Corrosion allowance factor

[CloudNine1]

Hi all,

I'm working on a project that comprises of building a heat exchanger.

The fluid inside the heat exchanger is sea water (with some algae, but let's ignore that for our matter) at 350 celsius degrees and 250 bar (I'm trying to perform HTL - hydrothermal liquefaction, hence the high pressure).
I've been surfing the web all day (including combing through various standards like ASME B31.3 and TEMA) trying to find which corrosion allowance should I take when calculating the pipe's wall thickness, but I couldn't find any decisive answer.
The pipes' material that I chose to use is Stainless Steel 304L, which, as far as I know, pretty much resistant to corrosion. But can I completely ignore this corrosion factor? I doubt that...
I know that there's an official formula to calculate the corrosion factor, but I don't know what values to plug in it as well...
The heat exchanger will eventually be built, this is ain't a theoretical work, thus I need to be 100% sure of all of my calculations.
Another detail that you need to know: it is a laboratory-scale heat exchanger, so the flow in it will be quite little and short-timed, mainly to see if the HTL process was done successfully.

Would appreciate any of your help!

P.S I also bumped into a few related threads from this very forum, but it didn't really help.

Thanks!

 

[GD2]

Try NACE Corrosion Data Survey

Ganga D. Deka, P. Eng
Canada

 

[CloudNine1]

Is there anything similar, but for free?
It'll take me a month to order such thing, and I can't progress without this value..

 

[Dhurjati Sen]

Deae CloudNine1,

If the sole purpose of this exchanger is to carry out HTL, just fabricate it without any corrosion allowance as per ASME Sec VIII Div 1.

Regards.

DHURJATI SEN

 

[LittleInch]

Cloudnine.

You really need to talk to a materials engineer, but turn up with some data like the type of fluid ( "seawater" is very vague), is it aerated, what is the chloride content?, duration of use etc.

Aerated hot seawater will eat many materials in a very short period of time. 304L stainless will suffer pitting corrosion in seawater so a CA is not the way to go.

You need to be very careful here. HX tubes are often very thin and even a small hole at 350C and 250 bar will be near lethal if it escapes to the outside.

check out the corrosion engineering forum and you should find some charts and graphs of suitable materials.

Is this the tube side? What is the shell side?, what are the tubes outside of the HX made of?

I think you should be looking at Super Duplex myself.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[CloudNine1]

Dhurjati Sen - I have the section you mentioned, but I couldn't find there any reference to HTL process, nor a tip on how to estimate this factor.
Can you show me where you saw this statement there?

LittleInch - I appreciate your elaborated answer.
I don't know the chloride content, I guess the normal concentration you can find in seawater. The duration of use is, as I said, only for proofing the concept of the HTL, not something industrial and not something continuous.
I'm not sure whether the fluid I'll use is considered aerated or not - I will simply feed a tank with seawater with some shredded algae, which will be then pumped into the heat exchanger. This fluid will be heated with an oil.
The design is shell & tube H.E - on the outside (shell) the oil will flow and on the inside the water.
I'm planning to design all of the H.E pipes with the same material.

 

[XL83NL]

@LI: Super duplex stainless steel @ 350 deg C wont work

 

[LittleInch]

XL83NL - I bow to your greater knowledge - I usually work with much lower temperatures, it's just I don't think 304L will work either...

The difficulty here for me is the short duration element and how you make sure that it is only used for said small duration or small number of times before being scrapped. My concern is that it is used a few times, then left for a while not drained down or dried then used again etc etc

If the tube side is the issue then the shell side needs some sort of pressure relief, probably bursting disc vented somewhere safe.

But if the rest of the tubing is wandering around the lab and you've got 350C, 250 bar seawater which will be aerated by the sounds of it then I think your material needs to be bullet proof. 304L isn't bullet proof.

I'm not a materials man, but this is ringing alarm bells to me.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[LittleInch]

Do a search for sweater on the corrosion engineering forum and things like this turn up.

TBF most are low pressure/temp combinations and I know you say it won't be used much but how do you know for sure??

https://www.eng-tips.com/viewthread.cfm?qid=135064

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdStainless]

Seawater at 350C will cause crevice corrosion in Ti gr2, and attack every stainless alloy that there is.
You are into the realm of some high performance Ni alloys or alloyed Ti grades (you would likely need gr 11, 17, or 27).

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P.E. Metallurgy, Plymouth Tube

 

[GD2]

CloudNine1,
My field experience with HX in sea water application is Titanium tubes. Attached is a study report that should give you some confidence. I looked up the NACE Corrosion Data Survey but couldn't find anything on sea water.
You also mentioned that you intend to use 304 piping material in the process circuit. 304 may not be the best material as others had pointed out. It will corrode in sea water. How much will it corrode depends on a number of variables. LI had given you some pointers.
Usually, GRE, non metallic pipings are used for sea water cooling system in a process plant due to exorbitant cost for metallic piping but it has limitations on pressure and temp. Here the challenge is high pressure and high temp.
Look up for a similar industry application. Engage a Corrosion Engineer. The sea water application material selection is an evolution that has evolved around Ni, Cu alloys leading into some outstanding proprietorial materials. One way for cost reduction could be providing internal coating to some cheaper base material.

Ganga D. Deka, P. Eng
Canada

 

[EdStainless]

To answer your question directly, you cannot use a CI for this application.
Because the failure mode will be pitting/crevice corrosion it will be highly localized.
Adding material thickness will not translate into extended life.
You will still have 99.5% of the surface unaffected and pits that go through wall in some locations.

And you will get scaling probably.
At least you won't have to worry about biofouling.
This is serious service, high temp and high Cl make this difficult at best.

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P.E. Metallurgy, Plymouth Tube