The net working capacity of floating roof tanks is the product inventory that is stored between the maximum and minimum operating levels of the floating roof. The product that remains in the tank when the floating roof is at its minimum operating level is residual inventory, referred to as the product heel. This trapped inventory is a valuable product asset that is not part of the tank net working capacity. This paper describes considerations that must be made when lowering the minimum operating level of floating roofs, both for new and retrofit tank applications, and presents methods of achieving these improvements.
Some tank turnover operations require that the floating roof be landed and the tank drained dry. Tank turnover operations include those where it is important to avoid cross contamination of products.
Recent studies have shown the importance of the emissions that occur during heel turnover operations. This paper describes a method for determining the heel turnover emissions and presents abatement options for controlling these emissions.