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Trip schedule (under slung equipment) , Trip schedule (RMPU) , Monthly schedule , Quarterly schedule , POH schedule
AIR CONDITIONED COACHES
1. INTRODUCTION
Types of AC coaches on Railways can be classified broadly as under :
Power Supply System: As far as power supply system is concerned, the coaches are of the following two types :
(i) End-On-Generation (EOG) :
(ii) Self Generating (SG) :
In this system two types of Power cars are used
a. Coaches mounted with 50 KVA, 750 V/415V, 3 Phase transformer.
b. Coaches with out stepdown transformer suitable only for old low capacity power cars.
Based on AC equipment, there are two types of Self Generating coaches.
a. 110 V DC with under slung type AC equipment working from 110 V DC.
b. 110 V DC with Roof Mounted AC Package Units working from 415 V, 3phase obtained with the help of 25 KVA inverters mounted on underslung as well as onboard.
MAJOR EQUIPMENTS USED IN AC UNIT :
1. Compressor (open type for under slung, sealed type for Roof Mounted Package Unit (RMPU)
2. Condenser including liquid receiver and dehydrator.
3. Expansion Valve
4. Evaporator with heater element.
5. Motors for compressor, condenser, evaporator .
6. Other protective devices and control panels.
7. Thermostat, Filters etc.
2.MAINTENANCE SCHEDULES FOR SELF GENERATING AIR CONDITIONED COACHES
(Ref: RDSO’s maintenance schedule No EL/TLAC/Maint.Sched./Rev.1) Back
TRIP SCHEDULE (PRIMARY AND SECONDARY MAINTENANCE) For UNDER SLUNG EQUIPMENT
TRIP SCHEDULE (PRIMARY AND SECONDARY MAINTENANCE) For ROOF MOUNTED AC PACKAGE UNITS
i. Clean all dust from panel by dry compressor air from the panel.
ii. Check that all the safety and protection devices are in working condition and not in the by passed condition.
iii. Replace defective/by passed components including indication LEDs and lamps, if any.
iv. Remove fresh air and return air filters by opening the access doors provided under the bottom of unit. Clean these filters with pressurised air and jet of water and place them in their place or replace them with pre-cleaned/new-filter and close access doors properly.
v. Check the log sheet maintained for each AC coach and attend the defects noticed during run as reported by escorting staff.
vi. Check for working of Roof Mounted Package Unit (RMPU) and Control panel as following:.
a) Switch `ON’ RSW-I and check that all the three pilot indication lamps (Red, yellow and blue) for R.Y.B. phases and power `ON’ indication LED
(Green) are glowing.
b) Put RSW-2 in ``ON’ position and keep RSW-3 in `VENT’ position and check that:
1. Indication LED (green colour) for Blower `ON’ is glowing and Blower fan is working .
c) Check for satisfactory operation of vane relay by moving the flap by hand gently.
d) Check for satisfactory operation of the package unit by moving RSW-3, in AUTO, MANUAL HEATING & MANUAL COOLING modes. This
can also be verified from indication LEDs (green colour).
e) Check that cooling system is working even if only one condenser fan out of the two is working. This can be done by simply switching off MCB 2
or MCB 3/taking out fuses of condenser motor 1 or condenser motor 2.
f) Check that cooling and heating thermostats works properly, i.e. A/C system “cut-off” and “cut-in’ in auto-mode.
g) Check that compressor by pass switch RSW-5 works satisfactorily
h) HP1 & HP2 Cut-outs
Switch ‘ON’ the compressor with condenser fan ‘OFF’. Take out fuses /switch-off MCB-1 and MCB-3 of the condenser fan motors and keep the package in manual cooling mode. Compressor should trip within 10 minutes. HP cut outs should be reset after each tripping.
i) LP-1 & LP-2 Cut outs
Switch `ON’ the compressor with condenser. Take out fuses/switchoff MCB-1 provided in the power circuit of blower motor and short terminals of vane relay. Keep the package in manual cooling mode. Compressor should trip with 10 minutes.
j) OHP1 and OHP2
Switch ‘ON’ the heaters with blower off, take out blower motor fuses or put off MCB-I and short the terminals of contactors AC-I or vane Relay. In old control panels where AC-I is not provided, keep the package in manual heating mode. The heaters should trip with 10 minutes.
k) CONTROL PCB
Keep the AC package unit in Auto Mode. Run the blower short terminals of cooling thermostat on PCB. The compressor LED indication should come ‘ON’. Open the terminals of heating thermostat on PCB Heater LED should come `ON’.
i. Run the plant for half an hour and check the current drawn by various equipment with the help of clamp tester. Normal currents for various equipment and mode of operation shall be as under:-
a) Package in cooling mode : 20-23 Amp.
b) Package in heating mode : 11-13 Amp.
c) Compressor motors : 7-10 Amp.
d) Condenser motors : 1.5-2 Amp.
e) Blower Motor : 1.5-2.5 Amp.
