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Case No.16


Caught in machinery because of the sudden movement of a stopped trolley hopper at an asphalt mixer
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[Circumstances of Incident]

The accident occurred at an aggregate silo at a plant that manufactures road-paving materials by means of an asphalt mixer.

Aggregate received on the ground is processed in the following order: receiving hopper --> belt conveyer -->  top of the silo -->  tripper belt conveyer -->  belt conveyor trolley hopper.

Shortly before 17:00 on the day of the accident, the victim had finished work as usual. While returning aggregate remaining inside the asphalt mixer to the aggregate silo, the trolley hopper suddenly stopped moving in the middle of the process.

When the victim checked to see what was wrong, he found that the chain connecting the trolley hopper motor to the wheels had become detached. He reattached the chain and switched the power on again at the power panel, but the chain became detached again.

The victim and another worker checked the machinery again and found that the gear shaft of the trolley hopper motor was broken. They stopped the trolley hopper and removed the motor, and decided to empty the macadam remaining in the dump hopper into two other silos.

At around 18:40, when the person in charge of production at the plant switched on the power to operate the belt conveyer and the tripper belt conveyer, the tripper belt conveyer came to an emergency stop after a couple of minutes. The production manager rushed to the top of the aggregate silo to see what was wrong and found the victim lying next to the conveyor.
[Causes]
1 The victim did not realize that because the malfunctioning motor of the trolley hopper had been removed, there was no motor brake to keep the trolley hopper from moving. Accordingly, it suddenly started to move when the tripper belt conveyer was engaged.

2 The victim entered a dangerous area despite the fact that the belt conveyer, etc., was moving.

3 Delayed operation of the emergency stop equipment

While the victim pulled the emergency stop rope when he felt some danger, this failed to stop all operations immediately.

4 In a site involving joint work, directions were not issued regarding entering into a dangerous area (inside the belt conveyer).

5 There was no operation manual covering repairs to the motor of the tripper belt conveyer.
[Type of business] Petroleum and coal products manufacturing
[Type of accident]Caught in
[Number of victims]One fatality
toptop