RECONDITIONING OF SWITCHES &

1. RECONDITIONING OF SWITCHES & CROSINGS. PRAKASH KADIYA S I T – 7.

2. Inspection of Points and Crossings • Tongue Rails should be replaced/reconditioned when exceed the limits as follows • Vertical Wear > 8 mm (for 60 Kg) > 5 mm (for 52 Kg and 90R) • Lateral Wear > 8 mm (for 60 Kg) > 6 mm (for 52 Kg and 90R)

3. Inspection of Points and Crossings • Wear on Stock Rails should not exceed the following limits; • (Para 302 of IRPWM) • Vertical Wear - 13 mm (for 60 Kg) • - 8 mm (for 52 Kg) • - 5 mm (for 90R) • Lateral Wear (for Curve) • - 8 mm (for Group A and B Routes) • - 10 mm (for Group C and D Routes) • Lateral Wear (for Straight) • - 6 mm (for Group A and B Routes) • - 8 mm (for Group C and D Routes)

4. SELECTION OF P & C COMPONENTS FOR RECONDITIONING : -> Condition of components • It shall be in good condition. • It shall have sufficient residual life. • Normally not have exceeded wear limits. BY KEEPING IN MIND ALL THESE POINTS, SECTIONAL ENGINEER WILL DECIDE SUITABILITY FOR RECONDITIONING. * P & C containing cracks of more than 3 mm beyond the condemning size in worn out area, shall not be Selected for Reconditioning. * Having inherent defects shall also be avoided. 10 mm WEAR LIMIT But on RAJDHANI/SHATABDI ROUTE RECONDITIONING SHALL BE DONE BEFORE WEAR REACHES : -> BUILT UP CROSSING -- 6 mm. CMS Crossing -- 8 mm.

5. Suitability for Reconditioning • Only suitable components should be taken up for reconditioning • Component should be in sound structural condition • Components containing cracks on the worn-out portion having depths more than 3 mm beyond condemning size should not be taken up for reconditioning • Wear should be within prescribed limit. • DPT should be carried out to check for cracks.

6. * RLY BD. L. NO. Track/21/2007/0401/7/CMS No. of reconditioning to CMS crossing is Limited to 3 subjected to its structural condition. As the chemical composition of Built Up and CMS crossings are different, we have to adopt different methodology for reconditioning work.

7. MECHANICAL PROPERTIES OF DIFFT. GRADE OF STEEL * - Initial hardness value which increases to about 450 BHN under passage of traffic.

10. RESURFACING TECHNIQUE:-> A. Single electrode technique. B. Flux cored continuous wire welding technique. 1. Depot Surfacing. 2. In Situ Surfacing Welding Electrodes • Only H3 series of Electrodes approved by RDSO. • List of approved suppliers are being issued from time to time by RDSO> • List may be obtained from RDSO website. Different Electrodes having different Traffic carrying capacity.

11. List of Equipments : -> • Welding Generator DC set/AC set with 80 OCV or more. • Welding cables • Electrode holder • Ground clamp • Welding Electrodes • Pre heating oven for electrodes • Pre heating arrangement for crossing body. (Torch) • Gouging Equipment • Chipping hammer, wire brush etc. • Protective clothing including hand gloves, apron, shoes etc. • Welding hand shield • Magnaflux kit • Dye penetration testing kit • Tong Testing • Thermochalks • Grinding machine • Templates for finishing switches, crossings, SEJs. • Hammer • Wire feeder , in case of flux cored continuous wire welding process. • FOR CMS- Except item no. 7, all equipments required. • In addition- A WATER TANK IS REQUIRED OF SUITABLE SIZE.

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13. DEPOT - RECONDITIONING : -> A. SURFACE PREPARATION * By Grinding preferably with the help of electric/pneumatic grinder to ensure the surface free from adherent scales, deformed & work hardened metal and cracks. Crack removal shall be ensured by Magnaflux / Dye penetration test. For CMS –ONLY DPT CAN BE USED. B. Electrodes to be used & Precautions to be taken -> • Only RDSO approved H3 class to be used. • Packing of Electrodes –intact & all electrodes shall be consumed • within 6 hours of opening of the pack. Otherwise it shall be • dried to a temp of 130-170 `c for at least an hour immediately • before use. • Current, polarity, angle of electrode and welding technique shall • be as recommended by the manufacturer of electrodes. • Only 4 mm electrodes shall be used & shall be stored into dry place. • Electrodes having damaged/cracked flux covering shall be discarded.

14. Reconditioning of Switch • Recondition the Stock Rail first. • A worn-out Tongue Rail shall be reconditioned in closed position i.e. resting against the stock rail. • In case of broken tip the TR is to be built up initially in the open condition and thereafter it should be closed with SR to attain final profile. • Welding Current – The current range as recommended by the manufacture of electrode should be adhered to. • Electrical Appliances – All appliances should be properly earthed. Generator should be capable of supplying 200 amperes at 60% duty cycles. OCV (Open Circuit Voltage) should be in the range 65V to 85V.

