- Myth Kerosene Storage tank top sample has lowest Flash Point - Part 7 of X

Myth -  Kerosene Storage tank top sample has lowest Flash Point


Fact -  Kerosene Storage tank top sample may not have lowest Flash Point


Properties of petroleum products in a storage tank may not be same at all levels. As product leaves the refinery, it may be received further at intermediate storage locations (terminals or depots) by different modes of transportation like pipeline transfer, ocean tankers, Rail and/or Road. This and also previous products remaining in the tank and the fresh new product being received in the storage tanks usually have different densities. some tanks receive products from different refineries. There is usually no product circulation facility at such location to make the product homogeneous and also practically it is not a desired requirement that the product after receipt in storage tank is homogeneous, as long as it meets relevant specification. 

In view of above, the petroleum products in a storage tank usually remain non-homogeneous ie. having different properties at different height levels.  This phenomenon is referred as "storage tank Product Layering" in petroleum industry. The layering is primarily function of petroleum products density only and storage tank design, receipt pipeline design,  product receipt flow rate etc which remain constant for given tank. 

Thus, a layered petroleum product tank will have certainly lowest density for the topmost layer and highest  density for the bottom layer.  Each layer will have different properties other than density.

It is not necessary that higher the density of Petroleum product higher the Flash Point.

Thus, when flash point is not directly proportional to the density of petroleum product,  it is also not necessary that the top layer of the petroleum products tank (having lowest density) will have higher flash point than the bottom layer.

Example:

A Kerosene tank contains 2000 KL of product having density @15C = 786 Kg/Cu. M and Flash Point = 45 Deg C.  A new parcel of 5000 KL Kerosene received has Density @15C = 797 Kg/Cu.M and Flash Point = 40 deg C.

The resultant product in the tank will have Top layer having Flash Point = 45 Deg C  and bottom layer Flash Point = 40 deg C.

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