Hi there,
We have a new steam line designed and built from 316L running at 203degC from our boilers.  It feeds a variety of process equipment.  I have subsequently picked up from B31.1 that acc to note 1 that 316L is not allowed for boiler external piping.
Does this mean our new line with around 2000 welds is not allowed and should be stopped?
If it is can one mitigate the issue by controlling the Chloride feed to the boiler to low levels and possibly have an preventative maintenance effort on the pipe.
Your comments would be greatly appreciated.
Regards

not sure, but by providing isolation valves at the inlet of the piping it becomes "non boiler external piping" and note 1 is avoided.

I would think you would strive to minimize chlorides to the boiler in any case. But I do not understand why you  are using 316L in an application where everyone else uses carbon steel.  

if the boiler has no continous oeration be careful, under insulation, because o corides streess corrosion cacking
carbon steel is cheaper for thet service, Icant understand why using stainless steel

It could be for live steam injection into a color sensitive process, but that is usually downstream of high efficiency moisture/particle removal.

Good luck,
Latexman

Hi thanks for the answers,
Yes chlorides in the feed water is controlled to normal low levels.  We need to use 316L because of corrosion from the outside in an H2SO4 plant environment where a lot of fumes are present.  Even our hand railing and structural steel is 316L.

We have fortunately used an insulation with very low Chlorides to protect the pipe.

We actually have a manual isolation valve so I will speak to the designers on the classification as "non boiler external piping"

Regards