John A. Shaw
Process Control Solutions
April 25, 2002
Abstract
Storage is typically used in processes to absorb differences in flow rates when the supply by one part of the process will equal, over a long period of time, the demand by the next part of the process, but the demand and supply will not be equal at any one particular time.
A larger storage capacity will decrease the chance that, at some point in time, either the stored material will not meet the demand or the excess capacity will not absorb the supply. However, larger storage costs more.
Monte Carlo simulation techniques can be used to predict the chance that, for a given amount of storage and for a given time period, the storage capacity will be insufficient to meet both the supply and the demand requirements. The result of the simulation is a table that, for different sizes of storage capacity, will list the confidence (from 0% to 100%) that the storage will be sufficient.
This paper describes the use of a Monte Carlo simulation, based on a computer spread sheet, that was used to determine the size of a tank to receive liquid from one process area and supply that liquid to another process area.