In the age of digital rail, with IP and radio-based communication and control systems, cable troughing can (on first glance) appear an uninteresting and low-tech subject. However, cable containment and protection is still an important part of the communication and control network. Over the last 10 years or so, the introduction of polymer-based cable troughing has contributed to safety, sustainability and security; and has been the catalyst for the introduction of other polymer-based rail products.
With future rail communications and control systems being radio based, why are cable troughing routes and containment systems needed at all? Well, the answer is that radio systems, be they GSM-R, Tetra or Wi-Fi, all require fixed radio base stations connected to a central control system to manage the radio base stations and the data connection, typically using fibre optic cabling.
There is also a need for cabling for level crossing treadles, wheel detectors, and point operating equipment.
Often overlooked, or taken for granted, is that all this electronic equipment requires power, and we haven’t yet found a way around the laws of physics in order to transmit the required power by radio.
Network Rail made significant savings with the Fixed Telecoms Network (FTN) on some routes by scratch burying a Double Insulated Super Armoured (fibre) Cable known as DISAC and not providing cable troughing. DISAC is no longer available, unless significant orders are placed, so cable troughing is still needed, especially if other cables require protection.
Cable troughing history
The traditional method of cable containment and protection is by using ground level concrete troughing. Concrete is heavy to carry and install, and is not a sustainable product.
For embankments and viaducts, lighter post-supported products are available, but these are sometimes too light and are easily damaged. Where the earthwork quality is poor, there have been occasions when the cable holds the troughing up (sometimes at alarming angles!) rather than the other way around.
Other materials have been tried over the years, including wood, asbestos and various plastics. Wooden cable routes were expensive to install and quickly rotted and asbestos was fragile, and of course led to another safety hazard and an expensive problem for current asset managers.
Various plastic based products have been tried, but have all suffered from expansion and contraction problems and have not provided adequate cable protection. Some years ago, I was involved with the trial of a plastic troughing manufactured in Germany. We installed a significant length and monitored its performance. The results were mixed, but at the final on site decision assessment we asked the (sturdy) site supervisor to jump on the cable route – it broke, and several times. Not a scientific assessment but it justified the decision not to approve the product.
In May 2014, Network Rail issued Safety Bulletin 323 which placed restrictions on the manual lifting, carrying and team handling of conventional concrete troughing. This was followed in January 2015 with safety bulletin NRB 15/01 which mandated a risk assessment policy for all concrete troughing products supported with a risk chart.
On 22 April 2015 ORR issued Prohibition Notice PN40/22042015 prohibiting ‘’single individual employees or contractors manually lifting or carrying 10 or more units of troughing weighing 40kg or more in a 12 hours period’’ and Prohibition Notice PN70/22042015 prohibiting ‘’two employees or contractors manually lifting or carrying 10 or more units of troughing weighing 70kg or more in a 12 hours period’’.
Trojan Services, based in Hove, Sussex, was the first to suggest a trough route constructed from recycled polypropylene. The product and material needed to be UV stable and tough enough to survive the installation process and the rigours of a 25-year-plus life next to busy railway lines. The material needed to have the correct processing characteristics to produce big, heavy mouldings in viable cycle times.
There was some nervousness with introducing yet another ‘plastic’ troughing product. Initial samples were produced and exposed to rigorous testing and acceptance procedures through independent laboratories. The cable route was developed in collaboration with experienced Network Rail engineers who had learned dearly from mistakes in the past.
Made from 100% high-grade recycled polymer, the system complied with HSE manual handling requirements and was awarded a green rating on Network Rail’s Manual Handling Assessment Chart (MAC). Being lightweight, the product also benefited from reduced handling and transportation costs. While initially more expensive than concrete troughing, the whole life cost was cheaper. This illustrates how sometimes procurement and investment decisions should not be based on initial purchase costs. The cable route was designed to be compatible with the traditional C1/9 concrete cable troughing, which has not always been the case with other cable containment systems.
The TroTrof product has won several awards for innovation and environmental performance (including the Network Rail Environmental Award for Innovation 2008) and all predictions suggest that it will outlast the specified minimum lifetime requirements. In particular, the product is well suited to areas where access is difficult or weight bearing is an issue.
Cable theft and security has become an increasing problem with the price of copper rising. Buried cable routes are the obvious answer, but these are expensive and problematical if regular cable entry and exit to the main cable route is required.
An easy and simple mitigation against cable theft for the TroTrof product was simply to drill the trough and install tamper-resistant screws. To secure conventional concrete troughing would require expensive brackets to lock the lids together, or the use of clamps that compromise the trough capacity.
