CHAPTER III
MAINTENANCE AND OVERHAUL SCHEDULES OF
LOCOMOTIVES
30300 Maintenance and Overhaul Schedules of Locomotives
Indian Railways have gained considerable experience with the maintenance of electric locomotives since 1960. Based upon the safety requirements, various checks have been evaluated and already standardized. Also, based upon investigations into failures instructions (SMls) are issued by RDSO. Even, for new type of locomotives, standard equipment like pantographs, circuit breakers etc., continue to be used and established maintenance practices for such equipments will, therefore, be applicable.
The scope of maintenance work to be followed in each maintenance schedule is arrived at. based upon the following :-
i) Maintenance Instructions supplied by locomotive manufacturer for a new type of rolling stock.. Copies of these manuals will be made available for reference by maintenance staff.
ii) Maintenance Instructions that are evolved on zonal railways for standardized equipments.
iii) Specific instructions already laid down regarding safety / fire prevention requirements etc. of the rolling stock.
iv) Experience on the system taking into account environmental conditions in which electric locomotives are expected to perform satisfactorily like temperature, humidity, dust, etc.
On the above lines, maintenance schedules for electric rolling stock of different classes and types already in service have reached an optimum level. However, there may be necessity for marginal changes as dictated by further service experience.
As far as new types of electric locomotives and their sub-assemblies that may be introduced from time to time, the principles enumerated above are to be followed for arriving at optimum scope of work consistent with periodicity of prescribed schedules
30301 Alterations in Maintenance Schedules
Presently individual railways might have made minor alterations in the schedules based upon their own experience. Considering the wide variations in operating and duty cycles and environments as experienced in different systems, this would be considered logical. However, the recent trend is to enlarge the field of operation of electric locomotives. Thus today electric locomotives of one system are running in other systems. Thus alterations in schedules based upon local experience would have to give way to standardization of schedules so that the locomotives of one system would perform satisfactorily when called upon to operate in other systems.
In the light of experience and improvements based upon trials of modifications, it may become advantageous either to reduce the scope of maintenance work or the periodicity already prescribed and standardized. The following procedure -should be adopted for effecting such changes.
i) Those which are connected with safety requirements, a comprehensive proposal indicating the actual experience of the railways, the benefits that are likely to accrue due to proposed changes and the particular reasons for suggesting the change will be sent to RDSO with the approval of the Chief Electrical Engineer. Such modifications to the maintenance requirements shall only be implemented after RDSO's approval.
ii) Proposals other than item (i) above .- A similar procedure must be adopted excepting that the Chief Electrical Engineer may authorise provisionally the introduction of the change subject to post-facto approval from RDSO. In case RDSO convey an opinion to the contrary, the original schedule shall be brought back. The Railways can however continue to pursue the matter with RDSO and if the latter agrees finally, adopt the change to the extent agreed upon.
30302 Scheduled Inspections
The maintenance and overhaul schedules to be followed for AC electric locos are as under.-
| Nature of Inspection/overhaul | Place where to be carried out | | i) Trip Inspection, IT | Outstation shed or homing loco shed as convenient. | | ii) Monthly Inspection, IA + 5 days | Homing or nominated Electric Loco Shed | | iii) Two-monthly Inspection, IB + 5days. | Homing Electric Loco Shed | | iv) Four monthly Inspection, IC + 10 days | Homing Electric Loco Shed | | v) Annual overhaul, AOH + 15 days. | Homing Electric Loco shed | | vi) Intermediate overhaul, IOH 300,000 km after POH or first commissioning or 3 years whichever is earlier ± 1 month. | Homing Electric Loco Shed or Nominated Workshop. | | vii) Periodical overhaul (POH) 600,000 km after commissioning or last POH or 6 years whichever is earlier ± 3 month. | Workshop nominated for the purpose |
Detailed instructions for IT, IA, IB IC AOH and IOH and POH will be issued by CEE for each type and each series of locomotives keeping in view inspection schedules issued by RDSO. The scope of work is broadly covered in Annexure- 3.01.
Inspections as detailed above may need revision based on experience accrued on new types of locomotives. For example with WAG 6A locos the schedules are monthly inspections, 6 monthly inspections, annual inspections and 3 year schedule.
