Steam pressure drop and line sizing
Steam pressure drop and line sizing
(OP)
I have a 3" steam line (sized for 4800 #/hr) coming off the header, 120 psig, 350 degF, going to a 3" pressure reducing valve for an outlet pressure of 8 psig. The line after the valve is sized for 6" to maintain the same 4800 #/hr, given the pressure drop.
My question is: If I have a few feet of 3" after my valve, before I go to a 6", will this have a negative effect on my line capacity? Should I immediately go to a 6" instead?
Thanks for any insight into this.
-Adam
My question is: If I have a few feet of 3" after my valve, before I go to a 6", will this have a negative effect on my line capacity? Should I immediately go to a 6" instead?
Thanks for any insight into this.
-Adam





RE: Steam pressure drop and line sizing
If you have a pilot operated or pneumatic valve, then if you take your reference pressure AFTER the steam is in the 6" valve, then the pressure drop through the 3" portion will not really effect anything (unless the valve used is already at full capacity).
RE: Steam pressure drop and line sizing
RE: Steam pressure drop and line sizing
In a former life, I sized a LOT of steam PRV stations. A pretty good rule of thumb is size the PRV. The inlet piping is typically one pipe size larger, and the outlet piping is double the inlet piping size. An 1-1/2" Spirax Sarco pilot operated PRV will JUST be big enough. 2" is LOADS. A few feet of 2" pipe (or 3") won't be long enough to matter. This includes the downsteam isolation valve, if there's a bypass around the PRV. For what it's worth, I dislike bypasses. They get abused by the unknowing, and have caused me far more problems than they've ever solved.