GREAT SITE !!! I was wondering if someone can explain how the pressure drop occurs in a surge drum , ( example being a blast freezer nh3 or r22) ,as far as I can tell there is no expansion devices, so does this occur through the metering of float device into drum controlling the pressure or through flashing in drum , Im am really confused on this application , I do understand that coils are gravity fed, my only question is" how" for example the low pressure temperature conditions are met , any info is greatly appreciated !! stan