Top of Flare Boom/Stack Material Selection

[HOWDOO]

Hello,

I am wanting to determine if 316 stainless would be suitable for some load bearing components we would supply to the top of an offshore flare stack (>1m from the tip). Historically my company has employed a 'belts & braces' approach in selecting Alloy 800H. The main rational being the combined heat (~600°C), the salt-laden environment and the flare gases (I believe H2S is a typical concern in this type of service?).

Are there any studies/literature that show 316 would be suitable in this application, ideally including estimated corrosion rates per year?

 

[EdStainless]

I wouldn't use 316 for something that sees cyclic heating in a high chloride environment.

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P.E. Metallurgy, Plymouth Tube

 

[HOWDOO]

Thanks EdStainless, I'm assuming this is because of potential Stress Corrosion Cracking? I should add we are aware of several competitors using 316 for a similar application.

 

[EdStainless]

It depends on service. If it is always on then the hot end you only have to worry about molten salt corrosion, at this is with any alloy.
As long as there is no place that is intermittent wet/dry that is 316 you might get away with it. It sounds like a foolish way to trim a couple percent from the cost.

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P.E. Metallurgy, Plymouth Tube

 

[blacksmith37]

For heavy use 316 is poor. I have seen a lot of 310 but 800 is better , 825 very good. What has your experience been with 800 , use that as a guide to determine if you can upgrade or down grade.

 

[georgeverghese]

I've seen an Incoloy 800 Coanda HP flare tip cracked and sooted on an 800mmscfd production rate offshore CPP - reason stated was extended operation at very high turndown - flame lick in simple language.

 

[HOWDOO]

Blacksmith37. Our experience with 800 has been very good, we have empirical knowledge of our equipment lasting as long as 25 years. However, most of our supply would not be in service that long, so we've been looking at the alternative material (316) to reduce costs for our clients. What I was hoping to get what an indication of corrosion rate in this environment (mm/year).

 

[EdStainless]

If you are looking to downgrade from 800 then perhaps 310 might be a good option.
When you go to lower Ni than that you really start loosing resistance to high temp.

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P.E. Metallurgy, Plymouth Tube