Wear note
Quarry Monday standups
Wear notes that fit a standup beat novels that nobody reads.
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
Monday standups at the quarry are never only about last week’s haul or production tonnage. For me, they’re a quick-fire chance to catch jaw plate issues before they become the reason the bakkies are parked and the plant sits quiet.
First glance at the jaw set
Before anyone gets stuck into the numbers, I always walk the floor with the shift boss and check the jaw plate set. On the Highveld, dust gets in everywhere, and you spot tell-tale silvery streaks on the manganese long before you measure anything. If it’s been a wet week, mud bakes on the seats and can ‘cushion’ the plate, messing with nip angle and reducing effective grip.
A jaw plate set can weigh anywhere from 180 to 420 kg per piece, so safe lifting and proper rigging are non-negotiable. I always take a look at the condition of the lifting lugs. If someone has torched or ground them, that’s a stop right there: no plate moves without a sound lug.
Measuring wear before it bites
Too many times, plates run right down to the backing plate or even through it. Every Monday, I run a tape across the jaw face. Any less than 20 mm at the thinnest point, and you’re living on borrowed time. On most OEM profiles, that’s the wear limit.
We also check the closed side setting (CSS) with feeler gauges and a calibrated rod. If the CSS is creeping open, it’s often because the lower jaw plate is worn to a banana, or the cheek plates are chewed up. Remember, excessive CSS not only drops your product size control but also hammers your throughput, especially if you’re feeding direct from a face with variable rock hardness.
Bolts, torque and lockout safety
Jaw plate bolts are a classic spot for shortcutting, especially after a long weekend or during Eskom power cuts. I make sure every standup includes asking if plates were changed under proper lockout, no exceptions. There’s no shame in delaying a start if you aren’t sure.
Torque on jaw plate bolts (and wedge bolts) must follow the OEM manual, not guesswork. I’ve seen plates walk out of position and damage the toggle because a spanner wasn’t big enough, or a pneumatic gun was used without a torque chart. Bolt stretch or thread galling is a sure sign someone’s been heavy-handed.
If the toggle plate is marked or fractured, it’s done its job as a tramp-metal fuse. Don’t refit anything until the cause is found, could be an uncrushable got through or jaw plates are too loose.
- Always check jaw plate thickness at multiple points
- Verify correct CSS with proper tools
- Inspect lifting lugs for damage
- Follow lockout and torque procedures strictly
- Investigate any toggle plate damage immediately
Wear profiling over the campaign
Every site runs differently, but successful teams keep a wear profile log for each jaw set. When wear starts to accelerate, it’s usually about feed distribution or running too dry. A well-choked jaw with even feed wears slower and gets the best out of the austenitic manganese work hardening.
If you see scalloping or uneven wear, check the grizzly and the feeder settings, maybe fines are bypassing or the feed is off-centre. On the Lowveld, humidity can make fines stick and load unevenly, while Joburg’s winter mornings can cause plates to crack if pre-heating procedures are skipped.
A proper wear profile lets you plan your next jaw change around your campaign schedule, not the other way around. That keeps the team busy on Mondays for the right reasons and not because the plant’s stopped with a blown jaw.
Related parts: Jaw Plate Set. You can also browse all parts and plant guides.
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