5. CAPÍTULO 5: SOBRE LA NOCIÓN DE FORMADORES EXPERTOS
5.4. EL FORMADOR EXPERTO Y SU DOMINIO DISCIPLINAR
L E N G T H TO S U IT S L E E P E R T H IC K N E S S
M IN IM U M a: 25 mm.
b: 40 mm.
a
a
b
b
O L D
P L U G G E D U P H O L E
M IN . 2 5 m m .
M IN . 2 5 m m . N E W H O L E S
74 PART ‘E’
Rails and Fastenings
248. Standard Sections of Rails – (1) General – Rail sections are normally selected to suit the standard of loading and the speeds. The other
Routes
Traffic density A B C D Spl. D E Spl. E
in G. M. T.
More than 20 60 kg 60 kg 60 kg 60 kg 60 kg 60 kg 60 kg
10 - 20 60 kg 60 kg 60 kg 60 kg 52/90 60 kg 52/90
5 - 10 60 kg 52/90 52/90 52/90 52/90 52/90 52/90
Under 5 52/90 52/90 52/90 52/90 52/90 or 52/90 *52/90
or 60 kg 60 kg or 60 kg (SH) or
(SH) (SH) (SH) 60 kg (SH)
Loop line 52 kg IRS-T-12 second quality rails or 52 kg (SH)
Pvt Siding For sidings with operating speed more Track structute specified for ‘D’ route.
than 80 kmph and upto 100 kmph
For sidings with operating speed more Track structute specified for ‘E’ route.
than 50 kmph and upto 80 kmph
Where BOX‘N’ or 22.1 Tonnne axle 52 kg IRS-T-12 Second quality rails wagon ply or operating speeds on or 52 kg (SH).
sidings exceed 30 and are going uptr 50 kmph.
For other sidings with operating speed 52 kg IRS-T-12 third quality rails also called upto 30 kmph ‘Industrial use rails’ or 52 kg (SH).
Note : 52/90 represents 52 kg/90 UTS rail section.
(i) Existing 90-R rails may be allowed to remain for speeds not exceeding 110 kmph.
(ii) On routes identified for running of 22.1 Tonne axle load wagons, 60-kg rails shall be used on all routes.
(iii) Head hardened rails should be used on (a) Local lines where dedicated EMU stock is running. (b) Ghat section with gradients steeper than 1 in 150 and / or curves sharper than 2 degree, (c) Locations where due to grades, curves, traffic density and type of stock, the rate of wear of rails is such as to necessitate rail renewal, on wear considerations, at a frequency of 10 years or so. (d) Routes where predominantly captive rolling stock is moving in close circuit movement, particularly with heavy mineral traffic. (e) The HH rails should be laid on continuous & long stretches.
(iv) *Second hand 52 kg rails may be used on case-to-case basis, with the prior approval of Railway Board; depending upon quality of released rails available.
important factor which must govern the choice of a rail section is the traffic carried so that adequate service life could be obtained.
(2) Recommended Rail Section - (a) Broad Gauge – The following minimum rail sections are recommended based on the speeds obtainable and the traffic condition :
(b) Metre gauge – The following rail sections are recommended on M .G.
routes:-Route Rail Section recommended
‘Q’ and ‘R1’ .. .. .. .. 52 Kg (SH)/90 R (New)*
‘R2’ and ‘R3’ .. .. .. .. 52 Kg (SH)/90 R (SH)
‘S’ .. .. .. .. 52 Kg (SH)/90 R (SH)/75R (SH)
* 90R (New) to be only used with specific approval of railway Board, in case no suitable 52-Kg (SH) rails are available for use on MG during renewal.
(c) Narrow gauge (762 mm.) – Suitable new or second hand rails 50 lbs. and above.
249. Causes of Rail Deterioration – The principal factors causing rail deterioration are detailed below :
(1) Corrosion and rusting – Corrosion is caused not so much by the dampness as by acid gases dissolved in the film of moisture which frequently coats the rails. Corrosion is generally heavy in the following locations :
(a) Platform lines where trains make prolonged halts.
(b) Sidings where saline or corrosive goods are dealt with .
(c) Where the rails are affected by the dropping of engine ashes, such as at ash pits.
(d) Near water columns due to insufficient drainage.
(e) Tunnels and damp cuttings.
(f) Areas near the sea coast.
(g) Industrial belts.
Corrosion is generally noticed on the web and foot of the rail.
(2) Wear on Rail Table – Normally this is of a very small order. The amount of wear increases with heavy traffic density as in suburban section, though not proportionately.
