Murphy innovates with mobile tower system

UK engineering company J. Murphy & Sons (Murphy) put its innovation skills into practice by creating a mobile scaffold system to provide faster access to a railway tunnel as part of a challenging reinforcing project.

Farnworth tunnel is a twin Victorian brick tunnel near the town of Bolton. As part of a Network Rail project to achieve a faster and more efficient train service between Manchester, Bolton and Preston, the up tunnel required re-boring to allow for electrification. The enabling works included reinforcing the down tunnel to ensure it was able to withstand the effects of the UK’s largest tunnel boring machine reboring the adjacent tunnel.

The reinforcement involved spraying shotcrete onto reinforcement cages installed to the 270 m long tunnel to a depth of 200 mm. With work due to be completed over ten weekend possessions lasting 54 hours each, efficiency on site was essential.

In addressing the key drivers of working as quickly as possible while protecting the track and ensuring staff safety, Murphy designed a bespoke alloy scaffold tower mounted on a road-rail vehicle (RRV) trailer which enabled three staff members to easily and safely install pre-cut 1.2 x 2.4 m steel reinforcement to the tunnel arch. The bespoke components produced by manufacturer Youngman consisted of cantilever platforms fixed to the midsection of the main frame plus feet bolted to the tower and located in specially fabricated rails which were attached to the Chieftan RRV trailer.

The rails allowed the tower to slide to within 100 mm of the edge of the trailer, the cantilever working platform overhanging to enable easy access to the arch. As well as installing the steel reinforcement, the platform was used for installing ten steel rib arches in a 12 m section of the tunnel. This was necessary as the existing brick lining had been deformed, reducing the clearance, and required a double layer of mesh reinforcement. Upper sections of the rib arches required an additional hydraulic lifting arm which was specially designed by Murphy and attached to the RRV.

The mobile unit was moved in and out of the tunnel as required, minimising mobilisation time and ensuring the project was delivered safely and on time. The working platform enabled access to the existing arch at both crown and axis level providing the site team with a Safe System of Work certification for working at height, ensuring staff safety and maintaining efficient progress. Another RRV trailer was customised to accommodate the Meyco Oruga robot which handled the precision shotcrete work.

The platform provided a safe working load of 275 kg per platform level up to a maximum of 950kg per tower. The manufacturer, supported by Murphy’s site team, incorporated key design features such as an ergonomic integral ladder system for increased grip and safety, Advanced Guard Rail and 3T (through the trap) fall protection and frame horizontals with 500 mm spacing and ribbed tubing for increased grip. The design also had a patented double action trigger-operated locking claw, floating spigots for easy assembly and dismantling, self-cleaning adjustable legs and deck board edge protection and an easy to use toe board system.

Michael Boyle, Murphy project manager, said, “Creating a bespoke scaffolding solution so that the challenging Farnworth down-tunnel enabling works progressed smoothly and safely was essential to the success of this project. It is just one of many great ideas across Murphy that shows our ability to approach a problem from a different angle so that we can achieve results for clients. The Bright Ideas initiative brings innovation to the forefront of Murphy’s culture. Teams are not only recognised for being innovators using their expertise creatively, but also help to make future projects a success.”