1 contains typical ASTM standard specifications for different product forms in frequent use. 

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While there is some justification for using such rankings as a general guide to material selection, there are shortcomings in the approach. The most obvious is that... 

A simplified material selection guide has been provided to determine the general chemical compatibility between the membrane (and its accessory components) and the process su eam. The guide is primarily for relatively low temperature applications. 

From the vast literature on RMs, overall general impressions may be obtained from the chapter by Maier (1993) on CRMs for the quality control of measurements in the book edited by Barcelo (1993), from books by Clement et al. (1997b) on reference materials for environmental analysis, by Fajgel and Parkany (1999). The use of matrix reference materials in environmental analytical processes, by Zschunke (2000) on Reference Materials in Analytical Chemistry - A Guide for Selection and Use, and by Stoeppler et al. 

Table 52.3 presents a brief selection guide for different feeding equipments used in drying based on the material characteristics. The information presented in Tables 52.1 through 52.3 is helpful as a general checklist for the preliminary selection of the feed system. Before a final decision is made on the type of equipment, method of operation, initial cost, operating and maintenance costs should be considered. 

Some plastics can be used with many different processes, but certain others require a specific process. Generally, process selection takes place before material selection, as a range of materials may be available for different processes or only one method of processing may be available. The one process situation could be very unprofitable or restrictive to product performance. Figures 11-2 through 11-7 provide summary guides to selection procedures for processes, products, and materials (3). It is important to realize that the fabrication process can markedly influence product performance. 

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