E.ON Tests Guided Wave Radar From Emerson
An E.ON power plant has successfully trialled a guided wave radar (GWR) from Emerson Process Management. When setting up the test, E.ON instrument manager, Per Lundmark, decided to additionally test a GWR instrument in parallel with the existing pneumatic displacer. E.ON needed a level transmitter that was not affected by steam or turbulence and could follow very rapid changes in the water level. Per Lundmark installed an electronic displacer and a Rosemount 5301 GWR, both in parallel with the old pneumatic displacer.
When Per Lundmark and his colleagues reviewed the measurement results after a few months of operation, they found that the electronic displacer and the Rosemount 5301 GWR followed the exact same variations in the level, but with a difference of 11 per cent. On further investigation they discovered that the new displacer had an offset of 11 per cent, probably due to the fact that it had been calibrated at the factory for a higher temperature. In addition, the chambers are installed at a distance from the hotwell and the temperature in the chambers, while not known, is lower than that in the hotwell.
This temperature difference did not affect the GWR, but, because the displacer was calibrated at a different temperature, its accuracy was significantly affected. The Rosemount 5301 GWR measured correctly and with high accuracy throughout the entire test. One of the key features of GWR is that it is unaffected by the temperature at which it makes a measurement, which is particularly important in this application, as the comparison with the electronic displacer showed.
Furthermore, the response time of the GWR was faster than the response time of the displacer, which is useful in an application such as this where there are very rapid level changes. The GWR also enables the use of a PID-regulator to improve the level control during disturbances. Other advantages of the Rosemount 5301 include a stronger signal due to Rosemount’s signal technique, which provides a stronger echo and higher readability in difficult operating conditions, and compliance with the SIL 2 safety standard.The head-to-probe connection has no wires and so is easy to replace without removal of the probe. The company will test in the Orebro plant for a further 12 months or more before it has sufficient data to support the replacement of the existing pneumatic system.
