Blowdown Tank - Impact Force Calculation for Inlet Diverter

[Pavan Kumar]

thread798-445071

Hi All,

I need to provide the impact force on the Impact Weir plate inside my Blow Down tank which separates the Steam Condensate and Steam. To calculate this force, I estimated the Liquid and Vapor flow rate based on the % flash and determined the velocities of liquid and gas in the 2.5" Blow down line that is connected to the vessel assuming that 50% of the pipe area for liquid and 50% for the vapor. I then calculated the stagnation pressure(Ps) for the liquid and vapor stream separately. I multiplied the stagnation pressure with the impact area ( assumed it arbitrarily to be 4" as the B/D pipe is 2.5").Then added the impact force due to liquid and vapor to give the total impact force. I wanted to check if this is right way to calculate the impact force. Attached are the Schematic drawing and the calculations in excel sheet. Your input would be very helpful to me.

Thanks and Regards,
Pavan Kumar

 

[Pavan Kumar]

Attaching the schematic drawing here

 

[Pavan Kumar]

Hi All,

I request you all to reply on this.

Thanks and Regards,
Pavan Kumar

 

[casflo]

The saturated water flowing through the piping to the blowdown tank, has some flashing and at the tank inlet, the flashing increases to 30 or 40%, depending on the tank dimensions and pressures. It may be more realistic consider that the homogeneous flashed water impacts on the plate.
As the flashed water has not friction between the tank inlet and the plate, assume an isentropic expansion from the pipe inlet pressure to the tank pressure to calculate the specific volume of the impact stream and use it to calculate the impact force.

 

[gerhardl]

Your worst case would probably be 'water hammer' condition: a plug of liquid shot through by the steam pressure. Check this with a simpel calculation and see if this gives an acceptable construction with reasonable cost.