Valve Materials Selection for sodium hypochlorite service

[sw007]

I need to select a material for a valve which will be served in 12.5% sodium hypochlorite solution. The normal operating temperature is 35 DegC and Design Temperature is up to 65 DegC. At first, we selected Carbon Steel with PTFE lining. But the valve is too small to be lined. Please advise an alloy material we can offer as an alternative.

Thanks.

 

[metengr]

For this design temperature and concentration, your alloy selections will be very limited for corrosion less than 2 mpy,

Tantulum
Titanium
and Zirconium

Source; Corrosion Survey Database from NACE International

 

[strider6]

Sw

Here you can fin some info on materials for hypochlorite. It seems that one candidate material is Hastelloy C:
RESISTANCE OF NICKEL AND HIGH-NICKEL ALLOYS TO CORROSION BY HYDROCHLORIC ACID, HYDROGEN CHLORIDE AND CHLORINE

http://www.enia.org/index.cfm/ci_id/15786/la_id/1/ci_doc_id/3143/search_keyword/metal/method/.html

Selection of stainless steels for handling sodium hypochlorite (NaOCl)

http://www.bssa.org.uk/topics.php?article=35

HASTELLOY® C-276 alloy Information*

http://www.haynesintl.com/HASTELLOYC276Alloy/HASTELLOYC276AlloyPF.htm

http://www.corrosionist.com/isocorrosion_curves.htm

hope this help

S

Corrosion Prevention & Corrosion Control

 

[moltenmetal]

If the pressures are low, look at solid PVDF (Kynar) or PFA.

The smallest PTFE-lined CS plug valves available are 1/2" flanged(they cost a little more than 1" valves of the same design), so I presume this is a tubing valve.

Otherwise you're looking for the wrong valve type.

In PTFE-lined, the plug valve is king- it is used for both block and throttling (with gearwheel actuator and characterized plug if required).

 

[sw007]

May be the PTFE-Lined valve is available on the market. But our supplier can not make it. That's the reason the want us change to alloy valve.

If we use solid PVDF or PFA, what is the plug or other internal material?

Thanks.

 

[moltenmetal]

Umm- change suppliers to one who makes what you want to buy?! Plenty of vendors make these-

PVDF or PFA valves have PVDF or PFA internals (or other fluoropolymers like ETFE, PTFE etc.). O-rings where required can be viton or Kalrez etc. Sometimes seats are made of machinable ceramics or tantalum etc. where they're needed. Sometimes PEEK etc. is used- check compatibility as PEEK is not a fluoropolymer.

 

[EdStainless]

I like mm's response.
I am a metals guy, and trust me this not a service for metals if you can avoid it.
The are some structural ceramics that will do well in this environment, so perhaps a solid ceramic plug or ball in a flouropolymer body might be an option.

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