Planned Maintenance and Condition Monitoring
Planned Maintenance and Condition Monitoring
This domain tests the maintenance regime for fixed installations and plant: the legal basis, planned preventive maintenance, condition-based monitoring, records and asset criticality.
Legal and standards basis
- EAWR reg 4 requires electrical systems to be maintained so as to prevent danger; PUWER 1998 reg 5 requires work equipment to be maintained in an efficient state, in efficient working order and in good repair.
- BS 7671 itself does not set inspection intervals. IET Guidance Note 3 Table 3.2 gives recommended maximum intervals, for example 10 years for domestic, 5 years for rented domestic and 3 years for industrial, adjusted for use, environment and history.
Condition monitoring tools
Thermography of busbars and terminations, insulation resistance trending, partial discharge detection, power quality logging, reliability-centred maintenance analysis, and a CMMS holding the asset register, work orders, spares and MTBF/MTTR data.
Worked example
An annual thermographic survey of a 400 A distribution board records a 62 K rise on the line terminal of a 100 A MCCB carrying 55 A, while comparable terminals show 8 K. Load is only 55 % of rating, so the rise is not load-driven; the differential indicates a loose termination. The board is isolated, the termination re-torqued to the manufacturer's stated value, and the joint re-scanned under the same load to confirm the rise has fallen to single figures.
Traps
Recording temperature without load or ambient reference; re-torquing to feel rather than the specified value in newton-metres; maintaining only on failure; keeping no baseline so deterioration cannot be judged; forgetting that maintenance work that alters the installation requires verification and a certificate.