The crossing shall be accurately moulded and finished to the form and dimensions shown on the drawings to be supplied by the purchaser or RDSO/Lucknow. Unless otherwise permitted by the purchaser or the inspecting official in writing the dimensions/tolerances shown on the drawing (s) shall be adhered to. Manufacturer should have adequate in-house facility for sand preparation, testing and recycling as per moulding practice specified in QAP.
Sand selection, moulding and core practice, mould and core paint selection shall be such that there is no metal mould reaction, which shall cause defects with bad/rough surface finish.
Internal/external metallic chills or chaplets shall be avoided to ensure the consistent internal quality requirement.
Marking ‘Unique Identification (UID) Number’ on CMS Crossing
Following scheme for allotting UID number to each CMS Crossing shall be followed: The UID Number shall comprise of 11 characters. However, for easy handling of core in order to control it from breakage, the UID number can be cast in two separate parts comprising of 6 & 5 characters in close proximity such that no break should appear in the UID Number.
e.g., the UID Number shall therefore be e.g., XXYYMMµZZZZ,
XX – First & Second character will denote ‘Firm’s Plant ID’
YY – Third & Fourth character will denote ‘Year of casting’
MM – Fifth& Sixth character will denote ‘Month of casting’ (the date of completion of casting to be considered)
µ – Seventh character will denote ‘Type of crossing’ (either ‘C’ or ‘W’ will be used, C for CMS crossing and W for Weldable CMS crossing)
ZZZZ – Eighth, Ninth, Tenth & Eleventh character will denote ‘Serial number of crossings’
All crossings shall have the markings of drawing number of crossings, rail section, maker’s name or initials, month and year of manufacture and such other markings as may be specified by the purchaser or the inspecting official cast in an approved manner. These markings shall be cast in raised letters 40mm high and 3mm deep on outer faces of webs of the crossing unit. All these markings shall be sharp,
clear and distinct.
- All characters in the UID number shall be numerals except the Seventh character which shall be an alphabet.
- The UID number of CMS crossing shall encompass all the designs manufactured by an approved vendor in a particular year.
- The ‘Firm’s Plant ID’ i.e., ‘XX’ shall be allotted by RDSO to all the approved vendors of CMS crossing.
- The ‘Serial Number of Crossing’ i.e., ‘ZZZZ’ will be given by the firm themselves starting from 0001 as the first crossing. Series will start from 1st of January ending on 31st of December every year.
- The UID number of CMS crossing, as indicated above, drawing no of crossing, Rail section designation shall be cast in raised letters 40mm high and 3mm deep. All these markings shall be sharp clear and distinct.
- On one of the outer faces of web of the crossing unit, UID number of CMS Crossing shall be provided and other outer face of web of the crossing unit shall have the ‘Rail Section Designation’ & ‘Drawing Number’ as per the existing scheme given in the respective drawing of CMS Crossings.
Marking for ‘Angle of crossing’ shall be done on CMS Crossings as per respective drawings.
Suitable efforts shall be made for selection of proper scrap and use of correct melting process with proper refining operation shall be ensured so as to control the detrimental tramp elements in steel. Moreover, the sulphur and phosphorus
contents in the steel shall be achieved as mentioned in Clause 4.1.
Metal should be poured by bottom pouring ladle and mould filling time shall be recorded. Further, each manufacturer will indicate pouring start and pouring end temperatures in his QAP after ensuring that all castings from first to last are sound and no adverse effect are noticed due to high or low temperature of pouring.
Pouring start and pouring end temperatures will be measured and records kept.
Any casting for which witnessing of melting & pouring is mandatory, the manufacturer shall give prior notice to the inspecting authority. Inspecting official shall witness melting & pouring as per clause 10.2.1. Casting for which witnessing of melting & pouring is not mandatory, the manufacturer may cast the same keeping records as indicated in clause 10.2.2.
During knock out, casting should be handled very carefully to avoid development of cracks in the castings. Any impact shall be avoided.
