Wear parts are the one cost on a crusher plant that is certain. The rock will take the steel. The only question is how many tonnes it gives in exchange, and on two sites running the same crusher the answer can differ by a factor of two or more. Most of that gap comes from the rock and from how the machine is fed, not from whose name is cast into the plate.
This is what the parts are made of, what wears them, how a set is managed through its life and when it comes out. Life figures are given as ranges and labelled, because a single number for jaw plate life or cone crusher liner life would be wrong for most of the people reading it.
What crusher wear parts are
Crusher wear parts are the replaceable surfaces that touch the rock: the fixed and moving jaw plates and the cheek plates beside them in a jaw crusher, the mantle and the concave in a cone crusher, the rotor tips and anvils in a VSI, and further down the line the screen media and the conveyor belts.
- Jaw plates and cheek plates. The two plates do the crushing; the fixed one usually wears faster. Cheek plates line the sides of the chamber and protect the frame.
- Mantle and concave. The mantle rides on the gyrating head, the concave, or bowl liner, sits in the bowl above it. They wear as a pair and are changed as a pair.
- VSI rotor tips and anvils. The fastest-wearing metal on a plant, because the stone meets them at speed.
- Screen media. Wire mesh or moulded panels. A worn deck does not stop the plant. Its apertures grow, the product creeps coarse, and the first sign is a failed grading.
- Belts. Worn at loading points and by seized idlers more than by distance run.
Manganese steel jaw plates and how work hardening works
Jaw plates and cone liners are cast in austenitic manganese steel, often called Hadfield steel. IS 276, the Indian standard for these castings, lists seven grades: five with 11 to 14 per cent manganese and two with 16 to 19 per cent, carbon mostly between 1.05 and 1.35 per cent, and 1.5 to 2.5 per cent chromium in two of them. Crusher makers and foundries sell on a simpler ladder of about 14, 18 and 22 per cent.
As it leaves heat treatment the steel is soft for a wear material. IS 276 caps its 11 to 14 per cent grades at 229 Brinell, and foundries quote about 200 to 220. Hit it or squeeze it hard enough and the working surface hardens to around 500 Brinell while the metal underneath stays tough. That is the whole trick: a hard skin that wears slowly, on a body that does not crack, renewing itself as it wears because the metal beneath hardens in turn.
The condition is force. Sliding, scratching wear from fine or soft material removes the surface before it has hardened, and the plate wears at its soft, as-cast rate. That is why manganese does poorly on abrasive fines, and why the same grade can look excellent in one crusher and poor in another.
| Grade | Where it is used | Trade-off |
|---|---|---|
| About 14% Mn (the 11–14% band) | Softer, low-abrasion rock; heavy impact | Toughest of the three, least abrasion resistance |
| About 18% Mn, often with about 2% Cr | The all-round grade for jaw plates and cone liners | Middle of the road on abrasion and on hardening rate |
| About 22% Mn and above | Very hard, abrasive rock with enough impact to harden it | Most wear resistance, more brittle, wasted where impact is low |
Bands as described in crusher makers' and trade selection guides. Alloy names and exact chemistry differ by foundry, and guides do not agree on every pairing of grade and rock, so start from the crusher maker's specification and change one thing at a time.
What decides jaw plate life and cone crusher liner life
- Silica in the rock. Quartz is harder than work-hardened manganese steel and cuts it. Rock low in free silica, good limestone above all, is cheap in steel. Quartzite, quartz-rich sandstone and granite are not. How the common rocks compare is in which rock makes good road aggregate.
- Fines in the feed. Material already smaller than the setting does no useful work in the chamber. It fills the space between the teeth, raises the contact area and grinds. On a jaw it is scalped out at the grizzly. On a cone, fines under about 4 mm are screened out ahead of the crusher, where they would otherwise pack.
- Feed size. Oversize overloads the top of the chamber. Feed that is too small for the cavity does all its crushing at the bottom, wears a groove there and leaves the upper half of the liner unused.
- Choke feeding. A full chamber crushes stone against stone and spreads the wear over the whole liner. A trickle-fed cone wears in a band, the profile cups, and the set is scrapped with most of its metal still on it.
- The setting. A tighter closed side setting is more work per tonne and more wear per tonne. Closed too far, the chamber packs.
- The shot. Slabby oversize and a muckpile full of fines both cost liner life before the plant has made a tonne, which is one more reason blast fragmentation decides crusher output.
Typical wear life, and why it is only ever a range
Nobody can give an honest table of hours. The pattern is steadier than the numbers: as a rule VSI tips go first and jaw plates last, and every part lasts longer in low-silica rock. As a single published reference point, a trial at a granite quarry reported 20,000 to 30,000 tonnes from a set of standard jaw plates and 50,000 to 55,000 tonnes after nothing more than a change of tooth profile, with the quarry's own rule of thumb that limestone would give about double. Treat that as one site's range, typical of nothing but itself.
The same lesson is in our own project record in fewer words. The hard basalt on the Nanded to Jalna expressway is noted as heavy on liners and generous on strength. The hard granite on Challakere to Hiriyur in Karnataka is noted as different bits, different liners, different penetration rates. The only wear figure worth planning on is your own: tonnes over the weighbridge per set, logged per crusher and per rock. After two sets you know your number.
Turning and rotating jaw plates
A jaw plate wears most toward the bottom, where the chamber is narrowest and the crushing is hardest. One-piece plates are cast symmetrical so they can be turned end for end. Metso's guidance for its own one-piece jaw dies gives the timing.
- 01
First turn
When about 30 per cent of the tooth profile has worn. The lightly worn, already work-hardened top goes to the bottom.
- 02
Second turn
When the teeth at the bottom of the plate have worn flat. The plate goes back the way it started for the last of its life.
- 03
Change
Before any part of the plate wears through, and by the minimum thickness the crusher manual gives for that design of plate.
Two-piece plates do the same thing in a different way. The worn lower piece comes out, the hardened upper piece moves down, and the new piece goes in at the top. Either way there are two reasons to do it on time. All the metal gets used. And the nip angle between the plates holds, where a hollowed lower jaw lets rock slip, drops throughput and opens the effective setting so the product coarsens.
When to change a set
The hard rule is never through to the seat. Once a jaw plate or a liner wears through, the rock is cutting the pitman, the head or the bowl, and those are not wear parts. In normal wear only about half the weight of a cone liner has been used by the time the set is finished, so a scrapped mantle that still weighs nearly what it did new is evidence of uneven wear, not of thrift.
The softer rule is that a set is often finished before the steel is. Watch for throughput falling at the same setting, power draw rising, the adjustment running out of travel, and chips drifting toward the limit on the flakiness and elongation index. On a cone, the amount the bowl has been turned down to hold the setting is a running measure of liner wear that needs no stoppage to read. Then plan the change for a day when there is stockpile ahead of the road, with the new set already on site.
Who carries the wear parts
On a hired or contract-operated plant, settle in writing who buys the wear parts, who stocks them, and whose clock is running while a liner is on a truck. Under our contracts they are our cost. Jaw plates, cone liners, screen mesh, belts and bearings are stocked at the plant, so a wear failure costs hours instead of the three weeks it takes to get a liner shipped in. That arrangement is set out on crusher plant operations, the plants themselves are on stone crushing, and if you are weighing it against buying a plant, own versus contract crusher plant covers the rest of the sum. What each of these parts does in the line is in jaw, cone and VSI.