A 16-month programme of works was completed at 04:40 on 29th November when Invensys Rail successfully commissioned the Oxley resignalling project on behalf of Network Rail, culminating in a nine-day blockade. This saw the decommissioning of Oxley signal box with control of the Shrewsbury line’s Wolverhampton-Madeley section transferred to a WESTCAD workstation at the West Midlands Signalling Control Centre (WMSC). In total, 12 miles of main line plus loops were resignalled as well as a 25-siding depot which stables part of Virgin’s West Coast Main Line Pendolino fleet.
The Oxley area had been controlled by a conventional signal box which was built in the mid-1960s and featured a 60-lever frame, together with a mixture of mechanical and electric controls. This renewal programme was undertaken to eliminate existing life-expired equipment, renewing the signalling and interlocking for the section between Wolverhampton North Junction and Bilbrook Station, including the branch from Stafford Road Junction. Oxley box was demolished two weeks after the commissioning on 11th December and its lever frame disposed of, but by then Network Rail’s maintainer had already removed all valuable assets from it for strategic spares.
Signalling inventory
Invensys Rail’s multi-disciplinary Type B project covered 81 Signal Equivalent Units (SEUs). WESTLOCK, the company’s powerful computer-based interlocking, has been successfully installed in a range of projects across the UK including Glasgow Central, Reading and the Durham Coast line. However this scheme saw the system installed for the first time with two trackside interfaces at the WMSC, controlled over the Fibre Transmission Network. Invensys was responsible for all civils work, using the company’s own installation team, as well as managing the telecoms and E&P subcontractors.
In addition to the commissioning of WESTLOCK and WESTCAD, the scope of the signalling works at the control centre also covered the provision of emergency alarms and a WESTRONIC 1024 alarm management system. Trackside work included the installation of Dorman LED signals and route indicators, mounted both on new posts and existing structures. Modifications were also made to the existing train describer and emergency alarm systems at Madeley Junction and Wolverhampton, allowing control to be taken by the WMSC. And AWS equipment was installed within the recontrolled area.
“The complex nature and limited availability of land, specifically at the south end of the depot, caused major issues for signal siting” comments Invensys Rail’s Senior Project Manager Matthew Kent, “and was a huge risk to our delivery programme. Because of this, the signal siting forms were constantly evolving – even up until the commissioning morning – and it’s a credit to the Network Rail project delivery team and Invensys Rail’s construction team who worked through all the reiterations to deliver a successful scheme.”
Making the point
Within the programme of work, Invensys also managed the set-up of new HW-type point machines fitted with plug couplers together with the provision of new trackside equipment within the recontrolled area. These included data links, track circuits and axle counters, as well as REBs and high security location case suites.
The programme called for the complete remodelling of the depot’s south end. New point machines were fitted to the layout, tested and commissioned. However, existing p-way was reused at the north end such that the HW point machines were added to the existing switches and crossings. Although the poor state of the existing infrastructure made this both a complex and time consuming exercise during the commissioning blockade, the equipment was all made good and signed into use.
Signal support
Of the 81 SEUs, Invensys supplied 25 main signal heads, 14 subsidiaries, nine ground position light signals, two ‘limit of shunt’ signals, 30 remotely worked point ends and one machine on a double slip arrangement.
The new signals were accommodated on a combination of concrete precast bases, on-site poured bases and piles. On the periphery of the project, screw piles were deployed due to the tight possession constraints whereas precast bases were used inside the depot areas and the through lines where they could more easily be produced and then dropped into pre-dug pits during the blockade. The construction team developed an innovative approach for this using an A-frame supporting an RSJ, enabling the base to be trolleyed along an adjacent line, winched across and then down to its designated position ready to be dressed with the signal structure and head.
The one exception was the two-track bespoke cantilever unit which was sited in a position where 600mm below ground level was bedrock. Eight steel rock anchors were drilled using specialist piling equipment, followed by pouring of the concrete base. This was in a very tight location between two converging lines, meaning that the structure had to be thinner than usual due to clearance constraints. Rock was discovered in the path of the under-track crossing which had to be removed over eight separate weekends with machines peckers and Kango hammers.
Limited reach
The overall programme was complicated by two other factors – firstly, the limited number of possessions available as Virgin Trains used the depot 24 hours a day, seven days a week. Careful planning of all the works and the use of T4 possessions were needed to overcome this. Secondly, isolations of overhead line equipment were also restricted as power outages in the depot area were limited. The project team adapted to this by not using any possession but instead planning all works and operations using RRV equipment with electronically and mechanically restricted booms, so as not to encroach within the OLE envelope.
It’s worthwhile noting that the Oxley project has an excellent safety record. Despite many of Invensys Rail’s main activities being carried out on site – lifting, excavations, on/off tracking and complex movements – the only injury sustained throughout the whole 18-month programme was a minor cut to which a plaster was applied and the individual immediately returned to work. Much effort went into achieving this including weekly safety reviews and monthly stand-down days.
“This was a technically challenging project which contained some complex midweek temporary block working” continues Matthew. “It was also complicated by the fact that an unusually high level of works had to be undertaken during the blockade period – 12 signals were installed over that time, of which we were only able to pre-install five bases. In addition we had to lay 14 ends to points, convert ten and recable six others. Great credit goes to the entire project team who delivered the programme on time, despite some particularly arduous conditions which saw temperatures drop to -12C during the commissioning.”
