Point Machine For Railway Signaling

1

TEACHING NOTES

ON

POINT MACHINE

SIGNAL & TELECOMMUNICATION TRAINING CENTRE, BYCULLA, MUMBAI ( I S O 9001-2000 CERTIFIED )

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CONTENTS

PAGE NO.

1. Requirements of Point Machine

03

2. Classifications

03

3. Sequence of operations

04

4. Point mechanism

05

5. Ground connections

06

6. Installations

07

7. Precautions while working on points

08

8. Maintenance

11

9. Measuring voltage and current

12

10. Testing of: a) Friction clutch

13

b) Obstruction test

13

11. Do’s and Don’ts

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12. Essential requirements before interlocking

15

13. Siemens point

16

14. Crank handle

17

15. Trouble shooting

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3 Electric Point Machine is an electrically driven machine used for the operation of points in Railway yards and comprises of an electric motor, point mechanism and circuit control device. REQUIREMTNTS OF POINT MACHINE a. The switch operating mechanism must be of substantial design, securely fixed and protected from unauthorized interference. b. The mechanism must be provided with means for emergency operation in the event of failure. c. The use of the crank or other apparatus for emergency operation, should disconnect the power supply to the motor. d. With the exception of motor commutators, a surface leakage of not less than 6mm should be provided between any exposed metallic part carrying current and any other metallic part of the mechanism. e.The mechanism should be so constructed that it can not give a “normal “ or “reverse” indication, unless the closed switch be within 5mm of the stock rail and in the case of facing point, the switch are properly locked. f.The mechanism should be so constructed that it can be stopped, reversed or obstructed at any point of its movement without damage. g.In order to prevent the movement of points while train is passing over them, facing points should be provided with a lock bar, or alternatively with track circuit locking to the point lock lever or ground track lock. h.Where the movements of trains over the points are not within easy visibility of the cabin man, occupation of the section between the stop signals reading over the points and the fouling point ahead of such points should be electrically indicated in the cabin. POINT MACHINE ARE CALSSIFIED AS FOLLOWING IN REGARD TO: i.

FIELD ARRANGEMENT a. Single field type machine (GRS 5A – Nippon) b. Split field type machine (GRS 5E, IRS Type (Podanur) M-63, Siemens)

4 ii.

VOLTAGE a. High voltage type (110 VDC) working current at 3 Amps. b. Low voltage type (24v, 36v) working current (6A/4.5A)

iii. SPEED a. High speed machine – 3 seconds. b. Low speed machine – 5 seconds. iv. LOCKING a. In and Out type (FPL Type) – GRS 5A, 5E & Nippon b. Straight through type (SLM Type) – M – 63 c. Rotary type (Siemens) SEPARATE TYPE AND COMBINED TYPE SEPARATE TYPE:

This type enables a pair of points to be operated, while retaining the point equipment to mechanically operated points. These two sets of drives, one for switch and other for lock operating are independently brought out. As the machine is not provided with point lock, separate point locking arrangement is to be provided.

It also requires a separate

detector. COMBINED TYPE:

This type is so called because the machine is complete with point lock and detector. Point machines other than Podanur type are combined types. MOTOR: The type of motor used in point machine is a D.C. series motor; since its initial starting torque is high. SEQUENCE OF OPERATION OF POINT MACHINE 1. Opening of the detection contacts. 2. Unlocking of point 3. Operation of point from ‘N’ to ‘R’ or ‘R’ to ‘N’ 4. Locking of the point 5. Closing of detection contact.

5 POINT MECHANISM: This consists of a friction clutch, reduction gears. Cams and bars used for converting the rotary movement to linear movement. For the operation of switch and lock the main gear wheel in the mechanism revolves less than one revolution. FRICTION CLUTCH: The point motor and the driving gear assembly are not rigidly connected together but through a friction clutch. Whenever the load on the motor shaft increases beyond a limit, the friction clutch declutches the motor from the gear assembly and prevents them from damage. The friction clutch declutches the motor from the mechanism. 1. After the point has been completely set and locked and point supply has been cut off when the motor rotates due to momentum 2. Whenever there is an obstruction in point. 3. During mid stroke reversal, in which case the motor changes its direction suddenly before the gear. The friction clutch is an adjustable one. It should be adjusted in such a way that it trips when the motor current reaches the 160% the normal working current. It is adjusted by trail and error method. The clutch should be tested at regular intervals of 2 to 3 months. SNUBBING: The snubbing arrangements so provided in addition to the friction clutch are to minimize the shock of mechanism while stopping at the end of operation. After the point is set and locked, the control contacts (NC/RC) cuts off the supply to the motor. But the momentum of the motor will keep it rotating. Due to residual magnetism in field because of rotation of motor, a voltage is induced. This voltage & thus the current are in opposite direction of early rotation and thus bring the motor to a smooth stop. The presence of friction clutch between the point motor and mechanism ensures that undue strain on motor does not take place.

