Detecting blockage in process connections of differential pressure transmitters

This paper presents the results of a study of methods for detecting blockage in process connections of differential pressure transmitters. Due to its simplicity, the combination of an orifice plate and differential pressure transmitter is widely used for flow measurement in process industries. However, one problem with this method is that the process connection of the DP transmitter is easily blocked by congealed fluid, or by accumulations of impurities from the fluid. At present, plant operators deduce that there is a blockage of the process connection based on their experience and intuition, when they observe abnormal output signals. If a blockage could be detected before the transmitter output signals become abnormal, it would improve the plant control. Usually the fluctuating "noise" component of process pressure is removed by a low-pass filter in the signal processing circuits of the transmitter. However, we found that this "noise" could be used to detect blockage of the process connection.