(3) Flattening of rail table — This mostly occurs on the inner rail of a curve by high contact stresses combined with horizontal forces. The vertical pressure may be due to heavy axle load, large unsprung mass or under equilibrium speed on canted track. The horizontal forces are associated with slow running on canted track, which condition produces slipping of wheel sets. Spreading of rail table is an indication of overloading on one rail and such tendency can be reduced by providing appropriate cant.
(4) Wear on Gauge Face – The outer rail of a curve has to withstand heavy pressure from the wheels which results in the running edge becoming worn or ‘side-cut’. Wear on gauge face is specially pronounced in case of suburban sections where multiple unit coaches are provided with laterally unsprung traction motors.
(5) Hogging of rail end – A hogged rail is one with its end or ends bent in vertical direction. A hogged rail end in the track is ascertained by unfishing the joints, removing the fastenings and then measuring the extent of hog at the rail end by placing a 1 metre long straight edge over the rail table, centrally over the joint as shown in the sketch below–
(6) Battering of rail ends – Rail end batter occurs where the joint gaps are excessive. It is caused by the impact of wheels on end of a rail particularly if the fish-plates do not fit snugly. Rail end batter is measured as the difference in heights of the rail at its end and at a point 30 cm. away from the rail end as shown in the sketch as shown below.
76 (7) Wheel burns – Wheel slipping occurs usually on adverse gradients or while starting on rising grades when considerable heat is generated and top of the rail is torn off in patches, causing depressions known as wheel burns, from which cracks may develop. This also occurs when train brakes are applied suddenly and wheels lock and slide. Wheel burns cause the wheels to hammer the rails and lead to difficulties in keeping the sleepers packed firmly and fastenings tight. Such rail should be kept under observation and changed, in case repair by welding is not feasible. The incidents of wheel burns is predominant where the mode of traction is electric or diesel-electric.
(8) Corrugation – In certain locations, rail table develops ridges and hollows called corrugation and when vehicles pass over these rails, a roaring sound ensues. Such rails are called “roaring rails”.
In such locations, excessive vibrations are caused, due to which fastenings and packing tend to get loose, track needing frequent attention at these places.
250. Rail Maintenance to reduce Rail Deterioration – (1) Efficient maintenance of rails results in increased service life of rails. The following precautions/maintenance practices if observed ,will effectively reduce rail deterioration.
(2) Prevention of corrosion (Anti-corrosive measures)– (a) Anti-corrosive paintings –
(i) Anti-corrosive painting of rails should be carried out in locations which are prone to corrosion.
(ii) While carrying out renewals in these areas, anti-corrosive treatment should be given before the rails are laid in the track. The rust is removed and scales are loosened by wire brushing/scraping.
Thereafter rails are painted with –
One coat of Red oxide zinc chromate primer to IS:2074.
Two coats of Bituminous emulsion to IRS-P-30-1996 to a dry film thickness of 350 microns (each coat to a minimum thickness of 175 microns).
(iii) In the case of rails that are already laid in track and subject to corrosion the rails should be given the treatment in the track itself. The rust and scales are first removed by wire brushes and thereafter painted
with-One coat of Red oxide zinc chromate primer to IS:2074.
Two coats of Bituminous emulsion to IRS-P-30-1996 to a dry film thickness of 350 microns (each coat to a minimum thickness of 175 microns).
(b) Rail flanges/web should be kept free of the ashes particularly near the ash pits in watering stations.
(c) Periodical cleaning of rubbish should be got done in goods shed siding lines.
(d) Water column should be avoided on the run through lines as far as possible. Where however water columns are necessary to be retained, proper drainage of water column should be ensured.
(3) Reducing side wear on rails-(Gauge face of outer rails) – (a)On sharp curves where the tendency to wear on the outer rail is noticeable, lubricators should be installed or hand lubrication of gauge face should be done, care being taken not to apply the lubricant on the top of the table.
(b) Increased life can be obtained by turning the rails when side wear reaches the permissible limit. At the time of turning, matching of rail ends on the gauge face should be ensured. Spot renewals should not be carried out with new rails particularly, if the heads of the existing rails are worn badly. These should be spot renewed with matching sections of serviceable rails.
(4) Repairs to wheel burns – This could be carried out at site by in situ welding.
251. Maintenance Of Rail Joints – (1)Special care is needed for maintenance of fish-plated joints to get better rail life as well as improved running.
(2) The efficient maintenance of joint depends on :
(a) Efficiency of fastenings.
(b) The efficiency of packing and correct spacing of sleepers.
(c) The provision and maintenance of correct expansion gaps.
(d) The proper lubrication and fishing of the joints.
(e) The correct maintenance of gauge and cross levels and proper packing.
(f) Efficient drainage.
