Prematurely Decaying Sleepers 2017-08-22T02:27:50+12:00
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Prematurely Decaying Sleepers

Service: Asset Management


Client: KiwiRail


Dates: 2013 – 2015


Project Location: Nationwide


In 2013 Frequency were engaged to assist KiwiRail in programming for the replacement of around 160,000 sleepers as part of their Prematurely Decaying Sleepers (PDS) Project. These hardwood sleepers were installed on the network between 2003 and 2012 and were initially sourced from Peru prior to 2012. Structures and Track Inspectors started to quickly notice that these sleepers had started to show premature decay and needed urgent attention.

Frequency’s role on this national project, was to manage the condition of track assets affected by early decay sleepers. This involved handling the inspection process, corridor evaluators and reporting to KiwiRail.

An evaluation method was developed by Aurecom and SCION which researched into the ‘modes of failure’ of the sleepers on the network such as bed plate “weetbixing”, bedplate cutting in, loss of gauge and section loss of the PDS sleepers. Initial inspection focused on priority passenger networks and critical assets in Auckland Metro, Wellington Metro and the West Coast areas for the trans-scenic route.

As compliance managers we were responsible for the inspection process and inspection teams and reporting. The benefits of this project allowed KiwiRail to quantify the track assets condition and rate of decay and therefore how to cash-flow the replacement programme for each financial year.

Innovation opportunities included the use of composite sleepers instead of concrete or HW sleepers due to the worldwide shortage of hardwood sleepers and the use of Edilon solutions for level crossings.

Key Challenges:

  • Widespread decay with white or black mould.
  • Risk management and the need to quantify the current risk for KiwiRail immediately.
  • The possibility of a track failure causing a serious harm / incident and the negative Public Relations that could be generated as a result.
  • The possibility of a track failure causing loss of revenue on freight lines for KiwiRail.
  • Development of a repeatable field test and a testing regime to monitor the rate of decay of assets.
  • Training the team of inspectors who undertake the field testing and implementing quality assurance on condition assessments.
  • Forecasting budgets required to keep the network risks acceptable for priority lines.
  • Replacement of PDS to be undertaken as business as usual (live operating environment).
  • Stakeholder management between the regions and nationally within KiwiRail.