Thameslink – the final countdown

With just a few months to go, including two major commissionings, the rebuilt, remodelled and resignalled London Bridge becomes fully operational on 2 January 2018. The Thameslink service resumes through the high level station via the new segregated alignment between Blackfriars and Bricklayers Arms Junction, engineered into the remodelled layout as a key objective of the project together with the introduction of Automatic Train Operation (ATO) overlay to ETCS.

This highly complex and challenging capacity-improvement project, conceived by British Rail’s Network South East back in 1990 when passenger numbers were rapidly outstripping the capacity of Thameslink’s inaugural service of six trains per hour, is nearing completion on time and budget.

Network Rail recently invited Rail Engineer along to hear project director Mark Somers describe the plans for the final two big blockades taking place this year, and to meet the team fitting out the track, signalling and electrification at the south-eastern approach to the station.

Already complete

To date, all six terminal platforms at the low level are open and through-Platforms 7, 8 and 9 are currently in service for Charing Cross trains. Whilst Costain, the contractor rebuilding the station, continues to work on preparing Platforms 1 to 6, and the remaining one third of the street level concourse below is off limits to the public, Cannon Street services are passing non-stop through Platforms 1 and 2.

Essentially, all major demolition and construction works are complete at the high level with all the new bridge decks in position. Behind the hoardings, escalators and lifts are being installed in readiness for the complete concourse opening in January 2018, with retail unit fit-out and other concourse and passageway works continuing through to May 2018.

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August blockade

On Saturday and Sunday 26/27 August, the Cannon Street and Charing Cross lines close, as do low-level Platforms 10 to 13, to facilitate a major signalling data changeover and commencement of the track remodelling described below. Low-level services will use Platforms 14, 15 and line 11 only, as lines 9 and 10 are shut to provide protection for the adjacent track slew works.

For a week from Bank Holiday Monday 28 August, the Charing Cross lines remain shut but services are restored to Cannon Street (trains again running non-stop as the concourse below isn’t ready) and all the low-level platforms. During the period that Charing Cross is closed, Southeastern trains will run from Lewisham to either Blackfriars, Victoria or, via Linford Street Jn and the curve formerly used by Eurostar, into the Waterloo International platforms that will be temporarily reopened for the duration. By Saturday 2 September, all track, signalling, and traction feeder section testing will be complete, allowing test trains to run during this day, with any snagging attended to overnight once the possession has been re-taken. All lines are to open on Sunday 3 September.

Charing Cross services are currently using lines 3 and 4, facilitated by temporary slews near London Bridge and at New Cross respectively. These slews will be removed during the blockade, and Platform 6 brought into service.

At the country end of the station, new switches and crossings (S&C) will be installed in order to connect Up lines 6, 7, and 8 to Platforms 6 and 7 (Down), and 8 and 9 (Up), thereby providing full flexibility in the final configuration of two platforms for Charing Cross trains. Previously, at the London end of the station, with Platform 6 unavailable, a temporary crossover was provided to allow Platform 8 to be used in either direction to suit the tidal flow (typically Up in the morning peak and Down during the evening). This crossover is being removed.

At the New Cross end, no new S&C is needed where the Kent Fast lines will be re-aligned to pass through the new Bermondsey Dive-Under (built by Skanska), meshing into lines 6 (Down Charing Cross), line 7 (Charing Cross Reversible) and line 8 (Up Charing Cross).

Lines 3 and 4 will then be taken out of use and resignalled in the original direction with line 3 reverting to its original purpose of Up Canon Street, and line 4 becoming the new Down Thameslink. A new signal gantry is to be craned in during this phase of the work.

Assets commissioned/decommissioned during this period include:

• S&C point ends: 19 new, 2 removed, 20 clipped and padlocked;
• Plain line: 9.7km installed (lines 6, 7, 8), 8km removed (lines 3,4);
• Signals: 37 new, 23 recovered;
• Track circuits: 65 new, 36 recovered;
• AWS: 36 new, 18 recovered;
• TPWS TSS/OSS loops: 45 new, 25 recovered;
• Location cases: 24 new;
• Disconnection boxes: 63 new;
• REBs: 13 new.

Christmas 2017

From Saturday 23 December 2017 through to the morning of Tuesday 2 January 2018, all the Cannon Street, Charing Cross, Thameslink core, and high-level platforms lines will be closed. The low-level remains open except on Christmas Day and Boxing Day.

Line 3 reverts to its original purpose of Up Cannon Street whilst lines 4 and 5 become the Down and Up Thameslink respectively.

The new Down and Up Thameslink lines will mesh into the platforms 3, 4, 5 and 6 at London Bridge and utilise Platforms 4 and 5 for Thameslink services. These lines run atop the Bermondsey viaduct and on to New Cross Gate via Bricklayers Arms Junction.

