OHE Overhead Equipment Pantograph Entanglement PDF

PANTOGRAPH ENTANGLEMENT 9.0 INTRODUCTION Electric locomotive gets power from overhead contact wire through pantograph. For smooth operation of locomotive, the movement of pantograph should be even and unobstructed on the contact wire, when any part of pantograph comes in between overhead w...

PANTOGRAPH ENTANGLEMENT 9.0 INTRODUCTION Electric locomotive gets power from overhead contact wire through pantograph. For smooth operation of locomotive, the movement of pantograph should be even and unobstructed on the contact wire, when any part of pantograph comes in between overhead wires or vice versa, panto entanglement takes place. Panto entanglement causes damage to pantograph and overhead equipment resulting in dislocation of Electric Traction traffic. Pantograph entanglement occurs due to following reasons. 1. OHE detects. 2. Pantograph defects. 3. External detects 9.1 OHE DEFECTS Damaged OHE components such as insulators, cantilever tubes, jumpers, droppers etc may foul with the movement of the pantograph and result in entanglement. To avoid them :- Check insulators, droppers and other OHE component periodically for any cracks. Ensure provision of C jumpers to avoid dropper failure. Ensure provision of double PG clamps on G jumpers and feeder wire locations. 9.1.1 Turnout And Crossovers It has been observed that about 43% of the total OHE failures are due to improper adjustment at turnout and crossover. Improper adjustment of stagger and height at turnout or cross over results in pantograph getting entangled with overhead wire while moving on the main line. To avoid this, it should be ensured that he height of turnout/crossover contact wire is kept 5 cm above the main line contact wire at obligatory locations. Ensure that panto is not touching the turnout and crossover contact wire while going on main line. The height and stagger should be strictly as per RDSO Drgs. 9.1.2 Procedure For Adjustment Of Turn Out And Cross Over. Before adjustment of Turn-out and Cross-over at any location. ATDs of both main and Loop lines shall be checked for its free movement. 1. Measure the implantation of obligatory Mast from L/L & M/L tracks, track separation and adjust the turn-out as per SED at obligatory point. Over Head Equipments Page 153  2. ‘C’ Jumpers should be provided at 5.6 and 3.0 m distance from obligatory mast for cross-over and turn-out points respectively towards parallel run side. 3. Height of turn out contact wire should be 5 cm more than that of M/L contact wire at Cantilever location of obligatory mast. 4. Adjust A&B droppers as per schedules & their distances from obligatory mast for M/L & turn out OHE both. 5. Hogging on M/L contact wire be removed by increasing the length of ‘B’ and adjoining droppers upto a distance of 10 m from obligatory mast towards turn out side on M/L OHE contact wire. 6. Adjust the height of Contact wire on L/L one mast before obligatory taking into account the track level diff. of M/L & L/L 7. At a distance of 10 mts. Towards turn out side, adjust the loop line contact wire height +3cms. (loop line B and adjoining droppers may be adjusted for this purpose) as compared to main line contact wire height. 8. At obligatory mast, contact wire height diff. of M/L & L/L OHE should not be less than 5 cms. 9. Now, while running the tower wagon on M/L, panto should not touch the L/L cross over contact wire. 10. Take the tower wagon to turn out track and M/L contact wire should take in / take off panto pan at about 65 + /- 2 cms. From centre of panto of Tower Wagon. 11. On cross type turn out, height diff. should be +1.5 cms at obligatory, 5 mtrs and 10 mts from mast & panto should not touch turn out contact wire while tower running on M/L for this A&B dropper can be adjusted if required. 