Opened in 1863, London Underground (LU) is the oldest metro system in the world. Alongside Beijing and Shanghai, it is also one of the largest networks with 11 lines covering 402km. And alongside Paris and Moscow, it is also notable for being one of the busiest networks, getting around five million passengers from A to B every day. With its station platforms sometimes located more than 50m below street level, maintaining and upgrading the escalators and lifts is crucial for keeping people safe and on the move.
The figures speak for themselves: today, the London Underground has a total of 217 lifts (compared to 167 in 2017) for its 270 stations, 144 of which are now operational 24 hours a day on Fridays and Saturdays as part of Night Tube. As for escalators, 448 are in use up to 20 hours a day, seven days a week, 364 days a year. Together, they support the movement of 1.3 billion people per year!
Yet with only three escalators in some stations, having just one out of action can disrupt passenger flow and create bottlenecks. In order to mitigate the risks, Transport for London (TfL) has a continual programme of maintenance and renewal in place for its lifts and escalators.
Escalators are re- furbished every 20 years and replaced every 40 years to meet high performance levels. By way of comparison, lifts are replaced every 20 to 30 years depending on the model; they receive a routine maintenance check every two weeks, full safety and operational testing every six months, and a partial refurbishment every ten or fifteen years.
OPEN THINKING, CONFINED SPACE
Given the sheer depth of many stations, the works are often carried out in a challenging physical environment. “We’re working within concrete or steel cast tunnel rings that we can’t move,” Dan Marsh, senior project manager at TfL, told Pulse. “It’s not like building an extension on your house; you are physically constrained. You can’t get more space. This puts a lot more emphasis on the planning side of the sequence of activities.”
Furthermore, each station has its own unique characteristics when it comes to layout and access routes. This means that TfL has to dismantle the escalators into smaller, modular sections in order to transfer them through the station to the work site.
The maintenance teams may have to work within a tight box but they have to think outside it, too. Access is complicated not only by the limited space available in the narrow 19th-century shafts but also by the drainage, electricity and fire sprinkler networks which crosscut the escalator and lifts shafts.
Beyond access issues, the considerable size and weight of the escalators and lifts can present challenges, too. By way of example, a typical heavy-duty escalator weighs 40 tonnes and a heavy-duty lift 5 tonnes. The deepest lift haft — 58m — is at Hampstead, while the longest escalator at 60m, with a vertical rise of 27.5m, is housed within Angel station.
TO OPEN OR CLOSE: THAT IS THE QUESTION
As far as possible, during renovation and upgrading operations, station closures are avoided, and work goes on out of public sight behind hoardings, day and night. “Because we work behind hoardings, we’re not really constrained by working access,” says Dan Marsh. However, for passenger safety reasons, activities like cutting and welding, and larger equipment deliveries can only go on when the station is closed to minimise risks to the public.
Traditionally, when escalators are completely removed, the station in question would normally close, or service to a particular line would shut. However, this was not an option for the replacement of the three escalators at Wood Green station, on the Piccadilly line, as TfL looked to change its delivery model to improve passenger access. Instead, TfL broke with tradition and decided to keep the existing equipment running while installing the new machines one by one, and retaining the existing escalator frame — or truss as they are known.
This task involves a team of five skilled escalator installers to deliver the main works assisted by a support team of ten designers and construction supervisors. Interface contractors such as tilers, painters and builders are deployed during the day, whilst others — such as electricians, fire detection and suppression technicians and mechanical vent experts — work the night shift.
Work at Wood Green began in October 2017 with a 12-month design and manufacture period. Installation of the first new escalator began in November 2018; the third and final escalator will be in place by March 2020.
Keeping the station up and running during a replacement project means the works can take longer, sometimes running from months into periods of over a year depending on the number of assets. Yet crucially these projects allow TfL to avoid interrupting services. There are other benefits too, including requiring significantly less works and lower overall costs. Looking to the future, the newly installed escalators are modular and no longer bespoke, making them much easier to refurbish and replace deep underground in tight and difficult-to-access spaces.
RESOURCES AND PLANNING — INSIDE AND OUT
To maintain and modernize the lifts and escalators TfL uses in-house maintenance and project staff as well as external con- tractors. “If external staff underperform or if their company goes bust, we will always have in-house staff in case of a Doomsday scenario,” explains Marsh.
“The mix of internal and external delivery allows for retention of specialist knowledge, development and utilisation of global best practices and the flexibility to change delivery to better meet business and customer needs. It also allows for good value and performance benchmarking to inform business strategy,” Marsh adds.
On a typical project, up to seven people usually work on the installation per shift, with two shifts a day overall, five or six days a week. “Planning of the works mean that we only do what is required, when it is required,” says Marsh. “Coordination with the broader access and planning teams enable us to have visibility of other LU project works, closures or access opportunities.”
He adds: “Working weekends and extended shifts as well as smart shift patterns with good coordination of contractors’ access are also essential for smooth project management.”
The escalators and lifts on the Tube are in increasing demand. TfL is continuing to modernise the Underground to provide faster and more reliable journeys. For example, state-of-the-art signaling on the Circle, District, Hammersmith & City and Metropolitan lines will significantly increase capacity at peak times, and new trains will serve the Piccadilly line from 2024 as part of the Deep Tube Upgrade Programme. In addition, TfL is continuing to invest in improvements to make the Tube more accessible for Londoners and visitors to the city. There are currently 78 step-free Tube stations on the network and, as part of record investment, 34 per cent of Underground stations will become step-free by 2020.