I’m sure most have heard someone say, “Oh, that’s just a bad material.” I would suggest that, “There are no bad materials, only bad material selections.” There is no silver bullet in materials, i.e. one material that is good for every application, and cheap too. Most materials are judged on a number of characteristics based on physical properties, corrosion resistance, cost, availability, ease of fabrication, weldability and available certified labor.
I am of the opinion that each material has its place, that service environment that meets all of the plant’s priorities. I would define a successful application of a material as one that provides safety and reliability for a desired service life. Of course, there must always be an understanding of the budget constraints.
Carbon steel is one of the most commonly used materials of construction, with countless successful applications, but if put in a corrosive environment it may fall short on expectations. 316 Stainless Steel is a common alloy material frequently used, but put it into a weak sulfuric acid service and it may only last a matter of days. Yet in a higher concentration and temperature sulfuric acid application, 316SS is well proven. Like most things, it is all about the details.
When materials do fall short, it can be due to insufficient information. There are times when the principal chemical constituents are defined, but maybe there are some secondary or trace chemical elements in the flow stream that may be overlooked. Operating conditions may be defined, although significant thermal or pressure excursions may not be evaluated or understood. Communication and thorough investigation are important components of the material selection process as well.
Non-metallic materials are less understood and have their challenges at times. There have definitely been some cases of misapplication or poor execution of nonmetallic materials in the past. Today, knowledge and resources for non-metallics are more reliable and available. This progress has led to more consistent success in corrosive or hazardous applications, where only high-end alloys may have been considered in the past.
In today’s competitive environment, project and process engineers are challenged with budgetary pressures as well as expectations of higher performance. To best meet these demands, engineers must conduct a comprehensive investigation of all materials to select the optimal material for the priorities.
For corrosive applications within defined temperature ranges and other conditions, non-metallic materials of construction, such as FRP, dual laminate and thermoplastics can be cost effective and reliable material choices. Selecting and specifying the best materials is just the first of many steps of project execution, but a very important step. One of many choices to be made for a successful project.
What are your priorities for selecting materials???
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