| In power plants, pressure transmitters are usually installed away from the power generating process in order to reduce the effect of ambient temperature, radiation, and vibration on the operability and qualified life of transducers. To transport a pneumatic or a hydraulic signal from the process to a transmitter, sensing lines are employed to connect the pressure transducer to the process piping, reactor vessel, or primary flow elements.;In this dissertation, the existing modeling techniques of sensing lines and pressure sensors are reviewed and an improved pressure sensing system model is developed based on the electric transmission line equivalent pi circuit. Computer simulations of sensing line blockage and voids inside the impulse line that are based on the proposed model, in conjunction with analysis of operational data from a nuclear power plant and field test measurements from an operating coal-fired power plant are presented. The operational data and the field test analysis results demonstrate behavior consistent with the simulation results, and thereby validate the developed model. According to the developed pressure sensing system model, spectral features associated with sensing line blockage and voids are presented and four diagnostic indicators are delivered to facilitate fault detection and isolation on pressure sensing systems.;Sensing lines can encounter a number of problems that can affect the pressure sensing system accuracy and response time. For instance, blockages, voids, or freezing in sensing lines can cause errors in pressure measurements and also affect the dynamic response of the pressure sensing system. Although provisions against these problems are usually made in the design of sensing lines, experience has shown that they do occur. |