6 In addition to this, to provide a smooth stopping, an electrical circuit known as “snubbing circuit” is provided, the kinetic energy of the motor is dissipated (i.e.) when the armature rotates due to momentum after the supply cut off, an EMF is induced in it due to residual magnetism in field magnet. This emf is dissipated through the field armature and the circuit employed for the purpose, which develops an opposite torque on the armature and brings the motor to a smooth stop. Snubbing circuits are provided through: (1) Snubbing relays (2) Directional contacts and (3) Rectifiers. Snubbing is achieved mechanically in siemens machine by the friction clutch itself. NC/RC CONTACTS: These contacts 1. Cut off the feed to the motor when the motor is set & locked. 2. Keeps the motor circuits ready for next operation. 3. Facilitates mid stroke reversal. POINT POSITION

NC

RC

ND

RD

1. Pt. set & lock in “Normal”

Break

Make

MAKE

BREAK

in Make

Break

BREAK

MAKE

Make

Make

BREAK

BREAK

2.

Pt.

set

&

Lock

“Reverse” 3. Pt. un locked

GROUND CONNECTIONS The point fittings (ground connections) comprises of following. 1. Switch extension bracket on ‘D’ plate

2Nos.

2. Lug

1 No.

3. Throw rod along with adjustable sleeve and nuts

1 No.

4. Lock rod (short and long)

2 Nos. (one each)

5. Detector rod (small and big)

2 Nos. (one each)

7 Suitable lugs are also required for connecting the point fitting with the drive rod, lock rods and the detector rods of the machine along with insulator. INSTALLATION AND ADJUSTMENT OF POINT MACHINE 1. Install the machine as per standard layout distance between machine centre and inner gauge face shall not be less than 950mm. In case of raised point machines the distance shall not be less than 1050mm. 2. Hand crank the machine to centre position. 3. Keep the switch rails in mid position. 4. Connect the throw rod between the gear rack and the lug of the driving rod. 5. Hand crank the machine to & fro and adjust the switch rails for proper setting with stock rails on both sides. 6. Check the spring on the points in both position it should be equal on either side. 7. Connect the detector slides and adjust them such that the roller falls inside the groove only when point is fully set and the control disc completes its rotation (i.e. point is fully locked). Test that the groove does not receive the rollers when a 3.25mm obstruction is placed at 150mm from the toe of the switch. Tighten the nuts and check nuts after adjustment. 8. Connect the split lock stretcher bars to the lock rod. And adjust them through their serrated faces and bolt screws such that the locking segment can enter the notches only when the point is correctly set. Ensure that the notches are not available to receive the locking segment when 3.25mm obstruction is placed at 150mm from the toe of the switch. 9. Operate the machine several times to see that the locking notches of the stretcher bar and gear rack. 10. Make the electrical connection for point control and detection circuits. Operate the machine several times and ensure that detection contacts make only at the end of locking operation and the control contacts make with the beginning of unlocking stroke.

8 11. Operate the machine by power note the working current by connecting an ammeter in series with CW terminal (2.5Amp. to 3Amp.) 12. Check the correspondence between the points and point controlling lever/group 13. Carry out contact break test in operation and detection circuits. 14. Check the correct functioning of friction clutch. The friction clutch must trip when motor current reaches 160% of normal working current but not more than 200%. 15. Carryout obstruction test with 5mm, 3.25mm and1.6mm test piece. 16. Centre of 1st sleeper to centre of second sleeper should be 685mm. 17. Inner edge rail to centre of machine Machine on sleeper 950mm Machine raises 1050mm. Main parts of IRS rotary type point machine. 1. Motor with reduction gearbox. 2. Transmission assembly 3. Switching unit / control unit 4. Throw bar or driving slide 5. Independent lock slide 6. Detector slide 7. Crank handle contact 8. Cover lock. Whenever point is failed or when the maintenance work is to be carried out under disconnection point should be clamped. PRECAUTION WHILE WORKING ON POINT MACHINE CLAMPING WHEN AND HOW:

How? Procedure of working of trains during failure of electrically operated points of cross over. 1. On receipt of information about the failure of the point S&T staff will try to ascertain the nature of fault and put right the failure.

