Many process plants handle harmful and corrosive liquids. To assure the best possible protection of life and property, operators need to focus special attention to their inventory- or day-tanks. These vessels are the points with the highest accumulation of dangerous fluids on their facilities.
The right combination of dedicated sensors and controllers can be used to design a redundant filling level control monitoring system; their continuous and limit switches which are taking care of crucial filling levels.
Continuous Level Control
Ultrasonic, radar or hydro static level sensors generate a continuous signal which allows precise filling and emptying control. They are used e.g. in batching or mixing processes but also for simple inventory control. The sensors directly control the process during daily operations.
Even most advanced continuous technologies can be prone to measurement errors or malfunctions. But the handling of harmful fluids does not leave any room for loss of control. That is where limit switches play an important role as a redundant safety system.
At least one pair of limit switches is placed into a tank – one at the maximum and another one at the lowest allowed filling level. Most limit switches are designed to react as soon as they get in physical contact with the process media – as soon as the minimal or maximum level had been reach. This usually only happens if the continuous sensor fails. Still the environment is safe due to the fact that the switches directly connect to the power supply of the pump or the valve of the inlet.
Only by applying both technologies operators can guarantee protection of life and equipment, even if one system may fail.