Dual sensors are connected to a designated alarm panel, activating visual and audible alarms for "belt and braces" security if anything affects readings from the level-measurement system.
Recently, the facility installed a multipoint level-measurement system for waste oil transfer from Hycontrol after its aging pressure sensors had become unstable, delivering unreliable results. Based on new microwave-based Time Domain Reflectometry (TDR) technology, the system monitors seven tanks ranging from 50,000 to 120,000 liters in capacity. The Reflex VF03 TDR sensors deliver individual tank level readings within an accuracy of ±5 millimeters. In addition, a large custom-built display panel of readings is mounted adjacent to the fill points.
The devices can also be applied to measuring other liquids, powders and granules. Originally used to detect breaks in subsea cables, the time domain reflectometry uses pulses of low power microwaves sent along the conducting probes. Where waves meet the air-product interface, the product reflects them back along the probe. The measured time between emission and reception back at the sensor head is proportional to the distance. This information is then converted to a measured tank level.
The measuring principle is unaffected by pressure, temperature, viscosity, vacuum, foam, dust, product buildup or changes in dielectric constant. The durable probes allow a narrow measuring profile up to a maximum range of 24 meters, which is particularly useful for measurements in tanks that have internal structural supports.
Spillages caused by tank overfilling are expensive and can cause major environmental problems. Although the level measurement includes an early warning high level alarm, an independent high level alarm system based on tuning fork sensors is also mounted at the top of each tank.
