MechChem Africa July 2017

⎪ Automation, process control and instrumentation ⎪

specialty chemicals, generally in powdered form, which are mixed with a solvent to form a liquid. If this solution is not of the correct quality,thentheflotationunitwillnotperform at its maximum capacity. Measuring that the pH value of this mixture is in the required range can ensure that the chemical solution is optimumfor theminerals recovery required,” Gheewala explains. “When talking to metallurgists, they tell me that they cannot always believe the pH readings from the meters. These pH sensors are exposed to harsh conditions. Particles are continuouslyhammeringagainst theglass and the chemicals affect theglass impedance. This changes the instrument’s calibration: causing zero point or the slope drift,” he explains. “The metallurgist needs to know when this is happening and whether the sensor is experiencing zero point or slope drift. In ad- dition, big chunks of materials can break the pHsensor’s glass, which takes the eyes off the mineral recovery efficiency. “It is important to get this information im- mediately. That is why we monitor the glass on these instruments and track thecalibration performance,” Gheewala adds. By upgrading to Endress+Hauser Memo­ sens pH sensors, the performance of the flotation cell operation at this gold mine was substantially improved. “Because of the big

data and advanced diagnostics coming from these sensors, metallurgists can now rely on the pH data,” he reveals. “Also, this sensor enables the use of the expensive chemical, sodium metabisulphite, to be reduced by up to 50%, increasing process efficiency as well as occupational safety. Quoting the senior instrumentation engi- neer at this plant, Reijo Mammioja of Agnico Eagle mine in Sweden, Gheewala says that the Memosens pH meters, were are able to reduce calibration effort from 2 200 hours per year to only 240 hours, a 90% reduction in calibration-related maintenance costs – simply by switching over to smart pH meter- ing with Memosens’ digital connectivity and advanced diagnostics. “With Memosens, we are able to run the (flotation) plant at tighter limits and there- fore more precisely and reliably,” said Russi Ruokanen, the plant’s metallurgist. Gheewala moves on to describing similar developments Endress+Hauser has put in place to improve condition-based mainte- nance tasks on other instruments. “Coriolis meters use a symmetric spring mass balance system. This can become imbalanced in adverse loading conditions: the mass of the Coriolis tubes increase from the effects of settling solids, coating and particulate build up. An underlying need for all customers is

With the Proline Promass F 300 Coriolis mass flowmeter, customers now know exactly when to clean and calibrate their sensors.

to know when to run the tube cleaning cycle. This is a critical issue for custom- ers who use density as a control point or when

they rely on volumetric flow,” he explains. Using smart instruments such as the Proline Promass F300, customers nowknow exactlywhen to clean and calibrate their sen- sors and exactly how often. Concluding, Gheewala notes three simple steps to get advanced diagnostics started: Step 1, get more data from existing smart sensors; Step 2, upgrade the network to en- able more data to be collected; and Step 3, generate the analytics necessary to help find solutions to the challenges of the plant. q

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