30303 Technical Instructions
A set of the technical instructions relevant to the work of each section should be made available so that they may carry out their work correctly. These can be classified under the following heads :-
i) Inspection Books
ii) Inspection Charts
iii) Trouble-shooting Charts
iv) Technical Charts
i) Inspection Books: These give the scope of work of the various scheduled inspections viz. IT, 1A, IB. IC etc. itemizing the works and the order in which they are to be carried out, arranged section-wise. The responsibility of each section supervisor is defined.
ii) Inspection Charts: These charts are prepared for each component individually. These cover a comprehensive list of all the points to be checked, the observations to be made, clearances to be ensured, specifying the conditions under which such verification should be made and the measuring equipment to be used for the purpose.
iii) Trouble-shooting Charts. Clear instructions should be issued in the form of trouble-shooting charts for each type of defect, which detail the checks to be made and the order in which they are to be made. Before the locomotive is given back to service, a competent supervisor should satisfy himself regarding the correctness of the investigations and the rectifications made. In trouble shooting, the investigating team quite often discovers a pattern of failure on the basis of which modifications and improvements to designs may have to be initiated.
iv) Technical Charts: These cover full details of all repairs, major adjustments and refitting of equipment which are to be carried out. Where such repairs are not possible, the item will have to be replaced by a new component. In the technical charts the detailed description of the material, the tools to be used and the procedure to be followed and the defects to be checked after completion of work are detailed.
v) The CEE's office will be responsible for ensuring that (a) the instructions received from RDSO are forwarded to the Loco sheds and (b) the superseded instructions are cancelled, withdrawn and destroyed, preserving one copy only for future reference. Instructions received from RDSO require constant review and a system of generating feedback information on the implementation of these instructions will be followed. Any modifications required in RDSO's instructions should be carried out only after approval from RDSO.
These instructions require constant review in the light of experience. If any modifications become necessary, Sr. DEE(RS) may introduce changes provisionally with the approval of CEE. Such changes should, however, be advised to RDSO for scrutiny and final incorporation in the documents (see para 30301).
30304 Engine Fitness Certificate
Whenever a loco for passenger service is issued from a loco shed or outstation depot after scheduled inspection or unscheduled repairs, an "Engine Fitness Certificate" will be issued, a sample form for which is appended (proforma 3.01 Part A and 3.01 Part B). 
Annexure - 3.01
INSPECTION OF ELECTRIC LOCOS
A. Trip Inspection (TI)
The trip inspection is mainly required for topping of oils, distilled water in batteries and attention to various minor defects which have been recorded in the log book. In addition certain checks are necessary mainly due to severe environmental conditions (hot, humid and dusty) existing in the country.
1. Periodicity of trip inspection shall be as follows:
Type of service Periodicity
i) Passenger/Mail/Express Train locos Every 2500 km or one trip
whichever is later.
ii) Frieght locos 5000 km or 10 days
whichever is earlier.
2 During trip Inspection the Engine Examiner will —
a) Carryout detailed checks in regard to any unusual occurrence reported by the drivers in the loco log book.
b) Visually inspect the auxiliaries for satisfactory starting and operation.
c) Feel by hand the temperature of axle roller bearings.
d) Visually inspect mechanical components like springs, equiliser pin, dampers etc. and the brake rigging to detect any abnormality.
e) Check the controls and indication and alarm circuits for correct functioning. 3. Specific items to be attended in TI are-
a) General roof inspection : Check the roof generally for any foreign materials such as wire pieces; clean the Insulators and check visually for cracks or chips; Check for abnormalities such as flashovers;
b) Pantographs : Check for copper deposition, grooving of strips and proper lubrication; visually check springs and articulation and also test raising and lowering;
c) Air Blast Circuit Breakers/Vacuum Circuit Breaker : Check for satisfactory operation.
d) Return Current Shunt : Check the shunt connections between the body/ bogie frame/axle boxes, traction motor/axle are intact, tighten if necessary.
e) Bogies : Remove foreign matter and dirt picked up on run. Visually inspect for loose, defective or missing parts.
f) Battery : Check and record battery voltage; top up cells as required.
g) Auxiliaries : Check all auxiliaries for correct operation;
h) Oil level: Check and top up oil in suspension bearing, exhausters, compressors, auxiliary compressors and gear cases and record in the log book.
i) Air Reservoirs : Drain all accumulated water from all reservoirs.
j) Cab and Floor : Clean the cab and dust the flooring; and remove oily deposits.
k) Controls and Indications : Visually check and test for proper operation of the master controller, the tap changer, all EP contactors, wipers, whistles, brakes, auxiliary equipment and indication and alarm circuits.
l) Transformer oil level : Check oil level; ascertain the cause if it is low/high. m) Clean look out glasses.
n) Adjust the brake block, if the locomotive moves on the second notch (with N32 tap changer)/fourth notch with N40 tap changer) with full application of locomotive brakes.
o) Check the following safety items.
Speed recorder / speed indicator for any abnormality
Flasher lights, head lights, marker lights etc.
Wipers
Sanding gear for any abnormality. Fill sand boxes with sand of specified quality.
Wheel and axle for visual defects such as shelling cracks, flat spots etc.
Brake gear for (i) loose fasteners (ii) brake shoe wear, (iii) brake shoe release, (iv) operation of all the brake cylinder pistons and (v) leakage in the bogie hose pipe.
