Notes on SGE block instrument

CONTENTS

DESCRIPTION PAGE NO.

FORWARD iv

PREFACE vi

CORRECTION SLIP viii

CONTENTS x

INTRODUCTION 1

BASIC CONSTRUCTION 3

OPERATION 10

TYPES & DIFFERENCES 12

POWER SUPPLY ARRANGEMENTS 13

EARTHING 13

TESTING 14

MAINTENANCE 16

TOOLS 19

PRECAUTIONS 19

DISTRIBUTION LIST 22

CAMTECH/99/S/SGE BI /1.0

DOUBLE LINE BLOCK INSTRUMENT

1. INTRODUCTION

This instrument is used for double line block working. One pair of instruments is provided between two station i.e. for one side block section. One station will have two block instrument, one for station in advance and another for station in rear as shown in Fig .1 for station B .

Fig No.1

The instrument is simple, compact and robust in design. It requires simple regular maintenance & scheduled overhauling to ensure its trouble-free working.

It is a 3 wire, 3 position block instrument. It shows three positions of block section for each line

In NON-RE area, it requires 3 wire (min.) along with earth return for its working.

One for Top indicator.

SGE D/L BLOCK INSTRUMENT JAN` 99

1

BLOCKINST.

STN A STN B

UP LINE

DN LINE

STN C

BLOCKINST

DOUBLE LINE SECTION


One for Bottom indicator. One for Block bell and Telephone.

In DC traction area instead of earth return, metallic return is used to avoid interference from stray current.

In RE area, it requires two Phantom lines along with earth return and two pair of cable, one for bell code exchange and other for block telephone.

One phantom for Top indicator. One phantom for Bottom indicator. One pair for telephone. One pair for bell

(A 150 Hertz Oscillator feeds the line for bell working. This in order to avoid the time lag in DC bell code transmission.)

2. BASIC CONSTRUCTION

The block instrument mainly consists of two parts :

2.1 Indicators and commutator assembly.

2.2 Bell Unit consisting of Bell Relay, Bell coil and their termination.A telephone is also connected as an external part of Block Inst.


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2.1 Indicator & Commutator Assembly

This unit is divided into two parts, viz. top and bottom. The top portion consists of two indicators, one for controlling Up trains and other for controlling Dn trains. The bottom portion is made up of cast iron and consists of commutator, bell plunger and S.M’s key.

Sealing & double locking arrangements are provided on the back side of the block instrument.


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LINE CLOSE

D

LINE CLEAR

LINE CLOSE

D

LINE CLEAR

TRAIN ON LINE

UPPER NEEDLE

LOWER NEEDLE

SM’s LOCK

BELL PLUNGER

SCREW

COMMUTATOR

TRAIN ON LINE

Front view of Block InstrumentFig.No.2

Upper Portion

Bottom Portion


2.1.1 Top Indicator

It deals with train going into and out of block section at train sending station. It indicates three positions of block section i.e.-

Line Closed Line Clear Train On Line.

The indicator is shown in fig.-2. It is a polarised Galvo indicator. It consists of a permanent magnet having adjustable pole pieces and an electro-magnet coil. The coil is wound to a resistance of 140 Ohm and requires 17-25 mA currents for its operation. A needle is pivoted at the center of soft iron drum, placed in between the permanent magnetic poles. The needle deflects leftwards or rightwards, depending upon the direction of current in electromagnetic coil. This indicator operates in series with bottom indicator of the adjacent block instrument through line wire between two stations. The needle operation is controlled by the distant station.


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2.1.2 Bottom Indicator

It deals with train arriving at a block station. It indicates three positions of block section i.e.-

Line Closed Line Clear Train On Line.

The design of this indicator is identical to the top indicator. It is placed nearer to the commutator & gets operated when ever the commutator is turned. It is connected electrically with the top indicator of block instrument at station in rear.


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S

N

NS

Line clearTrain on

lineLine closed

DIAL

NPRP

RPNP

INDICATOR COIL

S

N

ADJUSTABLE POLE FACE ON PERMANENT MAGNET

PERMANENTMAGNET

Top IndicatorFig. No. 3


2.1.3 Bell Plunger

This is threaded through the middle of the commutator. The metallic ring of this plunger rod normally bridges two springs.

In Non RE area, every time the plunger is pressed, + ve of Bell battery is applied on the line completing the circuit through bell relay & earth at distant station. Thus registering the bell beat at the distant station.