9.2 AUTO TENSIONING DEVICE ATD keeps OHE in correct tension. If ATD drum is not moving freely, the OHE tension will not remain correct. This will cause sag in OHE at higher temperature, any sag in OHE is prone to panto entanglement when pantograph is moving at high speed. Ensuring free movement of ATD and providing 100 mm sleeve on anti falling device rods in short tension length prevents sagging of OHE. Contact wire consists of joints within the running length. These joints are made during manufacturing. Their failure results in snapping of contact wire. If a locomotive is moving in the same zone where such a snapping takes place panto entanglement will result. Therefore it is necessary to check frequently all the joints, specially those in the polluted area where they are prone to more failures. Provide slice at such joints which may work out to avoid snapping. We have seen that OHE defects that can cause panto entanglement are 1. Improper adjustment of crossover and turn-out and 2. Malfunctioning of ATD. 3. Damage of OHE components. Apart from this if locomotive goes in unwired section by mistake it may damage both the panto and 9 tonne insulators. To avoid this, it should be ensure that Loco stop boards are placed at correct locations. Over Head Equipments Page 154 9.3 PANTOGRAPH DEFECTS The defects of pantograph which cause panto entanglement are:- 1. Spring box failures. 2. Improper static force on OHE. 3. Missing pins and fasteners. 4. Cracks in mechanical parts and 5. Improper leveling of pan. 9.3.1 Spring box failures attributes large share of pantograph defects. To check for any cracks, LPT should be carried out in cylinder, welding portion of the steady link, cylinder support and submounting assembly. Proper lubrication of plunger ensures dampening of vibrations of panto pan and prevents cracks in plunger socket. Plungers should move freely inside the spring box. Ensure that the panto pan strips are replaced when worn upto 2 mm. Sharp edges must be filed. 9.3.2 The static force which pantograph exerts on the contact wire prevents undue oscillations to OHE-pantograph system while the locomotive is in motion. This static force is normally kept at 7 kg. If this force is less, a large oscillation will cause the pantograph to leave its contact with OHE resulting in sparking and local heating which may damage the contact wire. 9.3.3 To ensure static adjustment and counter balancing of pantograph, a weight of 7 kg is put on the panto pan and tension of upspring is adjusted so that the pan remains balanced at a height of 2.25 m. The static adjustment of pantograph is required to be done in the maintenance shed during every IA schedule. 9.3.4 Leveling of panto pan and provision of split sin must be ensured during every inspection and also whenever the pan is changed. The split pins at critical locations of articulation arrangement and full complement of copper shunt helps in reducing pantograph defects. The split pins should be opened out upto 60 degrees, so that they do not work out during running. 9.3.5 The effect of broken and missing components of pantograph such as cracks in plunger, balancing rod and articulation rod lead to damage of panto pan, ultimately resulting in panto entanglement during run. Such broken components can dislodge the panto pan to cause entanglement. Liquid dye penetretant test of these critical components, (preferably during IC maintenance schedule) should be done to detect any such defects. This will reduce failures. 9.3.6 Improper leveling of Pantograph pan lead to tilting of Pantograph pan. Maintaining the level of panto pan should be ensured in the maintenance shed during every inspection and whenever pan is changed. Over Head Equipments Page 155 9.4 CHECKS AFTER PANTO ENTANGLEMENT Even after ensuring all these precautionary items, panto entanglement may occur. In such causes, it is necessary to quickly check the following items pertaining to the OHE and pantograph. This should be done without causing any delay in the restoration work. 9.4.1 Measurements Measurement of height and stagger of contact wire of main line and turnout crossover and vertical height of steady arm clamp from register arm. The measurement so recorded should tally with the measurement in structure erection drawing for those locations. (Show actual on OHE). It should also be checked whether steady arm holding contact wire is freely moving vertically or not. 9.4.2 Locations of Hit Marks Search for hit marks in steady arm and the registration arm tube, PG clamps, droppers, contact wire, dropper clip, splice and jumpers. Any hit mark observed in these locations should be noted. 9.4.3 Condition of Cracked OHE Fittings The condition of cracked OHE fittings such as clamps, suspension brackets and clips should be checked to record whether the cracks are fresh or old. 9.4.4 Pantograph Wearing Strips Pantograph wearing strip should be properly fastened with panto pan. There should be no bent strip or deep grooves. Strip joints must be smooth. The grease plate should be properly fastened. 