CBC & draft gear
Safety sling of brake shoe holder Brake pull rod safety brackets Safety brackets
Cattle guard Rail guard
RSI & RS2 emergency brakes
Gear case for any missing parts and loose fasteners.
Hand brakes
VEF
HQOP position
Isolation of any component
Vacuum on disc and dummy/BP and FP pressure and leakage
4. Wherever time and facilities are available, the passenger locomotives should immediately be washed.
5. Test the locomotive on HT and LT and record observations on the test proforma.
B. IA, IB, IC, AOH Inspections.
The following tests should be carried out before and after inspection of a locomotive :
a) Preliminary tests with 25 kV supply on - i) Measure and record battery (BA) voltage.
ii) Measure and record Generator (GE) or battery charger voltage.
iii) Check time taken to build up compressed air pressure from 1 kg to 8-9 kg/ cm2
iv) Check cut in and cut out pressure of compressor Regulator (RGCP).
v) Check blowing out of safety valves.
vi) Check vacuum obtainable with Driver Braking control Valve (MPF) on 'run' and quick release positions.
vii) After building up vacuum, check for vacuum leakage for 5 mt.
viii) Check vacuum drop required for brakes to apply.
ix) Note: pressure guage reading when brakes are applied.
x) Check working of braking electro-valve VEF.
xi) Check working of blowers under "direct' and 'automatic' starting conditions,
xii) Note and record air leakages for one minute in main reservoirs and brake cylinders,
xiii) Test headlights,
xiv) Test working of cab heaters and fans.
b) Preliminary tests with 25 kV supply off --
i) Measure and record time required for raising and lowering both the pantographs.
ii) Measure and record time taken for various time-delay relays.
iii) Test functioning of Auxiliary circuits Earth Relay (QOA) by creating an earth fault.
iv) Test functioning of Power circuit Earth Relay (QOP) by creating an earth fault.
v) Check functioning of all lights.
vi) Check wind-screen wipers and horns.
c) Test under High Tension before and after inspection successively from cab 2 and cab 1. i) Raising of pantographs.
ii) Working of Auxiliary Compressor motor (MCPA), Amo and Generator (GE), particularly observing behavior during starting and for abnormal noise.
iii) Working of main compressor, charging time of main reservoir from 0 to 10 kg/cm2 and from 8.5 to 10 kg/cm2 with one compressor working. Record rate of leakage in reservoir and brake pipe and brake and feed pipe pressure.
iv) Check up proper functioning of autodrain, HS4, HB5, RS, D1 emergency valve and air flow indicator.
v) Record rate of vacuum leakage and vacuum on test plate and dummy.
vi) Check up all brake cylinders for leakage from exhaust port and record brake cylinder pressure.
vii) Working of both exhausters for various positions of exhausters isloating switch and driver braking valve.
viii) Working of blowers particularly watching for abnormal noise.
ix) Observation of contactors for abnormal sound and sparking.
x) Observe deviation of main ammeters taking two traction notches in forward and reverse directions.
xi) Test differential (QD), progression and regression relays.
xii) Test electro-valve VEF.
xiii) Measure and record depression in loco with all blowers functioning.
d) Low tension test before and after inspection-
i) Testing of master controller for notch by notch progression and regression and total time for regression.
ii) Test VER
iii) Test working of sanders.
iv) Test working of Exhauster isolating lever (ZPV) 
2.4 Clean the cable trenches. Examine for any damage to cable, lugs and repair it. Provide proper cable sheathing and cleats. Measure and record insulation resistance of all HT and LT cables. Tighten all the terminal connections.
2.5 Dismantle bogie, brake riggings and clean the bogie in washing tank. Check up for any crack and weld it as per the instructions laid down by RDSO. Overhaul these equipment and replace all worn out components. Ensure squareness of bogie frame. Overhaul axle box bearings and all wheels should be reprofiled.
2.6 Overhaul all traction gears and check up their P and K values and record them.
2.7 All approved modifications which can be executed in the shed should be carried out.
3. On compaction of IOH, the loco should be subjected to detailed HT and LT testing and should also be given a short trial run before it is declared fit for traffic.
D. Periodical Overhaul (POH)
1. The nominated POH workshop should issue a programme for POH of locos at least six months in advance giving the individual numbers of locos to be called in, each month. The homing shed will then send to the workshop a list of the important points to be specially attended to during POH and the list of modification to be carried out. This will enable the workshop to plan the POH work and arrange for the procurement/ shop manufacture of components required.
2. The loco should be sent on its own power from the homing shed to the workshop under escort and along with its History Book. A complete list of all deficiencies in the loco should be handed over to the workshop representative who should jointly check the loco along with the shed representative.
