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Fundamentals of Corrosion
1. What is the normal operating temperature and temperature range?
2. What peak temperatures can be reached during shutdown, startup,
process upset, etc.?
3. Will any mixing areas exist where exothermic or heat-of-mixing
temperatures can develop?
4. What is the normal operating pressure?
5. What vacuum conditions and range are possible during operation,
startup, shutdown, or upset conditions?
6. Will there be temperature cycling?
7. What cleaning methods will be used?
Finally, consideration should be given the conditions external to the vessel
or pipe:
1. What are the ambient temperature conditions?
2. What is the maximum surface temperature during operation?
3. What are the insulation requirements?
4. What is the nature of the external environment? This can dictate finish requirements and/or affect the selection of the shell material.
5. What are the external heating requirements?
6. Is grounding necessary?
With the answers to these questions, an appropriate selection of a material of
construction can be made.
11.2 Selecting Materials of Construction
Although cost is a consideration in the selection of materials, it should not
necessarily be considered in the first cut of materials that can be eliminated
from consideration. The cost factor must be considered but only after the
list of materials that fulfill the other requirements has been narrowed for
technical reasons. There are several ways to approach the elimination process. Following is a suggested format. The actual format will depend on the
requirements for each specific application.
1. Temperature. For an application requiring elevated temperature usage,
there is no point in considering low-melting-point metals, polymers,
or polymer composites. For operating temperatures above 932°F
(500°C), the list of potential materials can be greatly reduced. On the
Fundamentals of Corrosion
1. What is the normal operating temperature and temperature range?
2. What peak temperatures can be reached during shutdown, startup,
process upset, etc.?
3. Will any mixing areas exist where exothermic or heat-of-mixing
temperatures can develop?
4. What is the normal operating pressure?
5. What vacuum conditions and range are possible during operation,
startup, shutdown, or upset conditions?
6. Will there be temperature cycling?
7. What cleaning methods will be used?
Finally, consideration should be given the conditions external to the vessel
or pipe:
1. What are the ambient temperature conditions?
2. What is the maximum surface temperature during operation?
3. What are the insulation requirements?
4. What is the nature of the external environment? This can dictate finish requirements and/or affect the selection of the shell material.
5. What are the external heating requirements?
6. Is grounding necessary?
With the answers to these questions, an appropriate selection of a material of
construction can be made.
11.2 Selecting Materials of Construction
Although cost is a consideration in the selection of materials, it should not
necessarily be considered in the first cut of materials that can be eliminated
from consideration. The cost factor must be considered but only after the
list of materials that fulfill the other requirements has been narrowed for
technical reasons. There are several ways to approach the elimination process. Following is a suggested format. The actual format will depend on the
requirements for each specific application.
1. Temperature. For an application requiring elevated temperature usage,
there is no point in considering low-melting-point metals, polymers,
or polymer composites. For operating temperatures above 932°F
(500°C), the list of potential materials can be greatly reduced. On the