Fettling and shot blasting
The crossing shall be free from embedded sand particles and risers, flow off shall be knocked off, ingate at ends and other thick fins, if any, shall be removed by Arc Air or oxy-cut. If oxy-cut, then the cut should be at least 25mm away from the crossing body. The casting shall be suitably shot blasted thereafter, so that they are free from sand etc. and surface inspection can be done visually by the inspecting official without any difficulty. In no case, crossing shall be placed on shaker for removal of sands. Fettling & shot blasting shall be done in such a way so as to avoid any impact to the crossing.
When ingate riser etc. are removed by thermal operation, care shall be taken to make the cut with sufficient allowance (at least 25mm away from the crossing body) to prevent any defect being introduced into the main body of the crossing due to local heating.
Enlargement of bolt-holes and making of any new holes by thermal operation shall not be permitted.
All crossings shall be free from gas pockets, sand holes, cracks, cold shuts and other injurious defects. Lumps and sharp fins, if any, on the edges of the casting shall be suitably removed.
Repair of defects by welding that will not ultimately impair the strength or utility of the crossing, may be carried out with the consent of the inspecting officer, as per approved process as mentioned in Appendix-III.
During fettling for removing risers, runners and ingates from castings, no excessive heat should be generated to avoid any thermal shock to the casting.
Heat treatment of crossings
All crossings along with integral test bars shall suitably be heat treated to render them tough. It shall be ensured that integral test bars meant for further testing is not detached from the crossing even after heat treatment and shot blasting to facilitate inspecting officials in carrying out the test related to particular crossing.
This treatment shall consist of uniform heating of the crossing to a suitable temperature holding it at that temperature till uniformly heated throughout and quenching in water within 60 seconds from a minimum temperature of 1050oC. The crossing should be kept in the quenching tank in head down manner. The initial temperature of water in the quenching tank shall be less than or equal to 300C and should not rise by more than 100C during and immediately after quenching of crossings. Water in quenching tank shall be agitated and circulated properly and a continuous temperature measuring system should be installed to record before and after quenching temperature of tank for each heat-treated batches of crossings. The recording of temperature should be kept preserved for checking of inspecting officials.
The heat treatment shall be done in a furnace fitted with recorder type pyrometer. The number of castings for each heat treatment batch indicating melt heat number shall be recorded on the heat treatment chart and it shall be signed by the manufacturer’s representative and produced to the inspecting official on demand.
On completion of heat treatment, the crossing again shall be shot blasted.
A record of the heat treatment of the crossing shall be maintained by the
manufacturer, details of which shall be supplied to the inspecting official.
Surface Preparation and defects removal
The castings shall be suitably prepared for the removal/rectification of castings defects as permitted by the inspecting official without resorting to any thermal operation.
Continuous grinding at one location shall not be done to avoid raising of temperature of the surface during grinding beyond 2500C.
The casting after complete repair work and certification to that effect by the manufacturer shall only be straightened by application of gradual load under a suitable heavy duty hydraulic press. Casting shall be summarily rejected, if end- to-end straightening is beyond 40mm. After the pressing operation is done, the casting shall be offered to the Inspecting official for inspection by dye-penetration test and records shall be maintained. In no case, straightening operation will be allowed before undertaking repair welding.
Surface finish shall be ensured to minimize machining on any part of crossing. Ideal finish shall be taken as glass finish. The bottom of crossing shall be machined by milling machine so that the bottom surface of crossing which rests on PSC sleepers shall be straight without twists and shall be free from such imperfections which may prevent a good and even bearing of the crossing on PSC sleepers. End section faces (both toe and heel end) shall be machine-finished by milling machine to provide machined joints in turnout as mentioned in the drawing. Fishing plane shall be finished by milling for achieving required surface contact between fish plate and casting to have sturdy joint for proper transfer of dynamic load. Fish bolt holes shall be drilled and have a 1mm chamfer at each end to achieve tolerances mentioned in the drawing. Bond holes in fish plate area for DC traction shall also be drilled for getting bond wires force fitted. The top edge contour (gauge face) upto tangent points shall be machine-finished by planer/miller in order to achieve uniform radius all through running faces and to eliminate local misalignment. Other locations shall be finished either by machining or by hand grinding operation depending upon the facilities available. While grinding, clause 8.8.2 shall be adhered to. Machining facility shall be generally available in the same premises to have dedicated flow line for manufacture of this sophisticated safety related item.