Ball valves are suitable for aggresive media?

[felix201012]

Hello everybody,

Although I am sure this kind of topic was somewhere enlist, please help me out in the following question mark:

--> ball valve, SS304 or 316 are a safe choice for fitting over NaOH pipeline, 50% concentration? And here I am referring to 3 piece ball valve, in a temperature control ambient, no freezing, on a NaOH distribution line.

Many thanks in advance,

Felix

 

[bimr]

Yes, safe choice.

http://www.nickelinstitute.org/~/Me...lloySelectionforCausticSodaService_10019_.pdf

 

[felix201012]

Hello,

Thank you very much for the answer. From compatibility point of view is clear = ok.

Regarding the design? Ball valves, flanged, are ok for this purpose?

Many thanks again,

Felix

 

[moltenmetal]

Experience has shown that if the caustic isn't hot, austenitic stainless steels work well. As for ball valves, just make sure that they contain no Viton O-rings or glass-reinforced Teflon parts, as both are susceptible to attack by caustic.

That was a surprisingly lightweight treatment of the subject for a Nickel Development Institute publication- they're usually excellent. There's only passing mention of the fact that the membrane cell caustic product is contaminated with chloride in substantial quantity, and apparently may also contain chlorates too. Obviously those contaminants would have a major influence on the alloy selection.

 

[felix201012]

Thank you for clarifications.

So in terms of safety check, I should go to diaphragm type of closing.

With regards,

Felix

 

[bimr]

PPG, a manufacturer of sodium hydroxide provides these handling recommendations.

Use Teflon® brand fluoropolymer resin-lined plug valves, which are gear-operated above the 4” size. Iron or steel plug valves of the lubricated type give good service for normal use.

For high-temperature use, nickel-cast iron plug valves or nickel gate valves with deep packing glands should be
used. Stainless steel can also be used in some cases.

Other types of valves commonly used include non-lubricated ball valves and gate valves made entirely of iron or steel.
Brass valves should be avoided, especially at high temperatures or concentrations of 50% or above, because they are corroded by caustic soda and will leak. They can also introduce copper contamination that can be harmful to certain manufacturing processes.

http://www.ppg.com/chemicals/chloralkali/products/Documents/CausticSodamanual2008.pdf

It is also a general recommendation to use an Alloy-20 material of construction plug valve shutoff at the tank.

 

[felix201012]

Thank you a lot for the info and details.

The planet is saved! Me as well

Cheers to all