Electricity + Control October 2018

CONTROL SYSTEMS + AUTOMATION

pressure switch controlled the switching on and off of the mostly three-pump operation system, with the fourth pump being on standby. It was also not- ed that in normal operating conditions, only two pumps would run. The third would switch on and off only at intervals where a sudden increase in de- mand was reached. This caused challenges both in the flow dynamics of the long piping system, and in terms of mechanical stresses.

um Efficiency IE3 Motors, and that this would be incorporated in the next phase of the project. With AngloGold’s requirements explained – and the information obtained on the existing equip- ment on site – the Zest WEG Group team devel- oped a solution and returned the following week with an offer on VSDs in panels to run the pumps. The offer was within the allowed budget, but An- gloGold also wanted assistance with calculations on the energy reduction anticipated with the pro- posed upgrade of the system. Calculations like this needed proper measurement of flow rates (work done), as well as the energy (kilo- watt hours) used to create the flow rates. A baseline needed to be established, and fortunately there was instrumentation already installed: a flow meter on the delivery pipe and a kilowatt-hour meter measur- ing the electricity used at the pump station. Data was obtained with the help of the control and instrumentation department, and this was used to create a baseline showing the flow rate demand over a period, with the electrical power required for the same period. Baseline and opportunities to reduce speed on pump

AngloGold Ashanti has for years been at the forefront of pursuing energy reduction initiatives and has worked closely with universities and energy efficiency institutions in the past.

Inside the pump station with the delivery side of the pumps connected in parallel.

Reservoir supply piping manifold to pumps connected to the suction side of the pumps.

Pressure sensor situated on the high pressure side of the pumps.

Upgrade requirement The water transfer system needed a smooth flow and pressure control to balance the supply and de- mand of water. This needed to be achieved within the allowed budget. It was also noted that the al- located budget did not include upgrading to Premi-

Zest WEG Group compiled the energy reduction report, considering the pump curves (power and flow rate) provided, and presented the estimated savings to AngloGold Ashanti for discussion.

Electricity + Control

OCTOBER 2018

21