Case Study

Drax power station - Award-winning freight wagon design

Drax power station - Award-winning freight wagon design
Published: 17 February 2015 Client name: Drax Power Station Service provided: Rolling Stock Design and Engineering

A new freight wagon design to transport biomass material on the UK rail network

In 2012 Ricardo was asked by Drax Power Station to design a new super-sized freight wagon to transport biomass material along the UK rail network to its facility in North Yorkshire.

Since entering into service in 2014, the wagons have played a central role in transforming the station into one of Europe's largest generators of renewable power.

The design also won the 'Rolling Stock Excellence' category at the UK’s Rail Business Awards.

A unique design with several patented features

Biomass is a biological plant-based material sourced from forestry and agricultural by-products and is imported into the UK from locations as far away as South America.

Unlike coal, though, biomass pellets must be kept dry at all times. This means that the open-top wagons typically used to transport coal on the rail network would be unsuitable for carrying the pellets from the UK's ports to the power station.

An initial solution, also developed by Ricardo, saw a retrofit of protective top doors to an existing fleet of coal wagons. Even this early work had to overcome some design challenges. For example, freight wagons have no electricity supply to open and close the doors. In response, a system was developed using magnets attached to both the wagons and the lineside: as the train approaches the hopper house at the port it passes a magnet that causes the pneumatically operated top doors to open. A similar magnet then closes the doors upon leaving.

A safety feature was added that meant the train driver turned a key to send a pressure signal along the rake that primed the wagons for opening. This ensured the doors could not be activated by other magnetic activity during their transit and risk damaging overhead wires, bridges and tunnels. 

However, Drax Power Station's plans to increase the use of biomass in its operations meant a new, more efficient wagon design would be needed. 

The UK's largest volume freight wagons

As biomass is less dense than coal, each wagon must carry more load  for biomass to remain an economically viable option.
  
This required a design capable of carrying larger volumes of material yet remaining within the limits of the UK’s loading gauge and operating in compliance with industry regulations.

As biomass is less viscous than coal, it does not require the steep tapering at each end of the wagon that helps loads exit through the bottom doors. This meant extra volume could be gained by 'squaring off' each end.  A new product flow control system was also developed to channel the flow of material and reduce spillage.

Further capacity was gained by relocating the wagon's pipework, structural supports and control equipment.

At 18.9m long, the 'super-sized' wagons offered a capacity of 116 cubic metres - allowing for a biomass load weighing 70 tonnes - which is almost 30% cent bigger than any other freight wagon on the UK network.

Today, Drax Power Station receives more than 7 million tonnes of biomass a year, almost all using its fleet of 225 wagons. Around 17 trains of 25 wagons arrive each day. Such quantities enable the station to provide 15% of the country's renewable power.

Design and analysis

Design and analysis

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