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API 950

1983 Edition, April 1983

Complete Document

Survey of Construction Materials and Corrosion in Sour Water Strippers

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Product Details:

  • Revision: 1983 Edition, April 1983
  • Published Date: April 1983
  • Status: Not Active, See comments below
  • Document Language: English
  • Published By: American Petroleum Institute (API)
  • Page Count: 95
  • ANSI Approved: No
  • DoD Adopted: No

Description / Abstract:

SUMMARY: In December of 1977, questionnaires were sent out to gather information on experiences with corrosion in sour water strippers. This survey was sponsored by the Panel on Materials of Construction for Sour Water Strippers of the Subcommittee on Corrosion. It updates the results of a 1972 survey, which were presented in API Publication 944, November 1974.

Replies were received from 13 companies and affiliates, representing 92 strippers at 71 locations. The tabulated data are presented here in the same general format as the 1972 report, except that Appendix Tables 2, 3, and 4 have been separated into materials experience and process conditions sections.

The major conclusion of the 1972 report was that the location and severity of corrosion varied with the design of the sour water stripper. In acidified type units, corrosion was severe in the feed section, the stripper tower, and the bottoms section, while corrosion in the overhead section was negligible. The corrosion was caused primarily by inadequate pH control on the acid injection. The lack of corrosion in the overhead section was believed to be due to the absence of ammonia in that section, the ammonia being neutralized by the acid injection. Ammonium sulfide salts in the overhead section were cited as causing under-deposit corrosion and contributing to erosion-corrosion. In non-acidified, condensing type units, severe corrosion and erosion-corrosion occurred in the overhead section, while corrosion in the feed section, stripper tower, and bottoms section was negligible. In non-acidified, non-condensing type units, corrosion throughout was negligible. In addition to the corrosion characteristics of the various units, the 1972 survey found that plugging of non-acidified type units presented a major operating problem. Plugging of the tower and bottoms was due to carbonate deposition and corrosion products. Plugging of the overhead system was due to ammonium sulfide salts and corrosion products.

In general, the results of this most recent survey bear out the conclusions of the earlier survey. One discrepancy exists in that the number of plants indicating that they acidify the feed dropped from eight in 1972, to three in 1978. This lack of information makes it difficult to draw specific conclusions about the relationship between plant design and corrosion experience. However, the data presented in this report does not contradict the findings of the earlier study on any point, and it should be noted that these two surveys were never intended to make broad conclusions that will apply in every case. Further study is needed to fully define the relationship between corrosion of materials in these units and the sour water chemical composition, temperature, and fluid velocity.