3. All electrical, mechanical and pneumatic equipment should be taken out of the locomotive and overhauled during POH. All wom out rubber components and bearings should be replaced.
4. All panels should be removed from the locomotive and cleaned/overhauled. They should be tested for their proper functioning.
5. All the dimensions of the under frame should be recorded. The deformation, if any, should be set right.
6. Super structure and underframe should be thoroughly cleaned. Corroded and damaged portion should be rehabilitated. All body joint gaskets should be replaced.
7. All axle and axle boxes should be overhauled and rediscing/retyring should be done. All wheels should be reprofiled.
8. All reservoirs should be cleaned and tested for their safe working.
9. All approved modifications should invariably be carried out during POH. Deferment of any item may be done only with the personal approval of CEE controlling the POH shops in concurrence with the CEE controlling the homing shed and under advice to the homing shed. In addition to all the items indicated against IOH renewal of liners, bushes, etc. should be done so as to ensure clearances and tolerances mentioned in 'F' with adequate margin for wear in service till the next POH.
10. In addition to complete LT and HT testing of the locos on completion of POH, individual items should also be subjected to detailed tests after overhaul and repair. Detailed test schedules should be laid down for each item, for mechanical as well as electrical tests, and standard proforma should be available for recording the test results for each equipment. A typical list of tests to be carried out on equipment is given below.
a) Rotating Machines : Insulation resistance by megger, no load tests, full load tests (except for traction motors) drop test of armatures, resistance measurement of field coils, temperature rise measurement.
b) Transformers : For small transformers in control circuits, ratio test and insulation resistance measurement.
For main transformer, testing of oil for BDV and acidity, insulation resistance measurement, ratio test of regulating windings and auxiliary windings, induced high voltage tests if any repairs have been carried out.
c) Relays : Measurement of resistance and insulation values for operating coils, pick-up and drop-off values of voltage/current/temperature, time delay where applicable, opening and closing of contacts.
d) Contactors : Measurement of pick up and drop-off values for operating coils, check for simultaneous closing of all phases where applicable, leakages from valves and cylinder in the case of electro-pneumatic contactors.
e) Cables : Insulation and continuity test, high voltage tests for rewired panels.
f) Resistors, condensers and reactors : Measurement of insulation resistance and ohmic values of resistance / reactance.
g) Air-blast circuit breaker : Insulation resistance of coil-windings and live parts, minimum pick up voltage for operating coils, opening and closing time for primary and secondary contacts, minimum pressure for locking in sequence of opening and closing of auxiliary contacts.
h) No-fuse breakers : (MCBs) Tests for tripping at rated instantaneous trip value.
i) Tap-changer : Insulation resistance. BDV and acidity testing of oil, correct functioning with minimum air pressure, correct progression and regression sequence.
j) Silicon Rectifiers : Forward voltage drop, inverse resistance, HV test for complete assembly, voltage sharing between diodes, testing of cell-check device.
k) Compressors and exhausters: Volumetric efficiency and leakage tests. 1) Speedometers : Calibration by comparison with a standard meter, m) Meters and Gauges : Calibration with sub-standard instruments.
11. On completion of POH, the loco should be taken over by a representative of the homing shed after a joint inspection at the workshop. Details of work done and modifictions carried out should be entered in the History Book which should be returned along with the loco.
12. On completion of POH, the loco should be subjected to detailed HT and LT testing and should be given a short trial run. Loco will be returned working on its own power, and if possible working as a train, after POH to the Homing Railway.
E. Rebuilding and Recabling of Locomotive
1. During every alternate POH, depending upon the cable/pneumatic pipe condition, which will be advised by Sr. DEE of the Shed, the locomotive will be recabled and repiped. Recabling and replacement of air and vacuum pipe during the third POH will be an essential item if it could not be replaced during 2nd POH. The workshop should therefore plan these works well in time.
2. During every 4th POH, mechanical components and traction gear may need rehabilitation. Some of the major components will also need replacement. POH shops should plan for such works. Opportunity should be taken to upgrade the parts and use the state of art equipment during- such extensive repairs.
F. Mechanical Inspection of Locos
i) Locos provided with renewable steel tyres will have tyres as per Specifications IRS : RI5-64 - Oil quenched with tensile strength of 100-110 kg/mm2.
ii) Locos provided with solid wheel disc will conform to Specifications IRS M2-65 and IS 1030-1962.
2. All springs should be checked up for any crack and damage. Free height and loaded height should be recorded. Only matched tested springs should be provided in the locomotive bogies.
3. An important part of the maintenance of the locos is the checking, at prescribed intervals, of important mechanical clearances and dimensions which have a bearing on safe and efficient operation, to ensure that they are within the prescribed limits. Such measurements should be recorded suitably either in registers or on printed cards and preserved so as to be readily available for reference in the PPO at all times. The items and interval at which they are to be checked up are indicated. Limits will be specified for each type of locomotives by the CEE based on the manufacturers'/RDSO recommendations.
