Electric Point Machine 220 mm throw for Thick Web Switch and Spring setting device (SSD)

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Electric Point Machine 220 mm throw for Thick Web Switch

Introduction

The traffic density is increasing day by day on Indian Railways and to increase the sectionย capacity higher speeds of trains are always aimed at. To meet this demand higher powerย locomotives were developed and high speed turnouts i.e. more than the existing 1 in 12ย turnouts are being laid. In most of the new works such as the work of freight corridor (thirdย line) high speed turnouts with higher section of rails i.e. Thick web switch (TWS) with 60ย Kg rails are being installed. For operating TWS, the existing design of Electric Pointย Machine was modified with the incorporation of clamp type lock for additional safety.

Salient features of TWS

The crossing angle has been broadened so that the train negotiating at higher speeds doesย not pose any danger.

The switch opening is of 160 mm as against of 115 mm of ordinary cross over.

The web of the switches is made thicker to make than them strong enough to withstand loadย of train at high speeds.

Clamp type lock and its advantages

A CLAMP LOCK clamps together the closed switch against the stock rail and achieves theย locking of the switch. For the working of clamp lock, the throw bar of point machine isย provided with a total of 220 mm stroke the distribution of which is as given below:

60 mm for the unlocking,

100 mm for the throwing of points and

60 mm for the locking of closed switch.

Advantages:

(a) It ensures and proves the proper setting of switch rail against stock rail.

(b) Due to the 160 mm opening of thick web switch (TWS) at toe the clearance at junctionย of rail head (JOH) is 60 mm. This prevents the repeated striking of the open switch atย junction of rail head (JOH) by inner side of the wheel, which in conventional switchesย leads to chances of under wheel flashing.

(c) It prevents vibration caused in the switch due to train movement which in turn preventsย disturbance to detection and control contacts assembly unit directly. In conventionalย switches this leads to reduction in efficiency of the unit.

(d) Due to complementary tapers in switch and stock rail, the switch rail toe fits undersideย the stock and therefore the wheel of the train engages the switch rail well after 6โ€ณ fromย toe. Therefore, damage and wear and tear of the switch is prevented.

(e) Provides direct locking between tongue rail and stock rail in closed position.

(f) Firmly holds the tongue rail in the open position. Checks any relative movementsย between tongue and stock rail

(g) It ensures and proves the proper setting of switch and stock rail.

Spring setting device (SSD)

(a) In a TWS turnout, no stretcher bar is used and hence switches are able to moveย independently.

(b) A spring setting device (SSD) is provided at junction of Rail head (JOH), in lieu ofย stretcher bars, to assist in proper setting of switch upto JOH, which is placed betweenย sleeper number 13 and 14.

(c) Adjustment of locking is done by means of packing shims between switch rail and stockย rail bracket. Three each of 1 mm and one of 0.5 mm shims are provided for each switch.

Spring setting device (SSD)
Spring setting device (SSD)



Spring setting device (SSD)
Spring setting device (SSD)



Main parts of point machine are:

(a) DC series split field Motor withinย built reduction gear unit.

(b) Transmission assembly.

(c) Throw rod, lock slides andย detection slides.

(d) Detection and control contactย switch Assembly.

(e) Cast iron Case with cover.

(f) Crank handle.

Operating data ofย point machineย as per IRS: S 24/2002

Motorโ€“ DC series split field

Throw of point machine โ€“ 220 mm + 4 / -1

Time of operation (Max.) โ€“ 5.0 sec.

Current consumption โ€“ < 5.5 Amp.

Rated voltage โ€“ 110 VDC

Max. Throw โ€“ 450 Kg.

Slipping load โ€“ < 580 Kg.

Stalling load (Min.) โ€“ 1000 Kg.

Main parts of Clamp Lock and Functions

(a) Locking bar (L.H.)

(b) Locking bar (R.H)

(c) Insulating plates

(d) Locking washers

(e) Locking arms

(f) Stopper

(g) Drive lug

Locking bar (L.H) and locking bar (R.H) are joined with insulating plate and lockingย washer at both ends are inside of both switch rail and stock rail brackets. Its movementย depends on the stroke of drive rod, which is attached to one end of locking bar by driveย rod.

Locking arm assembly: it consists of L.H. and R.H. Arms. Its main function is to lock andย unlock the clamp. It is attached with the stock rail with the help of bracket and to the lockย bars with guide.