In RE area, every time the plunger is pressed, 150 Hz AC signal is sent to distant station to operate bell relay at that station. Thus registering the bell beat at the distant station.

2.1.4 Commutator

This is mounted below the bottom indicator in the bottom portion of the block instrument. It has three positions, “LINE CLOSED”, “LINE CLEAR” and “TRAIN ON LINE”.

An arrow indicates the position of the commutator. It is free to be turned from ;

(i) “Line closed to Line clear”.(ii) “Line clear to Line closed”.(iii) “Line closed to Train On Line”


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(iv) “Train On Line to Line closed” (Only when commutator was been turned from “Line Closed” position and not from “ Line Clear ” position directly/indirectly.)

The commutator is turned through 20° from normal position to either “Line clear” or “Train On Line” position.

The commutator gets locked in “Train On Line” position when turned from “Line Clear” to “Train On Line”.

2.1.5 Door Lock Assembly

This is an electromagnetic device mounted centrally just above the commutator disc.

The door lock coil mechanism prevents locking of block handle in “Train On Line” position, when turned directly from “Line Closed” position to “Train On Line” position and thus facilitates block forward and block back operations without failure of block working.

The mechanism economies the power consumption of door lock coil by holding the armature mechanically once the door lock is energized momentarily.


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The displacement of holding pawl distinctly proves whether the block handle was earlier turned to “Line Clear” position or not in case of any dispute.

When the conditions of lock and block are fulfilled, the door lock coil is energized and its armature is lifted out of the notch which in turn lifts up the releasing bracket thus pushing the releasing lever upward. This removes the obstruction at the holding pin as a result of which the holding pawl swings back to its normal position, below the armature and is now ready to catch the latter when it drops down.

The commutator is now free to be turned from “Train On Line” to “Line Closed” for clearing block section.

2.1.6 Bell Unit

The bell unit is made of cast iron body. A bell gong is fixed on the top of the bell unit. It consists of bell relay, bell coil and termination blocks. The bell gong is a single stroke bell worked by a relay, called a bell relay.

A telephone is placed on a hook provided on the left side of block instrument’s body.


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2.1.7 Bell Coil

The bell coil is energized through the pick up contact of bell relay.

2.1.8 Polarised Relay

A polar relay complying to IRS S 31/80 is included in series with the top indicator to control the last stop signal & fulfill the requirements of absolute block system.

The relay has one arm with three positions. When there is no current flowing through the relay the arm remains in the center.

The relay resistance is 77 Ohm & requires a minimum operating current of 15-16 m.A. for it’s operation. The nominal working current is 25 m.A.

The polarised relay not confirming to IRS 31/80 should not be used.

3. SM’s Key

To prevent unauthorised operation of the block instrument, a SM’s key is provided on the front side of the Inst. as shown in Fig No. 2. When SM`s key is taken out the commutator gets locked in its last operated position i.e. either in Line Closed or Line Clear or in Train On Line. In this position bell beat can be sent & received from the other Station.


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4. OPERATION OF BLOCK INSTRUMENT

Fig.No. 4

A & B are two Stations on double line. To dispatch a train from Stn. ‘A’ to Stn. ‘B’, following operations are performed :

‘A’ gives LINE CLEAR signal to ‘B’ by bell code (Pressing Bell Plunger).

‘B’ acknowledges LINE CLEAR signal & turns the commutator of his block instrument to the right by 200.

This changes the indications of the lower needle at B & of the top needle at ‘A’ into LINE CLEAR.

‘A’ on observing the upper needle in its instrument now pointing to line clear, takes off last stop signal (LSS) for the train to start.


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Dn

A Stn. B Stn.

Up


When the train passes the last stop signal, i.e. On entry of train into block section `A’ sends train entering signal to ‘B’

‘B’ acknowledges train entering into block section s ignal and turns the commutator of his block

instrument to the left by 400 indicating TRAIN ON LINE on lower needle at Stn. ‘B’ and upper needle at Stn. ‘A’.

‘A’ restores the LSS lever to Normal.

‘B’ takes off the Home signal. On arrival of the train into the station puts back the home signal which has been automatically replaced to ON.

‘B’ verifies the complete arrival of train & puts back the home signal lever to normal. Thereafter gives train out of section signal & turns the commutator to LINE CLOSED position.

‘A’ acknowledges the train out of section signal.


