Heat exchanger with sour fluid on tube side

[CKC66]

Hi

I have few shell and tube heat exchangers with sour gas on tube side, whereas shell side fluid is only water.
Both shell side and tube side materials are carbon steel.
There is no doubt that tube side materials shall be in compliance with NACE MR0175.
However there are different views on whether shell material shall also comply with NACE MR0175.
One of the views, is to consider tube rupture scenario, therefore shell side material shall also be suitable for sour service.

So my questions are
1. Is tube rupture case must be considered based on NACE MR0175 or any other code/standard? I can't seem to find any relevant clause
2. In case if tube rupture scenario must be considered according to NACE, how should I determine the boundary to apply on shell side, i.e. should I have the connecting pipework suitable for sour service also?

 

[r6155]

It is the equipment user's responsibility to select materials suitable for the intended service to avoid the consequences of sudden failures of metallic components.
See NACE MR0175 again

Regards

 

[EdStainless]

This is a risk analysis question, not material codes.


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P.E. Metallurgy, consulting work welcomed

 

[georgeverghese]

Not necessary - materials selection is usually not based on some internal mechanical failure scenario. There may be small tube leaks that may go undetected for a long time that may make the local shellside environment sour; see if you can do an annual tubeside leak test and plug off leaking tubes. But there may be more aggressive corrosion mechanisms on the shellside, like microbe induced corrosion (MIC) plus underdeposit corrosion resulting from salt and scale accumulation from poor quality water - you may choose between a CRA material for the shellside or a laborious, expensive and painful long water treatment regimen that may not yield any desired results.

 

[r6155]

You must consider the consequences of failure. You must maintain a safe pressure vessel and avoid possible accidents dangerous to people.

Regards

 

[EdStainless]

Applications that I know of that have not designed the shell side to handle sour service have very sensitive H2S monitors on the shell side water. An alarm requires immediate shut down of the process. Or else you treat heavily and take your chances.

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P.E. Metallurgy, consulting work welcomed

 

[Dhurjati Sen]

I have seen in many plants where such equipment exist, and shell side material has NOT been considered as sour service in the event of a failure scenario.

They are all running for decades, with occasional tube leakages.

Actually, it all depends on how much money one can spend, to make cooling water come under sour service you need to hike the budget a lot.

Some would say that you simply increase the zeros, though.

DHURJATI SEN

 

[r6155]

@ CKC66
I think you chose seamless tubes, right?

Regards

 

[EdStainless]

seamless vs welded doesn't matter, without robust QA either may be a disaster.

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P.E. Metallurgy, consulting work welcomed

 

[CKC66]

Thank you all for your feedback.
So I believe in general there is no code or standard addressing this subject, it is user's responsibility to evaluate and decide.

 

[georgeverghese]

Also, it is going to be more difficult to clean shell side, given that there will be sediment and microbial growth with water. It will a little easier to clean the shell side with 90deg square or 45 rotated square wide pitch. From a cleaning perspective, water on tubeside would be better, plus it will be cheaper to get CRA materials on tubeside than on shellside.