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Emergency Depressurizing Philosophy

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#1 moongazer


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Posted 06 July 2011 - 03:51 PM

I am currently dealing with LNG emergency depressurization systems and need to develop a philosophy for EDP calculations.

API 521 and BP GN 44-001 are my two main references. It seems that BP and other major oil & gas companies developed their own emergency depressurizing philosophies based on API 521.

However, my friends and I couldn't locate BP "GP 81-31 LNG ESD and depressuring system" and "GP 81-41 LNG Overpress prot'n, flare & vent sys" (see attached).

I'll need to estimate maximum blowdown rates using a simulator (not HYSYS) for stainless steel systems with various thicknesses. Since the API 521 example is for 1" carbon steel plate, the 15-minute time frame won't apply to S.S.? In addition, should I calculate rupture stresses of those EDP systems using "ASME Boiler and Pressure Vessel Code - Section II Materials - Part D Properties - Subpart 1 Stress Tables"?

What would be some good sources of emergency depressurizing philosophies?

Thank you in advance for your help! :)

Attached Files

Edited by moongazer, 06 July 2011 - 03:53 PM.



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Posted 06 July 2011 - 09:12 PM

Hi Moongazer,

If you are using BP guidelines I believe you are doing on BP project
as different companies may apply different guidelines for Emergency Depressuring Systems

Since depressuring is not only about reducing the pressure to 100 psi or 50% pressure in 15 minutes
but also some consideration regarding to Inventory volume and also Large Flowrate are to be considered
that is why sometimes the term of 100 psi or 50% pressure in 15 minutes are not considered in some application, due to large HC inventory or due to characteristic of the fluid or due to location of the equipments.

For some good resources of depressuring guidelines, you can try to find Shell DEP

Hope it help

#3 moongazer


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Posted 07 July 2011 - 10:16 AM

Thanks Erwin!
I downloaded Shell DEP. "DEP Pressure relief, emergency depressuring, flare and vent systems" is helpful.

However, I still want to find two BP documents (GP 81-31 LNG ESD and Depressuring Systems, and GP 81-41 LNG Overpressure Protection, Flare, and Vent Systems) since this client prefers BP's guidelines...

#4 pallavikhatri


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Posted 11 February 2012 - 01:22 PM

hi monogazer
Can u provide the shell Shell DEP. "DEP to me through this forum as an attachment as at present am working on a reactor depressurization and need some guideline for calculating the relieving flowrate?

#5 ankur2061


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Posted 12 February 2012 - 06:44 AM

Pallavi / moongazer ,

Soliciting and providing links of filesharing websites such as rapidshare and other similar sites for copyrighted books, company standards, copyrighted journal articles is prohibited as per the forum regulations. Please refrian from asking and discussing copyrighted stuff.


#6 Bharathiraja


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Posted 12 February 2012 - 12:22 PM

Hi Moongazer,

If you are doing project for BP, and they insist you to follow a particular standard, then, you can ask them (client) to provide those standards for your reference. They are obliged to give those documents. You can contact them via your Project Manager. It is normal practice.

Shell DEP can be referenced only for Shell and it's group company projects. It can be used by others with permission from shell. Otherwise you can not specify Shell DEP as calculation basis/reference. It is prohibited. Hope You understand this.

#7 john.longden231


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Posted 11 August 2012 - 07:36 AM

Hello, I wonder if you could help me? I am searching for publications on emergency depressuring systems as I have been asked to prepare an introductory level training course on the subject. Can anyone recommend any books or publications that I could use as reference material.
Thanks a lot, John
john.longden231@btinternet.com all; replies to this address please.

#8 ankur2061


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Posted 11 August 2012 - 09:34 AM


Plenty of stuff related to emergency depressurization is available on the internet. Did you try looking?






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