december 2012 | the rail engineer | 33
feature
writer
Clive Kessell
Track inspection
those in the signalling or rolling stock F orprofessions, it is all too easy to think of track maintenance as an old-fashioned undertaking, devoid of modern technology and dependent on technicians with jacks, spanners and shovels. However, this perception is totally wrong. Civil engineering track maintenance equipment has developed into the most sophisticated across all of the engineering disciplines. The advancement does not stop there and new methods of automating the inspection of track are evolving all the time. the rail engineer was recently invited to ride on Network Rail’s New Measurement Train (NMT) from London to Bedford in order to see the Plain Line Pattern Recognition (PLPR) technology which is now being introduced as a means of monitoring the condition of the track without the need for patrolling and visual inspection in the time-honoured way.
Secondly, using a risk-based approach to get more work done in the busy high-traffic areas and less in rural locations focuses the resources into where they are needed most. Then there is the squeeze on track access times as the pressure to extend the hours of train services is adversely affecting the time for doing work. This leads to a need to maximise the available time within a possession, especially where isolations are needed in third-rail territory. Automating these procedures would have a very real benefit. The safety of track workers, and avoiding the need to have them out and about when trains are running, should be part of an improved productivity initiative. Finally, the quest for more mechanisation to do things in a more efficient way with fewer manual tasks is all part of the ongoing plan.
Inspection at speed Setting the Scene Robin Gisby, Network Rail’s managing director of network operations, explained the mounting challenges that the company faces in the track maintenance arena. Firstly, there is the pressure on cost. Each maintenance delivery unit employs about 240 direct and 80 indirect staff. Getting more value from these units is important and using them for renewal work, such as switch and crossing replacement in the remoter areas, is one initiative. However, this can distort the revenue and capital budget allocations.
Trains to monitor various aspects of track condition have been around for many years. These have tended to be regionalised in deployment and only capable of specific tasks. The NMT, a converted HST with five coaches including testing and analysis vehicles which is capable of 125 mph, has been the test bed for seeing whether all the necessary monitoring can be undertaken by a single train. The NMT is 115 metres long and weighs 337 tonnes. Whilst track condition measurement is the primary task, the train is
PHOTO: MATT BUCK
at 125mph
additionally equipped for OLE monitoring via on board pantographs such that wire wear, height and stagger can be monitored. Knowing the train position is essential to meaningful measurement and this is achieved by a combination of on board GPS readers, odometry tachometers from a starting reference point, an inertial unit so that the systems know when the train has changed tracks and an underlying map, called the Network Rail Infrastructure Model (NRIM). This gives positional information to a general accuracy of 2 metres and guaranteed accuracy of 16 metres. Getting time-consuming labour out of track inspection is the primary focus, and this is done both by the examination of the actual condition of track components and by the measurement of track geometry. Initially, PLPR is concentrating on continuous welded rail, but ongoing work will use the same techniques for assessing switches and crossings as well as jointed track. So successful have the results been that four additional trains are now being formed. One of these, for the third-rail area in the South East, will be formed by two Class 73 electro-diesels sandwiching three Mk 2 coaches and a Mk 1 generator vehicle giving a maximum operating speed of 90mph.
New measurement train at speed. (Left) Live monitoring of plain line pattern recognition displays.
Robin Gisby checks the results.