Assessing plant condition from analysis of pressure and differential pressure measurement signals

It is well known that, although the output from a centrifugal pump operating under normal conditions is essentially steady, there are small fluctuations in the flow rate. These fluctuations are manifest in the measurement signals and, in most applications, are classified as noise which for process control purposes is regarded as a nuisance and is attenuated or removed by filters etc. If, however, the noise component is separated out and the frequency spectrum analysed, useful information regarding the status of both the measurement system and the associated process plant can be recovered. This paper describes how the noise component of signals from an orifice plate/differential pressure measurement system in a variety of applications can be analysed to identify changes in the operation or status of process plant as well as in the measurement system itself