Vibrating level switch with turbo drive ensures reliable measuring signal

Sometimes, seemingly difficult measurement situations can be solved by applying simple technologies – provided these are robust enough to withstand the challenging environments. This is what happened at the Jining Thermal power plant of China Huaneng Group Co, Ltd. in Jining, in the eastern Chinese province of Shandong. There, the vibrating level switch VEGASWING 66 simplified in one fell swoop the level measuring point that had previously been considered hopelessly complicated.

The production process in the Chinese thermal power plant in Shandong (capacity 380 MW) employs a high-pressure steam bypass system, which, to be sure, mainly takes effect only when the turbine is started up. When the turbine starts, water in the boiler is heated, generating steam. At this point, however, the steam parameters do not yet correspond to the operating state of the turbine. The temperature of the steam is still too low and it contains too much moisture. And it is exactly this that is problematic for the turbine, since very fine water droplets hit the turbine blades at high speed, possibly damaging the turbine blades. For that reason, the steam from the boiler is first passed through a bypass system. Only when the steam is in the right condition – i.e. without water droplets and at operating temperature – is the system switched off and the steam fed into the turbine.

When the steam bypass system is used, water collects at the bottom of the pipe. If the water is not drained in time, the pipe gets flooded, which can lead to problematic situations. So the water level must be accurately measured and lowered at the right time. In the past, the water in the turbine's steam bypass system was detected by a float switch. Due to frequent error signals, system shutdowns occurred again and again. To remedy this situation, the plant operator tried to find a level switch that would function reliably even at high temperatures (up to 325.5° C) and high pressures (38 bar).