Incident Report

Subject:                              Failure of a lighting fitting - Dangers of Sodium Fittings

Date of Email reporting Incident:  Sun 31/08/2003 19:29

Report Detail:

Failure of a lighting fitting - Dangers of Sodium Fittings

Please be aware of an incident which has recently occurred at our  Teesside facility passed on by our Responsible Electrical Engineer.

Lighting fitting failure caused by the explosion of a capacitor within the fitting . This occurred in the tunnel headhouse and was heard by people in the tunnel .I think this is relatively rare and I will ask to follow details via THORN ,but I don't expect much of a response from THORN based on other concerns we have raised.

Power factor capacitors usually have a small sealed container so that the dielectric does not become contaminated . Failure can causes the dielectric to vaporise and the vapour pressure subsequently splits the case with a loud bang. Failure of Capacitors is more likely if the lamp or the igniters is faulty as the circuit can generate repeated high voltage pulses which themselves can cause failures .

The fitting concerned was a SON (High pressure Sodium) and although the lamp was not the cause of the problem in this case its a useful reminder of the hazards of sodium . Every Sodium lamp contains some sodium metal . On exposure to air this burns spontaneously and intensely .

Sodium lamps should not be used in hazardous areas, nor carried through hazardous or fire areas .

Sodium lamps should be handled with care and disposed of correctly . The Electrical Dep't has a water fed crusher for this purpose ,but this should only be operated by persons familiar with the equipment and wearing the appropriate PPE .