Measuring the high-level on ash hoppers

Suspended particles that are filtered out of the process exhaust air are collected in hoppers. If the level in these hoppers rises too high that the fine dust touches the electrostatic precipitators, these precipitators will short-circuit causing a process upset condition. To prevent this, the high level must be reliably measured. Radiometric level switches offer best in class reliability for this application. 
Geiger-Müller (GM) technology radiation level switches were historically used for these applications. However, in plants that have been in operation for a long time, the activity of the radioactive source has decreased significantly due to natural source decay. The sensitivity of the GM detectors is then no longer sufficient to reliably continue limit switch measurements. Replacements or retrofit solutions become necessary.