pressure drop

[marcosta78]

Dear all,

first of all I would like to introduce myself. I'm a chemical engineer and after many years of working as project engineer I have to do some hydraulic calculations...they are very simple but I have some doubts, sorry if they look dumbs.

The attached scheme describes the system: liquid with flow rate of 2,8 m3/h comes from a system (column+condenser)to a gravity separator (E-1). The scheme simplifies the situation in which the bottom valve is closed and the liquid exits from the top of the separator.
The plant manager asked me to verify that liquid doesn't go to vent line. My idea is calculating
pressure drop along the discharge line to the second vessel (E-2) and demonstrate (converting it to mcl from bar) that is lower than the distance DH (that is the vent height). Is it correct?
From my calculation the pressure drop will be negative (due mainly to the difference in height between the two vessels).
Thanks in advance for your help
Marco

 

[micalbrch]

First of all: Welcome on board!

I'm not 100 % sure if I understand your system but from what I understand you are right - under two conditions:
- the second vessel isn't pressurized
- the second vessel has a vent line, too.

 

[marcosta78]

thank you very much, the second vessel has the same pressure of the first one (both are connected to the same vent system)
So, you confirm that as far as the pressure drops through the discharge line (from the maximum flowrate of the system I got negative value= -1 meters) are lower than 1,5 meters (the distance DH) I'll avoid the overflow through the vent line?
Thanks

 

[micalbrch]

Sorry Marco for the late reply but I was travelling the whole week.

Your problem might be solved but I think I still owe you an answer. The pressure in both vessels is the same. Both vesels are connected to each other. Both vessels have a vent line and the vent lines are connected. The difference in height leads to the flow of the fluid from the first into the second vessel. If that all is correct, the fluid level in the second vessel will rise until it corresponds to the level in the first vessel. And if the vent line of the second vessel is needed to achieve this, fluid will enter the vent line.