Which material makes a better autoclave chamber? 2

[betinc189]

I would like to know which is better for an autoclave chamber. I’ve seen stainless steel, used in smaller tabletop models (8 – 10” round x 21 – 23” deep) and large models 16 x 16 x 30, 20 x 20 x 34” or 24 x 36 x 48”, but have only seen nickel plated steel used in the large models. Is it a cost, weight or physics factor? The chamber is heated and cooled often and rapidly. The chambers are vacuumed down to 29”Hg and raised to typically less than 35psig of saturated steam several times during a 30 minute cycle. It also seems that the thickness of the chamber is a lot thinner using the stainless steel. Is stainless steel stronger at theses temps? I am a biomedical technician who works on sterilizers and I have wondered why the difference. Thank you for any insight that you can share.

 

[EdStainless]

The temp isn't high enough for strength to become an issue. There are two reaosns not to use staniless for larger units. First is cost. The larger units require a lot thicker walls, and the price fo stainless is too high.
The second reason is that stainless has a larger thermal expansion, so for big units the overall dimensional change would be greater.
There are other options, but I am not sure that you want to discuss those.

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[betinc189]

Ed: Thank you for answering my question. if i may ask one more, What grade stainless steel would be used for the smaller application and at what thickness?

thanks again!

 

[EdStainless]

I have seen both 304 and 316. The thickness is a function of diameter, but 0.375" wall isn't uncommon.

You would be better off using a duplex stainless grade. An alloy like AL2003, LDX2101, or even 2205 would give you more strength (thinner walls), better corrosion resistance (espe stress cracking resistance), and lower thermal expansions.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[betinc189]

Ed thanks again, you've answered all the questions i have. i look forward to reading your responses to other questions on this site.