9 2. If the S&T staff anticipate that the rectification of the failure is likely to take a long time they will inform the operating staff in writing on a disconnection memo to initiate action as under. 3. On receipt of such a written information from the S&T staff on a disconnection memo, the ASM/CASM will ensure the correct setting on the affected point to the Normal position and will the clamp and padlock both ends of cross over in normal position. ASM/CASM will under no circumstances remove the clamp in the normal setting, unless and until he receives the memo from the S&T staff that temporary modification have been removed and the condition in para 12 are complied with. 4. After so clamping and padlocking the point the ASM/CASM will advise the S&T staff in writing stating that “single” ended point / both ends of cross over point No.

have been

clamped and padlocked in the normal position and the necessary temporary modification to the installation may please be made ”S&T staff will then carry out the temporary modification as given in para 5 below. 5. S&T staff of not below the rank of a sectional engineer, on receipt of such a written advise from ASM/CASM as per para 4 above will carry out temporary modification the installation so that point steady “NORMAL” indication is available on the panel, by making NORMAL detection available and restricting the clearance of signal reading over the said point (unchanging overlap) to yellow aspect only. 6. After carrying out the temporary modification the S&T staff shall advise ASM/CASM in writing that temporary modification with respect to point No.

have been carried out and clearance of_______ signal Nos.

_______and _______ have been restricted to yellow aspect only. 7. On receipt of the advise as per para 6 above, ASM/CASM will arrange for issue of caution order to the train for observing 15km on the route

10 of concerned signal. This may require advising the ASM/CASM of the adjacent stations. 8. ASM/CASM shall arrange for posting suitable operating staff not below the rank of a guard near the affected point for the purpose of monitoring the condition of clamps and the point after every movement. The staff deputed to monitor the point should be equipped with telephone communication with CASM, HS lamps and flags (red and green), fuses, detonators and shall arrange for protection of train in case the condition of affected point or clamps on it warrants the same. In such a condition he shall also advise the ASM/CASM on phone to restore the concerned signal to ‘ON’ position and retain from taking them to “OFF” for any subsequent move till the condition of the point and clamps is set right. 9. After ensuring that caution orders are being issued ASM/CASM shall allow the first train on the affected line and over the affected point to pass “ON” ‘A’ marker in the semi automatic territory and on the calling on signal or relevant authority in non-automatic section. 10. ASM/CASM shall pass the subsequent train by taking “OFF” signals after setting route in the normal manner, however, due to temporary modification made by the S&T staff, the concerned signal will work as free signals and will clear to yellow aspect only. 11.a.

After the defect is rectified, the Sectional Engineer in consultation

with CASM will remove the temporary modification done as per para 5 and will give a memo to CASM stating work with respect to point no. over No.

cross

has been completed and temporary modification have been

removed and the point is ready for testing. b. Before acknowledging a memo ASM/CASM will ensue none of the route section once the affected point is set and the signals controlling the movement over it are at ON position and the track are clear. This is for ensuring that no train passes over the affected point during the testing.

11 12. After the point is fully tested the sectional engineers will give re connection memo indicating in a written declaration that till the temporary modification to the installation have been deleted and the installation is made fully normal with respect to point no. ______ 13. ASM/CASM on receipt of re-connection memo can resume normal working over the affected point under advise to SCOR MAINTENANCE Lubricate thoroughly all-internal and external parts. Lubricating oil specification (a) For internal: SAE 30 or shell 100 (b) For external: IS 1628 Grease specification: all templ grease IS 507/508 SCHEDULE OF LUBRICATION 1. After 10,000 operations or 6 months which ever is earlier apply: a.20grease gun stokes through each nipple of transmission clutch (2 nipples) b.4 grease gun stokes through each nipple of contact assembly ( 2 nipples) c. 4 grease gun strokes through each nipple of bearings of throw bar, locking bar and detection slides (4 nipples) d. 400 cc of SAF 30 or shell 100 oil through the oil hole of reduction gear assembly. 2.During regular maintenance a. Pour 100cc of SAE 30 or shell100 oil per pill filler opening on lubricating pads over the throw bar and locking bar. b. Apply, 10 drops of spindle oil (3 in one) over the helical spring, which actuates the contacts. c. Apply lubricating oil IS 1628 over external moving parts.

