The HSE have issued a safety alert following fire and explosion caused by the failure of a high voltage circuit breaker.
High and Low voltage circuit breakers are required to operate at high speed to disconnect electrical faults with a high degree of reliability from the associated electrical system. To ensure the required performance is retained it is vital that the circuit breaker operating mechanism is regularly checked and maintained.
When the mechanism is slow to operate it may require relubricating, in extreme cases where the circuit breaker mechanisms are observed to be sticking due to old, congealed lubricant, it is common practice to apply a cleaning product to remove this prior to re-lubrication.
When carrying out cleaning and re-lubrication it is important that the correct type of lubricant is used and that any cleaning products are compatible with the circuit breaker. Cleaning should be carried out following the recommended procedure given in the manufacturer’s instructions before reapplying the manufacturer recommended lubricants.
The HSE’s investigation into the recent failure found that this may have been the result of an incorrect aerosol based multipurpose lubricant being applied to the circuit breaker mechanism.
Independent forensic analysis work conducted during the investigation showed that the multipurpose lubricant used during the maintenance of the failed circuit breaker prior to the incident, evaporated by 75% of its original weight within 2 weeks of application. The analysis concluded that for this reason, multipurpose lubricants containing solvents (e.g. white spirit) are unsuitable for use as a lubricant of this type of switchgear.
The safety alert recommends that duty-holders e.g. owners and operators of relevant pant and Specialist Electrical Contractors with responsibilities for operation and maintenance of such circuit breakers should review their current maintenance procedures associated with cleaning and lubrication of high and low voltage circuit breakers and ensure they meet with requirements and manufacturer’s instructions.
In particular, the maintenance procedure should ensure that the manufacturer instructions on cleaning and lubrication of the circuit breaker mechanism are followed at appropriate intervals, including the selection and application of the correctly specified lubricants (typically this will be two separate types of product).
The HSE state “This activity is unlikely to involve the use of aerosol based multipurpose lubricants other than for cleaning, following an approved procedure as prescribed by the manufacturer”.
Full details of the Safety Alert can be found on the HSE’s website at: https://www.hse.gov.uk/safetybulletins/lubrication-circuit-breakers.htm?utm_source=govdelivery&utm_medium=email&utm_campaign=circuit-breaker-safety-notice&utm_term=intro&utm_content=safety-notice-29-sep-21
Please speak to your normal PIB Risk Management contact or get in touch using firstname.lastname@example.org if you have any questions about electrical safety at work.