Working of Clamp Lock

Initially the point is lying in normal and right hand switch is locked whereas left handย switch is open with an opening of 160 mm.

When the lockbar is pulled by the electric point machine the open switch starts movingย towards the stock rail.

The lock barโ€™s initial stroke of 60 mm is used to unlock the clamp lock at closed switch.

After unlocking of the clamp lock the closed switch starts opening.

When the lockbar travels 160 mm, open switch completes the stroke and closes fully withย stock rail.

However, the closed switch which had started opening, opens up to about 100 mm only.

When the lock bar further travels and completes the total stroke of 220 mm, the openย switch completely closes with the stock rail and gets locked.

The earlier closed switch which has opened upto 100 mm now further completes theย opening to 160 mm.

To summarize the above operation, 220 mm throw of Point machine is distributed asย follows:-

(a) First 60 mm throw of Point machine

(i) Unlocking of Closed switch and

(ii) Open switch moves 60 mm towards its stock rail.

(b) Next 100 mm throw, both switches move

(i) Closed switch opens by 100 mm and

(ii) Open switch completes (60 mm+100 mm) =160 mm and it is now closed.

(c) Last 60 mm throw

(i) 100 mm Opened switch further movers to 60 mm = (100 mm+60 mm)=160 mm.

(ii) Locking of Closed switch by 60 mm.

Installation guidelines ofย Point Machine

The IRS Point Machine with Clamp Lock and Ground Connection arrangement 60 Kgย (with Thick Web Switch) for B.G shall be installed as per RDSO as per RDSO DRG. No.ย RDSO/S3454.

(A) Preparatory steps

(a) Bring the toe of switch at 32 mm in advance of centre line of sleeper No.3 and distanceย between sleeper No.3 and 4 to 685 mm. (centre-line to centre-line). (As per RDSOย drawing no. RDSO/S 3454 Sleeper spacing has been modified as 685 mm instead ofย 745 mm vide ALT 4 dated 28.12.2001).

(b) Ensure that insulated gauge tie plate is provided on sleeper No. 3.

(c) Remove all leading and following stretcher bars.

(d) Provide spring setting device of approved design at junction of rail head (JOH).

(e) Maintain gap at junction of rail head (JOH) not less than 57 mm for every flange wayย clearance.


(B) Marking & drilling holes for Clamp Lock Assembly

(a) Stock rail

(i) For marking holes in stock rails mark centre-line on the web of stock rail at the height ofย 76 mm from bottom of stock rail up to the length of 550 mm from toe.

(ii) Mark centre punch to the length of 450 mm for 1st hole and 530 mm for 2nd hole from theย edge of the tongue rail toe.

(iii) Ensure that there is a gap of 80 mm between both the holes (Centre-line to Centre-line ofย the holes) as shown in figure given below.

(iv) Drill two holes of 22mm dia in the web of both stock rails for fixing stock rail brackets.

(b) Tongue rail

(i) For marking in tongue rails, mark centre-line on web of the tongue rail at the height ofย 55 mm from bottom of tongue rail up to the length of 500 mm.

(ii) Mark centre punch to the length of 428 mm for first hole and 498 mm for second holeย from toe.

(iii) Ensure that there is a gap of 70 mm between both holes (Centre-line to centre-line of theย holes).

(iv) Drill two holes of 22 mm dia in the web of the tongue rail for fixing switch rail bracket.

(C) Marking & drilling holes for ground connections (Lock and detector rods)

(a) If point machine is connected to Left hand- side.

(i) First make the centre-line in the foot of both tongue rails up to 350 mm length from toe.

(ii) Mark centre punch up to the length of 148 mm for first hole and 328 mm for second holeย from the toe in the LH tongue rail.

(iii) Mark punch up to the length of 200 mm for first hole and 272 mm for second hole fromย toe in RH tongue rail.

(iv) Drill two holes of 24 mm dia in the foot of the switch rail at the markings for connectingย lock rod and detector rods.

(b) If point machine is connected to Right hand- side.

(i) First make the centre-line in the foot of both tongue rails up to 350 mm length from toe.

(ii) Mark punch up to the length of 148 mm for first hole and 328 mm for second holeย from toe in RH tongue rail.

