A 4-year test of HP335 rail in a heavy haul application at Drax power station has delivered a £92,000 cost saving on just one curve.
The as rolled hypereutectoid rail - HP335 / HPrail® - has been installed and monitored over a period of 4 years following the recommendations of our Rail Technologies team.
Drax is the largest power station in the UK providing ~6% of the country’s electricity. Two thirds of the power station has been converted to use sustainable wood pellets instead of coal, with plans to switch the remaining two coal generating units to use high efficiency gas. The solid fuels for power generation are brought to site by rail using freight wagons with the maximum permissible axle load on UK national railways of 25 tonnes.
Historic performance of standard R260 grade rails had been poor under arduous conditions with a life of ~2 years being typical in the freight arrivals curve. The rails suffered both from excessive plastic flow and also rolling contact fatigue and spalling of the rail surface.
Plastic flow of the rail steel under high loads has led to lipping and spalling of the R260 rail surface
The spalling damage to the rail surface progresses and eventually makes ultrasonic testing of the rail un-testable necessitating its replacement.
British Steel was asked for advice on how to improve the performance of this track and the first HP335 rails were installed in October 2014. Working in partnership with Drax engineers to assess the performance improvements, the improvements made have led to all subsequent renewals being completed using HP335 rails on this site.
R260 Low rail showing spalling and rolling contact fatigue damage after ~35MGT of traffic
HP335 Low rail showing significant improvements in performance at 38MGT of traffic.
High rail rolling contact fatigue damage was also greatly reduced.
R260 rail ~35MGT
HP335 rail at 35MGT
One of the main performance benefits demonstrated was the elimination of gross plastic flow to the rail profile combined with greatly reduced levels of wear.
When combined with a suitable maintenance regime, the expected lifespan of the HP335 rail is now 7 times longer than the previous R260 grade rail.
This equates to a customer validated minimum cost saving of £92,000 for just 1 curve on the site. Also importantly, it removes the disruption of rail renewal to normal site operations 6 times over, and provides greater track availability to keep the freight flowing and the lights on in our homes and industry.
For more detailed technical information this case study has been presented at the 2018 contact mechanics conference in Delft. You can view the presentation here.