Stainless Steel and Domestic Hot Water Storage Tanks 1

[PEDARRIN2]

thread391-154102

I read the thread above and it told me there is no consensus on the use of 304/316L for potable hot water storage tanks - although the research I have done indicates a preference to not use 304/316L.

I have a vendor who has tanks that use 420 stainless. I am not familiar with that type. My research indicates it is used for cutlery among other things.

Would 420 stainless be good material for lining or constructing hot water storage tanks (~160 F with normal chlorine/chloride levels for drinking water)?

 

[EdStainless]

there has been a fair amount of 439 used. There also has been a lot of 304 used, but the insulation must have no chlorides in it and the jacket must seal well.

How much experience does this guy have? Can he show you some 10 year old tanks? I wouldn't use 420. It has too much carbon and the welds will be brittle and susceptible to localized corrosion.
Look at 439, don't go with less than 17% Cr, you'll be sorry.

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Plymouth Tube

 

[strider6]

SS 316 is used for potable water service. The problem of the temperature is the possibility of pitting and stress corrosion cracking, but it is related to the concentration of Chlorides. The other possible problem is on the external surface, for temp above 60°C, if there is possibility of chlorides accumulation (for example in marine atmosphere.. but if it's inside a building and not close to the sea is not an issue..) unless as Ed said there are chllrides in the insulation..
in my opiion you've first to define how much chlorides in in the water then you can assess if SS is suitable or not..

http://www.bssa.org.uk/cms/File/DWI Final 4Jan02.pdf

Selection of stainless steels for water tank applications

http://www.bssa.org.uk/topics.php?article=88

S

Corrosion Prevention & Corrosion Control

 

[EdStainless]

In industrial water heaters 304 and 439 are standard. 316 is rarely used as it is more expensive and offers little improvement in corrosion resistance.
If you can't do it with 439 then you need to be looking at coated tanks instead of SS.

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Plymouth Tube

 

[PEDARRIN2]

Most of the tanks I spec are either glass lined or a Cu/Ni coating. I will use the glas if the tank is just for storage but will use the Cu/Ni if there is some type of immersion heat source involved.

This manufacturer is trying to sell his 420 SS lined tanks over the 304/316 or even the other (glass or Cu/Ni) linings.

 

[EdStainless]

420 has no chance of cutting it. It is a lower chrome, higher carbon martensitic stainless. It should not be used as-welded and probably does not have enough Cr to resist long term exposure.

I have seen 300 tanks fail in restaurants from external SCC. People were careless and got cleaning fluid on them and such. I have done some consulting work in this field.

Stick with your glass lined tanks if they have been working.

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Plymouth Tube