Class 91 – systems integration

If there is one word that sums up the aims and aspirations of everyone working on the railway, it is reliability. Reliable timetables are adhered to, reliable trains don’t break down or get delayed, reliable infrastructure allows trains to pass as planned and reliable working practices are safe ones. Writes Nigel Wordsworth


So teams of engineers and designers are working throughout the industry to improve reliability. They are upgrading systems, checking processes and developing new technology – all largely out-of-sight.

One good example of this process in practice is the Class 91 locomotive. Owned by Eversholt Rail Group, a fleet of these locomotives has operated express passenger services on the East Coast main line (ECML) since 1991. Each one is operated in push-pull mode with nine Mk4 coaches and a driving van trailer (DVT) to form an IC225 train.


Intensive services

The ECML is an intensively-used route with high average operating speeds and short headways. Much is only double tracked, so any failed locomotive quickly causes severe disruption as it blocks one of the lines. Even if recovered quickly, the operator can still incur high penalty charges as delays, diversions and service cancellations impact upon a number of train operators, both passenger and freight.

The Class 91 locomotive was designed and built with only one pantograph. Whenever the pantograph/overhead line system is damaged, a visual examination is required, causing an initial delay. If the damage to the pantograph is serious and it can no longer be used, trains will be stranded, often without the ability to maintain essential on-board passenger amenities such as heating, ventilation and lighting.


To improve reliability, the trains’ operator, East Coast, undertook an exercise to quantify the costs of pantograph/overhead line system failures. This was compared with the cost of retrofitting the locomotive with a duplex pantograph which has two arms mounted on a single base plate. Pantograph manufacturer Brecknell-Willis had already developed such a system to provide built-in redundancy.

As a result of this analysis, Eversholt Rail agreed to fund the system design and a trial fit of one locomotive. After considering a number of proposals for management of this exercise, ESG was selected to be the installation designer and project manager. The actual fit would take place at Wabtec Rail in Doncaster during a planned overhaul.


Why ESG?

Today’s ESG takes its initials from the Engineering Support Group, British Rail’s engineering team for its freight operations. Being freight orientated, ownership on privatisation passed to EWS and thence to DB Schenker.

However, as ESG and its subsidiary Railway Approvals Ltd work for a number of freight and passenger operators, it has kept its own identity and is managed at arms length by DB.

ESG managing director Martin Horsman was at pains to stress this. Sitting around his office table, which had once graced the offices of the Gloucester Carriage and Wagon Company, he explained the relationship with the parent company.

“People do ask about that,” he told The Rail Engineer. “They wonder how becoming part of Deutsche Bahn has affected the business, and whether our customers now see us as a potential competitor.

“The truth is that we are in no way connected with DB Schenker except at the highest level. ESG and Railway Approvals are part of DB Systemtechnik, the engineering and testing side of DB. Managing director Hans Peter Lang is also Deutsche Bahn’s chief technical officer.

“DB Systemtechnik carries out testing on railway vehicles and components at several sites in Germany, and also looks after customers’ fleets of rolling stock operation and maintenance. What they don’t do is project management and railway approvals – that’s what we do here at ESG. So while we are part of DB Systemtechnik, we do things that the German operations don’t.”

It’s a job that is becoming increasingly international. Of course, the UK is still the major market, with traditional engineering projects taking up a lot of the time, such as integrating new cab air-conditioning into existing trains. In addition, over the last 18 months, a significant amount of work has been undertaken advising on refranchising. ESG has evaluated options such as the cascading of fleets, general fleet strategy, depot improvements, environmental impact and the passenger experience.

But overseas markets are growing. In Australia, where there was no traditional DB presence, ESG and Railway Approvals are leading the push.

The competence of the 100-strong ESG team, which Martin Horsman calls “lean and mean”, was a major factor in the company’s selection to lead the duplex-pantograph project.