(iii) Mark centre punch up to the length of 200 mm for first hole and 272 mm for secondย hole from the toe in the LH tongue rail.

(iv) Drill two holes of 24 mm dia in the foot of the switch rail at the markings forย connecting lock rod and detector rods.

Ground connections of RH tongue rail
Ground connections of RH tongue rail



Ground connections of RH tongue rail
Ground connections of RH tongue rail



(D) Connection for Clamp Point locks

(i) Connect the stock rail bracket to the stock rail as in Fig. below.

Connecting stock rail bracket
Connecting stock rail bracket




(ii) Assemble the LH and RH Lock Arm assemblies

(iii) Now fix tongue rail bracket with the lock arm assembly

(iv) Remove both the stoppers from locking bar assembly.

(v) Lock slides of the locking bar assembly are then inserted in to the groove of the stockย rail bracket (under the rail) through the guide of the lock arm. Fish tailed end of theย lock arm should be housed in the notch of the lock slide while inserting the lock slideย in the stock rail bracket.

(vi) The tongue rail brackets are then bolted to the web of the switch rail.

(vii) Fix the stopper of both locking bar assembly. Bend longer end of the lock washer onย the side of the stopper end on to the nut.

Inserting Lock slides into the groove of the stock rail bracket (under the rail)
Inserting Lock slides into the groove of the stock rail bracket (under the rail)



Fixing of Tongue rail brackets
Fixing of Tongue rail brackets



(E) Connection of drive rod

(i) Connect drive rod lug to theย throw slide (Driving rack) ofย point machine.

(ii) Connect the drive rod betweenย the drive rod lug and end ofย locking bar assembly.

(iii)Adjusting screw of the drive rodย should be adjusted for 160 mmย opening of the switch.

(iv) Keeping the drive rodย perpendicular to track; fix theย point machine on the extendedย sleepers on gauge tie plate.

Connection of Drive rod
Connection of Drive rod





Note: It is advisable to install theย point machine at the side whereย the tongue is normally closed.ย This shall be advantageous forย maintaining bars, which are thenย inside the machine as much as possible.

(F) Connection of the Lock rodsย and Detector rods

(i) Lock and detector rods are to beย assembled at site by inserting drop lugย in the threaded portion of the rods. Theย drop lugs can be suitably turned to suitย LH/RH mounting.

(ii) Put tapered washer on the footย of the switch rail such that the thickerย portion of the washer is towards theย edge of the rail.

(iii) Now connect jaw of theย detector/lock rods with the foot of theย tongue rail and drop lug with theย detector/lock slide of the pointย machine.


Connection of Lock & Detector rods
Connection of Lock & Detector rods

Adjustment

(a) Lubricate all the moving parts of the clamp lock assembly.

(b) Put grease on the bronze brush in the lock arm assembly.

(c) Put grease on the notches of the lock slide and fishtail portion of the lock arm.

(d) Loosen the nuts of stock rail bracket so that it can move freely in its oblong holes and

take its own portion.

(e) Operate the machine with crank handle and adjust the lock and detector slides (usuallyย Near end first)

(f) If clamp lock is not locking the point then do the following:

For proper locking on both sides additional numbers of packing shims have beenย provided between switch rail and tongue rail bracket.

Required no of shims will be put outside the tongue rail bracket to facilitate locking onย either side.

Six numbers of packing shims are provided with each clamp point assembly.

(j) Now tighten the nuts of the stock rail bracket.

Position of notches on fish tail portion of lock arm for closed switch
Position of notches on fish tail portion of lock arm for closed switch



Position of notches on fish tail portion of lock arm for closed switch
Position of notches on fish tail portion of lock arm for closed switch



Position of notches on fish tail portion of lock arm for open switch
Position of notches on fish tail portion of lock arm for open switch



Position of notches on fish tail portion of lock arm for open switch
Position of notches on fish tail portion of lock arm for open switch



Testing

After installation the following test should be carried out.

Obstruction Test

The detector slides, lock slides and drive rod must be so adjusted that with 5 mm thick testย piece placed between the switch and gauge face of stock rail at 150 mm from the toe of theย point:

(a) Friction clutch de-clutches the motor from mechanism.

(b) The point cannot get locked either by clamp lock or by locking segment inside the pointย machine.

(c) Lock segment does not enter into the notches of locking slides.