Clearances .-
| SNo. | Items to be checked | Periodicity of check up | | 1 | Clearance of spring plank from rail level | IC, AOH, IOH, POH | | 2 | Buffer height | IA, IB, IC, AOH, IOH, POH | | 3 | Coupler height 1105 (max.) 1030 fain.) | IA, IB, IC, AOH, IOH, POH | | 4 | Clearance between top of axle box and bogie frame | IB, IC, AOH, IOH, POH | | 5 | Clearance between bogie horn cheek and axle box horn face | IB, IC, AOH, IOH, POH | | 6 | Clearance between bottom of axle box and horn stay | IB, IC, AOH, IOH, POH | | 7 | Distance between two parallel beam of equaliser | AOH, IOH, POH | | 8 | Clearance between safety bracket and equaliser | IC, AOH, IOH, POH | | 9 | Clearance between spring seat face and equliser | AOH, IOH, POH | | 10 | Clearance between two equalisers on middle axle box | IC, AOH, IOH, POH | | 11 | Clearance between axle box collar and inside horn faces | IC, AOH, IOH, POH | | 12 | Clearance between axle box liner at horn faces | IC, AOH, IOH, POH | | 13 | Clearance between spring and spring seat | AOH, IOH, POH | | 14 | Clearance between spring and top cap | AOH, IOH, POH | | 15 | Clearance between spring and equaliser | AOH, IOH, POH | | 16 | Clearance between equaliser and bogie frame at all sides at horn location | IC, AOH, IOH, POH | | 17 | All clearances of plain bearings for suspension and axle boxes | IC, AOH, IOH, POH | | 18 | Clearance between bogie frame and axle | IB, IC, AOH, IOH, POH | | 19 | Clearance between bolster and bogie frame | IB, IC, AOH, IOH, POH | | 20 | Clearance between bogie end stops and under frame | IB, IC, AOH, IOH, POH | | 21 | Clearance between traction pads on bolster and bogie frame . | IB, IC, AOH, IOH, POH | | 22 | Clearance between axle collar and bearing brass (end float). | IB, IC, AOH, IOH, POH | | 23 | Clearance between axle box flange and horn leg | IB, IC, AOH, IOH, POH | | 24 | Clearance between side stops | IB, IC, AOH, IOH, POH | | 25 | Clearance between stops on bogie and under frame | IB, IC, AOH, IOH, POH |
* These items are applicable to Bo-Bo and Monomotor bogies
4. Wheels : Check the following.
| S.No. | Items to be inspected | Periodicity | Permissible clearance | | 1 | Tyre profile to be Root wear Y checked Flange wear X with condemning gauge | IA, IB, IC | 6 mm for freight 4mm for passenger loco | | 2 | Flats on the running surface | All inspection | 50 mm for locos having speed less than 100 km/h.40 mm for locos having speed of 100 km/h more. | | 3 | 'A' proud metal at the edge | do | less than 6mm | | 4 | 'B' block thickness of the flange | | Condemning=40mm |
Standard "thick" and "wear adapted" profiles are shown in the Fig. 3.01 and Fig 3.02 The condemning wheel profile is shown in the Fig. 3.03.
G. Bogies
1. Squaring of bogies.
Due to heavy mechanical stress and impacts suffered by bogies in service, some of them get out of shape and distorted. During IOH and POH, it is essential to restore the bogies to their correct shape and alignment. To check this, at every major shed and POH shop, a test rig with a substantial foundation should be provided over which the bogie can be placed and the amount of distortion which has taken place accurately measured. By application of adequate pressure at appropriate points either hydraulically or by other means, frame distortions should be corrected as required, so as to ensure proper mechanical alignment of all parts assembled over the bogie.
2. Cracks on Co-Co bogies.
The bogie shall be thoroughly cleaned as per RDSO's recommendations. The extent of cracks shall be located by visual inspection as well as with magnetic particle/dye-penetrant method. After marking out the full extent of the cracks, arrest-holes of suitable size of minimum dia. 10mm shall be drilled at least 25 mm away from the vicinity of the cracks. The entire cracks shall be eliminated by opening the affected section right upto the bottom. The removal of defective area shall be done by grinding/arc gouging/chipping. The section thus opened out shall extend into the arrest holes and shall be checked up with the help of dye-penetrant or magnetic particle technique to ensure freedom from any other cracks. The welding shall be carried out as per the procedure laid down by RDSO with the help of specified electrodes. It shall be also ensured that all modifications recommended by RDSO are carried out during POH on the bogies.
