The Equipment Design Process
331
they travel over at speed, and the height of the local surf. Mixtures of marine
and industrial effects are common in many areas, with each type of contaminant aggravating the other.
In addition to these general air contaminants, there may also be specific
pollutants found in a localized area. These may be emitted from a manufacturing operation on a continuous or spasmodic basis and can result in a
much more serious corrosion problem than that caused by the presence of
general atmospheric pollutants.
Because of these varying conditions, a material that is resistant to atmospheric corrosion in one area might not be satisfactory in another area. For
example, galvanized iron is perfectly suitable for application in a rural atmosphere but is not suitable when exposed to industrial atmospheres.
To compound the problem, there is no clear line of demarcation between
these atmospheric types. In many cases, there is no “pure” rural or urban area.
Contamination from industrial or marine areas may find its way into these
areas based on the prevailing winds and other atmospheric conditions.
Indoor atmospheres may be free of corrosion in “clean rooms” or subject to
severe corrosion, as around a pickling bath in a steel mill.
Atmospheric conditions should be defined in terms of temperature, humidity, and contaminants, as well as their corrosivity to the specific materials
of construction being considered. In addition to the general atmospheric
conditions, special conditions such as cooling tower drift or spray, spills, or
releases of water or chemicals should not be overlooked and must be taken
into account.
If the application is a process vessel, storage tank, or pipeline, the following information must be known about the process and/or the material
being handled:
1. What are the primary chemicals being handled? And at what concentrations?
2. Are there any secondary chemicals? And if so, at what concentrations?
3. Are there any trace impurities or chemicals?
4. Are there any solids present? And if so, what are their particle sizes
and concentrations?
5. If a vessel, will there be agitation? And if so, to what degree? If a
pipeline, what are the flow rates (maximum and minimum)?
6. What are the fluid purity requirements?
The answers to the above questions will narrow the selection to those materials that are compatible. The next set of questions will narrow the selection
further by eliminating materials that do not have the required physical and/
or mechanical properties required:
331
they travel over at speed, and the height of the local surf. Mixtures of marine
and industrial effects are common in many areas, with each type of contaminant aggravating the other.
In addition to these general air contaminants, there may also be specific
pollutants found in a localized area. These may be emitted from a manufacturing operation on a continuous or spasmodic basis and can result in a
much more serious corrosion problem than that caused by the presence of
general atmospheric pollutants.
Because of these varying conditions, a material that is resistant to atmospheric corrosion in one area might not be satisfactory in another area. For
example, galvanized iron is perfectly suitable for application in a rural atmosphere but is not suitable when exposed to industrial atmospheres.
To compound the problem, there is no clear line of demarcation between
these atmospheric types. In many cases, there is no “pure” rural or urban area.
Contamination from industrial or marine areas may find its way into these
areas based on the prevailing winds and other atmospheric conditions.
Indoor atmospheres may be free of corrosion in “clean rooms” or subject to
severe corrosion, as around a pickling bath in a steel mill.
Atmospheric conditions should be defined in terms of temperature, humidity, and contaminants, as well as their corrosivity to the specific materials
of construction being considered. In addition to the general atmospheric
conditions, special conditions such as cooling tower drift or spray, spills, or
releases of water or chemicals should not be overlooked and must be taken
into account.
If the application is a process vessel, storage tank, or pipeline, the following information must be known about the process and/or the material
being handled:
1. What are the primary chemicals being handled? And at what concentrations?
2. Are there any secondary chemicals? And if so, at what concentrations?
3. Are there any trace impurities or chemicals?
4. Are there any solids present? And if so, what are their particle sizes
and concentrations?
5. If a vessel, will there be agitation? And if so, to what degree? If a
pipeline, what are the flow rates (maximum and minimum)?
6. What are the fluid purity requirements?
The answers to the above questions will narrow the selection to those materials that are compatible. The next set of questions will narrow the selection
further by eliminating materials that do not have the required physical and/
or mechanical properties required: