stainless steel cool down 3

[scottyspi]

I have a piping system made out of stainless steel. We use a cleaing method that heats the water running through the pipes to 200 degrees C. After the cleaning is done we the temperature drops too 100 degrees C rapidly in 1 minute and I was wondering if there was anything I should worry about?

 

[EdStainless]

How good are your pipe supports? Is there any thing in the design to allow for thermal expansion?
A 100' run of tubing will only change by about 1/8" with this temperature change. It probably isn't a big deal unless your piping is very rigid.

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[gr2vessels]

You should check the water composition for chlorides and the oxygen content. At the given temperature, you should limit the chlorides to no more than 25 ppm or even less. Also, how do you cool the water down to 100 deg C, with treated cooling water in an exchanger? Same principle applies to prevent the SCC.
Cheers,

gr2vessels

 

[unclesyd]

I think you should be aware that differential thermal fatigue is a very distinct possibility if this procedure is done very often.

How often is this procedure done?

How do you cool the system from 200 C?

 

[scottyspi]

oh wow, i am sorry... the temperature change is in F not C. The water never reaches boiling point.

 

[EdStainless]

In addition to gr2's comments, There is also a concern about external chloride stress cracking. At 200F 300 series stainless will crack quickly. If there are chlorides on either the inside or outside you could be in for some serious issues.

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Rust never sleeps
Neither should your protection

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[BouzidLazhar]

If the surface of the steel is free from pits and scratches and the welds are well dressed it is more than likely that steam containing up to, say, 50 ppm chloride could be used for cleaning without initiating SCC providing that the surface is rinsed thoroughly with low (<5 ppm) chloride water immediately after cleaning.

 

[JStephen]

In order to affect the metallurgical properties, it would have to get a whole lot hotter- so you shouldn't have quenched-and-brittle type issues at least.