H. Axle Roller Bearing
These bearings are used on electric locomotives using trimount Co-Co bogies. The assembly consists of two cylindrical axle roller bearings capable of taking radial as well as axial thrust loads. The bearing is composed of inner and outer race along with rollers and cages. The cages while carrying no load keep the rolling elements axially apart and also prevent the latter from falling out while handling. The outer ring is slide fit in the axle box housing while the inner ring is an interference fit on the axle journal forming part of the axle when in place. The rollers are plain, straight, solid cylinders and are flat on both ends. These bearings should be maintained as per RDSO Maintenance Instructions No. MPMT-98/81, March 1981.
The riding properties of these locomotive fitted with Co-Co bogie have been further improved upon by using axial resilient thrust unit on axle 1, 3, 4 and 6. Axle 2 and 5 are provided with float bearings so as to permit negotiability over sharp curves and turn-outs. This arrangement involves changes in bogie frames and axle boxes. Axle box roller bearings fitted with resilient thrust units should be maintained as per RDSO's Maintenance Instructions No. MT. 04.004.
Proper service tools should be used for servicing and maintenance of axle roller bearing which are also indicated in the Maintenance Instructions. Whenever bearings are removed for overhaul, inspection, repairs replacement or lubrication, proper precautions should be taken to avoid ingress of dust, metal contents, etc. Grease specified by RDSO should only be used.
I. Suspension roller bearing
In WAG-5 with Hitachi motor, axle suspension roller bearing have been used. In this arrangement, taper roller bearings are used on either end of the suspension tube. The maintenance of these bearings should be done as per approved Instructions. While overhauling, various defects due to stains, discolouration, spalling smearing, indentation, brinelling and electrical burns etc., should be examined. Proper precaution should be taken to ensure that bearings are overhauled in dust-free environment and all clearances should be maintained as given in the Maintenance Instructions.
Annexure 3.02 Dual Brake System on Electric Locomotives
WAG-5 and WAP-1 & 3 locomotives manufactured at CLW are fitted with twin pipe dual brake system. Railways have also converted some WAG-4 locomotive to twin pipe dual brake system. Dual brake system is designed for hauling stock equipped with either graduated release type single pipe or twin pipe air brakes or vacuum brakes.
The instructions contained herein are in supplement to GR and SR. Simple schematic diagram explaining the principle of operation of working of dual brake system, vacuum brake system and charging of main reservoir is attached as Annexure 3.02 A, 3.02 B, 3.01 C.
1. Description of the brake system
The main features of the system as fitted on these locos are-
1.1 Self lapping type independent brakes on the locomotive, i.e., the brakes on locos can be applied and released in steps with pressure maintaining feature in all positions.
1.2 Braking of air braked passenger/freight trailing stock and at the same time proportional brake application on locomotive through distributor valve.
1.3 Braking of air braked passenger/freight trailing stock fitted with graduted released type of brake equipment, and at the same time proportional brake application on locomotive through distributor valve.
1.4 Dynamic brake interlock to prevent simultaneously application of automatic air brakes and dynamic brakes on loco. Automatic brake application of brakes on loco and trailing stock in case of failure of dynamic brakes.
1.5 Multiple unit operations with locos fitted with similar type> of brake system.
1.6 In an emergency, brake pipe and vacuum train pipe can be directly vented simultaneously by the emergency brake valve provided in front of assistant driver's seat.
1.7. Loco brakes can be released independent of the train brakes.
1.8 Provision for freight/passenger change-over cocks to regulate locomotive air brake application timings depending upon the type of stock to be operated by locomotive.
1.9 Provision for the driver to apply independent brakes on leading loco in MU operation in case of parting between locomotives.
1.10 In case of very heavy leakage in the feed pipe or failure of feed pipe inter-coupling equipment, twin pipe brake system on trailing stock can be worked as single pipe system by simply isolating the feed pipe of trailing stock from locomotives.
1.11 Power cut off during emergency brake application.
1.12 Visual indication on driver's cab through air flow indicator device during train parting, alarm chain pulling or Guard's emergency brake valve operation or loco parting while hauling air braked stock.
1.13 Audio/visual indication in driver's cab to indicate the failure of D-24B feed valve which feeds air pressure for electrical controls.
2. Compressed air system . (Ref: SKDP-2350 Alt. 4)
2.1 Compressed air delivered by the motor driven compressors is stored in the main reservoirs after being cooled by after coolers. Three safety valves set at 11.5 kg/cm2 are provided to safeguard the compressors against build up of air pressure to a very high value, in case of failure of check valves. The compressors are controlled by electro-pneumatic governor to cut in at 3.5+0.1 kg./cm2 and cut out at 10±0.1 kg/cm2 pressure. One more safety valve set to blow off at 10.5±0.1 kg/cm2 is fitted between the second and the third main reservoir in case the pressure governor fails to operate.
