Ro Downstream Of Lcv Sizing Calculation

Hi, I am trying to size an orifice downstream of an LCV for cutting down the pressure to protect downstream closed drain drum from overpressure in case of LCV failure and gas blow by. I am trying to make sure I use the correct flow and other conditions for sizing. The gas flowrate is 3 MMSCFD (max) and the pressure is 600 PSIG. For sizing the orifice can I assume 600 PSIG as the upstream pressure and downstream pressure to be operating pressure of closed drain drum i.e. 7 PSIG. Will that be a good assumption for sizing the orifice? Are there any other considerations or something that is missing from my assumption?? aatched simple sketch

Hi, 

Can you specify the design pressure difference between the upstream and the downstream. Also please check the following:

- Why a PSV can't be located downstream the control valve to mitigate gas breakthrough. No credit shall be considered for control valve for reducing the pressure and hence the difference between the design pressure of the interconnected vessels require overpressure protection analysis. 

-Check if a liquid swell scenario can happen in case the closed drain drum has a submerged inlet nozzle or its initially filled with liquid to beyond 50% of its diameter. 

-The pressure class rating shall extend up to the last isolation valve upstream the drain drum , please confirm.

- Please confirm you will have vapor only through the orifice, consider potential additional vapor flashing as it enters the downstream lower pressure drum. 

Hi, I am trying to size an orifice downstream of an LCV for cutting down the pressure to protect downstream closed drain drum from overpressure in case of LCV failure and gas blow by. I am trying to make sure I use the correct flow and other conditions for sizing. The gas flowrate is 3 MMSCFD (max) and the pressure is 600 PSIG. For sizing the orifice can I assume 600 PSIG as the upstream pressure and downstream pressure to be operating pressure of closed drain drum i.e. 7 PSIG. Will that be a good assumption for sizing the orifice? Are there any other considerations or something that is missing from my assumption?? aatched simple sketch

Edited by SawsanAli311, 05 April 2019 - 12:13 PM.