12 During maintenance round check the following: 1. All nuts and bolts are tight. 2. All pins are tight. 3. All split pins are opened correctly. 4. All the wires inside the machine are bunched (No loose wire) and electrical connections are tight 5. Commutator is clean and bright. 6. Carbon brushes of the motor have sufficient pressure 7. All parts are clean and moving parts are well lubricated. 8. Ensure that gear transmission works smoothly without any crackling sound when machine is operated by power 9. Brass strip between the detection slides is intact 10. The rollers moving over the frication clutch are not worn out and moving freely. 11. Locking segment moves freely inside the notches on throw bar and locking bar with an obstruction of 1/16” (1.6mm) and gets obstructed with an obstruction of 1/8”(3.25”) placed at 150mm from toe of switch between stock and switch rails. 12. Check that spring contact close with fixed contacts with sufficient contact pressure. The springs are not loose and shaky. MEASUREMENT OF VOLTAGE AND CURRENT OF POINT MACHINE: 1. Voltage is taken on motor terminal 2. Voltage is taken on terminal no. 0 and1 and terminal no.0 and 2, one for normal another for reverse. 3. Obstruction voltage by putting 5mm test piece between stock and tongue rail is also taken and recorded as above. 4. Current is taken in series by inserting and turning CH key and measuring current in between CH1 and CH2 and recorded as: a. INITIAL CURRENT or peak current. b. Normal working current c. Obstruction current.

13 These parameters are taken every 3 months and record maintained in respective register. TESTING OF FRICTION CLUTCH AT SITE AND ITS ADJUSTMENT: 1. Place an obstruction test piece between closed switch and stock rail. 2. Connect an ammeter in series with the motor feed. 3. Shunt operating winding of the over load relay if provided. 4. Operate the point against the obstruction. 5. Read the motor current as the clutch slips. 6. Remove the shunt of the over load relay after the test. 7. Remove the armature from the motor feed. 8. Adjust the clutch at a desire current 1.5 to 2.0 times of the normal operation current). Friction clutch adjustment:

If adjustment is required at site,

transmission assembly should be disconnected and motor and contract unit dismantled. After dismantling transmission assembly tighten the hexagonal bolt. Friction clutch becomes stronger and obstruction current increases. Loosen the hexagonal bolt, friction clutch becomes weaker and obstruction current decreases. Now re-assemble friction clutch, contact unit and motor and test. OBSTRUCITON TEST AND ADJUSTMENT OF LOCK AND DETECTORS a. Hand crank the machine to the centre point. b. Keep the switch rails in the centre position. c. Hand crank the machine to and fro and adjust the driving rod for proper setting of switch rail with stock rail on both sides. d. Check the spring of points in both positions. It should be equal on either side or make it equal by adjusting nuts near the sleeve tighten the nut to ward lug increase the spring loosing the nut from lug decrease the spring. e. Connect the detector slide and adjust them in such a way that the roller falls inside the notch only when the point is set and

14 locked. Test that the notch does not receive the roller when 3.25mm obstruction is placed 150mm from the toe of switch. f. Connect the lock slide to lock rod and adjust them by loosening/ tightening of nuts of slides such that the locking pawl can enter the notch only when the point is correctly set. Ensure that the notches are not available to recover the locking pawl when 3.25mm obstruction is placed at 150mm from the toe of switch. g. Operate the machine several times to see that the locking pawl goes. Smoothly inside the locking notches of the lock slides and driving slide.

DO’S 1.Disconnect the point machine before carrying out obstructions. 2.Keep out you tools in proper working place 3.Watch always for unusual noise while machine is under operation. 4.Always use proper lubricant wipe out any excess in oil and grease. 5.Ensure schedule of maintenance 6.Test the working of friction clutch 7.Check effectiveness of CH contact. 8.Ensure tack-locking correspondence of point with lever/group 9.Use proper rating of fuse

DON’TS 1. Forget to exercise safety checks during and after disconnection 2. Forget to carry necessary tools while attending failure. 3. Leave any discrepancies noticed in the point machine. 4. Use too much lubricant. 5. Allow grease/oil to drop or collect over electrical conductor contact. 6. Leave the transmission assembly to continue if obstruction and operating current are equal. 7. Allow concerned CH to remain in CH box while working on point 8. Forget to check proper working of lever lock if provided 9. Loose connection of fuse.

