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Materials of Construction

General notes
1. The materials for pump parts for each material class are given in Appendix H.
2. Separate materials recommendations should be obtained for services not clearly
identified by the service descriptions listed in this table.
3. Cast iron casings, where recommended for chemical services, are for nonhazardous
locations only. Steel casings (S-1 or I-1) should be used for pumps in services located
near process plants or in any location where released vapor from a failure could create
a hazardous situation or where pumps could be subjected to hydraulic shock, for
example, in loading service.
4. Mechanical seal materials: for streams containing chlorides, all springs and other
metal parts should be Alloy 20 or better. Buna-N and Neoprene should not be used
in any service containing aromatics. Viton should not be used in services containing
aromatics above 200~

Reference notes
5. Oxygen content and buffering of water should be considered in the selection of
material.

6. The corrosiveness of foul waters, hydrocarbons over 450~ acids and acid sludges
may vary widely. A materials recommendation should be obtained for each service.
The material class indicated above will be satisfactory for many of these services but
must be verified.
7. If product corrosivity is low, Class S-4 materials may be used for services at
451~176 A separate materials recommendation should be obtained in each
instance.
8. For temperatures greater than or equal to 160~ all welds should be stress relieved.

9. Alloy 20 or Monel pump material and double mechanical seals should be used with a
pressurized seal oil system.
10. For seawater service, the purchaser and the vendor should agree on the construction
materials that best suit the intended use.
11. Class A-7 materials should be used, except for carbon steel casings.

Reproduced with permission of the American Petroleum Institute

--~251 m