Reactor Effluent Air Condenser inlet piping 1

[ispengg]

Greetings,

I want to get clarified on few things on selection piping metallurgy for the inlet of Reactor Effluent Air Condenser [REAC] for Hydro processing Units i.e Hydrocrackers & Hydortreaters.

1. Is anybody is using Austenitic Stainless steel [300 series] in these sections?

2. If yes,what is chloride content in the feed?

3. Above which threshold limit high nickel like Alloy 625, Alloy 825 or Duplex stainless steel is selected to avoid Chloride stress corrosion cracking?

 

[pradipgoswami]

Hi ,
This equipment one of the complex equipment in the hydro processing circuit.The failure of REAC could take the entire hydro processing unit out of operations.API-RP-932B has detailed description about various operational and design issues. According to to this RP:-
MATERIAL SELECTION CRITERIA:-
Materials currently in use in REAC systems include carbon steel, Type 400 series stainless steels, Type 300 series stainless steels, duplex alloys such as 3RE60 and 2205, Alloy 800, Alloy 825 and Alloy C-276. Alloy 400 has also been used in some units. The selection of a material and its performance in service vary depending upon operating conditions and fabrication practices. None of these materials are entirely immune to corrosion in these services although some deterioration mechanisms are easier to manage with some alloys than others. Potential high alloy upgrades that could be considered are Alloy C-276, Alloy 625 and a super duplex stainless steel Alloy 2507.

300 series alloys have inherent problems to Chloride Pitting & Chloride Stress Corrosion Cracking. Duplex 2205 and 2507 & Few Other Super/hyper Duplex Grades(2707)fits perfectly into the budget , if fabricated with due care. API-RP-582 & RP-938C addresses the critical issues with duplex/super duplex fabrications.

Alloy 625 & 825 are high end expensive alloys, and have to be considered when the feed chemistry and the operating parameters are beyond the ranges of DSS & SDSS.

I hope the attached paper(highlighted areas) would give you more insight to the issues, in addition to API RP-932B.

Ideally the piping specification should match or be exceed the base metals of the REAC coolers.

It would be nice to know the final outcome.

Thanks.

Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299
All provided answer are personal opinions or personal judgements only. It's not connected with any employers by any means.

 

[EdStainless]

In general the progression that I have seen is 430(or 439), 2205, AL-6XN, C276.
The is no real reason to bother with 3xx alloys.
If a ferritic won't handle it then a standard duplex may, the 6%Mo super-austenitic has good pitting and SCC resistance and is generally superior to 825. Once you need something better than that the price difference between 625 and C276 is small and C276 has much better corrosion resistance.

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P.E. Metallurgy, Plymouth Tube

 

[ispengg]

Thanks for the rply,

Yeah I am aware of the API 934B guidelines. Can you please share your field experience in using Austenitic stainless in REAC upstream piping.

The major corrosion mechanisms which plays key role in Metallurgy selection for these sections are:

1. NH4HS corrosion
2. NH4Cl corrsion
3. Wet H2S - SCC,HIC
4. PTASCC

Based on hydro processing unit which i have come across,

1. Normally in these sections [including REAC] ferritic steels with PWHT is used, if NH4HS concentration is less and NH4Cl corrosion is not prominent [even though trace of Chlorides may be expected in the feed].

2.a.If NH4HS concentration is high, for eg. more than 8%, then either Duplex or High Nickel alloys like 825,625 or C-276 is used.

2.b. If NH4HS concentration is high and high amount of chloride is expected in then mostly High nickel alloy 825,625 or C-276 is used.

3. Normally 300 series is not preferred [even 904L also- at least I have not seen]because of its Chloride stress cororosion cracking. High nickel [average 42% Ni] is required to resist Chloride SCC.

4. Usage of Duplex stainless steel for thick sections of REAC requires special attention [a few major failures have occurred] and I believe its not recommended by major licensor unless there is a economical reasons.

I just want to know, is anyone is using 300 series austentic stainless steel in these section and what is the experience with corrosion and cracking issues