(3) Defects in rail joints – Some of the major defects, noticed at the rail joints and the preventive measures suggested to rectify or minimise the deficiencies /defects noticed are detailed below –
(a) Slack sleepers – Maintenance of joints by Measured Shovel Packing in case of flat bottomed sleepers improves the condition of the joints. In the case of conventional maintenance by beater packing it should be ensured that the sleepers do not get tilted.
(b) Loose Fish-Plates – Fish bolts must be kept tight, but not so tight as to prevent expansion or contraction of rails, by using standard spanners.
(c) Wear of Fish-Plates and Rails at fishing surfaces – When wear takes place on the fishing planes of rails and fish-plates, the joint dips down.
The wear is generally greatest at the centre of the top of the fish-plates and least at the ends.
Two types of devices are used for compensating the wear of the fishing planes :
(i) Repressed fish-plates.
(ii) Tapered shims.
(i) Repressed Fish-Plates – The repressed fish-plates are those which are hot forged so as to form a bulge in the middle part of the fish-plate conforming to the wear most prevalent.
(ii) Tapered shims – Tapered shims are pieces of steel, shaped to fit the usual pattern of wear between the top fishing surfaces. They are made in varying thicknesses, each size being designated by the wear in mm. between the fishing surfaces multiplied by 10. Thickness of shim is varied in steps of 0.5 mm. from 1.5 mm. to 3.8 mm. Length of the shims should be determined on the basis of actual wear pattern of different sections of rails. Shims are tapered in thickness from one to the other to conform to the wear. The sketch shown as below indicates the type of tapered shim, which is commonly used :
(d) Battering of Rail ends – Battering can be avoided by packing the joint sleepers firmly and by maintaining correct expansion gaps. Battering of rail ends can be repaired by in situ welding. It can also be improved by end cropping.
(e) Hogged Rail Joints – De-hogging can be done by de-hogging machines. De-hogging of rail ends can be done by Measured Shovel packing. In this method the joint sleepers are normally packed to a specified height above the normal, taking into consideration the dip at the joint and voids below the sleepers, leaving the shoulder sleepers without packing. After allowing traffic for about two days, the shoulder sleepers are packed without lifting them.
De-hogging is effected by traffic passing over the joints. Use of repressed fish-plates helps in improving the hogged joints. Hogging can also be eliminated by cropping the rail ends.
(f) Broken Fish-plates – Broken or cracked fish-plates must be replaced with new or reconditioned fish-plates.
(g) Cracked or Broken Rail ends – The fish bolt and bond holes at rail ends weaken the rails.
When maintenance is poor, rail end fractures occur, the fracture almost always starting as a fine crack from the fish bolt or bond holes. During lubrication of rail joints, opportunity should be taken to observe the rail ends carefully for any fine cracks. If cracks are noticed rails should be replaced. Chamfering of bolt holes and bond holes should be done. Ultrasonic testing of rails helps in detecting the cracks which are difficult to detect by visual examination.
(h) Pumping of Joints – Immediately after the monsoon, the ballast at such joints should be removed. Sand blanketting should be provided on the top layer of the formation which will prevent upward rise of clay slurry. On top of this blanket clean and adequate ballast should be put. Cross drains should be provided between first and second shoulder sleepers. Geotextiles can also be advantageously used.
(4) Other important points regarding joint maintenance – (a) Gap survey should be undertaken periodically and gap adjusted, as detailed in Para 510.
(b) Use of wooden sleepers at fish-plated joints, on a metal sleepered road, is desirable.
(c) Ordinary fish-plated track could be converted into three rail panel, wherever all other conditions for SWR are satisfied.
e L
E
E = M A X . T H IC K N E S S . e = M IN . T H IC K N E S S . L = L E N G T H O F S H IM
78 (5) Chamfering of bolt holes in
rails-(a) General : (i) Chamfering of bolt holes work hardens the periphery of holes and thereby delays the formation of star cracks. The chamfering of hole takes 5 minutes per hole. Each drilled hole shall be chamfered.
(ii) Existing bolt holes in fracture prone zones should be chamfered if not elongated. In case of elongated holes, the chamfering bit will not be in contact with the full edge of the bolt holes and there will be uneven hardening of the metal resulting in stress concentration in weaker-zones. Therefore, such portion of rail should be removed; holes should be drilled and chamfered.
(b) Equipment for chamfering of bolt holes: Work hardening of bolt holes should be done with chamfering kit of approved make. The chamfering kit consists of the following:
Equipment (as per Fig.1)
Qty.
(i) High tensile bolt M-20 1 No.
(ii) High tensile nut for M-20 bolt 1 No.
