Common Relief headers..

[jamesbanda]

Dear sirs,

We have been reviewing our common relief stacks for a design of a plant. Can i ask if the relief stack is pointed a high elevation say 40 meters or ~120 feet and say 10-15 relief valves discharge into the commnon header..

is their merrit in nitrogen purging the header..

- dp calcs on rv's limit pressure rise to <1 barg (or lower)
- worse case pipework withstand an explosion 10x pressure rise..and probably unlikely carbon steel equipment and relief valve force would push air out..and it is every unlikely
- does n2 purges prevent atomspheric corrision ? probably not as carbon steel forms a corrision barrier after time
- prevent water ingress - maybe but we have drains anyhow.. and these are regually checked..
- so with no process vents into a common header why would you use a nitrogen purge..

 

[Armen75]

Possibly to keep an inert atmosphere in the purge piping (to prevent oxygen ingress) or to flush acid gases (corrosion issues) or ensure dry piping....
however Fuel Gas is more common when available (and you won't risk snuffing out you pilot)