Speed measurement / alarm
In a coal-fired power plant, steam is produced by pumping highly purified water through boiler tubes. The water is heated to a high temperature and pressure, and then flows through several orifices into the steam turbine. Once past the orifice, the water pressure drops and it immediately flashes into superheated steam, which is directed toward the turbine blades at high velocity. Due to the high velocity of the superheated steam, the turbine blades inside the steam turbine start to rotate and turn the turbine shaft, which is connected to the generator through reduction gears, and thereby ultimately generates electricity.
Valve position, pressure and temperature measurements are all necessary to ensure stability in this process. A solution for this application is a setup with a potentiometer for valve position measurement, a 2-wire style pressure transmitter and a 4-wire RTD for precise temperature measurements. All 3 signals are connected to individual PR 4114 universal transmitters, which output 0...10 VDC signals to the PLC. The 4501 display / programming front allows local readout of both input and output signal and the process calibration function, found in the advanced menus, provides very easy and precise calibration of the open and closed valve position.
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