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Midland Main Line Insulator Replacement

Bedford to St Pancras

Working in a three hour white period each weekend, VolkerRail eliminated a large risk to the Midland Mainline by replacing 1,406 middle insulators at 703 structures, which were prone to failure causing seven incidents, including two major dewirements.

VolkerRail challenged Network Rail’s initial tender specification of 18 months with a detailed programme to deliver the project in 12 months. Through advanced planning, immaculate time management and two way communication the project was completed seven months ahead of completion date with zero accidents.

The existing insulators along the Midland Mainline, required replacing. This was due to a structural failure phenomenon known as ‘cement growth’ which causes cracking of the insulator discs leading to a breakdown of the insulation and subsequent failures, which resulted in several incidents.

To remove the risk 1,406 middle insulators at 703 structures need to be replaced. Initial thoughts by Network Rail was that it would take ten Christmas blockades to complete however due to design configuration within the four track area and site access restrictions Network Rail required a different solution.

VolkerRail's plan was to work within the three hour white period available each weekend, utlising advance planning and all available time prior to and after the white period. With only one white period a week to complete the work, the team had to ensure each shift was planned correctly. 

All man power and road rail vehicles (RRV) were booked a year in advance, allowing the work to be delivered by the same team and all engineering acceptance certificates obtained. VolkerRail took the initial isolation and possession as well as ‘on tracking’ and manoeuvring the RRV’s into position prior to the white period. After each white period the RRV’s then went back into gauge and travelled back to the access point.

Not once throughout the entire project were the team behind on schedule. On average 23 insulators were replaced each weekend, with replacements taking less than 20 minutes per insulator by the end of the project. This included testing, commissioning and approval to bring the equipment into operation.

Throughout this project the highest standards of management, delivery, quality, safety, engineering, and reporting were maintained by VolkerRail enabling this project to receive the maximum PRISM score of five out of five on each of its six inspections.

Facts and figures

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