"In the process of shale gas extraction, separators are used for de-sanding the mixture of oil, gas, and water. The level of sand in the separator needs careful monitoring to ensure it does not
cause pump abrasion due to sand being drawn through the lines and into the pumps.
The contents of the separator includes both solids and liquids. As the layer of settled sand and sediment builds in the base of the vessel, an alarm is required to alert operators that the critical level has been reached so cleaning may be scheduled before sediment is drawn into lines."