Contextos sintácticos

Railway track is constructed from various components. Each of these components (rails, fastenings that attach the rails to sleepers, stone ballast that supports the sleepers and the embankments on which the ballast rests) wear out with usage or age and must be replaced when their condition can no longer be managed with a reasonable level of assurance of safety.

To assure the on-going safety of the track and to effectively manage the condition, repair and replacement of components, RailCorp carries out a schedule of inspections. Each inspection targets identified aspects of track and is carried out at a frequency that has been established through analysis and experience to identify signs of the track wearing out or varying from design. These inspections allow RailCorp staff to program repairs whilst the track is still safe for normal operation.

The inspections include:

C10-1 Track Patrol

A visual inspection of the track either by hi-rail vehicle at slow speed, or by walking in areas where hi-rail vehicles are not allowed to operate (basically the inner Metropolitan and Newcastle CBD areas). Generally the track is patrolled twice a week on passenger lines and heavy freight lines. Lightly trafficked freight lines are patrolled less often.

The patrollers look for signs that the track is deteriorating, particularly where immediate action is required to maintain track safety. This involves looking for obstructions, track geometry defects, broken rails, signs of earthworks or drainage failure and the visibility and security of track signage. Detailed inspection is undertaken during the patrol when visual signs are identified.

At some locations a proportion of the walking patrol has been replaced by Engine Patrols in which patrollers ride the front of trains and examine for defects. Any identified defects are inspected on-foot at the end of the Engine Patrol.

Patrol staff will take action to protect the track (stop or slow down trains) if bad defects are found.

C10-2 Mechanised Track Patrol

Some walking patrols have been replaced by Mechanised Track Patrol. This patrol is conducted with a vehicle fitted with multiple video cameras that record views from fence to fence, of a specific track and of the inside and outside of individual rails. A patroller rides the vehicle to mark points of interest (potential defects) and reviews the recorded images in detail after the run.

Figure 228 – MTP vehicle Figure 229 – Screens used for Detailed Review of defects

Figure 230 - Views available from MTP cameras

C10-3 Detailed Walking Inspection

A walking inspection of track is conducted every 3 months to view the track behavior in detail. This inspection provides information on the condition of all aspects of the track and its components.

C10-4 Engine Inspection

Every two weeks in the Metropolitan area an inspection is conducted from the cab of a train to assess the effect of track condition on the ride comfort of trains. Some types of track geometry variations are best found by this inspection. The inspection is also an opportunity for track staff to find out from train crew areas that drivers consider need attention.

C10-5 Detailed Examinations

Specific elements of track are examined, measured and recorded at 6 monthly, yearly or 2 yearly intervals. The elements include turnouts, insulated rail joints (which are essential components of the signalling system), rails, lubrication, level crossings, drainage and clearance to structures beside and above the track.

The examinations form an important part of the process of measuring condition, assessing performance and determining how quickly the different parts of the track are wearing out. The extent and timing of repair and replacement is determined from the information recorded.

C10-6 Track Geometry Recording Car

The rail mounted recording car (commonly known as the AK car) operates on Metropolitan lines every 4 months. It records the condition of the track geometry, compares it to established standards and provides real time information to track staff of locations where maintenance work is required to correct variations in top, twist, alignment and gauge (the distance between the rails). The recording software also applies statistical techniques to assess the overall condition in comparison to standards and other locations in the RailCorp network.

Figure 231 – Track Recording Car

Figure 232 – Track Geometry recording

C10-7 Rail Flaw Detection

The visual examinations detailed above cannot find defects inside the rails. Testing of rail to detect microscopic internal defects is conducted by ultrasonic testing with the Rail Flaw Detection vehicle. The testing is undertaken every 4 months in most areas of RailCorp, less frequently on lightly trafficked lines. Because of the incidence of Vertical Split Head (VSH) defects in 2002 some sections of track are now tested every 2 months.

Some areas of track, particularly in turnouts, cannot be tested by the Rail Flaw Detection vehicle. These are tested every 6 months by staff using portable ultrasonic and magnetic particle testing equipment.

Figure 233 – Rail Flaw Detection Car Figure 234 - Rail Flaw Detection trolley

C10-8 Misalignment Prevention

When rail track heats up in extreme summer temperatures it will misalign (also known as a buckle) if it is not properly controlled. RailCorp track is designed to resist buckling at high temperatures by maintaining the right amount of rail in track, stopping the rail from moving and bunching up and providing resistance to the sideways movement that occurs when track buckles. To provide assurance that the design conditions are maintained during the summer period track stability examination, analysis and correction are conducted between August and October each year.

This involves inspection of rail adjustment, ballast profile and condition, fastening condition and areas of potential concern, analysis of the contribution of these factors to the overall stability and programmed, prioritised improvement at identified locations.

C10-9 Heat Patrol

During the hotter months of the year, when temperatures reach 38⁰C, staff conduct patrols of the track to detect early signs of instability leading to misalignments. These patrols are normally conducted by hi-rail or the front of a train so that track can be inspected in a short period of time in the hottest part of the day.

C10-10 Out of Course Inspections

In addition to the programmed inspections mentioned above, RailCorp staff conduct special inspections of track in periods of extreme rainfall and flooding, bushfires and at locations where track conditions warrant more frequent monitoring, to provide assurance of the on-going safety of the infrastructure.

More information on track inspection practices can be found in Engineering Manual TMC 203 – Track Inspection.