Improving the reliability and availability of railway track switching by analysing historical failure data and introducing functionally redundant subsystems

Samuel D. Bemment, Roger M. Goodall, Roger Dixon, Christopher P. Ward

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Track switches are safety critical assets that not only provide flexibility to rail networks but also present single points of failure. Switch failures within dense-traffic passenger rail systems cause a disproportionate level of delay. Subsystem redundancy is one of a number of approaches, which can be used to ensure an appropriate safety integrity and/or operational reliability level, successfully adopted by, for example, the aeronautical and nuclear industries. This paper models the adoption of a functional redundancy approach to the functional subsystems of traditional railway track switching arrangements in order to evaluate the potential increase in the reliability and availability of switches. The paper makes three main contributions. First, 2P-Weibull failure distributions for each functional subsystem of each common category of points operating equipment are established using a timeline and iterative maximum likelihood estimation approach, based on almost 40,000 sampled failure events over 74,800 years of continuous operation. Second, these results are used as baselines in a reliability block diagram approach to model engineering fault tolerance, through subsystem redundancy, into existing switching systems. Third, the reliability block diagrams are used with a Monte-Carlo simulation approach in order to model the availability of redundantly engineered track switches over expected asset lifetimes. Results show a significant improvement in the reliability and availability of switches; unscheduled downtime reduces by an order of magnitude across all powered switch types, whilst significant increases in the whole-system reliability are demonstrated. Hence, switch designs utilising a functional redundancy approach are well worth further investigation. However, it is also established that as equipment failures are engineered out, switch reliability/availability can be seen to plateau as the dominant contributor to unreliability becomes human error.

LanguageEnglish
Pages1407-1424
Number of pages18
JournalProceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit
Volume232
Issue number5
Early online date13 Sep 2017
DOIs
Publication statusPublished - 1 May 2018
Externally publishedYes

Fingerprint

Availability
Switches
Redundancy
Rails
Nuclear industry
Switching systems
Maximum likelihood estimation
Fault tolerance

Cite this

@article{56656a5e36b442cf935b8d9187cd8f7c,
title = "Improving the reliability and availability of railway track switching by analysing historical failure data and introducing functionally redundant subsystems",
abstract = "Track switches are safety critical assets that not only provide flexibility to rail networks but also present single points of failure. Switch failures within dense-traffic passenger rail systems cause a disproportionate level of delay. Subsystem redundancy is one of a number of approaches, which can be used to ensure an appropriate safety integrity and/or operational reliability level, successfully adopted by, for example, the aeronautical and nuclear industries. This paper models the adoption of a functional redundancy approach to the functional subsystems of traditional railway track switching arrangements in order to evaluate the potential increase in the reliability and availability of switches. The paper makes three main contributions. First, 2P-Weibull failure distributions for each functional subsystem of each common category of points operating equipment are established using a timeline and iterative maximum likelihood estimation approach, based on almost 40,000 sampled failure events over 74,800 years of continuous operation. Second, these results are used as baselines in a reliability block diagram approach to model engineering fault tolerance, through subsystem redundancy, into existing switching systems. Third, the reliability block diagrams are used with a Monte-Carlo simulation approach in order to model the availability of redundantly engineered track switches over expected asset lifetimes. Results show a significant improvement in the reliability and availability of switches; unscheduled downtime reduces by an order of magnitude across all powered switch types, whilst significant increases in the whole-system reliability are demonstrated. Hence, switch designs utilising a functional redundancy approach are well worth further investigation. However, it is also established that as equipment failures are engineered out, switch reliability/availability can be seen to plateau as the dominant contributor to unreliability becomes human error.",
keywords = "Asset management, Availability, Points, Railways, Reliability, System failure, Track switch",
author = "Bemment, {Samuel D.} and Goodall, {Roger M.} and Roger Dixon and Ward, {Christopher P.}",
year = "2018",
month = "5",
day = "1",
doi = "10.1177/0954409717727879",
language = "English",
volume = "232",
pages = "1407--1424",
journal = "Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit",
issn = "0954-4097",
publisher = "SAGE Publications Ltd",
number = "5",

}

TY - JOUR

T1 - Improving the reliability and availability of railway track switching by analysing historical failure data and introducing functionally redundant subsystems

AU - Bemment, Samuel D.