(d) Switch detection contacts do not make.

(e) The slipping current is not exceeding twice the normal working current

Insulation Test

Check the insulation for the following.

(a) Point machine

Check that point machine is insulated from ground connection.

(b) Spring setting device

Insulated from both the rails.

(c) Clamp lock assembly.

Check that it is insulated from both the rails.

(d) Leading and following stretcher bar (If point is operated without clamp pointย locking arrangement).

They are insulated from both the rails.

Maintenance

Points

(a) Ensure graphiting or lubricating of slide chairs at every week.

(b) Ensure that all nuts and bolts are tight and split pins are opened properly.

(c) Lubricate at the following moving parts of the clamp lock fortnightly.

(d) Stock rail bracket groove.

(e) Moving part of tongue rail and lock arm assembly.

(f) Between machine of lock bar and lock arm assembly.

(g) Ensure that the rodding and other connections are tight.

(h) Check that the point area is well ballast, packed and free from vegetation.

(i) Check that water does not stagnate in the vicinity of points.

(j) Ensure information to engineering department regarding to avoid any emergency failure.

Point Machine

(a) Ensure that wire connections of the machine are tight and laced properly.

(b) Ensure that the locking segment enters freely into the notches on the lock slides and withย a little pressure in the notch of drive rod.

(c) Ensure the point machine fittings are tight.

(d) Check all parts for any crack or breakage etc. and replace immediately if any defect isย found.

(e) Ensure smooth working of the gears without any cracking noise.

(f) The slipping of friction clutch during obstruction shall be ensured and slipping currentย shall not exceed twice the normal working current.

(g) Ensure that the carbon brushes are exerting sufficient pressure on commutator. Clean theย commutator properly by using chamoise leather.

(h) Ensure that all moving parts are free from dust and are well lubricated.

(i) Ensure that gauge tie plate is properly insulated.

(j) Ensure that the roller rolls freely on the periphery of the control and lift out disc.

(k) Check that the contact pressure of control and detection contact is adequate.

(l) Apply non-corrosive all temperature grease (IS-507/508) through the entire grease nippleย by a grease gun, after 8,000 operations or six months whichever is earlier or as perย instructions issued by the railway.

(m) After every six months or as per instructions issued by the railway pour lubricating oil,ย SAE-30/SHELL 100, through inlet in to the oil reservoir for lubricating gearbox of theย motor.

(n) Check the overload current.

Track Locking schedule

Check track locking once in six months or as per instructions issued by the railway.

Workshop overhauling schedule

After 4,00,000 operations or five years for bigger yard or seven years whichever is earlier.

The point machine should be taken out and should receive a general overhaul and thoroughย cleaning in an authorized workshop.

Insulation Testing schedule

Check insulation once in six months or as per instructions issued by the railway.

Doโ€™s & Donโ€™ts

Doโ€™s.

Get disconnection of point, before carrying out any work.

Always ensure schedule maintenance.

Test the working of friction clutch.

Do ensure that track locking, route locking, crank handle release locking areย effective.

Do test the correspondence of the points with indication at panel or cabin.

Always use proper lubricant. Wipe away excessive oil or grease.

Always use proper rating of fuse.

Dontโ€™s.

Do not operate the point manually except through specific crank handle.

Forget to exercise safety checks initially, during and after disconnection.

Forget to carry necessary tools while attending the failure.

Leave any discrepancies noticed in the point machine.

Use too much lubricant.

Allow unsquared notches on slides.

Tools & Spares

Recommended Tools and measuring instruments

Following tools and measuring instruments should be kept in the duty room for installationย and maintenance of Electric point machine:

Spanner set

32 mm (11/4โ€) single end spanner

Adjustable pipe wrench

Screw driver

Hammer

Tommy bar

Measuring tape

Test gauge

Cutting pliers

Wire cutter

Insulation peeler

DC Ammeter with centre โ€˜0โ€™ incase of Analog (0-30 Amp)

DC Voltmeter (0-250V)

Track shunt resistance.

Grease Gun

Spares and Consumables

Following spares and consumables are necessary for maintenance and inspection.

