The design of mine ventilation systems for the BHP Steel Division Collieries is based on the acquisition of ventilation survey data for the establishment of a realistic computer net- work model. The branches which form the net- work for the computer models are calculated from a range of resistance factors incorporat- ing both a frictional and shock loss component._x000D_
Since shock losses can account for up to 30 per cent of the total energy losses in mine airways the use of friction factors alone without accounting for shock losses will result in the choosing of an insufficiently performing fan._x000D_
Published tables of friction factors have in- variably been taken from metalliferous or single entry studies and consequently are not reliable for Australia's mining conditions where multiple entries with regularly spaced cut-throughs are the normal practice. Typical resistance factors for roadways of rectangular cross-section 5.5 m x 2.0 m, with coal sides, have been found to vary from 0.11 Ns2/m8/km where no timber supports are used, to 0.98 Ns2/m8/km where double centre legging together with wooden chocks is used._x000D_
In addition to the range of resistance factors due to varying support methods, the nature of use for a roadway is very significant because of the condition of repair and upkeep maintained.