Regarding the issue of the effective volume of fire dikes

Generally, the volume of a storage tank is its nominal volume; when in use, the tank has a safe height, and oil can only be poured in below this safe height. Calculating the volume can only be based on the relationship between the diameter and the safety height. What volume is the factor of 0.9 related to? Generally, such precise calculations are not necessary. As long as it is greater than, it’s fine; equality is not required.

To consider the effective volume of the fire dike, it is necessary to calculate the volume of hazardous substances that could leak out in the event of a leak in the largest tank within the tank farm, as specified by the relevant standards. Tanks are designed with a diameter and a height; the height includes both the top height and the height of the tank body. The volume calculated based on the diameter and height of the tank (with the tank wall volume being disregarded) does not represent the actual volume that can be contained. Moreover, even in the case of floating roof tanks, it is not possible to fill them completely. Therefore, all tanks have a volume coefficient, which accounts for this incomplete filling, with values ranging from 0.8 to 0.95； Therefore, the larger the storage tank, the greater the impact of the effective volume of this fire dike on the land area required for the tank farm. Our disagreement lies in regarding the volume of the storage tank as its actual volume or as its effective volume; for a 20,000 cubic meter tank, the difference between its actual volume and its effective volume can be several thousand cubic meters.

We have 4 storage tanks, each with a capacity of 20,000 cubic meters. Their height is 17.5 meters and their diameter is 42 meters; they are internal floating roof tanks. You can try to do the calculations yourself

The effective volume within the fire dike should not be less than the volume of the largest storage tank in the tank farm; when calculating the effective volume of the fire dike, the volume of the largest storage tank in the tank farm shall be taken as the \"nominal volume of the largest storage tank\".

According to the national standard GB50351-2005, the capacity of floating roof tanks and internal floating roof tanks should be no less than half of the capacity of the largest storage tank in the tank farm. And when calculating the effective volume, the height is the designed liquid level height.

The new rules came out in 08: it must be no less than the largest one

I attended a seminar on the new version of the standards, where it was clearly stated that as long as standard tanks are used, it is fine to use their nominal volume for calculating fire dikes; however, this is not the case when non-standard tanks are used. To correct some of the views expressed above, in future design projects, floating roofs should always be calculated based on a specific volume – there is no doubt about this. The main consideration is the incidents in China where uneven settlement of the foundation led to tearing of the bottom plates. This post was last edited by a Storage and Transportation Engineer on 2009-4-27 at 18:03

So, is the effective volume of the tank area reduced by the volume occupied by the other storage tanks? After the leak, the other tanks are still there and won’t float either, so what? Should the effective volume of the tank area be deducted?

The tank area serves primarily as a place for containment in the event of an accident; therefore, the capacity of the largest tank is sufficient. It’s a simple matter – there’s no need to overcomplicate it.