Reinforced VF800-based drive shafts rated to 2,200 kN·m for ball mills running heavy shock loads — two years in service without a single fork-root crack.
EquipmentØ3.6 × 6m ball mill
Torque demand2,200 kN·m
Swing diameter750 mm
Design changeReinforced fork root
BalancingISO 1940 G6.3
Year2024
Customer Background
The concentrator's ball mills handle coarse ore with frequent shock loads. The OEM drive shafts developed fatigue cracks at the fork roots within about a year, and each unplanned replacement meant stopping the grinding circuit.
The Challenge
Continuous heavy shock loads with a dusty, abrasive environment
The fork-root crack issue had to be solved without changing the mill foundation
Sealing had to keep dust out of cross bearings to protect lubrication
Our Solution
Upgraded alloy-steel forgings with a larger fork-root fillet radius, verified by FEA
Full-contact sealing on the cross bearings to keep out dust
Every shaft dynamically balanced to G6.3 before shipment
Agreed a 500h / 1,000h inspection and greasing plan with the plant
The Results
The first four shafts have run two years without any fork-root cracking, absorbing daily shock loads as designed. The plant has since ordered four more as scheduled spares.
