chemical compatability

[schick]

I have a situation where I am distributing a food product and the equipment is being sanitized with NaOH or Cl at a temp of up to 200 degF.

I know stainless will handle the job, but I am having to pass this through solenoid actuated air valve, the same type that actuate pneumatic cylinders, during cleaning. The standard materials for this part are aluminum, or magnesium.

I'm looking for ideas for materials which can handle the cleaning solution.

Don't know if it helps, but during production, the valves pass CO2 at about 36 deg F.

Thanks in advance for all (any) help!!!!

 

[TD2K]

How strong is the NaOH solution? I wouldn't recommend aluminum. CS is usually fine for NaOH.

 

[schick]

The max concentration is supposed to be 5% (either NaOH, or Cl), but you know how some people are...

"Make it stronger and it will clean better."

So I'm figuring between 5-10%

What's CS?

 

[TD2K]

By NaOH or Cl, I suspect you mean bleach. One of my reference books (and I'm not a metallurgist so take this only as a starting point) confirms regular CS (carbon steel) is suitable for caustic solutions up to about 30%. If the operating temperature is over 120F, it recommended post weld heat treating all welds to avoid caustic embrittlement and associated cracking.

 

[moeszu]

I have had poor results due to resistance properties of stainless steel with chlorine solution (dissolved the level probes in a 12.5 percent sodium hypochlorite solution) and would not be convinced that chlorine would not attack the SS. We needed to switch to titanium for the probes (other materials are acceptable but the titanium was reasonable for the requirements).

 

[joeswoes]

Is non-metallic construction an option for the valve ? The plastics are more forgiving than metals when chlorides may be present. Your temperatures are certainly in their range.

 

[polyman]

Does EPDM have a high chemical resistance to Propylene Oxide at ambient temperatures? In otherwords, is it a good application for PO service?

 

Don't use CS (Carbon Steel) while this material has a small acceptable corrosion rate for weak caustic service it is not acceptable for foodservice. The caustic or bleach will dissolve iron which could end up in a food product or contaminate the system. 316 ss should be used.

 

I am pumping Triazine for H2S reduction. Anyone have any info on compatability with chemical pump materials of construction????