Emergency Venting Due To Fire From Atmospheric Storage Tanks

Somewhere around October 2008, I came across an article in the magazine "Chemical Engineering" with the title "Understanding Atmospheric Storage Tanks" by "Siddhartha Mukherhee". The article was very well written and also gave an in-depth insight into venting of atmospheric storage tanks both normal as well as emergency venting. Equations for determining normal venting and emergency venting rates were provided in this article. This was the time when the new API STD 2000, the 6^th Edition had not been released. The new API STD 2000 was subsequently released almost a year later.

The equations sounded promising and as usual my urge to turn useful equations to a useful calculation tool led in developing a combined excel sheet for normal & emergency venting. After developing the excel sheet I asked "Joe Wong" who is a prominent member of "Cheresources" to review it and subsequently post it on his very own blog "Chemical & Process Technology". In his review he pointed out that the normal venting calculations for atmospheric storage tanks were in close agreement with what API STD 2000 – 5^th edition (1998) provided as normal venting rates. However, he was not convinced about the method for determining the emergency venting rate as given in the article and asked me to modify the excel program to exclude the emergency venting calculations. After due modification I submitted the excel workbook for posting on his blog which he did with due diligence and a covering introduction for the excel workbook. The excel workbook was well received and provided a calculation tool for normal venting to the chemical engineering community.

More than a year later somebody put a post in "Cheresources" regarding the dramatic changes related to normal venting calculations in the new API STD 2000-6^th Edition (2009). I was extremely curious and immediately got hold of the copy of the new API STD 2000. Indeed there was a total change in the methods to calculate the normal venting from atmospheric storage tanks specifically the thermal inbreathing rates which showed an almost 300% increase from the value calculated as per the previous edition of API STD 2000 and while discussing on the post "Joe Wong" suggested that I could provide a new normal venting excel workbook for the benefit of the chemical engineering community. I prepared a new excel workbook for normal venting calculations based on the latest API STD 2000 which was then posted on "Chemical & Process Technology". This excel workbook had an overwhelming response from chemical engineers worldwide and I received a lot of mails expressing their appreciation and asking questions. To follow the chronology of the development of the normal venting calculations readers can check out these links:

http://webwormcpt.bl...estimation.html

http://www.cheresour...h__1#entry35897

http://webwormcpt.bl...i-std-2000.html

All of the above discussion had related to "normal" venting from atmospheric storage tanks. I had probably forgotten about the "emergency venting due to fire" from atmospheric storage tanks. Just a week back I suddenly recalled the emergency venting calculation I had done using the method provided in the article mentioned above and I decided to check the results with the emergency venting rates tabulated against the tank capacity in API STD 2000-6^th edition with my calculations. To my very pleasant surprise the results tabulated in API STD 2000 and as calculated from my excel workbook were in close agreement.

The blog entry is meant to share my experiences regarding venting of atmospheric storage tanks as well as sharing that extra bit by providing the members of the "Cheresources" community with the excel workbook on emergency venting. The excel workbook has been recently modified to provide the methodology for wetted area calculations as per the recommendations of API STD 2000-6^th Edition.

I would be very happy to receive comments and discuss any queries from the esteemed readers of "Cheresources".

Download the MS Excel spreadsheet in the Download Section.

Regards,

Ankur.