A crusher jam is a mechanical event with electrical consequences. Repeatedly pressing start can heat the motor while tightening the trapped material, damaging couplings or defeating the evidence needed to find the cause.
Identify the actual jam state
Follow the plant isolation procedure before inspection or clearing. Determine whether the chamber is cleared, partially loaded, hydraulically relieved, mechanically locked or capable of approved reverse movement.
| Condition | Restart position | Required confirmation |
|---|---|---|
| Chamber cleared and shaft free | Normal controlled start may be possible | Protection reset cause and free rotation |
| Material remains but mechanism can move | Engineering review required | Crusher torque demand and drivetrain limit |
| Reverse jog proposed | Do not assume permission | OEM approval, backstop and control logic |
| Shaft cannot move | No electrical restart | Mechanical clearing and damage inspection |
Compare torque with the weakest interface
The allowed torque is limited by more than the motor. Check the motor shaft, coupling, gearbox, keys, crusher shaft and foundation, together with drive current limit and motor thermal state. A high-torque motor can move the failure to a more expensive component.
Separate starting protection from jam protection
A legitimate acceleration and a locked crusher can both produce high current. Set stall, jam, overload and acceleration supervision from time-current and speed behaviour, not from one current threshold. Preserve the first trip record before resetting it.
For VFD systems, verify low-speed torque, current duration, motor cooling and whether flying-start or catch-on-the-fly functions are relevant. These functions do not clear a mechanical lock.
Define the recovery procedure before the next event
The operating instruction should name who authorises clearing, how stored energy is controlled, whether reverse motion is allowed, how many restart attempts are permitted and what inspection follows an abnormal torque event.
RFQ data for crusher duty
Provide crusher type, normal and jam torque information, total inertia, starting method, starts per hour, supply voltage study, ambient, dust conditions and the approved clearing sequence. LEADGO can review motor torque and thermal capability against that defined case.