Electrical Safety Hazard: Vortex Mixer

32. (2002)

This hazard alert is a warning to all operators of vortex mixers and other aged, small laboratory electrical appliances.

Incident

An electronics technician was conducting electrical testing of laboratory appliances and discovered that a vortex mixer had burnt out its earth circuit during the test process. The vortex mixer was an earthed appliance and this requires any touchable metal surface of the appliance to be safely earthed.

The vortex mixer was found to have wiring that didn't conform to Australian Standards because the appliance's earth wire was connected to the appliance body via a conducting track on the internal printed circuit board (PCB). A PCB track is not capable of carrying the high amperage current in a fault situation, would burn out, and would leave the casing of the appliance live.

Preventive Measures

It is important that all small laboratory electrical appliances be treated as portable appliances for the purposes of the University's electrical safety hazard management procedures http://info.anu.edu.au/policies/_DHR/Procedures/Electrical_Safety.asp and be electrically tested annually. This is particularly so with aged appliances because, as has been documented in other hazard alerts /OHS/Hazard_Alerts/index.asp, the design standards of appliances with respect to electrical safety have improved significantly over the past decade.

All untested vortex mixers should be taken out of service, switched off and unplugged, and Budget Unit management notified. Testing, in accordance with the ANU electrical safety policy, should be organised and successfully completed before the appliance is brought back into service.

For further information contact:
OHS Officer, e-mail: OHS.Officer@anu.edu.au