Handling 99% Nitric Acid

[pumpking]

We have an application we are looking at handling 99% Nitric Acid which is quite specialist and higher concentration than generally commercially available.

We are offering virgin ETFE lined components, replacing Glass filled ETFE parts from another pump manufacturer - does anyone have experience of handling this concentration Nitric with filled ETFE materials ? What was operational life ? Did the components commonly swell ?

Ash Fenn

http://www.cdrpumps.co.uk

 

[Demon3]

No experience but I would make sure you do your own testing on that. Imagine the costs if the ETFE fails and your stuff is to blame. I'd be really careful and get the tests done rather than rely on advice from strangers. Many people here really know their stuff but why take the chance? The exception would be to get advice from the manufacturer of the ETFE.

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

 

[patprimmer]

I am with Demon3

You must do your own tests here. Even raw materials suppliers data cannot be really relied on. It probably does not exist for the exact same reagent, and even if it does, it will not be on real world normal mouldings. The tests will have been done on test bars under conditions that maximise it's performance.

Do your own tests on real world mouldings under real world loads and temperatures.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[pumpking]

Thanks for the reply's, were happy, along with the ETFE manufacturer that virgin ETFE is more than suitable for the application - we have a number of installations already on similar installations, i was just trying to learn more about filled materials that people may have and more reasons as to why the existing pump (not ours i add) sufferes so many problems.

You are right, it is nasty old stuff and need to be absolutely sure.

Ash Fenn

http://www.cdrpumps.co.uk

 

[Demon3]

OK, now I see what you're getting at. Glass fiber can help the nitric acid get inside the part because liquids can wick along the fiber/polymer interface. This means that in many cases you will be better off without the glass fiber. If you want some reinforcement but without the wicking then I expect a platy filler such as mica may be worth trying.

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

 

[patprimmer]

One problem with fillers and aggressive chemicals is that even though the chemical might not attack the filler itself, it might attack the coating or the coupling agent that is there to help the filler disperse and or bond to the matrix.

You really do need to do tests in real world conditions as there are more variables than you might at first imagine.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[unclesyd]

You might try the NASA websites for technical papers on Fuming HNO3 as all forms were used as an oxidizer early on in rocket fuels.

http://ntrs.nasa.gov/search.jsp

We used some small pumps to handle hot 65-70 % nitric that were made from PTFE and chopped PTFE molded together. A strange combination but it worked.

 

[mjh368]

Thats nasty stuff and if there is any heat that makes things must worse. I have done some stuff with high % HF using CTFE. Good results. Problem with Mica and other fillers is their resistance to strong acids.

 

[sarah79]

If you need an exact answer to your question, please take a look at

http://www.diffusion-polymers.com

This organization/platform has performed independent assessments with regard to similar cases, including the nasty chemicals (like Acids, Chlorine and Bromine in ETFE), for a pretty long time.

They developed a programme called "Instationary Diffusion & Corrosion Simulator for Advanced Composites" (IDC-SAC), which seemingly works for all sorts of reinforced and multilayer polymer based materials (coatings on steel, grp on concrete etc).

Good luck,
Sarah