2.2 Compressed air at reduced pressure of 8 kg/cm2 is stored in the control reservoir. This air is supplied for all electrical contactors. A pressure switch provided after the feed valve gives an audio visual indication through a buzzer and an indication lamp in each cab, in case pressure in the control reservoir falls below 6.0±0.1 kg/cm2 and cuts off the audio visual indication when the pressure rises to 6.0+0. 1 kg/cm2
2.3 In release position of the A-9 automatic brake valve, main reservoir air flows to the regulating portion of auto brake valve, where it is reduced to a predetermined pressure. The regulated air pressure flows through the auto brake valve to the C-2 relay valve to charge the air brake pipe. The air brake pipe pressure can be adjusted by adjusting the regulator of auto brake valve.
3. Independent brakes
3.1 Self-lapping SA-9 type independent air brake valve is provided in each cab for application and release of air brakes on locomotive. The leakage in the brake cylinder is automatically compensated and air pressure in the brake cylinders is automatically maintained between zero and maximum value depending upon brake valve handle position.
3.2 Isolating cocks are provided in the air supply and delivery pipes of the independent brake valve to isolate the defective or unused brake valve in the inoperative cab(s).
4. Vacuum system
4.1 Two exhausters, are provided to create vacuum in the vacuum system of the loco and the vaccum trains pipe (VTP) for operating vacuum braked trailing stock. Normally one exhauster is run to maintain vacuum in the system. Two exhausters can also be operated, if necessary.
4.2 Exhauster(s) create vacuum in the V.T.P. through VA-l-B control valve when A-9 (drivers automatic brake valve) is placed in "release" position. The vacuum in the V.T.P. is limited by two vaccum relief valves set at 60 cms max. with hose pipe on dummy. Exhausters are protected against ingress of dirt and dust by GD/80-H type oil bath filters. Leakage of atmospheric air through the idle exhauster is avoided by non-return valve. Vaccum relief values in the exhauster line protect the exhauster(s) against high vacuum when the VA-1-B control valve is the disconnected from train pipe during brake application. The desired vacuum in the VTP during release position is controlled by the HS-4 control air valve. In release position of the automatic brake valve A-9, VA-1-B control valve is actuated by the air brake pipe pressure and the. control valve piston is moved down to connect the the exhauster to the VTP.
5. Operation of brakes on trailing stock equipped with air brake equipment
5.1 In 'release' position of A-9 automatic brake valve, main reservoir air flows to the regulating portion of automatic brake valve at a pre-determined pressure, normally 5kg/cm2. The regulated air pressure flows through MU-2B valve to the C-2 relay valve. This control pressure actuates C-2 relay valve which in turn connects main reservoir to brake pipe and charges the brake pipe and the connected system to the same pressure level through out the train. Any leakage in the train system is automatically compensated by this relay valve.
5.2 When the brake valve handle is moved to minimum reduction position, reduction of pressure in brake pipe by 0.2 to 0.5 kg/cm2 (3 to 8 PSI) is achieved and proportional application of brakes on loco and trains takes place. In full service position of the automatic brake valve handle, the BP pressure is reduced to 3.5 kg/cm2.
5.3 The A-9 automatic brake valve handle when placed in emergency position, vents brake pipe pressure-at a very fast rate to atmosphere to initiate an emergency brake application. Regression of power also takes place due to the actuation of H-5 relay air valve. Reduction in pressure in the brake pipe actuates the distributor valve on the loco and trailing stock to apply brakes.
5.4 The C-3-W distributor valve provided in the brake circuit, is connected to the brake pipe and responds to the variations of pressure in the brake pipe. It applies proportionate brake application on locomotive when train brakes are applied either through Automatic or Emergency brake valve. The C-3-W distributor has a built in Goods/Passenger changeover cock to regulate brake cylinder pressure depending on whether it is hauling Passenger or freight train.
5.5 32 mm feed pipe through-out the train is charged from the first two main reservoirs, through duplex check valve and feed valve set at 6.0 ± 0.1 kg/cm2 and is used for filling auxiliary reservoirs of the trailing stock initially as well as after the air from these reservoirs has been consumed during braking. The main advantage of this additional pipe is to reduce the release and recharging time of the train after brake application.
6. Operation of brakes on trailing stock equipped with vacuum brake equipment
6.1 In release position of the automatic brake valve handle, the brake pipe is charged to 5.0 kg/cm2 and vacuum in vacuum train pipe is created through VA-l-B control valve. When the brake valve handle is moved from release position towards application position, the brake pipe pressure and vacuum in VTP is reduced and maintained to a value depending on the handle movement.
