Benefit Estimation for Improved Regulatory Control

At the regulatory control level there are the obvious benefits of keeping the process stable, safe and operable by a reasonable number of process operators. The process design team will most likely have already met these requirements, so we take this as our base case above which we have to economically justify further costs. 

Improved regulatory control can reduce maintenance costs. It is self-evident, if pumps and compressors are subject to fewer pressure surges, temperature deviations and so on, then bearings, seals and gearboxes are less likely to fail. While virtually impossible to predict these savings there have been cases where the mean time between failures (MTBF) for machines in difficult services have increased by a factor of three. If the equipment is critical, in that its failure requires a process shutdown or turndown, then not only are maintenance costs reduced but process capacity is increased. 

Most processes are fundamentally nonlinear. If we examine some of the key equations governing process behaviour, this quickly becomes apparent. Heat transfer is fundamental to almost every process. Whichever way this is achieved involves nonlinearity. For example, in Chapter 10 we applied Stefan s Law to estimating benefits on a fired heater. 

The law states that the rate of heat transfer (2), in the radiant section of a fired heater, varies highly nonlinearly with the temperature (7). 

In the convection section the Five Fourths Power Law applies. 

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