(iii) Sets of 2 H.S.S. chamfering bits 1 set (iv) 19mm sq. drive sockets size 32mm 8 Nos.
(v) Set of 2 packing pieces (sleeves) 1 set (vi) T-400 torque-wrench with built-in
rachet Mechanism 1.25m length 1 No.
(c) (i) Chamfering of bolt holes in the welded rail panels should be done before despatch in the Flash Butt Welding Plants, if situation so warrants.
(ii) When rails in track are end-cropped, new bolt holes should be chamfered at site.
(iii) Bolt holes in new rails received directly from steel plant should be chamfered before rails are laid in track.
(d) Procedure for chamfering of bolt holes: (i) The nut of high tensile steel bolt is removed and one packing piece is inserted in the shank followed by one side of the H.S.S. chamfering bit.
(ii) The high tensile steel bolt is inserted with 2 pieces in the rail hole.
(iii) On the other face of the rail hole, the second half of the HSS chamfering bit is inserted over the shank followed by the second packing piece.
(iv) The nut on the high tensile steel bolt is replaced.
(v) Pre-set torque-wrench on nut at torque value of 52 Kg-m equivalent to an axial force of 12.5 tonnes, is applied. The nut is tightened with the torque wrench. As soon as the preset torque is attained, the torque wrench will automatically trip indicating complete tightening to preset torque value.
(vi) The nut by reversing the torque wrench is unscrewed and HTS bolt is removed. The process is repeated on other rail holes.
(e) Chamfering of each hole should be done under the supervision of Mate/Keyman.
252. Inspection of Rails In Service – (1) General – Rails should be inspected for flaws specially, when the rails show signs of fatigue and the rail wear is excessive. The detection of rail flaws is done either by visual examination of the rail or by ultrasonic rail flaw detection.
(2) Visual examination of Rails – Most of the rail flaws develop at the rail ends. Rail ends should be examined for cracks during the lubrication of rail joints by cleaning the surface of the rail by wire brushes and using a magnifying glass. A small mirror is of assistance in examining the underside of rails. Such an inspection on the important grider bridges and their approaches should be done twice a year.
Fig.1
20 Ø HTS BOLT SLEEVE CHAMFERING
TOOL
SLEEVE CHAMFERING
TOOL WEB OF RAIL
(3) “Ultrasonic testing of rails is specialized activity and the inspectors carrying out the ultrasonic testing of rails shall be trained by RDSO, in the technique of USFD testing. Each zonal railway shall create adequate number of ex-cadre posts of inspectors to ensure that entire track length in their jurisdiction is ultrasonicaliy tested at the laid down periodicity.
Detailed instructions for ultrasonic testing of rails and welds are contained in the Manual for Ultrasonic Testing of Rails and Welds, August, 1998, which along with its correction slips may be referred to as Annexure to this Manual, It is very important that instructions contained therein are carefully studied by the Permanent Way Officials connected with the laying and maintenance of track”.
(4) USFD Testing of Service Rails:- No rail untested by USFD shall be laid in the track whether for new lines or layouts or renewals or for repair works or even temporarily such as service rails for PQRS work. For repairs and casual renewals, a location-wise imprest of tested rails of various lengths (13m, 9m, 6m) shall be prescribed for each PWI by Sr.DEN/DEN.
253. Action to be taken in the case of Rail fractures/Weld failures – (1) It is of paramount importance that whenever a fracture of a rail/welded joint is noticed, immediate action is taken to restore the track, if necessary with restricted speed, with the least possible delay.
(2) The Mate/Keyman/Gangman, as soon as he notices the rail fracture/weld failure should first protect the track, while the repairs are being carried out. He should also send information to the P.W.I.
and the Station Master of the nearest station.
(3) If the fracture is with a gap of less than 30 mm. in the case of fish-plated/SWR track, the fractured portion should be supported on wooden block or by shifting the nearest sleepers on both sides. In the case of LWR the fractured rail should also be clamped.
(4) When the fracture gap is more than 30 mm., a closure of appropriate length should be used with a clamp and further action taken as in sub-para (3) above.
(5) In cases where a small portion or piece of rail has come off or in the case of multiple fracture, the rail has to be changed.
(6) In the case of weld failure, joggled fish-plates and clamps should be used.
(7) After doing the emergency repairs the trains may be passed at 20 km.p.h. by a Mate/Keyman, until the Permanent Way Official replaces the rail and restores full speed.
(8) If there is a spate of rail fractures, additional Keyman’s patrol should be introduced in the early hours of the morning.
254. Stacking of Rails – In stacking rails, care shall be taken that
-(a) The ground is level;
-(a) The ground is level;