AU - Goodall, Roger M.

AU - Dixon, Roger

AU - Ward, Christopher P.

PY - 2018/5/1

Y1 - 2018/5/1

N2 - Track switches are safety critical assets that not only provide flexibility to rail networks but also present single points of failure. Switch failures within dense-traffic passenger rail systems cause a disproportionate level of delay. Subsystem redundancy is one of a number of approaches, which can be used to ensure an appropriate safety integrity and/or operational reliability level, successfully adopted by, for example, the aeronautical and nuclear industries. This paper models the adoption of a functional redundancy approach to the functional subsystems of traditional railway track switching arrangements in order to evaluate the potential increase in the reliability and availability of switches. The paper makes three main contributions. First, 2P-Weibull failure distributions for each functional subsystem of each common category of points operating equipment are established using a timeline and iterative maximum likelihood estimation approach, based on almost 40,000 sampled failure events over 74,800 years of continuous operation. Second, these results are used as baselines in a reliability block diagram approach to model engineering fault tolerance, through subsystem redundancy, into existing switching systems. Third, the reliability block diagrams are used with a Monte-Carlo simulation approach in order to model the availability of redundantly engineered track switches over expected asset lifetimes. Results show a significant improvement in the reliability and availability of switches; unscheduled downtime reduces by an order of magnitude across all powered switch types, whilst significant increases in the whole-system reliability are demonstrated. Hence, switch designs utilising a functional redundancy approach are well worth further investigation. However, it is also established that as equipment failures are engineered out, switch reliability/availability can be seen to plateau as the dominant contributor to unreliability becomes human error.

AB - Track switches are safety critical assets that not only provide flexibility to rail networks but also present single points of failure. Switch failures within dense-traffic passenger rail systems cause a disproportionate level of delay. Subsystem redundancy is one of a number of approaches, which can be used to ensure an appropriate safety integrity and/or operational reliability level, successfully adopted by, for example, the aeronautical and nuclear industries. This paper models the adoption of a functional redundancy approach to the functional subsystems of traditional railway track switching arrangements in order to evaluate the potential increase in the reliability and availability of switches. The paper makes three main contributions. First, 2P-Weibull failure distributions for each functional subsystem of each common category of points operating equipment are established using a timeline and iterative maximum likelihood estimation approach, based on almost 40,000 sampled failure events over 74,800 years of continuous operation. Second, these results are used as baselines in a reliability block diagram approach to model engineering fault tolerance, through subsystem redundancy, into existing switching systems. Third, the reliability block diagrams are used with a Monte-Carlo simulation approach in order to model the availability of redundantly engineered track switches over expected asset lifetimes. Results show a significant improvement in the reliability and availability of switches; unscheduled downtime reduces by an order of magnitude across all powered switch types, whilst significant increases in the whole-system reliability are demonstrated. Hence, switch designs utilising a functional redundancy approach are well worth further investigation. However, it is also established that as equipment failures are engineered out, switch reliability/availability can be seen to plateau as the dominant contributor to unreliability becomes human error.

KW - Asset management

KW - Availability

KW - Points

KW - Railways

KW - Reliability

KW - System failure

KW - Track switch

UR - http://www.scopus.com/inward/record.url?scp=85043317303&partnerID=8YFLogxK

U2 - 10.1177/0954409717727879

DO - 10.1177/0954409717727879

M3 - Article

VL - 232

SP - 1407

EP - 1424

JO - Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit

T2 - Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit

JF - Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit

SN - 0954-4097

IS - 5

ER -