Wear note
Work hardening before romance
Mn only helps after the feed works it. Start with real rock, not brochure hardness.
By Mr Thabo Molefe, Parts manager
Thabo Molefe manages all parts operations at Crusher Consumables’ Sunnyrock yard, making sure the right crusher and screen spares reach the right place at the right time.
AuthorWhy this matters on the plant
Too many times, I see new jaw plates tossed onto a crusher and everyone expects magic from the manganese. The truth is, work hardening only starts with real rock and time, not just the numbers on a brochure or a hardness tester.
Work hardening needs real action
Austenitic manganese steel is unique for its ability to toughen up under repeated impact and pressure. This work hardening only happens when the feed is running, and the rock is genuinely bearing down on the jaw surface. If you just look at the plates straight out the box, the surface hardness won't be anywhere near what it can be after a good campaign. I've seen plates fitted and then run on soft start-up material, or even worse, used for dry cycling with no real load. That does nothing for the work hardening. You need to let the crusher chew through real, abrasive rock for the first couple shifts. This way, the outer layer compresses and hardens, building the resistance you paid for.
Avoid light or uneven loading
Here in South Africa, we see plants in the Karoo, on the Highveld and down in the Cape flats, all with different feed materials. No matter if you’re running quartzitic conglomerate or dolerite, the jaw plates need proper, even feed. Uneven or trickle feeding, common when there are power cuts or the plant is running on an old bakkie’s generator, will create dead zones on the jaw surface. Those untouched spots will wear away rapidly once the real rocks come through. Feed must be spread over the full width using proper chutes and a working grizzly. Choke feeding also helps ensure the whole crushing chamber is being used, maximising the work hardening effect.
- Always check feeders and grizzlies for blockages
- Inspect liner wear patterns weekly
- Use wear profiles to adjust closed side setting
- Avoid stop-start running on empty
- Don’t overload one side of the chamber
Don’t judge by the numbers too soon
I've been called out to plants where the maintenance team measured hardness after only a few hundred tonnes, then panicked because the readings were lower than promised. Manganese steel starts hardening after it’s been worked. If you test before the surface has seen enough real pressure, you’re just looking at the as-cast or lightly compressed layer. Allow at least one or two shifts of solid production, preferably with the crusher at its normal closed side setting and nip angle, before even thinking about hardness readings. The initial wear is meant to happen, so don't panic if you see some material coming off early on. That’s part of the process.
Practical steps for new jaw plate commissioning
When fitting a new jaw plate set, always torque the liner bolts to the OEM’s spec, using proper anti-seize. Double-check lifting lugs for integrity and use rated slings, as we’ve seen plates from 180 to 420 kg. Once installed, run the crusher at target tonnage with a steady feed of typical plant rock. Avoid over-tightening the closed side setting, and monitor the nip angle for proper bite. Keep a record of liner wear over the first two or three days. If you see spotty or accelerated wear, don’t be afraid to make small feed or CSS adjustments. Remember: patience in these first days gives you thousands more tonnes down the line.
Related parts: Jaw Plate Set. You can also browse all parts and plant guides.
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