TBM 156-275 Main specifications Cutterhead diameter 4.62 m operating thrust 748.4 t installed power 1,258.7 kW speed 12.156/4.052 rpm cutters 33 only, 432 mm diameter, maximum 222.2 kN/cutter Minimum turning radius 107 m Boring stroke 1,575 mm Belt width 762 mm speed 0-2.54 m/s capacity 552 [m.sup.3]/h Electrics primary power 12,470 V/60 Hz secondary voltage 600 V main motors 120 V control circuit/lighting 480 V supply to back up Hydraulics high pressure circuit 289.5 bar maximum pressure low pressure circuit 103.4 bar maximum pressure auxiliary circuit 241.3 bar maximum pressure total power 149 kW The TBM is a Series 150 from The Robbins Co., TBM 156-275, in the design of which both SMMD and FKC/DH personnel participated.
An important part of the planning process for putting the 240 t TBM underground involved Robbins' role in manufacturing the machine to exacting space and weight limitations supplied by SMMD. The 4.62 m diameter cutterhead and the heavy main beam were each constructed in two pieces.
SMMD purchased four new Brookville 30 t diesel locos (specified by FKC/DH) to haul the muck trains from the TBM.
SMMD, as well as its underground mining operations, has been mining from an open pit for many years.
Pre-production manpower on Lower K will peak at 293 in 1996 and combined SMMD mining and milling manpower will peak at 1,289 in 1999 as operations in the San Manuel and Upper K orebodies are terminated and manpower is transferred to the Lower K.
In 1990 SMMD mining costs were, in short tons, $5.94, falling to $5.11/t in 1991.
SMMD's underground productivity is the key to Magma's survival and results for the first six months of 1992 have been heartening, though the targets they have set themselves will still require further great effort.
As at SMMD, business team leaders have taken the place of 'superintendents', 'foremen' have been replaced by coordinators and work place decisions are made by work teams throughout the operations.