Fishbone has worked closely with Porterbrook Leasing Company and South Western Railway to investigate maintenance optimisation on legacy fleets. Significant operational and financial benefits were achieved on the Class 458/5 fleet by extension of the C4 overhaul mileage.


Client: Porterbrook Leasing Limited

Location: UK

Services: Engineering

Fishbone were asked by Porterbrook to develop a methodology to evaluate the existing C4 overhaul, and through a risk-based process and trial running, recommend and gain approval for achieving a significant mileage increase between C4 overhaul periods.

Fishbone delivered a 20% C4 overhaul periodicity increase by:

  • Reviewing current C4 component maintenance and condition at overhaul
  • Establishing a safe, monitored mileage extension trial
  • Reassessing component condition at extended mileages and presenting a case for extension based on expert condition assessment and mitigations
  • Reviewing overhaul maintenance tasks for suitability to run to extended mileages themselves based on unit maintenance histories and failure modes
  • Conducting a controlled programme of trial running to ascertain any requirements for change to wear limits, component inspections, and task periodicity
  • Presenting proposals for changes to C4 periodicity to the TOC / ROSCO, supporting the changes and other interventions required to optimise the overall benefit
  • The fleet was certified to run extend mileages for both regimes
  • The C4 overhaul periodicity was increased by 20%

Fishbone have successfully completed similar justifications to support change of C6 overhaul periodicity on the same fleet and are currently undertaking a series of maintenance optimisation reviews for Porterbrook with the aim of optimising C6 overhaul on other fleets.

Similar maintenance periodicity extensions have also been carried out for other operators and RoSCos, including full VMI revalidation.

How can we help?

Luke Essex

Head of Operations Engineering View Profile

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