A project to expand Newcrest Mining’s Lihir gold mine in Papua New Guinea proved challenging due to a high water table. To reduce the water level in the pit, Crusader Hose was brought in to provide a dewatering solution.
The Lihir gold mine is an open pit mine located within one of the Papua New Guinean island’s large volcanic calderas, the Luise Caldera, which borders the sea.
While the volcano is considered extinct, it is still geothermally active, evidenced by fumaroles or smoke emanating from the rocks within the pit.
Due to the pooling of rainfall and regular seepage of seawater through the crater rim into the pit, the pit needed to be pumped out in order for Newcrest’s mine expansion plans to go ahead.
Designing the dewatering system
The prime contractor for the project was a large New South Wales pumping company, which is an expert in designing mine dewatering systems.
The company was brought in to provide a solution to lower the water table so that mining could be expanded.
The final design included a dewatering system that used three 350kW submersible bore pumps suspended from flexible hose, inside an angled poly-pipe casing. Each pump was driven by a separate generator and connected to a platform, which cantilevered over the pit wall.
The bore casing used 900-millimetre diameter poly-pipe that was welded together to form an insulation sleeve. This rested at an angle along the pit slope and the length of poly-pipe into the pit was 175 metres long.
The bore casing was then securely anchored from the headworks, which incorporated a concrete-padded, steel-framed platform, and was surrounded with safety rails.
Once the bore casing had been secured, installation of the submersible pumps commenced.
Each 350kW stainless steel submersible pump was mounted on a skate that slid within the casing, allowing the pumps to be let down inside the poly-pipe, plus acting as a centraliser. The pumps were connected to Flexibore, the flexible layflat hose supplied by Crusader Hose, which had the pressure rating for pumping from the water table that was at 45 metres in the pit.
The hose of choice for the system
Flexibore was chosen for the project as it allowed for easy installation of the pumps over a roller while being clamped from a crane.
“As the hose is manufactured from woven fabric that acts like a lifting sling, a high tensile load of up to 16 tonnes can be suspended from it,” Crusader Hose managing director Francois Steverlynck says.
“The hose is also supplied in one continuous length. The new eight-inch Flexibore has a burst pressure of 700 metres, which gives a high safety pressure margin for this type of project.”
A successful installation
With the submersible pumps safely lowered inside the poly-pipe casing, they were then connected to the diesel generators via the power cables attached to the Flexibore hose.
Settings and flow rates were controlled until each pump attained a flow rate of 168 litres per second.
The CAT diesel generators were supplied by Taranis Power of Western Australia. Gabriel Hoascar, the Taranis engineer who connected the pump cables and fired up the generators, says, “I was impressed at how efficiently the system worked. Our company will look for more opportunities to partner with Australian manufacturers such as Crusader Hose.”
This article also appears in the November issue of Australian Mining.