1 reply to this topic

[BIG10]

Hello -

I need to find a calculation method to determine the amount of time required to relieve a butane pressurized vessel at 400 psig and 100 F. The discharge location is a flare drum approximately 300 ft from the pressure vessel at 5 psig. The butane will be relieved through 2 in schedule 40 piping. The concern is that the pressure and velocity maybe too great to overcome the flare k/o design and cause the liquid level in the drum to swell and puke over. The pressure vessel volume is relatively small (500 gal for calculation purposes). I understand initally when the valve is opened to the flare line that pressures will spike to 400 psig then drop quickly to the vapor pressure of butane at the noted conditions. Also, as the liquid expands into a gas there is a cooling effect. My questions are as follow:

1. How long will it take to depressure the upstream vessel to 5 psig?

2. What is the maximum pressure the flare k/o drum will see?

3. Can i restrict the flow through an orifice downstream to prevent a large pressure swing at the flare k/o drum?

Again, I thank everyone for your help. Thank you!

[ankur2061]

BIG10,

Have a look at the following links. These might just be what you need:

http://www.cheresour...ecrease-to-atm/

http://www.cheresour...depressurizing/

Regards,
Ankur