15 ESSENTIAL REQUIREMENTS BEFORE INTERLOCKING Before the interlocking work at point is put in hand, it must be ensured that the permanent way inspector has 1. Brought track to correct level and alignment. 2. Rail Joints are closed to fix lock bar and are associated with lock bar. 3. Fully ballasted and packed all points which are to be interlocked and taken adequate measures to prevent lateral and longitudinal movement of points. 4. Provided creep and level pillars. 5. Arranged the sleepers on adjacent tracks in alignment where rods and wires have to cross. 6. Seen that the gauge is correct. 7. Provided and fixed special timbers as required. 8. Provided means to prevent creep in the vicinity of points. 9. Fitted gauge tie plates correctly. 10. Made the stretchers to115mm at the toe of B.G. and 100mm at the toe of M.G. and N.G. points. 11. Adjusted loose heel switches so that: a. They can be thrown both ways with ease and can be housed against the stock rail by hand and remain there when the pressure is removed. b. The planed surface of the switch rail fully houses against the stock rail for a sufficient length. 12. Adjusted fixed heel switches so that: a. They normally lie in the mid-position and flex equally in the normal and reverse position b. The planned surface of the switch rails fully housed against the stock rails. 13. Fitted flexible stretches so that they flex equally in the normal and reverse position. 14. Provided a stop for the open position of single switch layout.

16 SIEMENS POINT MACHINE This machine consist of a cast iron housing with lockable sheet steel cover which contains: 1. A 110v DC split field series wound motor with normal operating current is 2.5 to 3 amps. 2. Reduction gear assembly, reduction gear up to 2nd stage is housed along with motor in one sealed unit. 3. Rack and pinion arrangement for converting rotary motion into linear motion. The stroke for the toothed rack (Throw bar) is 143mm. 4. A locking rod (split lock stretcher) with locking curves (notches). The main and auxiliary stretcher blades are provided with serrations for adjustment. 5. Rotary type locking is effected when the locking segment engages in the locking curves of the operating and locking rods. 6. 2 numbers of point detector slides. 7. Switch detection units, which consist of control and detection contacts. It is a spring-loaded unit with two rollers and crank. The position of contacts at different position of the point is as follows: Position of point

NC

RC

1.Set and locked in ‘N’ Break Make 2.Set and locked in ‘R’ Make Make

3.Unlocked

ND

RD

Make

Break

Break Break Make Make

Break Break

8. Friction clutch, to protect the motor in case of any obstruction in the point and also it take care of stopping the machine smoothly at the end of operation. 9. Crank handle key box with cut-off contacts.

The crank handle cut-off

contact gets disconnected as soon as the key is inserted and tuned and simultaneously gives access to the crank handle to engage with the motor shaft for operation.

The disconnected contact prevents motor from

electrical operations during crank handling and safety is assured. 10. Cable termination block.

17 SPECIAL FEATURES 1. Locking is rotary type. 2. The detection and controlling contacts are of self-wiping type. 3. Crank handle cut off contact is achieved by key and not by crank handle. 4. Crank handle has to be inserted to the motor shaft. 5. Felt pad is provided on the throw bar and detection slide for self clearing and lubricating. 6. Rubber liners are provided outside the hole provided for detection slides, throw bar and stretcher bar to make the machine dust proof. 7. The main and auxiliary stretcher blades are provided with serrations for adjustment. 8. The detector slides are provided with a brass liner in between to avoid sticky movement of slide during breakage of detector rod. 9. Less maintenance since parts are easily accessible, replacement is easy. CRANK HANDLE: During the failure of motor, point etc. due to power supply or for maintenance work, facility must be provided for locally operating the points manually. For this purpose crank handles are provided. The crank handle is inserted in the point machine and by rotating the handle drive is imparted to the point. For ensuring safety to the persons using the crank handle against a sudden operation by electric power, the crank handle whenever inserted isolates the power supply to the point machine through a contact known as crank handle contact. The crank handle and the key for uncovering the flap (which is required to be uncovered for inserting the crank handle) are kept under the custody of SM in a box which is kept and pad locked by SM and sealed by S&T staff.

