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11
The Equipment Design Process
Most engineers, at some point in their careers, are faced with the problem
of selecting a material of construction for a specific project or application.
This applies equally to mechanical, civil, chemical, aeronautical, or any other
engineering or related discipline.
In most cases the selection process requires that the engineer must refer
to more than one engineering discipline in order to select the most suitable
material of construction. For example, chemical engineers must be aware of
the mechanical properties of materials, as must structural engineers, while
both must be aware of the corrosion-resistant properties of materials — and
so with other engineering disciplines.
It is the purpose of this chapter to point out the various considerations that
must be taken into account, with primary emphasis being placed on corrosion resistance.
11.1 Understanding the Application
Before any consideration can be given to the selection of a material of construction, there must be a thorough understanding of the application.
If the application is a structure, whether it be a tower, bridge, or building,
it is important that the location be defined because it will be subject to atmospheric corrosion.
Because atmospheric corrosion rates are affected by local conditions, atmospheres are classified according to exposure conditions. The major categories, based on potential corrosion rates, are:
Rural
•
Urban
•
Industrial
•
Marine
•
Indoor
•
The first four categories can be further subdivided into arctic, temperate, and
tropical (wet or dry) because the differences in temperature, humidity, and
11
The Equipment Design Process
Most engineers, at some point in their careers, are faced with the problem
of selecting a material of construction for a specific project or application.
This applies equally to mechanical, civil, chemical, aeronautical, or any other
engineering or related discipline.
In most cases the selection process requires that the engineer must refer
to more than one engineering discipline in order to select the most suitable
material of construction. For example, chemical engineers must be aware of
the mechanical properties of materials, as must structural engineers, while
both must be aware of the corrosion-resistant properties of materials — and
so with other engineering disciplines.
It is the purpose of this chapter to point out the various considerations that
must be taken into account, with primary emphasis being placed on corrosion resistance.
11.1 Understanding the Application
Before any consideration can be given to the selection of a material of construction, there must be a thorough understanding of the application.
If the application is a structure, whether it be a tower, bridge, or building,
it is important that the location be defined because it will be subject to atmospheric corrosion.
Because atmospheric corrosion rates are affected by local conditions, atmospheres are classified according to exposure conditions. The major categories, based on potential corrosion rates, are:
Rural
•
Urban
•
Industrial
•
Marine
•
Indoor
•
The first four categories can be further subdivided into arctic, temperate, and
tropical (wet or dry) because the differences in temperature, humidity, and