Predicting Power Problems

Contract condition-based maintenance at BNSF's new Alliance, Neb., Reliability Center is improving locomotive efficiency and utilization.

In November 2002, BNSF Railway entered into a 12-year outsourcing contract with Alstom Transport for maintenance on 474 freight locomotives at various BNSF locomotive shops, many of which now incorporate "Reliability Centers." The agreement includes rollout of a relatively new approach to predictive diagnostics called CBM (condition-based maintenance). BNSF's newest Reliability Center, at the Alliance, Neb., shops, is now using CBM.

The Reliability Centers are the brainchild of BNSF Vice President- Mechanical and Value Engineering Craig Hill. They were developed to identify "bad-actor" locomotives and convert them into reliable power. BNSF defines bad actors as locomotives that experience mean- time between failures (MTBF) of fewer than 20 to 30 days or have a high defect rate, based on the mechanical department's DLD (defects per locomotive per day) measure. Reliability Center employees "are allowed to spend more time on troubleshooting a small pool of bad actors than would be practical in a scheduled maintenance environment," according to BNSF.

Alstom has deployed condition-based maintenance programs on rolling stock at railways worldwide, among them BNSF, TFM, London Underground, Virgin Rail, and Spain's high speed AVE. Data gathering incorporates several trainborne, trackside, and portable tools.

CBM is defined as "an advanced method of delivering cost- effective rolling stock maintenance by tracking the performance and reliability of equipment components. Monitoring vital systems and components, staff can predict when they should be repaired or replaced, thereby reducing the overall level of maintenance carried out and its cost. This leads to improved fleet availability and reliability and reduces capital expenditure on new vehicles."

At Alliance and other Reliability Centers, CBM is enabling the workforce to predict when parts should be overhauled and exchanged, improving locomotive reliability and operational efficiency, reducing road failures, and utilizing full component life cycle. Advanced technology is used to determine wear patterns of major components and sub-systems. The Alliance facility has been operational since Feb. 1, performing diagnostics on one locomotive per day on average. The facility is expected to be running three shifts and working at full capacity by mid2006.

The CBM procedures Alstom is using at Alliance are a bit different than those at other BNSF facilities. They incorporate stress wave analysis to predict mechanical failures, integrate all CBM data into one software database, and use Alstom's CCN (Core Competency Network) for streamlining diagnostics. Among the diagnostic tools are fixed and portable vibration analyzers that collect data from 32 points on the locomotive simultaneously; thermography cameras; ultrasonic guns; opacity testing; and electrical testing. Performing this work are one Reliability Center manager, one CBM analyst, and one electrician and two machinists per shift.

Alstom selects locomotives to be monitored under CBM based on previous failure history and age of major components. A two-tiered strategy is used. Level One (short term) is designed to reduce the number of road failures by identifying unscheduled component changeouts. Level Two (medium to long term) is designed to reduce inspection tasks and extend time periods between inspections and overhauls.

A good example of how CBM works at Alliance involves a main alternator vibration monitoring program. BNSF has found bearing deterioration to be causing catastrophic alternator failures. Since manual inspection is complicated and time consuming, Alstom is using a portable vibration device for stress wave analysis to locate bearing mechanical faults. A three-hour manual teardown and inspection procedure has been reduced to 10 minutes' worth of data collection. Age and vibration parameters are reviewed to determine suitable maintenance actions. The result? Since January 2004, 81 bearing changeouts initiated due to CBM have produced a 65% reduction in main alternator corrective maintenance costs.

Another CBM procedure known as "fragmented overhaul" eliminates the requirement for traditional, periodic backshop rebuilds on major locomotive subassemblies. It organizes overhaul requirements into small, independent modules performed during routine maintenance. Executed on a unit-exchange basis, it minimizes unscheduled maintenance downtime. Alstom's fragmented overhaul program at Alliance has been applied to EMD SD70MACs, with favorable results.

Copyright Simmons-Boardman Publishing Corporation Oct 2005

Source: Railway Age

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