9.4.5 Mechanical Movement of Panto Pan The panto pan should horizontal and free to move vertically. The bow plunger should be sliding free when pressed. 9.4.6 Availability of Split Pins Check availability of split pins at all the locations of pantograph. 9.4.7 Broken Components of Pantograph The broken parts of the pantograph should be inspected to check whether cracks are fresh or old. 9.5 MEASUREMENT OF PANTOGRAPH If panto pan is found intact these measurement are possible A-520, B=1800, C=300 and D=380. 9.6 CONCLUSION Following points must be ensured. 9.6.1 OHE height That the height of crossover contact wire is kept 5 cm above the main line contact wire. This should be checked every six months. Over Head Equipments Page 156 9.6.2 Free Movement of ATD At turnout and crossover locations, free movement of ATD should be ensured. 100 mm sleeve should be provided on the anti falling device rod to prevent sag. 9.6.3 Identifying Damaged OHE Components Check insulator and droppers for breakage. Prevent damage of such OHE component which can come in the path of pantograph movement. Secure G jumpers with double PG clamps and provide C jumper to avoid dropper failures. 9.6.4 Contact Wire Joints Identify the joints which are giving way by inspection and splice them. 9.6.5 Pantograph Wearing Strips Proper fastening of pantograph wearing strip, its thickness and fastening of grease plates required to be ensured. 9.6.6 RDPT of Pantograph Components Red dye penetretant test of critical pantograph components must be performed to detect cracks before they actually fail and cause panto entanglement. 9.6.7 Static Adjustment and Leveling of Panto Pan To ensure a constant force of 78 kg on OHE leveling of pantograph pan is to be done during each IC schedule. Even after taking the above precautions, if panto entanglement does take place, then it should be investigated thoroughly to identify the causes. The necessary measurements and checks required to be carried out at the site after entanglement are discussed. 9.7 PANTO ENTANGLEMENTS : ITEMS TO BE CHECKED ON PANTOGRAPH: 1. Check that the pantograph wearing strips are properly fastened with the panto pan and there are no loose fasteners or bent strip or deep grooves on the strips. Pantograph strip joints must be smooth so as not to hinder smooth gliding of the contact wire on the pan. 2. Check that the grease plate is properly fastened. 3. Check the bow plunger for free sliding where pressing. Check that the split pins are intact. 4. Check the horizontality of the pantograph pan and that the vertical movement in force. Check the transverse flexibility of the pan by pulling transversely at the middle cross member with a force of 50 kgf. The displacement of the pan at the middle cross member should be 36+ 5mm. Check that the positioning link is not bent/cracked or dislocated from the fixing pivots. Check that the split pins are intact. 5. Check the pantograph frame for signs of bending or cracks. Check the springs for any cracks. Over Head Equipments Page 157 6. If possible, take the measurement of the pan as per the fig. 9.01 7. Check the broken or cracked fittings of the pantograph and see whether the cracks are old or fresh. 9.8 PROFORMA FOR RECORDING MEASUREMENT / OBSERVATION IN RESPECT OF OHE IN CASE OF PANTO ENTANGLEMENT 1. Location 2. Height of contact wire of main line above RL. 3. Height of contact wire of turn-out / cross-over above RL. 4. Stagger of contact wire of main line. 5. Stagger of contact wire of turn-out/cross-over 6. Length of steady arm holding main line contact wire. 7. Length of steady arm holding turn-out / cross-over contact wire. 8. Position of registration tube and register arm dropper clip. 9. Tracks separation at obligatory point. 10. Position at which horn or pantograph jumped above contact wire. 11. Vertical height of steady arm clamp from register arm. 12. Hitting marks on the steady / registration arm tube, P.G. Clamps droppers, contact wire, dropper clip, splice, jumpers if any. 13. Condition of cracked or broken OHE fittings such as clamps splice and clips etc. Check whether the cracks are fresh or old. 14. Check free vertical movement of steady arm. Above observations will be made on every mast within at least 500 m in the rear of the location of entanglement. Over Head Equipments Page 158