1 reply to this topic

[suresh2]

Hi all,

I need to calculate the Blowdown rate through a 6" fullport valve, where the Initial pressure is 950psig and the final pressure is 15.7psig. Since the Flaretip can handle only 50MMSCFD of gas, i want to install a restricted orifice downstream of Blowdown valve to protect the Flaretip if the blowdown rate is checks out to be more than 50MMSCFD.

I tried using HYSYS depressurization utility. I would appreciate you help.

Thanks
Suresh Reddy Asi

[JoeWong]

Hi all,

I need to calculate the Blowdown rate through a 6" fullport valve, where the Initial pressure is 950psig and the final pressure is 15.7psig. Since the Flaretip can handle only 50MMSCFD of gas, i want to install a restricted orifice downstream of Blowdown valve to protect the Flaretip if the blowdown rate is checks out to be more than 50MMSCFD.

I tried using HYSYS depressurization utility. I would appreciate you help.

Thanks
Suresh Reddy Asi

Dear Mr Suresh,

Hope i address you correctly.

I hope my interpretation of your post are wrong. You mentioned that your flare system having limitation of 50 mmscfd and you are design / specify a RO to restrict the blowdown rate. This totally defeat the purpose of Blowdown and flare system.

My interpretation of Blowdown and Flare
- Blowdown is a means of removing inventory of a system to a considerable safe level (6.9 barg or 1/2 design pressure whichever is lower within 15 min per API 521) to avoid secondary hazard and catatrophic failures. Please check API 521 for definition of Blowdown system.
- Flare system is means to evacaute the relief / blowdown safely without causing further hazards.

You should protect your pressurised system rather than flaretip. Hence, your should determine blowdown rate before you worry about your flare system. If you found that the blowdown rate exceed the flare system capacity, you may investigate ways to reduce the blowdown rate e.g. reduced blocked inventory, increase SIL level, etc to the level where your flare system can handle.

regards,

JoeWong