2 replies to this topic

[Enrico Lammers]

Dear colleague engineers,

 

I'm involved in a design for a relief system for new storage tanks. It has been a while and I was used to the old version of API 2000. I found out in the different fora, the discussion of the differences between the old and the new API 2000 standards etc.

 

Something which is still concerning to me is the following:

 

The tanks are designed in accordance with European standard EN14015. This standard is also specifying calculation methods for fire relief cases, however I started with the latest API 2000 standard. For some reason, I thought the fire relief case sounded high to me and I checked it with the EN 14015 method and guess what? It's significantly different. 

 

Let's take the "standard fluid" Hexane. The wetted area is 22 m².

 

According to API 2000 6th edition table 7, this gives a relief rate of 6217 Nm3/h (see attachment)

When I calculate it via the formula in chapter 4.3.3.3.2 (see attachment) I get a relief rate of 6961 Nm3/h

When I calculate is via the spreadsheet of Ankur's Emergency Venting Due To Fire From Atmospheric Storage Tanks spreadsheet, I get 6245 Nm3/h.

So far, so good (slight differences might be due to different assumed temperatures)

 

 

When I calculate it via L.12 in EN14015 (see attachment) (which according to API is incorporated in API 2000: "This International Standard was developed from the 5th edition of API Std 2000 and EN 14015:2005, with the intent that the 6th edition of API Std 2000 be identical to this International Standard"), I get only 3004 Nm3/h. The simplified formula for hexane: UFB = 238 Aw0,82 obviously shows the same result: 238 x 22^0,82 = 3002 Nm3/h.

 

It must have to do with the ratio tankvolume vs. wetted area (see attachment). At larger diameters this ratio is getting higher (better). Still seems odd to me that API takes this phenomenon into account and EN does not. 

 

Any thoughts on this?

 

Thanks in advance,

 

Enrico 

Attached Files

•  Schermafbeelding 2014-01-22 om 09.53.30.png   82.85KB   16 downloads
•  Schermafbeelding 2014-01-22 om 09.54.07.png   71.79KB   8 downloads
•  Schermafbeelding 2014-01-22 om 10.35.18.png   93.14KB   7 downloads
•  Schermafbeelding 2014-01-22 om 11.59.40.png   17.81KB   7 downloads

Edited by Enrico Lammers, 22 January 2014 - 06:26 AM.

[CMA010]

The intent of "This International Standard was developed from the 5th edition of API Std 2000 and EN 14015:2005, with the intent that the 6th edition of API Std 2000 be identical to this International Standard" is that API STD 2000 and ISO 28300 are the same, not API STD 2000 and EN 14015. API STD 2000 / ISO 28300 is a combination of the 5th ed. of API STD 2000 and EN 14015 annex L: The API / ISO committees have taken the normal venting requirements of EN 14015 and the emergency venting (fire) requirements of the 5th ed. of API STD 2000.

[ankur2061]

Enrico,

 

Unfortunately I do not possess EN14015. However, a detailed explanation about emergency venting requirements is given in Annex B of API STD 2000, 6th edition and I suggest you read through it carefully to understand the genesis of the development of the emergency venting due to fire requirements based on actual experiments carried out by NFPA on tanks by exposing them to fire to determine emergency venting phenomena.

 

Regards,

Ankur.