The final line through the Bermondsey Dive-Under, called the Southwark reversible, also comes into service, and remodelling, resignalling/re-control will take place at Blackfriars. Extensive data changes are necessary overall to update the interlockings, GSM-R, workstations and to fully enable ETCS/ATO.

The Thameslink core stations will be fitted out with platform ramps to allow for level access onto the carriages of the Class 700 trains. Waterloo International will open again temporarily for the diversion of Southeastern trains.

On 2 January, all lines will be available for the full service.

Installing S&C

Balfour Beatty is the principal contractor undertaking the track and civil engineering work. From London Bridge to Bricklayers Arms, the railway is elevated on masonry arches interspersed with metallic and brick arch road bridge structures, so, in order to keep loadings within acceptable limits, it has been necessary to utilise the much lighter Kirow 250 cranes in tandem lift mode. Tandem lifting with the smaller cranes required the development of a new Lightweight Lifting Beam, saving weight as opposed to the standard Modular Self Levelling Beam and meaning that tandem Kirow 250 cranes can lift a concrete bearer FVS switch panel without using props, which speeds up installation.

Design philosophy that all S&C will be located on straight alignments has substantially been achieved and most S&C is of ‘modular’ design and delivered using the Kirow Tilting Wagon System. This modular S&C is being procured, via the Network Rail Route Services organisation, from manufacturers Vossloh Cogifer UK and Progress Rail.

All engineering trains, provided under Route Services haulage contracts, generally operate out of Hoo Junction Yard and, occasionally, Eastleigh. Network Rail Infrastructure Projects ensures that these critical logistics resources for plain line and S&C renewals are carefully managed and de-conflicted across the country around major bank holiday weekends.

Electrification

Life-expired 100/106lb conductor rail has been replaced with new 150lb/yard rail. New Controlled Track Switches (CTS) have been installed at key locations to enable isolations to be effected remotely without staff needing to operate hook switches and, where appropriate, some hook switches have been replaced by track isolating switches which are operable from the line-side rather than on track.

A new DC traction substation has been built within the arches at London Bridge to replace the existing Track Paralleling Hut (TP Hut). Impedance bonds are Bombardier B3 3000 Impedance Bonds to Spec BR 863 Type 3.

S&T systems

Modifications and extensions to the Cannon Street, Charing Cross and London Bridge central workstations, involving extensive data changes, will be undertaken during the blockades. The workstations are of the Siemens Controlguide Westcad PC-based control and display system.

Provided by Network Rail Telecommunications (NRT), fibre optic data communications networks utilise the Fixed Telecoms Network (FTNx) and, using Cadlock protocol and Cisco routers, link the Westcad at Three Bridges Rail Operating Centre (TBROC) with the Westlock interlockings located at the London Bridge equipment room.

To ensure resilience, a virtual private network has been created, known as Thameslink Signalling Private Network (TSPN), which provides for alternative paths between the ROC and London Bridge equipment room. Fibre-optic cables link the Westlock interlockings with the new Westlock trackside systems zone controllers located within the REBs. These are connected by conventional hard-wired cables to signals, points, AWS, TPWS and other equipment.

Bombardier EBI Track 400 track circuits are used for train detection with Cembre rail terminations. Unipart Dorman integrated lightweight signals (iLS) are used as these have a narrow three-degree beam, well suited to the multiple parallel tracks on the approaches to London Bridge where SPADs have occurred in the past through misreading or reading-through.

Vortok Modular AWS inductors are provided. The lid of the electromagnet is white instead of the usual dark green, to reduce solar gain as protection for the ECU that is provided to maintain the maximum current draw to 1.6 amps, balancing current draw against temperature to maintain flux density. This is to protect the Westlock trackside system which directly drives the AWSs.

In-bearer Rail Point Clamp Locks are used with the hydraulic actuation systems provided by SPX Rail Systems. Signalling power supplies are 650V DC dual end-fed with auto reconfiguration, Class II.

Relocatable Equipment Buildings (REB) house much of the lineside equipment. Some existing signal gantries have been re-used, with strengthened foundations and tie rods, giving improved access for staff including the bolt-on galleries for new signal heads, manufactured by Lundy and installed by Balfour Beatty.

Innovative CEMEX EG53 and GV54 cable management sleepers enable DC traction and signalling cables to cross the track without cluttering up the ballast cribs and removing the risk of tampers damaging cables.