Demanding timescales

The analysis of Class 91-related delays considered when a duplex pantograph system would have reduced or eliminated these over the previous four and a half years. It was found that East Coast had accrued £970,000 of penalty payments over the period, while Network Rail had racked up £2.8 million.

Calculating the cost of developing and fitting a trial design to one locomotive (£719,000) and then retrofitting the fleet (£750,000) gave an overall payback period of 3.44 years, allowing for a 50% mitigation factor in case the duplex pantograph would not be effective in all cases.

To achieve the goals set by Eversholt Rail and East Coast, ESG was asked to deliver the project for a budget of £719,000 and within 54 weeks – from project award to dynamic testing.


Mechanical alterations

Brecknell-Willis’ design paired two pantographs in an opposing configuration mounted on a single base frame. Each individual pantograph incorporated the improvements that had been made over the years of service on Class 91 locomotives. These included a Fast Acting Dropping Device (FADD), bonded carbons to increase the service life, and a chain guard which had been introduced to extend the chain’s serviceable life.

Although both pantographs were to be mounted on a single frame, the additional arm meant that significant alterations had to be made to the locomotive. ESG undertook the design for these and for modifications to the control and monitoring equipment.

As the new duplex pantograph was much longer when in the ‘down’ position than the original, the roof mouldings had to be reworked with a larger recess to accommodate this. ESG’s new design was optimised to reduce the build- up of foreign debris and snow and to disperse rain. It also included additional features such as an internal wire mesh screen and external strike plate to reduce the effects of electric and magnetic fields in the number two cab underneath.

The redesign of the roof necessitated alterations to the underlying structure. The main structural arch, an inverted C-channel, was replaced with a low profile beam assembly between the cantrails. This had to be carefully located as minimum clearances between the live pantograph and the access doorway into the number two end cab had to be respected.

All of these changes, which brought about a lowering of the cab roof, meant that ESG had to undertake an ergonomic assessment of the end cab internal area. The reduced roof height also resulted in a complete redesign of the HVAC (heating, ventilation and air-conditioning) system’s inlet and outlet configuration and the need to relocate and upgrade the cab lighting to a new LED system.


Is it up?

Of course, the new duplex pantograph raised its own challenges as it had to be integrated into the locomotive’s electrical control system. ESG developed a new complex logic control system, both for the locomotive and for the DVT. This introduced a new ‘pantograph status’ mimic panel to all three cabs which displays the status of each of the two pantographs to the driver displaying ‘Pan Up,’ ‘Pan Housed’ and ‘ADD.’

The new logic control uses opto-isolated circuits to pick up vehicle inputs, determine the status of each pantograph and output the correct logic sequence to illuminate the LED mimic panels with the current system status. New circuits convert the digital status signals to an Ethernet signal, communicate the data from the Class 91 to the DVT using the train’s existing Ethernet backbone, and then convert them back to a digital signal to drive the mimic panel.

The final element of the system integration was the Brecknell-Willis pneumatic control panel. Electrical inputs are used to activate solenoid valves to raise and lower the pantograph, and outputs from pressure switches are used as inputs to the logic control system to provide system status information and ADD functionality.


To test the new installation, a strategy was developed which would allow East Coast to demonstrate compatibility between the modified locomotive and the infrastructure. Significant elements of this included high- voltage testing of the new installation and in-service tests monitoring pantograph performance and uplift.

The basis of the compatibility argument is that the duplex pantograph is essentially two conventional pantographs mounted on the same base and that each behaves in a way that is equivalent to (if not slightly better than) the existing, well-proven design.

ESG did well to deliver this complex project, combining new technology with a 25-year- old locomotive, in the allotted time and to budget.

The duplex-pan Class 91 remains in passenger service, although retro-fitting of the entire fleet was put on hold pending new franchise agreements and a finalisation of the Department for Transport’s plans for the new Hitachi IET fleet. Meanwhile, valuable in-service data is being gathered and this is pointing to the new installation making a good contribution to overall train reliability.




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