INTRO: A London Underground project team examined ways of improving rail lubrication on the Circle Line. Metronet Rail has adopted a focused approach as part of its preventative maintenance regime, delivering a major improvement in rail replacement rates
ATTHE BEGINNING of May, work began on a major programme to relay the track on the southern section of London Underground’s Circle Line, which is also used by east-west District Line services. Weekend closures are due to continue at regular intervals for the rest of this year and into 2005 as London Underground and its infrastructure contractors get to grips with a backlog of deferred maintenance.
According to LU’s Service Director for the Sub-Surface Lines, Howard Collins, the programme has been planned to minimise disruption. ’These track works are absolutely essential, and when completed should help us provide a more reliable service on the District and Circle lines’.
Forming a 21 km loop with 27 stations around central London, the Circle Line includes some of the oldest, most intensively-used and sharply-curved sections of the London Underground network. As well as its own services making the complete circuit, it is used on the south and west sides by the District Line. On the the north side the tracks are shared by Hammersmith & City Line services between Whitechapel and Hammersmith and by Metropolitan services to and from the outer suburbs. Three different types of trainset currently operate over the Circle Line.
Because of the complex structure of the 19th century Sub-Surface Lines network, with many flat junctions, delays caused by infrastructure failures can easily ripple out across the network beyond the central area. This is recognised by the contractual regime adopted for LU’s Public-Private Partnership (RG 6.02 p319).
Under the PPP, Metronet Rail has been responsible since April 2003 for the maintenance and upgrade of infrastructure and rolling stock assets on the Sub-Surface Lines as well as four deep tube lines: Central, Victoria, Bakerloo and Waterloo & City.
One of the factors influencing rail life on the Circle Line has been lubrication on the curves. In December 2000 LU established a rail lubrication team, led by Project Manager Arun Bhalla who is now at Metronet. Work began with a survey of curves on the Circle Line. Locations experiencing high levels of friction between wheel and rail were selected for monitoring over an 18-month period, typically where the curve radius is less than 200m. The position of existing trackside lubricators, and the pattern of grease dispensed to the rail, was verified using train-mounted video cameras.
’Wheel and rail are one system’, says Bhalla. Thus Peter Gale of Ealing Common depot on the District Line joined the project team to provide a rolling stock perspective. Inspection of wheels during tyre-turning at the depot provided useful information such as cases where grease was being rubbed off by check rails.
Improvements undertaken as part of the programme included the installation of new lubricators and upgrading around 80% of existing units on the Circle Line, according to Track Section Manager Julian Urry. The total number of lubricators has increased by 20% over the last 31/2 years; there are now 62 lubricators on the inner (anti-clockwise) track and 68 on the outer.
Taking care not to apply grease to the rail top, the output of existing units was increased, initially every four weeks. Adjustments are now undertaken every six weeks. Other changes included ensuring that the temporary lubrication of new rail was put in place as soon as needed, as well as a ’very active’ programme of hand lubrication. During the programme six new types of hand-held grease applicator were tested, with final approval now awaited for the chosen model.
Maintaining lubricators and applying grease by hand is ’a very filthy job’, says Urry. ’Credit must go to the lubricating gangs’, stresses Bhalla; ’their involvement in the Circle Line has been crucial.’ Increasing the amount of lubrication also meant carrying more heavy drums of grease to the worksite and undertaking more ballast cleaning.
Bhalla singles out Track Section Manager Martin Norton for particular praise. He now heads a single 14-strong lubrication gang covering the Circle Line as well as the District, Hammersmith & City and Metropolitan Line as far as Finchley Road. Before, this work was divided between a north and a south team. Track maintenance staff are now provided with lubrication maps, as well as pocket-sized ’ready-reckoners’ setting out the temporary speed restriction to be applied on sections of new rail to minimise friction.
Within six months of the programme starting, ’you could see there was an improvement’, says Bhalla. Based on rail profile measurements taken during every four-week period, an interim report noted a ’general improvement’ in friction levels within six months, with a reduction of 22% at the gauge corner on both rails of both Circle Line tracks.
Longer-term, improved lubrication has had a dramatic impact on rail replacement rates. On the northern section of the Circle Line, including the Hammersmith & City and the Metropolitan as far as Finchley Road, a total of 906 rails (measured as 18·3m sections) were replaced in the 12 months to March 31 2002. This fell to 332 in 2002-03, and had reached 325 in the 2003-04 financial year. Using the same type of rail in the same location, Urry notes that rail life has typically been extended from three to 20 years in some areas and from 18 months to seven years on the tightest curves.
As well as a positive knock-on effect on switch and crossing life, reducing rail renewal rates has freed resources for deployment in other areas. High levels of friction were also behind the phenomenon of ’snowing’ on the District Line out to Ealing, with fine snowflake-like material produced by wear at the gauge corner tending to appear at six-monthly intervals. Now, ’we don’t get snowing’, says Urry, ’we don’t get delays due to that’. Friction between wheel and rail still requires careful monitoring, but Bhalla and his team are confident that they have made a breakthrough on the Circle Line.
CAPTION: ABOVE: Track relaying on the Circle Line during a weekend blockade at the beginning of June
RIGHT:Work in progress at the key District Line interchange at Hammersmith
CAPTION: Fig 1. Running average of side wear and side cut rates on curves for the whole of London Underground’s Circle Line as at January 2004, showing the improvements in rail life resulting from the lubrication programme
CAPTION: ABOVE RIGHT: Fig 2. Side wear rates on the Outer Road of the Circle Line by location in the direction of travel
RIGHT: Fig 3. Side wear rates on the Inner Road show that wear rates peak in other locations because of differences in both the alignment and condition of track
CAPTION: BELOW LEFT: Rail wear measurement on the Circle Line makes use of Miniprof supplied by Greenwood Engineering of Denmark
BELOW: As well as installing two new types of lubricator, exisisting lubricators have been upgraded