SAE 30/SHELL 100 oil

Grease IS 507/508

Chamois leather

Cotton waste grade A

Carbon brush

Contact assembly

MS-pins and split pins

D-bracket and stretcher bar insulation material sets

Tools and accessories to be supplied with new point machines

The following set of tools in a suitable box shall be supplied along with every set of eightย point machines or less:

1. Hand operated square drive socket wrenches of 12.5 mm driving square (short type) asย per IS: 7381 for M8, M10, M12 & M18 threads. (One 250 mm long 12.5 mm squareย extension bar as per IS: 7991 alongwith compatible Tee handle Square drive as per IS:ย 7975 suitable for above socket wrenches.

2. Open jaw wrenches (spanners) for M10, M12, M20, M24 & M33 threads as per IS:ย 2028.

3. Adjustable wrench.

4. Screw driver 300 mm long

Summary

(1) Throw of point machine

Throw of the point machine throw bar โ€“ 220 mm, which is distributed as follows:

(a) First 60 mm throw of Point machine

(i) Unlocking of Closed switch and

(ii) Open switch moves 60 mm towards its stock rail.

(b) Next 100 mm throw, both switches move

(i) Closed switch opens by 100 mm and

(ii) Open switch completes (60 mm+100 mm) =160 mm and it is now closed.

(c) Last 60 mm throw

(i) 100 mm Opened switch further movers to 60 mm = (100 mm+60 mm) =160 mm.

(ii) Locking of Closed switch by 60 mm.

(2) Main Parts of point machine

(a) DC series split field Motor with- in built reduction gear unit.

(b) Transmission assembly.

(c) Throw rod, lock slides and detection slides.

(d) Detection and control contact switch Assembly.

(e) Cast iron Case with cover.

(f) Crank handle.

(3) Components of Clamp Lock

(a) Locking bar (L.H.)

(b) Locking bar (R.H)

(c) Insulating plates

(d) Locking washers

(e) Locking arms

(f) Stopper

(g) Drive lug

(4) Operating data as per IRS: S 24/2002- Amendment 1

Motor- DC series split field

Throw of point machine โ€“ 220 mm + 4 / -1

Time of operation (Max.) โ€“ 5.0 sec.

Current consumption โ€“ < 5.5 Amp.

Rated voltage โ€“ 110 VDC

Max. Throw โ€“ 450 Kg.

Slipping load โ€“ < 580 Kg.

Stalling load (Min.) โ€“ 1000 Kg.

5) Installation

(i) General

Toe of switch at 32 mm in advance of centre line of sleeper No.3.

Distance between sleeper No.3 and 4 to 745 mm. (From centre-line to centre-line)

Insulated gauge tie plate on sleeper No. 3.

Removal of all leading and following stretcher bars.

Provision of spring setting device at junction of rail head (JOH).

Gap of not less than 57 mm at junction of rail head (JOH) for every flange wayย clearance

(ii) Holes for Clamp Lock Assembly

(a) Stock rail

Two holes of 22 mm dia in the web of both stock rails at the height of 76 mm fromย bottom for fixing stock rail brackets.

1st hole at 450 mm from the edge of the tongue rail toe.

2nd hole at 530 mm from the edge of the tongue rail toe.

Gap of 80 mm between both the holes.

(b) Tongue rail

Two holes of 22 mm dia in the web of both tongue rails at the height of 55 mm fromย bottom for fixing switch rail brackets.

1st hole at 428 mm from the edge of the tongue rail toe.

2nd hole at 498 mm from the edge of the tongue rail toe.

Gap of 70 mm between both the holes.

(iii) Holes for ground connection

(a) Point machine on LHS.

Two holes of 24 mm dia on the foot of both tongue rails for connecting lock rod andย detector rod.

LH Tongue railย 

1st hole at 148 mm from the edge of the tongue rail toe.

2nd hole at 328 mm from the edge of the tongue rail toe.

RH Tongue railย 

1st hole at 200 mm from the edge of the tongue rail toe.

2nd hole at 272 mm from the edge of the tongue rail toe.

(b) Point machine on RHS

Two holes of 24 mm dia on the foot of both tounge rails for connecting lock rod andย detector rod.

LH Tongue railย 

1st hole at 200 mm from the edge of the tongue rail toe.

2nd hole at 272 mm from the edge of the tongue rail toe.

RH Tongue railย 

1st hole at 148 mm from the edge of the tongue rail toe.

2nd hole at 328 mm from the edge of the tongue rail toe.

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