Parameters Required for Tuning Calculations

Care should be taken with the engineering units. AL is a percentage (hence the 100 in the expression). The duration of the test (f) should be in units consistent with the flow imbalance (AL)- So for example, if the flow is measured in m /hr, t should be in hours. If in USGPM (US gallons per minute) then t should be in minutes and if in BPD (barrels per day), t should be in days. 

Of course, if the vessel dimensions are known, it is possible to calculate the working volume. For a vertical drum, the calculation is trivial, i.e. 

The radius of the vessel is r, ho is the height of the 0 % level indication (measured from the base of the vessel) and hioo is the height of the 100 % level indication. Care should be taken in quantifying these values. They will usually not correspond to the location of the nozzles to which the level gauge is connected. The difference (hioo — ho) is the instrument range, usually found on the instrument datasheet. While a value for ho is not required for vertical drums, it is required for other shapes. 

care should be taken with units. If flow is measured in m /hr then r and h should be in m, if flow is in USGPM and r and h are measured in ft then a multiplier of 7.48 is required to convert ft to USG. If the flow is in BPD then the multiplier should be 0.178. 

Calculation of working volume for a horizontal cyhndrical vessel is more complex. Firstly we have to calculate the volume (Vq) between the bottom of the vessel and the 0 % level indication. The length of the vessel (1) is that measured between tangent lines - the point where any dished ends are welded to the vessel. The last term in Equation (4.3) determines the volume of Hquidheld in the dished ends. It assumes a 2 1 ratio between drum radius and depth of each dish. It should be omitted if the vessel has flat ends. 

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