Hawk Measurement Systems is a major provider of level measurement instruments as well as positioning and flow solutions for industrial applications.
Choosing the correct level technology for coal preparation and concentrator process sumps in the mining industry is a major issue, especially when specifying level instrumentation in process sump level applications.
Application: Process sump level
Service: Measuring slurry containing magnetite and other suspended solids
Foam/Froth: Nearly always present
Condensation: Condensation and slurry splash
Shape of sump: Conical and square with cylindrical cone bottom
Typical technology used: Pressure transmitters or ultrasonic transmitters
Since the density of the slurry is changeable, level controls must measure level and not hydrostatic pressure, making non-intrusive acoustic wave transmitters the correct choice.
Why Acoustic Wave Level Controls:
The sump pumps in these process tanks operate more efficiently when a stable high level head pressure is maintained in the sump. The acoustic wave transmitter is not affected by density change making it the preferred approach.
Even though they are simpler to install, their major problem is that they measure hydrostatic pressure. Since density changes in the slurry, one must set the high level lower in the sump so that it does not overflow the sump when the density drops. This also means that the slurry pumps cannot ever run at their optimum efficiency levels.
Sizing the Correct Acoustic Wave Transducers:
Frequency of the transducer is critical when considering factors such as power level and self cleaning abilities.
Froth, foam, condensation, conical bottom section of the sump, slurry splash and vortexing affect the performance of high frequency acoustic wave transmitters.
In a 6m sump with a conical shape bottom, the use of 20kHz and 15kHz transducers are required in order to perform under all these environmental considerations and self cleaning operation.
The choice of integral or remote 2-wire loop powered transmitters or line powered devices are available.