Paul Zammit - Asset Standards Authority Transport for NSW - Signal testing, detection and maintenance issues for turnouts


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Paul Zammit delivered the presentation at 2014 RISSB National Rail Turnouts Workshop.

The RISSB National Rail Turnouts Workshop gives all those involved an in-depth forum for discussion and the sharing of expertise. A key element of this workshop is participation and knowledge sharing from audience as well as the workshop leaders. It is a chance for you to bring your experience and to take away new approaches for best practice.

For more information about the event, please visit:

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Paul Zammit - Asset Standards Authority Transport for NSW - Signal testing, detection and maintenance issues for turnouts

  1. 1. Signalling Turnouts National Turnouts  Workshop May 2014 Paul Zammit Asset Standards Authority
  2. 2. • Track & Signals • Signalling Principles • Turnout Stability • Points Locking • Points Detection • Turnout Types • Switch Rollers • Back Drives • Points Strategy • Achieving Maintainability • Signalling Controls • Emergency Operation Contents +
  3. 3. Signals construction Track construction Track & Signals +
  4. 4. Turnouts are required to be: • Safe • Functional • Reliable • Maintainable Turnouts are challenged + Signalling Principles • Large steel structures that require significant force to move • Exposed to rolling stock forces • Exposed to the elements • Points operate occasionally or frequently, but their availability (locking and detection) is 24/7 • Effective track stability and geometry • Simpler effective signalling design • Proper installation (track and signalling) • Regular testing to ensure continued operation within specifications • Achieving maintainability objectives (track and signalling) Solution
  5. 5. • In accordance with the desired route request or overlap Operate the switches • Mechanically secure (lock) points in correct position • Fail the lock if points obstructed • Detect the position of the lock Provide & prove locking The aim of signalling turnouts • Lock the point position with train approaching • Hold the points in the route until train has passed Lock the route Detect the switch position • Prove the closed-switch and open-switch positions Designed on fail safe principles -including mechanical components Regularly maintained by competent personnel to ensure it performs its designed safety and functional requirement + Signalling Principles
  6. 6. The steel in-bearer arrangement is engineered to provide a solid square box Avoids the points going out of square Anchored fixings keeps the signalling square with the switch and stock rails Turnout Stability +
  7. 7. • Closed-switch cannot open by 3.2 mm* or more, nor can the point lock enter if the closed-switch is open by 3.2 mm* or more • For reliability, the point lock is adjusted to fully enter with a closed-switch opening of at least 1.6 mm** Power operated points Point lock test Exception for Claw Lock points * Extended to 4.8 mm ** Extended to 3.2 mm Points Locking +
  8. 8. • Open-switch openings (at the switch-tip) checked -typically 125 mm • Rear flangeway clearances checked to 60 mm +/-5 mm Points Locking Switch-tip & Rear flangeway Switch openings test +
  9. 9. Points Locking • The point lock does not permit the open-switch to close by less than 100 mm • The point lock is prevented from engaging if the open- switch opening is less than 100 mm Less Than 100mm 1. Point Lock Fails 2. Detector Contacts Broken (Open Circuit) Catchpoints switch-tip Switch openings test + Flank Protection
  10. 10. The amount of coverage the operating bar provides to the point lock (measured at the moment detection is broken) Points Locking Maximum Coverage Point Lock Coverage Operating Bar Point Lock + Point lock coverage test
  11. 11. Points Locking Minimum point lock coverage • Measured at the moment detection is broken Spherolock points >=25 mm Lock Coverage + >=25 mm Lock Coverage Claw Lock points
  12. 12. Points Detection • Closed-switch / Open-switch • Mechanical detection • Electrical detection • Combined with points mechanism • Stand alone • Dependant/independent on point lock Closed-switch Go at 3.2mm or less No-go at 4.8mm or more Exceptions available for trailing (only) points Detecting the switch position +