Stretcher bars

In the aftermath of the serious derailments at Potters Bar (2002) and Grayrigg (2007), Network Rail embarked upon a national roll-out of an innovative new design of tubular point stretcher bar (TSB) that has been designed to manage the forces that can be applied to a switch layout by the passage of a train or by the operation of the point operating equipment. The tube is designed to allow the length to be adjusted, and the stretcher bar fitted in the first position also features kicking straps that limit the amount the switch rail can rise.

At the end of each bar, the motion units are articulated to allow the stretcher bar to deal with switch creep and twisting when switches are thrown. If flange back contact occurs, the orange polymers within the motion unit absorb the forces without causing damage to the rest of the system. The retaining plate applies a compressive pre-load onto the polymers.

If the points have been run through, the retaining plate in the motion unit will bow towards the four-foot and the tube will bend upwards slightly.

There are five different types of tube, and four different types of motion units to suit the type of rail section used and the point operating equipment it is being fitted to. TSBs have been fitted throughout the project and are supplied by Howells Railway Products, Progress Rail Services UK and Tinsley Bridge Rail. A kit of specific tools is provided by Lawton Tools Rail Products and is used in conjunction with existing torque wrenches.

Enhancing reliability

A fault in the signalling system at London Bridge may quickly lead to a long queue of trains with thousands of passengers delayed, not to mention Network Rail incurring substantial Schedule 8 penalty payments. Whilst the new TBROC workstation controlled signalling today has much the same ‘entrance/exit’ (NX) route setting functionality as the 1975-vintage NX panel, technological improvements provide for a more reliable railway by means of the duplication of digital systems, and provision of remote condition monitoring (RCM) to pre-empt potential failures that may stop trains.

Setting routes in the large old relay interlockings involved electrical circuit paths spanning many relay contacts. Any single high-resistance relay contact could stop the job. However, there are three individual processing lanes within a Westlock Central Interlocking Processor (CIP), providing triple modular redundancy. This means that, should one processing lane fail, the control function can continue to operate as normal with no interruption to the train service, safety being maintained by mutual agreement of the two ‘good’ processing paths.

For external equipment such as points and track circuits, RCM monitors pump pressures of Clamp Lock points and certain electrical parameters of EBI track circuits. The results are reported to the maintenance unit’s back office, where a data analyst (known as a flight engineer) can initiate a fault log in the event of deviation from normal values.

Nevertheless, the harsh unremitting environment of the railway is such that point and track circuit failures do occur from time to time. Installed on the Thameslink line of route, and all controlled signals in the resignalled area, is the innovative ‘Proceed on Sight’ aspect known as the POSA signal. In the event of a track circuit failure, the signaller may over-ride this by selecting a POSA route, which displays two flashing white lights at 45º to the driver who may proceed cautiously, thereby obviating the delay incurred in stopping at a red signal and contacting the box for permission to proceed.

A track circuit failure may also prevent route locking from releasing behind a train, thereby holding points in the wrong position for other trains. A special Electronic Point Route Locking Release permits the signaller to free and move points in such circumstances. Alas, there is no quick fix for lost detection on points, which will require rectification before any signal reading over the points can be cleared.

Improving access

A visit to the lineside reveals a lack of the usual S&T equipment location cases and REBs. With eleven intensively used parallel tracks on the approaches to London Bridge, access for faulting and maintenance is challenging. Thus, the equipment is concentrated into a series of REBs which are located within the arches of the viaducts beneath the tracks (with the exception of one REB which is at track level at the site of the long-closed Spa Road station) and provide technicians with a weatherproof environment away from the live railway.

EBI track circuit transmitter and receiver units are mounted with protective covers in the four-foot. Signalling Lock-out Devices (SLODS) are provided throughout the London Bridge area to enable access to track-mounted equipment by blocking one line without the need to set up complex protection for crossing and re-crossing multiple tracks.

ATO goes live

With the infrastructure ATO equipment and ETCS level 2 data incorporated into the new interlockings going live in January 2018, the capacity improvements are complete to meet the 20tph (trains per hour) milestone in May aligned with the timetable change, with traffic management deployed later in the year and a period of introduction running prior to realisation of the full 24tph service.

During May 2018, the Lewisham area, along with the Hayes line, is scheduled to be re-controlled to a new workstation at TBROC. In Easter 2019, the Angerstein area, including lines from Charlton and Woolwich to London Bridge via Greenwich and North Kent East Junction, will be resignalled and re-controlled. Finally, in 2020, the remaining Hither Green area controlled by the London Bridge Area Signalling Centre will be re-controlled to a further new workstation, allowing the box to be closed after over forty years in service signalling trains in this highly complex area.

Thanks to Mark Somers, project director; Simon Pears, project engineer; and Alexandra Swann, communications manager for Thameslink, for their help in the preparation of this article.

This article was written by David Bickell.

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