Check working of both Roof Mounted Package Unit (RMPUs) with either of the inverter on.
ii. Check and tighten all terminals in the control panel.
iii. Check and clean contacts of contactors and replace pitted contacts if required.
iv. Check visually condenser fan blades and ensure there is no crack on the blades or the hubs.
v. Check and tighten mountings of blower and condenser motors and ensure that these are in good conditions.
vi. Check that all legend plates inside the control are intact.
vii. Check all connections on switch gears, terminal blocks are tight.
viii. Check that glass cover over indication PCB is intact.
ix. Check for proper tightening of cover provided over evaporators compartments.
x. Create single phasing in compressor circuits by taking out one fuse/removing one phase wire from incoming terminals of MCB-4/MCB-5.
Compressors should trip and CP1/CP2 over load trip indication should come ``ON’.
xi. Check for proper operation of time delay relays provided in compressor circuit. As soon as power supply is switched `ON’ first compressor should come in circuit immediately and the second one after 2.5 minutes.
xii. Inverter
Caution: Inverter must be switched off preferably at power panel itself before attempting to do any maintenance operation.
a) Cleaning of cubuicle : Dust deposit inside the converter should be carefully removed at regular basis. Unit should be cleaned with brush and vacuum cleaner or with dry compressor (Max. 1bar) – inaccessible parts.
b) Cleaning of PCBs : Using a soft brush, remove the dust collected on PCBs gentle.
4. QUARTERLY SCHEDULE
In addition to Trip and Monthly Schedule items, following are also to be attended.
UNDER SLUNG EQUIPMENT
i. Axle Pulley
ROOF MOUNTED AC PACKAGE UNITS
i. Inverter
Caution: inverter must be switched off preferably at power panel itself before attempting to do any maintenance operation.
a) Cleaning of cubicle :
a)Check grooves for wear and take necessary action.
ii. Alternator
a) Disconnect the regulator and measure the insulation by 500 V megger; if less than 2 Meg ohm, remove winding of alternator and heat in the oven at 80 degrees C for 1 hour.
Dust deposit inside the converter should be carefully removed at regular basis. Unit should be cleaned with brush and vacuum cleaner or with dry compressor (Max. 1 bar) – inaccessible parts.
iii. Compressor, Condensor And Evaporator Motors
b) Cleaning of PCBs :
a) Disconnect the motors, measure the insulation by 500 V megger; if less than 2 Meg ohms, remove and heat in air oven at 80° C for 1hour.
b) Check for the positive locking of rockers.
c) Lubricate the bearings of all motors with recommended grease.
Using a soft brush, remove the dust collected on PCBs gently.
c) Terminal Connections/Fixing :
d) Electrical -
iv. Condenser
1.Normally loose connections leading to wire burning/sparking are observed at connection terminals.Usage of spring washer mostly avoids this problem.
2. Gently shake the wire (especially power cables) near the joints and on observation of loose joints, tighten the same and also observe cable insulation for any deformation/brittleness. If so replace them with same size of the cable only.
a) Clean the compressor fins and copper tubes as per RDSO
SMI No. RDSO/SMI/AC/16
b)Check the condition of body frame and replace the condenser, if necessary.
e) Mechanical -
v. Dehydrator and Liquid Receiver
Inverter should be fixed at the bottom as well as top, tighten the bolts and nuts used for fixing the inverter and ensure that it does not vibrate in run. Also tighten the sub-assemblies if found loosened. In case of underslung inverter these shall also be regularly checked and tightened.
a) Clean the strainer in the dehydrator-cum-filter unit.
e) Protection circuit/ Indication circuit :
vi. Evaporator And Expansion Valve
1. Check the indication/ protection circuits ensure that all the protection and indication are working properly.
2 Uses of fuse of power rating in the inverter, don,t use wire fuses.
3 Remove both inverter and battery fuses in power panel before attempting
some fitting or wiring in the inverter.
a) Clean the strainer used before expansion valve.
b) Clean the assembly of evaporator coil and surroundings with vacuum cleaner.
c) Clean the drip tray and drain-pipe thoroughly and check for water leakages.
f) Capacitor -
vii. General
On observing leakage of any capacitor inside the inverter remove the respective capacitor and replace with new one of the same value and make.
a) Adjust the air distribution by measuring the temperature of each compartment.
g) Cooling Fan –
Check the cooling fan for operation. If damaged/burnt replace with new one of the same rating. Life of fan is about 3 years, replace, if due.
h) Instrument cooling fans-
Check if the instrument fan provided between inverter and chopper modules is working when the inverter is “ON”. If not working replace the fan, by taking out chopper and inverter modules. (in on-board type inverter).
