Requirements for the material of centrifugal pumps

Phase steel 2205 is recommended; it should meet your requirements!

The material of duplex steel is way too expensive. Is there any evidence?

316L can also meet your requirements in the absence of particles; using duplex steel would indeed be a bit wasteful, as it is more commonly chosen when the medium contains particles.

It was the first time I heard that A-8 material is required because the medium contains H2S, so I checked Table H1 in API 610 (version 11) specifically, and indeed found nothing such as that. But since it is noted that your medium contains chloride ions, then chloride ions must be the fundamental reason for your use of A-8. As for the relationship between chloride ion concentration and the material, I previously came across a Grundfos report (downloaded from their website a few years ago), which indicates that it is related to the operating temperature. Specifically, in an environment at 35°C with a neutral pH value, the tolerance limit of 316L to chloride ions is approximately 500PPM. Moving up, one needs to consider duplex steel. However, according to this report, at 35°C, the tolerance limit for duplex steel is around 700PPM. Furthermore, it should be noted that if the medium contains H2S at levels above 200PPM, the choice of mechanical seal has a significant impact. This conclusion was reached through technical discussions with experts from Flow Serve and Sulzer.

A8 is made of 316 steel, which is not resistant to chloride ion corrosion; you can refer to the material used for containers in similar environments as a guide

Thank you for your reply. Since the medium contains hydrogen sulfide, leakage must definitely be taken into consideration when selecting mechanical seals. The medium contains hydrogen sulfide; considering its corrosiveness, what type of material should be chosen?

Refer to page 168 of the first edition or page 88 of the second edition of the Industrial Pump Selection Manual.

Regarding the corrosion caused by H2S, according to NACE standards, it is mainly hydrogen-induced cracking and sulfide stress corrosion cracking. Regarding the material selection for gas field pipelines, the NACE standards are the main guideline; in other words, materials that comply with ISO 3183 plus NACE standards will suffice. Specifically, the material is primarily evaluated based on the contents of S and P, and hydrogen-induced cracking tests as well as sulfide stress corrosion tests are conducted. Other than that, it seems to have no special features compared to ordinary carbon steel. However, regarding the material to be used for the pump and which materials it should be combined with, research is still in progress; at the moment, we’re completely at a loss. But on a project I was involved in, it involved high-pressure amine-depleted liquid pumps for natural gas processing plants; the design standard used was API 610-BB2. The operating conditions were similar to those described earlier – there was Cl- present, as well as residual H2S. The design agency selected S-8 as the material to be used, but the manufacturer suggested changing it to A-8. Before posting in the morning, I checked the discussion records from that time; the manufacturer suggested changing it to A-8, mainly due to considerations related to chloride ions, with a chloride ion concentration of 200 PPM. For reference. Personally, I suggest you get in touch with manufacturers like Ford or Sulzer. These large manufacturers will let you know whether they will buy his equipment or not; they’re not that petty.

Refer to http://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1351679. Note: The NACE mentioned in the above document corresponds to ISO 15156, which can be found online. It’s time to go to work; there’s no time to explore this issue anymore. It seems that the main issue in this operating condition isn’t H2S, but rather Cl-: a 4% concentration of NH3Cl is equivalent to roughly 30,000 PPM in terms of Cl- equivalents; I doubt that A-8 will be sufficient. Referencing Appendix G of API 610, the D-2 material combination should be used.

The cost of 2205 duplex steel isn’t that high; it’s roughly similar to that of 316L