15. Reconditioning of MM/90 UTS Built-Up Crossings • Surface treatment by cleaning and grinding. • Welding to be done in flat position. • Preheating : The component should be preheatedon the surface by to and fro play of oxy-acetylene torchto obtain 2500C to 3000C. • Welding to start immediately after preheating. • Use short arc length. • Care to be taken to fill the crater to the full weld size before breaking the arc. • At restart arc should be stuck ahead of crater and then drawn back so as to fill the crater.

19. SPATTER

22. Built-up Crossing

23. Depot Reconditioning of CMS Crossings

24. C. Welding Sequence:-> In case of Reconditioning of switch - Stock rail shall be reconditioned before Tongue Rail Afterwards the wornout tongue rail shall be taken, in closed (set) position. In case of broken toe, the Tongue Rail is to be built up first & then hammer forged in open Position, afterwards Tongue Rail is set against Stock Rail and final profile is obtained. In case of Reconditioning of Crossing - Runs shall be deposited in turn on the Right Wing Rail, Nose & Left Wing Rail as shown. R/H Wing Rail- First L/H Wing Rail- Third Nose - second Filled metal in Layer

25. Welding Sequence

27. D. Welding plant & Accessory :-> • All equipments shall be earth properly. • Tongue tester shall be available to measure actual output of welding current. • Current shall be as per recommendation of electrode manufacturer. • In case of CMS Crossing DC generator with reverse polarity is preferred. E. Preheating :-> • Pre heating is required for reconditioning of Tongue rail, Wing rail and Nose of the Built Up crossing, • * Components shall be pre heated with the help of Oxy-Acetylene flame to a Temp. of 250-300C. • Temp is required to maintain throughout the welding process. • In case of interruption, Again pre heating require to maintain temp. • No heating require after welding. IN case of CMS- No preheating require. • Temp. must be checked with the help of Pyrometer/Thermal chalks.

28. F. CURRENT CONDITION :-> • Current range shall be as per specified by electrode selected for welding by manufacturer • In case of CMS crossing, Welding is carried out with reversed polarity to minimise vibration. • Current- Lower side of the range suggested by the electrodes manufacturer shall be used to • reduce the heat input in the base metal to reduce dilution of base metal which would otherwise • cause embrittlement in the WELD.

29. G. WELDER -> • Only skilled welder shall be trained and certified by competent authority in arc welding for P & C surfaces. • Welders shall be checked and certified by Chemist and Metallurgist of the Railway or by any other Officer • nominated by C E in case of departmental welder, RDSO in case of private welder or outside welder. • RDSO can authorise training center of welding electrode manufacturing firm to train contractor’s welders. • Competency certificate will be valid for 5 years. H. Welding Operation • Welding shall be carried out in flat position. The arc shall be struck to P & C and then the electrodes • shall be progressively advanced by maintaining the arc using uniform movement. Fill the crater to the • full weld size. During restart, arc shall be struck ahead of the crater and then drawn back. Slag should • be removed thoroughly in between runs. Depending on the wear, no. of layers shall be decided and so • deposited that at least 3 mm metal shall in excess which shall be finally finished by grinding. • An interpass temp. of 250-300 C shall be maintained throughout the welding process.(Switch + B/U Xing) • Slag inclusion shall be removed by hard wire brush having 3 rows of and suitably hardened hammer. • After completion of welding, reclaimed area shall be thoroughly checked for defects. Undercut, groove • or any other defect shall be removed by electrode cutting followed by re-welding.

30. In case of CMS crossing welding cycle shall be of short duration i.e. not more than • 2 minutes at a time and on no occasion more than one run shall be deposited. • Sequence of welding shall be followed in a such a way that the temp. of adjoining • area shall remain below 150 C. by means of compressed air jet or water bath in such • a way that only top 1 cm remains projected above water. • No heat treatment require after welding. • Normally, during welding weaving should be reduced to bare minimum, however, • in case of CMS crossing at a time a run of 7-8 cms length only shall be deposited by • using weaving technology with the electrode kept at 45 degree to direction of welding. • Width of welding in case of CMS crossing shall be the double the diameter of electrodes.

31. I. GRINDING :-> A straight edge and proper template should be used to check profile after grinding. Special provision for in situ reconditioning of MM steel / 90 UTS points and crossing:-> • Operations like surface preparation, preheating, welding, qualification of welder, sequence of welding are same. • Trains can be passed in full speed over the weld metal on crossing even before completion of hard facing operation. • Weld metal should be allowed to cool for 2-3 minutes before allowing train to pass over it.