i) PCB Terminal –
Gently tap the wires at PCB terminals and check for any loose connection. Tighten the screw or solder the terminals if found blackened, informed the inverter supplier.
j) Colour change in PCBs –
Check for any colour change in PCBs. Replace the PCB, if found blackened and inform the inverter supplier.
k) MCCB –
When MCCB is switched “ON” MCCB is tripping and fuse is blowing instantaneously, it is due to IGBT problems. They have to be checked and replaced, if they are found defective.
iv. NOTE :
ii. Drip Tray
a) SKF/FAG (imported) makebearings for alternator procured directly from manufacturers asspecified in the RDSO specification shall be used. Use of other makes of bearing is not permitted.
b) Shock pulse meter shall be procured by Railways and workshops to monitor condition of the bearing regularly during maintenance service and after replacement of defective bearings.
c) Induction heater/oil bath shall be used for heating the bearing to the required recommended temperature.
d) The pulley condition such as wear on V group, pulley key way, shaft key way, groove angle etc. shall be monitored during POH. Proper gauges shall be used for checking
“V” groove of the pulley.
a) Check the normal flow of water in drip tray by running the AC plant continuously for 2 to 3 hours.
b) Pour water into drip tray and ensure that the poured water is drained through the outlet pipe.
c) Some sort of cleaning agent should be used for cleaning the sludge inside the pipe walls.
iii. Others
a) Check all the motors for abnormal sound use shock pulse meter and replace the bearing of condenser and blower motor, if necessary.
b) Check anti-vibration mountings of compressor, condenser and blower motors and replace if necessary.
c) Charge refrigerant (R-22) if less cooling is noticed.(refer RDSO SMI No. RDSO/AC/SMI/7
d) Check that locking arrangement of control panel works properly.
e) Check insulation resistance of all the motor by 1000 V megger.Attend motors with poor insulated less than 2 Mega-ohm.
POH SCHEDULES OF UNDER SLUNG Self Generating (SG) TYPE AIR CONDITIONED COACHES
(Ref : RDSO doc. No. EL/AC/POH Schedule/002, Nov.,93)
SEQUENCE OF WORK TO BE DONE DURING POH
On arrival into shop place the coach on pit line and inspect electrical and A/C equipment. Note down the defects and deficiencies. Disengage the `V' belt
tensioning gear on both the bogies. Disconnect the alternator connection, and remove the belt-tensioning device.
i. Lifting
ii. Stripping
During this activity, the following airconditioning and electrical equipment will be removed:
Remove the alternator cables and carry out visual inspection on conduit and refrigeration pipes. Remove the alternators from bogies. Replace alternator, regulator and tensioning gears with over hauled alternator, regulator and tensioning gear. During this activity carry out repairs, if required, to equipment suspension arrangement on under carriage. Send the alternators and regulators to shop for overhauling.
a) Fresh air and return air filter
b) Compressors and their motors
c) Condenser including liquid receiver cum dehydrator and condenser motors
d) Evaporator unit and its motor
e) Water raising apparatus
f) Battery and battery box for repairs.
g) Battery charger-cum-pre-cooling transformer
h) Thermostats
i) Control p anel
j) Expansion valve
k) Gauges and cutouts
l) Carriage fans
m) Berth light fittings
n) Ammeters and voltmeters of power panel
iii. Dusting
With the help of compressed air
remove the dust of air ducts.
iv. Cleaning and overhauling
Before overhauling, measure the insulation resistance of all the electrical equipment such as alternator, motor and wiring to know the condition of equipment. Check and clean all the under frame suspension arrangements, lugs and terminals. After POH, test the wiring for insulation and fit the pre-cooling plugs.
v. Simulation testing
Check the alternator output on different load conditions. Check both the alternators for load sharing with the help of variable speed motors.
vi. Equipping
vii. Static testing
In this activity fit all the refrigeration and electrical equipment to their respective positions. Connect all the wiring and flanges in the refrigeration system wherever necessary. Charge the gas into the system.
.
Run the plant through pre-cooling terminal and check for proper functioning of electrical and AC equipment.
viii. Alternator Connection and Tensioning
Join the connections of alternators and fit the belt-tensioning device.
Provide the new 6+6 `V' belts for alternators
OVERHAULING ACTIVITIES OF MAJOR AC EQUIPMENTS DURING POH
POH SCHEDULE FOR SELF GENERATING (SG) TYPE AC COACHES FITTED WITH ROOF MOUNTED AC PACKAGE UNIT
(Ref. : RDSO maintenance schedule No. ELPS/SCH/AC/01 )
SEQUENCE OF WORK TO BE TACKLED DURING POH
OVERHAULING ACTIVITIES OF MAJOR AC EQUIPMENTS
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