The original weighbridges were installed in 1976 when the longwall began mining. West Cliff is based in New South Wales, near Wollongong.

“Their design consisted of a large steel table suspended on mechanical pivots with analogue strain gauges,” said coal prep manager Roger Bowman.

“Each bridge was located over a sunken concrete pit that houses all of the mechanical apparatus so that the bridge-working table was at pavement height.

“The weighbridges are adjacent to one another and so provide two traffic lanes for trucks to weigh and exit the site. These bridges were at the end of their working life and were difficult to maintain to an adequate standard.”

The mine also recently signed a six-year transport deal with Bulktrans which required the replacement of the truck fleet with 26m long B-Double trucks to improve efficiencies and enable lower transport rates. But the new larger trucks could not fit on the older existing weighbridges.

Measurement of the existing loading system highlighted significant loading and weighing inefficiencies. Truck drivers were loading from either stockpiles with FELS or from bins, then passing through a truckwash and weighing on the old weighbridges.

“An examination of this system showed that up to 60% of all trucks had to turn around and either trim or top up their load to meet legal load or efficiency requirements respectively,” Bowman said. “Some drivers were cycling around this loop up to three and four times at five minutes per cycle.”

To overcome excessive coal spillage on the weighbridges, related to malfunction of bin doors, a system of steel barriers was incorporated in the design to keep spillage on the weighbridge.

“The weighbridge system was successfully installed on time and within budget with only one near miss that involved wheel rim damage to a trick that failed to negotiate the new approach to a bridge and collided with a kerb,” Bowman said.

By December last year the mine reported that the bridges had improved truck-loading efficiencies significantly by pratically eliminating truck cycling around the site. Drivers are now able to load very precisely from either stockpiles or bins to legal llimits and axle weight distribution.

Spillage protection systems have also proved successful. Extra benefits include lower traffic movements on site and lower dust generation.

The upgrade was reported in a BHP Billiton Illawarra employee newsletter in December. Republished with permission.