6

General Notes:

1. The materials for pump parts for each material class are given in Appendix H.

2. Specific 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 non-hazardous locations only. Steel casings (2.11.1.4) 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 services.

4. Mechanical seal materials: For streams containing chlorides, all springs and other melal parts should be Alloy 20 or better. Buna N and Neoprene should not be used in any scrvicc containing aromatics. Viton should tie used in ser vices containing aromatics above 95°C (200°F).

Reference Notes:

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

6. The corrosiveness of foul waters, hydrocarbons over 230°C (450°F), acids, and acid sludges may vary widely Material recommendations 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 23P-370°C {451 "-TOCF). Specific material recommendations should be obtained in each instance.

8. All welds shall be stress relieved.

9. Alloy 20 or Monel pump material and dual mechanical seals should be used with a pressurized seal oil system.

10. For sea water 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.

aAPI Standard 610, 8th Edition (Reference 1)

where the differential head is mostly static, such as in mountainous areas, pumps are often installed in parallel. A series installation arrangement in a static system would be unsuitable because the differential head required could not be obtained unless all of the units were operating. In certain cases, however, where differential head requirements exceed levels practical for a single multistage pump, a combination of series and parallel arrangements may be desirable.

Construction A single-stage double-suction pump, a two-stage double-suction pump, and a four-stage pipeline pump are shown in Figures 9, 10, and 11, respectively. All the units are double volute and are of axially split construction. The single-stage double-suction

TABLE 2 Materials for pump parts (Courtesy of the American Petroleum Institute)0
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