Dear Friends,

API Std 521, mentinoed number of Vapor Passes (N) to calculate vapor velocity, as follows

Uv = (260/N)* (1/Av)

where

N = Number of Vapor Passes
Av = Segmental area for vapor in meter2.

Please any one will define the term "N", number of vapor passes, what does it mean.

Thanks
Nasiruddin