6.2 The reduction in brake pipe pressure operates the VA-1-B control valve to admit atmospheric air into the vacuum train pipe, to apply brakes on the vacuum braked trailing stock. During application, the exhauster connection with the vacuum train pipe is cut off by the VA-1-B control valve. After the desired degree of brake application has taken place, depending upon the extent of brake pipe pressure reduced the valve laps and maintains automatically the vacuum level against normal vacuum train pipe leakage.
6.3. When the driver feels that it is not necessary to apply brake on a loco, during automatic application the brake release pedal switch is pressed to release the loco brakes. The D-1 pilot air valve is energised to cut off automatic air brakes on the loco while train brakes remain applied on the trailing stock.
6.4 During train parting while hauling vacuum braked stock, the vacuum in the train pipe falls suddenly, with a drop of vacuum by about 10 to 15 cm an unbalance in the VA-1-B control valve is created allowing controlled air pressure to actuate HB-5 relay air valve to operate pressure switch through double check valve for regression of power.
7. The operation of emergency brake
Valve D-1 provided in each cab, near the assistant driver's seat, directly connects the vacuum train pipe and air brake pipe to atmosphere thereby applying brakes on loco and trailing stock at the quickest possible rate. The circuit for auto regression of the loco power due to the actuation of H-5 relay air valve is also automatically made. This relay valve also regresses power if the BP pressure drops due to any reason.
8. Dynamic brakes
8.1. D-1 pilot air valve cuts off loco brakes.
8.2. While controlling train with dynamic brakes, if the dynamic brakes fails, brakes on the loco and train will be applied automatically.
9. Air flow indicator
9.1. Air flow indicator, a relay valve, one pressure switch and two flow indicator gauges (one in each cab) have been provided to give an indication of the air flow rate in the brake pipe of the train. Any abnormal increase in air flow in the brake pipe because of train parting, loco parting, alarm chain pulling, heavy leakage in brake pipe, guard van valve application or bursting of air brake pipe hose would give visual indication to the driver by air flow gauge needle and by glowing of a bulb in the cab. On getting the indication driver should apply brakes through A-9 automatic brake valve/D-1 air/ vacuum emergency valve depending upon the condition of the train and the emergency.
1O. Multiple unit operation
10.1. When two or more locos are to be coupled together in multiple unit operation, the brake pipe, the feed pipe, vacuum train pipe ( if vacuum braked stock to be operated), the main reservoir equalising pipe and brake cylinder equalising pipe hoses must be coupled between the locos, and the respective angle cocks shall be opened.
10.2 The compressors and exhausters of the trailing locos would also be working during multiple operation. The automatic and independent brake valve handles in the trailing loco and on the unused cab of the leading loco shall be kept in 'Release' position and the isolating cocks provided near both brake valves should be closed.
10.3 MU-2-B valve provided to supply MR air to VA-1 release valve (B11) and F-1 selector valve should be kept in 'lead' in the leading loco and in 'Trail' position in the trailing locos. Isolating cock in the brake pipe charging line should be kept in lead position (open) in leading loco and trail position (close) in the trailing loco(s).
11. Gauges
There are five gauges in each driving cab. These gauges indicate BC, MR, FP, VTP, Air Flow, BP pressures to the driver. Apart from these, three single pressure gauges are provided. One single pressure gauge is fitted near the panto reservoir. The second gauge is provided in the brake pipe line to show the brake pipe pressure. One single pressure gauge is provided to indicate the pressure In the control side of the VA-1-B control valve, which is regulated by HS-4 control valve.
12. Genera
12.1 It should be noted that whenever the vacuum setting is done through the vacuum relief valve, this should be done by seeing the single vacuum gauge fitted in driver's cab.
12.2 The first two main reservoirs are provided with auto drain valve and the condensate is automatically drained off during the "cut out" and "cut-in" cycle of the compressor governor. All the other three main reservoirs are provided with manual drain cocks to drain off periodically the condensate collected in the reservoirs.
12.3 The main reservoir also supplies compressed air to auxiliaries such as wipers horns and sanders. The MR equalising pipe is charged from the main reservoirs through a duplex check valve set at 5.0±0.1 kg/crn2.
12.4 The main reservoir also supplies compressed air to electrical auxiliaries such as pantographs, tap changers, Board of gaduator etc At the time of initial energisation of loco or when there is insufficient pressure in pantograph reservoir to raise the pantograph, battery driven auxiliary compressor is operated to build up pressure in the pantograph reservoir and auxiliary circuit to energise the loco. The pantograph reservoir is protected against pressure leakage by a diaphragm operated cock. One safety valve to cut out at 8.5 t 0.1 kg/cm2has been provided to safeguard the baby compressor from excessive pressure.
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SWITCHGEAR INSPECTION AND TEST PROCEDURE PKR ELECTRICAL ENGINEERING CONFIDENTIAL TABLE OF CONTENTS 1) VISUAL INSPECTION 2) W...
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