Sugar Mill Crusher Drive — Surviving 24/7 Shock Loads

The Problem

The mill had been running generic locally-sourced worm gearboxes on its crusher drives. Every crushing season (October through March) at least one gearbox would fail — typically worm wheel teeth shearing off under shock load. Replacement took 3–5 days of downtime at peak crushing, and each lost day cost the mill roughly Rs 18 lakh in deferred throughput.

The existing gearboxes were nominally rated for the 75 kW motor, but were specified with a service factor of 1.25 — appropriate for a smoothly-loaded centrifugal pump, not for a crusher biting into cane with substantial shock impulses.

The mill engineer suspected under-specification but had been told by the previous supplier that the gearboxes were 'fine' and the failures were 'due to operator mishandling'.

The Solution

We surveyed the drive train, measured actual load cycles with a strain gauge on the output shaft for two full days of crushing, and confirmed peak transient torque was roughly 2.1× the nominal running torque. That justified a service factor of 2.5, not 1.25.

We specified an Anand Gears 180CD cast iron worm gearbox (one size larger than the previous unit) at 40:1, with the bronze wheel casting sourced from Lord Metal Foundry and finish-machined on our Bridgeport CNC lathe for tighter mesh tolerance than the generic unit had.

We also re-engineered the mounting: the original unit used four M20 bolts into a thin steel bracket. We switched to a machined torque-arm assembly with a rubber damper between gearbox and frame, which absorbs the shock impulse instead of transmitting it directly to the housing bolts.

Delivery: 4 weeks from order to commissioning, including a site visit to verify alignment and heat-run commissioning for 48 hours.

The Result

“The gearbox hasn't been touched in two full seasons. That's the first time in fifteen years I can say that.”

— Chief Engineer, Sugar Mill (Maharashtra)

Photos from the Job