How saline is the vent gas?
I have seen a number of these made from super stainless (Sea-Cure or AL-6XN) and work fine.
It depends more on the cooling water.
825 is not very chloride resistant, I would never consider it.
What's the chloride content, operating temperatures of the venting system? Why not attach some data and operating description of the component first?
Thanks.
I have read your fine responses to many questions on these fora for some years. I consider your experience and knowledge to be a real asset to this website ...
But could you better explain what you mean by your "super stainless" group ? Is this group defined by PREN number ?
I have been involved in supplying both super ferritic (Sea-Cure) or superaustenitic (AL-6XN) for these ejector coolers. This is often driven by the cooling water.
I have seen people move away from Ti or 400 because they will erode if (when) there is droplet impingement.
sorry for lack of data, i will add the following:
our heat exchanger shell made of S.S 316L suffering from chloride induced stress corrosion cracking (CSCC) when exposed to a combination of tensile stresses, chlorides, water, oxygen, and a temperature. This heat exchanger tube type combined with steam ejector, the combination work as venting system in evaporator unit in Tobruk Desalination plant, this venting system designed to provide vacuum in the unit to produce distillate water. The shell failed after few months from first start, the responsible company replaced S.S316L by DUPLEX S.S 2205 which is also failed after one year. The investigations show that AMMONIA present in the intake feed water due to the discharge of sewage water into the intake area. due to the fact that chloride present naturally in sea water and the injection of chlorine to disinfection of sea water against the marine growth, the chemical reaction between ammonia and chlorine produces chloroamines and bromoamines which causes the SCC of the condenser shell. the heat exchanger cooling medium is sea water inside the tubes,the motive steam coming from the boiler with 30bar and 245c inter the ejector which connected to suction pipe to evacuate the system, the mixture coming from the unit consists of vapor and non-condensable gasesabout 60c and pressure > 1bar
Our idea is to replace DUPLEX S.S 2205 with MONEL 400 another idea to use INCOLOY 825 instead of MONEL therefore we need your advice which is better in this environment?
I still prefer superferritic (Sea-Cure) or super austenitic (AL-6XN) for this service.
I have tested Sea-Cure in Br service and found it very resistant. See the attached paper.
I would worry about 825 pitting in high Br conditions, and with 400 I would worry about erosion from impingement. It is softer than any of the other alloys that you have considered.
I don't know why you expected 316 or 2205 to work with seawater cooling, neither of these alloy is suitable for seawater service.
Dear EdStainless
Thanks a lot for your fast response, i will send you my paper to clarify the problem, i think it will be more clear, then we will discuss the mater together, any way the idea to use SS316L and DUPLEX 2205 was from the construction company, we tried to solve the problem since 2003 by cutting the corroded area and welding new material just like emergency maintenance, later on i tried to find solution for this problem by introducing the attached paper(please read it)at the moment there will be complete overhauling for the plant and the responsible company for this work prefer to use INCOLOY 825 INSTEAD OF MONEL 400, i tried to advice them to use Monel as construction material for the heat exchanger shell because the experiment succeed in this environment, the discussion still going on till now, thats why i need your help because i consider your experience. its important to read my paper first then we can see.
Hi Mr Abubaker,
I presume you're referencing this paper as below. Appreciate if you share it in this forum.
Your problem looks to be complicated. 316L & duplex stainless steels generally preforms well in chloramine environment. There're numerous literatures supporting this. If I remember correctly this compound is used as disinfectant (Chlorination) in water treatment plants.
Corrosion in desalination plants could be severely compounded by presence of saline water with high level of chlorine, level of contaminants, high intake temperature in tropical countries (Libya) and many cases by bio fouling and many more… Why not engage a Laboratory to test different alloys under the simulated conditions. The results may provide you long term guidelines rather than taking shots at random. You may buy this information under license also.
Desalination is the most convenient process for drinking water in Middle East. There're limited resources in the web. The steels which standard out the best are the alloys with high PREN , typically SDSS 2507,Zeron100 254SMO.
Nickel alloys, e.g. 825, 625 are good where resistance to SCC are important, not Pitting or Crevice Corrosion alone.
254 SMO(AL-6XN) is also good and popular choice same applies for 654SMO also.
Sea Cure 446 is a good alloy, however fabrication/availability of matching electrodes may be a problem.
I believe Ed Stainless has already pointed out about some of these alloys.
Your Paper.
S.S 316L STRESS CORROSION CRACKING OF VENTING SYSTEM AT TOBRUK DESALINATION PLANT Paper’s Country of Origin: Libyan Arab Jamahiriya Authors: Mohamed Rezek Abubaker Presented by: Mohamed Rizig. Abubaker IDAWC REF: 51764
IDA World Congress on Desalination and Water Reuse Renewable Water Resources to Meet Global Needs August 30 - September 4, 2015
San Diego Convention Center San Diego, California, USA
Thanks a lot Mr.Pradip Goswami
I tried to upload my paper via attachment as mentioned above but not succeeded, any way here under the keywords of the paper as you mentioned it, you can downloaded from the web till i success ed to upload it.[S.S 316L STRESS CORROSION CRACKING OF VENTING SYSTEM AT TOBRUK DESALINATION PLANT Paper’s Country of Origin: Libyan Arab Jamahiriya Authors: Mohamed Rezek Abubaker Presented by: Mohamed Rizig. Abubaker IDAWC REF: 51764
IDA World Congress on Desalination and Water Reuse Renewable Water Resources to Meet Global Needs August 30 - September 4, 2015
San Diego Convention Center San Diego, California, USA]
Really i appreciate you information, we will be in contact through this forum.
