Published in September 2006 Australian Longwall Magazine

The Springvale job has allowed Schlumberger to introduce and refine a number of technologies into underground coal. It has used compression design pumps as a standard for the mining sector, special shafts for the high torques, modified motor shrouds to suit easy installations, and the use of variable voltage variable frequency (VVVF) drives to bolster system protection, operating cost and flexibility. Other mining applications have also seen special metallurgies and coating used for key components to survive the aggressive water quality.

Springvale Coal currently has three Schlumberger-Reda pump systems running at the mine, the first system was installed in March 2000 into bore 2-1. The second was run into bore 3-1 for a year before it was moved to bore 4-1 to follow the longwall. The third system was installed in December 2005 and is currently running in bore 5-1.

According to Schlumberger’s Noel Pereira, the Springvale pumps were designed for either a fixed speed or VVVF application. Bore 2-1 and 5-1 produce 70 litres per second at a fixed speed 50Hz 3.3kV switchboard at 394kW; whilst Bore 4-1 has a VVVF to enable the same pump to produce up to 102L/s at 618kW.

“They are multi-staged centrifugals so depending on the head requirements, utilising propriety software, Schlumberger models the number of stages required for the duty ... for Springvale it is a 10-stage pump providing about 420m total dynamic head,” Pereira said.

“The pumps are a compression-type design where the impellors are shimmed/locked to the shaft in the axial direction to eliminate the down-thrust issue, thus allowing the pumps to operate at very low flows without any detrimental wear to the impellers. For example, bore 4-1 has been as low as 17L/s at times when the water level was low, and right up to the full 102L/s,” he said.

The pumps use oil-filled motors, designed to operate with internal temperatures up to 204C, which together with the Reda Protector is one of the key design aspects to achieving system reliability, Pereira said.

“In fact, in bore 2-1 the motor ran for about four months without any cooling from the flow past the motor due to the motor shroud slipping off as a result of corroded bolts.”

He said the medium-voltage VVVF drive was a lesson Schlumberger had learnt in the oil and gas industry and brought to the submersible pumps ran in the coal industry.

“Springvale Coal already had experience with VVVFs on conveyor belts, but with our experiences with VVVF in the oil industry, we have shown their effectiveness to underground coal operations,” Pereira said.

“The fixed speed pumps in bore 2-1 run at a power factor of 82%, the VVVF of bore 4-1 runs at a power factor of 98%, this not only leads to an operating saving of about $10,000 per month on the full duty load, but also allows for better utilisation of electrical power.”

Schlumberger saw the contact at Springvale as a chance to prove itself in the Australian coal industry. It has already been supplying Reda pumps into US coal mines since the 1950s.

“Springvale Coal’s foresight and search for a reliable solution had them question the regular methods at hand, search for other technologies available and then push their regulatory bodies to ‘take a chance’ with the Schlumberger Reda Pump,” Pereira said.

“Our supply to and dealings with the Springvale engineers has given us the opportunity to demonstrate our capabilities and our commitment to success. From this, we are gradually making the reach to the mining network all around Australia.”

While Reda, acquired by Schlumberger in 1997, already had nearly 80 years in the submersible pumping industry and its founder had invented the submersible motor, there were several challenges in entering the Australian mining industry.

“With mining applications in general, the challenges has been with adapting to the relatively shallow setting depths – in oil we have gone to 3000m depth and even 21km horizontal reach, and the deepest Australian coal mine Schlumberger has is about 480m from surface.

“We also had to provide for operational flexibilities by way of equipment design and packaging; and then training, familiarising and transferring our lessons learnt from worldwide experiences to the customer because at the end of the day, run-life and reliability is only achieved by a joint effort – centred on the correct activities of the operator,” Pereira said.

Schlumberger has a team of 20 in Australia solely dedicated to the coal mining/water applications, backed by equipment and a wealth of knowledge via a network of experts, engineers and operators.