A problem arose with the first generation design of the TroTrof C1/9 cable trough with the lids expanding and lifting. “Here we go again,” was the first reaction in the industry. However, as soon as the issue came to light, the Trojan designers quickly came up with a solution that did away with the problem and the need to manually gap the lid. The injection moulds were modified and a section of material was added to the underside of the lid. At the same time, a non-slip surface was also added.
The re-designed units were re-tested at the British Research Establishment, confirming that their performance exceeded the original Network Rail specification for expansion.
Walking on ballast is extremely tiring and, of course, dangerous – even more so with modern quiet rolling stock and welded rail. It is often easier to walk on the concrete troughing route, but it is too narrow to be an official walkway and, while the location is safer than walking on ballast, loose or broken lids create another tripping and slipping hazard.
In order to improve track worker safety, lineside walking routes have been introduced over the last 10 to 15 years, one of which was the West Coast main line with the introduction of the 125mph Virgin Class 390 Pendolino. Various construction techniques were used, but often it was the existing concrete troughing route that made construction of a walkway difficult.
So why not create a combined walkway and troughing route? As a result of safety incidents, the Network Rail maintenance director asked the telecoms engineering team and Trojan to come up with a combined cable trough and walkway. There were initially some reservations with being able to provide a non-slip trip-free surface and what would happen to the walkway when the lids were off in order to run a new cable – isn’t that just the time when a safe walkway is required?
Working closely together, the Network Rail engineers and Trojan came
up with a solution based on two C1/43 cable routes side by side, but made from one mould with two separate lids and an overall width of 700mm. This provided the ability to segregate cables, for example power and communications, and the ability to maintain a reduced width walkway when laying new cables. Like the introduction of the TroTrof, the TroTred combined cable route and walkway was developed with the aid of scale mouldings and full size wooden models in order to refine the design.
Knock outs were introduced for cable entry and exit, and to allow cables to run between the two sides of the route. Slots were provided in the trough for posts to enable a safe cess fence to be quickly and safely installed. This resulted in the removal of another safety hazard with the knocking in of fence spikes and the risk of coming into contact with buried services – yet another win win.
Again produced from 100% recycled polymer, each TroTred section weighs 12kg and a complete unit 48kg. It was the winner of the Network Rail Partnership Award for Innovation 2010, which recognises excellence and best practice. TroTred offers significant cost savings in comparison to traditional separate cable and walkway systems and gained full Network Rail product approval in September 2012.
Airdrie-Bathgate rail link
Retro-fitting a combined walkway and cable containment system to an existing railway route is not easy and will introduce the risk of damage
to existing cables. Where the product really comes into its own is with installation on a new railway. This was the case with Airdrie to Bathgate in Scotland.
Completed in 2010, the 15-mile rail link between Airdrie and Bathgate was the country’s longest new railway for over a century, and the TroTred walkway and cable route was successfully installed throughout the route.
One issue that arose on the first installation in Scotland was static shocks after walking along the route. It was identified that when it was dry, windy and sunny, personnel would build up static through PPE clothing. If they did not ground themselves before touching a conductive material, such as an Overhead Line Electric (OLE) mast, then they may receive a static shock. There were concerns that the TroTred unit itself was responsible for the build-up of static but this was not the case. The polymer material used was non-conductive and does not hold a charge.
The solution was an ‘anti-static’ TroTred unit that could be installed before each OLE mast that would carry any static charge away from personnel before they came in contact with the conductive material. Another solution is for personnel to touch their boots onto the ballast or conductive material if they believe their PPE has built up a static charge before touching any metallic structure.
The TroTred product has since been installed at Paisley Corridor Improvement, Todmorden Curve, Crossrail, Thameslink, East West Phase 1, East Coast main line electrification, North Staffordshire improvement programme, Redditch and many other maintenance and minor improvement projects.
TroBord was the third product introduced by Trojan to the rail industry using recycled polymer. Its interlocking design makes for a reliable and effective ballast retention system that can be easily fitted, especially at sites with steep inclines and where shoring is a key consideration.
It provides the same light and strong construction characteristics as the other polymer products and, at 6kg per unit, the TroBord is easy to handle, requiring less manpower than conventional ballast boards. It can be fitted as a complete system or, being of the same dimensions as standard ballast boards, can be incorporated into existing concrete installations.
TroBord was the winner of a Plastics Industry Award for industrial product design in 2011.
Being manufactured from 100% polymer, all the Trojan products have
a significantly lower carbon footprint than traditional concrete troughing. They are ISO 9001 compliant and each unit is individually hallmarked during manufacture, allowing traceability back to the raw materials used in its construction.
During the manufacturing process all components undergo a demanding series of stress tests to ensure that quality standards are maintained. The units can be cut and screwed using standard hand tools, making them ideal for use on projects that require on-site adjustments.
No wonder Trojan’s website boasts: “Tomorrow’s Technology Today.”
Written by Paul Darlington