Industrial automation provider Rockwell Automation and mine dewatering company Ritz Pumps South Africa (SA) are partnering to address South Africa’s acid mine drainage (AMD) challenge.

Rockwell Automation and Ritz Pumps SA are providing variable-speed drives (VSDs) and pumps for the first phase of government’s AMD mitigation strategy for Gauteng’s Central basin, aimed at reducing the AMD in the basin before environ- mental critical level (ECL) is reached and to keep the water below ECL in the future.

The project is being implemented by the Trans-Caledon Tunnel Authority on behalf of the Department of Water and Sanitation.

In the Central basin, rising water levels and flooded underground pumpstations have negated any possibility of using conventional pumping solutions, thus requiring a specialised submerged pumping solution.

Therefore, two of Ritz Pumps SA’s pumps, heavy-duty mining duplex stainless steel and double-suction zero-thrust pumps, were bought by gold exploration and production company Central Rand Gold (CRG) as part of its contribution to solving the AMD problem and were donated to the government to ensure the successful implementation of the Central Basin AMD project.

The pumps are suspended from surface level by the Carl Hamm ZSM duplex stainless steel, high-pressure, high-tensile, quick coupling system and operate from within the mine shaft. This eliminates the need for maintenance teams to enter the mine and the necessity for secondary infrastructure such as man hoists, ventilation and conventional mining equipment.

“Although the equipment was procured by CRG for a deeper abstraction than the current water level, it is our PowerFlex 7000 VSDs and Carl Hamm piping that will enable the original equipment to draw down the [AMD in the] basin from the current depth to the designed depth,” Ritz Pumps SA MD Chris Munnick points out.

He notes that Ritz Pumps SA experienced some difficulty in finding appropriate VSD suppliers of these pumps, as the majority of suppliers’ products require secondary filtering equipment to develop suitable sinusoidal waves required for electric Ritz modular cooling technology medium-voltage motors.

“The depth for the application is important as many of our applications require cable lengths of up to 1 500 m. Rockwell Automation solved this problem for us without additional secondary filtering equipment requirements as their VSDs are well suited to applications with even longer cable lengths,” says Munnick.

Rockwell Automation medium voltage and South Africa and sub- Saharan Africa sales manager Henry Craukamp adds that the company has done successful tests with cable lengths of up to 15 km from source, therefore, 1 500 m poses no real challenge for its equipment.

He says this is achieved through a virtually perfect current and voltage output waveform that also has an added benefit for customers, as they can use standard motors and motor cables.

He says further contributing factors to the synergy in the collaboration between the companies are Rockwell’s local engineering and service personnel, the VSD’s performance with the electrical system and the motor, and its reliability and ease of use and maintenance.

He furthers reveals that the plant will be operating for 24 hours nonstop, which requires 99.9% availability of the pumps to ensure they can deliver the maximum capacity to guarantee full flow at all times.