Newpac is located between Singleton and Muswellbrook in New South Wales’ Hunter Valley. The mine is set to ramp up early this year and will produce 4 million tonnes per annum run-of-mine (ROM) coal. But to get it to this point, a lot of work had to be done to increase the conveyor system capacity to cope with the projected longwall coal output.

Resource Pacific had identified the Pikes Gully seam, where it had been operating as a bord and pillar operation, as the most suitable for longwall mining. But to reach the seam, extensive and costly heading development was required.

Patterson said while several previous owners of the mine had tried and failed to reach the Pikes Gully seam, Nepean worked closely with Resource Pacific to advise on conveyor system conceptual design, budget costing and to devise solutions regarding technical concerns.

“Despite the obvious need to replace the existing 1050mm trunk conveyor system at Newpac with a 3500tph 1500mm coal clearance system, disruptions to the bord and pillar operations were to be avoided at all cost.”

Unique to the Newpac installation, the existing four heading mains development prevented Nepean from relocating the existing low capacity conveyors into another heading while the permanent 1500mm system was installed.

“The decision made by mine management, in consultation with Nepean and Valley Longwall Drilling, was to install and commission a system allowing the existing 1050mm structure to be removed and the new 1500mm structure installed without stopping the belt,” Patterson said.

“With a great focus on safety for employees, VLD designed a structure changing jig to change out 3500m of structure without incident or lost production. The jig was a huge success, allowing approx 70m of structure per shift to be changed out.”

During the design phase, careful consideration was given to the robust design of major assemblies, to facilitate handling in confined space by underground vehicles.

The underground coal clearance system has a design capacity of 3500tph, with volumetric capacity to handle peaks of 4000tph.

Patterson said when the project began in June 2005, development of the mains headings was not due for completion until 12 months into the project, thus affecting the optimum design of the P01 and PG02 conveyors.

“Whilst a single conveyor would have provided operational benefits, a two-flight system was proposed to permit a staged installation, and to ensure equipment rationalisation between trunk and maingate conveyor systems,” Patterson said.

“This also permitted a fabric belt to be utilised on PG02, which was constantly increasing in length during the development phase of the mains headings.”

Describing the installation phase of the project, Patterson said Nepean commenced first delivery of the conveyor structure within six weeks of signing the contract to allow the new 1500mm structure to be installed as the existing development conveyors progressed, in lieu of additional 1050mm structure.

The new trunk conveyor structure features a bent pipe carry frame and five-roll 45-degree carry idler set, which was also suitable for use with the existing 1050mm belt. This arrangement allowed for structure change to occur without the need to immediately replace the 1050mm drives, take-up and belt.

“The advances made in the program with the structure changing jig allowed for the pre-installation of PG01 drivehead, gravity tower and tail take-up, and the PG02 drivehead, ready for an intense Christmas shutdown,” Patterson said.

“Over a three-week period Valley Longwall Drilling removed four of the existing 1050mm drivehead units, installed PG01 transfer equipment, remaining structure and completed the partial commissioning within the scheduled window of opportunity.”

A roadheader was then sourced by Newpac to remove 2m of stone from the floor of the mains headings, for approximately 400m to permit fitment of the larger 1500m conveyor system.

“As PG01, PG02 conveyor headings already had existing conveyors installed, tramming a miner into these areas was not an option,” Patterson said.

Reflecting on the whole process, Patterson said that getting the customer to commit to a design capacity was the first hurdle, followed by an understanding of the material properties, mining practices and environment in which the equipment will be expected to operate.

“As conveyor equipment typically has a long design life [15-plus years] and is capital intensive, future upgrade paths also need to be considered at the design stage,” he said.

Equipment Specifications:

• Existing 1500mm drift conveyor was upgraded from 2500tph to 3500tph, by way of increased belt speed and supply of new drives and conveyor substation. This involved supply of a new 3MVA surface substation, new 500kW VVVF drive modules, new LTU (Loop Take-up Unit), structural modification and upgrade of head end pulleys.
• All underground conveyors designed for 1500mm belt width, with all equipment rationalised to minimise spares holding. Modular designs for delivery jibs, driveheads, power modules, LTU, Belt Storage Units and pulleys have ensured maximum interchangeability of equipment.
• PG01, PG02, PG03 trunk conveyors are designed for 3500tph operation, each fitted with 3 x 500kW VVVF drives. All power and control solutions were provided in-house by another Nepean Group company, with M.I. Power designing and supplying the 3MVA 11kV/415V VVVF conveyor substations and air-conditioning units.
• PG01 (1510m centres x 90m lift) utilises a 1500mm Goodyear steel cord belt, type ST2000 8+6 “S” with a tail gravity take-up, whilst PG02 (2870m centres x 47m lift) and PG03 (final length 2090m centres x 17m lift) utilise a 1500mm Goodyear fabric belt, type PN2250/5 ply 4+4 “S”. All maingate conveyors utilise a 1500mm Depreux solid woven belt, type T1750 3+1.5 PVNi “S”.
• All pulley diameters are suitable for use with either the steel cord or fabric belt constructions.
• All conveyor substations employ that latest ABB VVVF drive technology for unmatched control of drives. Long acceleration (start) times, controlled deceleration, inspection speeds and continuous operation at reduced speed for development are all possible with the drives. Significant R&D was undertaken by Nepean and M.I. Power early in 1999/2000 to ensure compliance with CMRA (Coal Mines Regulations Act) and proving/testing safety systems exceeded minimum requirements in the event of critical component failure or transient supply conditions.