18 CRANK HANDLE KEY INTERLOCKING PROVIDED IN LATEST INSTALLATIONS Normally the key used for uncovering the flap for inserting the crank handle in the point machine is common (i.e. Master Key). In this, there is a possibility of crank handling a wrong point. To avoid this, an interlocking is provided as explained below: The points in the yard are divided into groups and each group is provided with an independent key. The wards of keys of each group are different. The keys are kept locked in separate key locked relays housed in a glass fronted wooden box in the panel room/location box. The key locked relay box is kept pad locked by operating staff and sealed by S&T staff. The crank handle key can be extracted from the relay only after getting the slot from panel, and once the control on crank handle key has been released from the panel, the corresponding routes and signals cannot be initiated. The crank handle key obtained can be used only for uncovering the flap of the point machine pertaining to the relevant group of point and thus crank handling of wrong point is avoided. After the completion of work, the key is put back into the key interlocked relay and control is resumed back to the panel. Once the control is returned to the panel, the signals and routes can be initiated.

19 TROUBLE SHOOTING POINT FAILURE:

Failure: Point starts flashing automatically in normal / reverse SI/ESM is available in the cabin. Go to relay room and observe the point group. Remove B60 fuse of that point group and reinsert

Is WKR2 picked up

Has WKR2 dropped and WKR1 picked up

Investigate the cause of picking up of WKR2

1. Replace B60 fuse by a new one if not ok. 2. Observe WKR1

Test the cable and Isolate the fault

Has WKR1 picked up

Investigate the cause of blowing of B60 fuse

Disconnect K-Rack links and check continuity on the field side between N110-Rw andNw-N60 with point normal and between N110-Nw and Rw-N60 with point reverse

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Check the following and rectify if faulty. 1. Crank handle switch and wiring 2. Motor terminal wiring. 3. NC/RC contacts. 4. Carbon brushes. 5. Disconnecting links in JB/LB.

Is continuity between N110Rw or N110 Nw ok? Is continuity between N60Nw or N60-Rw ok? Replace the point group by a spare one and operate the point

Investigate the fault in the point group

Check the following rectify if faulty. 1. Check detection contacts 2. Disconnecting links in JB/LB

Has indication become ok? 1. Check wiring on base plate bus bar 2. Check for dry solder on TAG-Block

Point operated from ‘N’ to ‘R’ or ‘R’ to ‘N’ But fails to respond in either position SI/ESM available in the cabin

Direct ESM/Khalasi to check physically the point machine and switches for any obstruction and remove if any

21

Check whether 110v DC supply is available or not

Is power supply monitoring panel available

Is supply available

Check 1. Output of 110v DC rectifier if not ok change over to stand by

Has WKR1 picked up

Investigate the cause of failure

Is the ammeter available on the panel

Operate another unimportant point if possible

Does that point also start flashing in both position

Check 1. Output of 110v DC rectifier. If not ok change over to standby 2. 110v bus bar fuse in L.T. panel or 3. B110 fuse of both the affected points Operate the point Does indicator become steady

1. 2. 3. Go to relay room 4. and replace the 5. point group & test 6. the point

DO THE FOLLOWING Megger main & tail cable Check detector & control contacts Wiring & motor termination Crank handle contacts Carbon brushes. Intermediate location lines.

Operate the point & see the deflection Does the meter show deflection Keep the point group in correspondence with the point position. Remove B60 fuse & insert Does WKR1 Pick up Investigate the cause of failures of blowing of fuse

Investigate the cause of failures

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TROUBLE SHOOTING SIEMENS POINTS FAILURE SIEMEN’S POINT FAILURE Failure: A point starts flashing automatically in normal (reverse) SI/ESM available in the field. Check 60v D.C. voltage between N110-NW at the 1st end motor if point is normal or between terminal in N110-RW at the second end motor if point is reverse.

Check voltage between N110&N60

Is voltage available

Is the voltage available

Check detection contacts & wiring of machine (s)

Is voltage available

Isolate the tail cable fault

Indicates that detection contacts are O.K.

Go to relay room & observe point group

Check voltage between NW-RW Is voltage available This indicates that no fault on the field

Check for any disconnection in intermediate location by measuring the voltage on the m/c side

Go to page No.1 of point failure at (A) for further action.

Check & rectify faulty a. Crank handle switch and wiring b. NC/RC contacts c. Motor terminal wiring carbon brushes

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