  13. 13. Points Detection Detecting other vital movements • Point lock position • Bolt lock position • Point lock coverage (operating bar) • Electro pneumatic types • Plunger lock position • Control valve spool position • Pos & neg motor air pressure • Back drive (in some cases) +
  14. 14. Points Detection Plunger Lock Dog Contacts Made Normal (NWKR) when Locking Plunger Contacts Made Reverse (Cut-off Valve) when Clear of Plunger Plunger Clearance Electro pneumatic points - Detecting plunger lock position +
  15. 15. Points Detection Electro pneumatic points - Detecting control valve spool position Air Motor Main Spool Micro SwitchMicro Switch Control Spool Cut-off Valve +
  16. 16. Points Detection Electro pneumatic points - Detecting pos/neg motor air pressure Negative Air Pressure Positive Air Pressure Back Contact Made Front Contact Made +
  17. 17. Turnout Types Electric combined mechanism Claw Lock mechanism Spherolock mechanism +
  18. 18. Turnout Types Conventional combined mechanism M3a Combined Mechanism Internal Point Lock & Detection Deflection Ramp Points Rodding Detector is dependent with the point lock Both switches are operated simultaneously +
  19. 19. Turnout Types Claw Lock mechanism Switches operate independently 84M Electric Mechanism Internal Detection External Point Lock Steel In-Bearer (contains rodding) Independent switch position & point lock detection +
  20. 20. Turnout Types Claw Lock operation +
  21. 21. Turnout Types Steel In-Bearer (contains rodding) T Style Crank Back Drive Spherolock mechanism External Lock Switches operate independently Independent switch position & point lock detection +
  22. 22. Turnout Types Spherolock operation Spherolock internal workings +
  23. 23. Schreck-Mieves (Teksol) switch roller for 60kg rail full height switches RotorRail switch roller type RIC294 toe end CDP in-plate switch roller CDP switch roller assembly Schreck-Mieves EKOS (Teksol) switch roller for conventional switches Switch Rollers +
  24. 24. Back Drives Single rodding back drive Spring assist mechanism Older types +
  25. 25. Back Drives Newer type Double rodding using T cranks +
  26. 26. • Spherolock or Claw Lock mechanisms • D84M electric machines or Electro pneumatic type • Trailable mechanisms in yards • Standardised layouts and switch drillings • T crank style double rod back drives Preferences • Improved stability …integrity & reliability • Facilitate tamping and mechanised track maintenance • Efficient due to reduced maintenance time • Safer due to minimal trackside infrastructure Benefits Points Strategy + for Sydney metropolitan area
  27. 27. Achieving Maintainability • On-track access and duration • Point mechanisms located on the safest side of the track • Affect on adjacent tracks • Spare parts standardisation • Turnout components and drillings standardisation • Familiarisation • Limit the number of different types • Provide specific performance requirements • Signals / Track co-ordination • Simplicity of mechanisms Considerations for achieving objectives +
  28. 28. Achieving Maintainability Physical Position M3A Mechanism 84M Mechanism Electro Pneumatic Mechanism On-track in danger zone Points detector Lock detector Drive detector Electric motor Clutch Cut out crank Points detector ………………….. Drive detector Electric motor Clutch Cut out crank Points detector ………………….. ………………….. Air motor ………………….. ………………….. Off-track out of danger zone Fuse and Switch Cut out timer ESML Fuse and Switch Cut out timer EOL Control valves Shuttle valves Pressure switch EOL (integrated within unit) Note: Circuitry on the interlocking side is considered similar for all applications +
  29. 29. Achieving Maintainability Supporting mechanised track maintenance +
  30. 30. Signalling Controls Evolution +
  31. 31. Emergency Operation ESML - Emergency Switch Machine Lock EOL - Emergency Operation Lock • Electric Points Trackside cupboard containing an indexed crank handle or fortress key that fits into specific points • Electro pneumatic (EP) Points Newer style EP points provide push button release & operation of the points Older style EP points do not have provision for emergency operation except by the maintainer Points can be manually operated in the field under failure conditions +
  32. 32. Thank you