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xxx, 01/03/-1,


5. DIFFERENCE BETWEEN THREE TYPES OF DOUBLE LINE BLOCK INSTRUMENTS(DLBI)

There are three types of DLBI’s: Byculla type (SGE) -Byculla make IRS type - HWH make SR Type -PTJ make

The main difference among them are tabulated below.

TABLE I

S.NO

NAME OF PARTS

Byculla type

SR Type IRS type

1. Door lock Mechanism

Mechanical stick

Electrical stick

Mechanical stick

2. Resistance of electric lock coil

50 ohm 48 ohm 14.8 ohm

3. Working current electric lock coil

200 mA 250 mA 250 mA

4. Resistance of bell relay

500 ohm 400 ohm 400 ohm

5. Working current of bell relay

20 mA 25 mA 25 mA

6. Resistance of bell coil

60 ohm 48 ohm 30 ohm

SR type instrument accommodates the following in the Instrument.

Polar Relay, Bell Relay, Bell Gong, SR Relay etc.


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6. POWER SUPPLY ARRANGEMENTS

Double Line Block Instrument requires following supply for its working in

a) Non RE area :

Block Needle battery (9 V + line drop) Bell battery (6 V + line drop) Telephone battery (3 V to 4.5 V) Local Battery ( 12/ 24 V)

b) RE area :

Block Needle battery (14 V + line drop) Telephone battery (3 V to 4.5 V) Local Battery ( 12/ 24 V)

Block Battery & Bell Battery shall be separatefor each Block instrument. No other circuit and/ or circuit of other block instrument shall be fed from Block Battery.

Resistance of Various Coils, Rated Current and Rated Voltage are given in TABLE-I

7. EARTH

A separate earth should be provided for Needle and Bell circuit of each block instrument.

The resistance of earth shall not exceed 10 Ohm.


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Where more than one earth is used, the distance between earthing pipes shall not be less than 3 mts. The conductors leading to these earthings should be electrically insulated from each other through out and also from metallic structures connected to different earth.

8. TESTING

Check double locking arrangement on back cover.

Ensure that sealing is intact.

Check that SM`s key is effective & commutator gets locked in its last operated position.

Check all springs for proper tension of 250 + 5 grams.

Check for the correspondence between commutator handle & Indicator ( except where auto “Train On Line” feature is provided.)

Check line battery & telephone battery voltage & also measure the working current of block instrument and compare with the standard value.

Check single stroke bell for its efficient functioning.


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Check door lock assembly for perfect working including force drop arrangement.

Check full notch & half notch on locking plate, they should be correctly shaped and are in square. Holding pin is not worn out, full notch should be square and half notch should be beveled.

Ensure that LSS can not be taken “OFF” without obtaining line clear from receiving station.

Ensure that LSS assumes “ON” aspect automatically when FVT is occupied by first vehicle & it could not be retaken “OFF” on same line clear.

Ensure that commutator could not be turned back from Train On Line to Line Clear position when turned from Line Clear to Train On Line directly, unless the train sequentially operates the two track circuits & after the passage of train, all reception signals have been put back to “ON”.

Check that Sealing of polarised relay is intact.

Check wiring of instrument, no loose wires get entangled in the moving part.

Measure earth resistance. Value should not be more than 10 ohm.


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9. MAINTENANCE

Needle indicators must be properly maintained so that they operate fully and return to the normal position, when the commutator is brought to Line Closed position.

It should be ensured that the commutator movement is smooth while turning it from one position to another position.

It should be ensured that commutator gets locked, when it is turned from Line Clear to Train On Line position, before Train On Line indication contacts are made.

See that all terminals screws, nuts, lock nuts and locking screws are tight and all split pins are opened.

Inspect the contact surfaces on the butterfly assembly. If pitted, clean them with chamois leather.

Check the resistance of indicator coil, lock coil and their working currents. If considerable difference is noted between subsequent readings, locate the fault and rectify the same .

Check the full lock notch and half lock notch on the locking drum, for their correct


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shape & squareness Correct them if necessary.

Check that no loose wire get trapped in the moving parts.

Check that only correct springs make when commutator is in “Line Clear” & “Train On Line” positions.

Check that the desired springs make when bell plunger is pressed and that bell beats are registered properly when bell plunger is pressed by the adjacent station.

Check the coil resistance of bell relay, bell coil and their working currents during inspections. If considerable difference is noticed between subsequent readings, locate the fault & rectify it.

Check the telephone battery, replace if necessary.

All batteries must be kept clean. Terminals must be free from dirt and corrosion.

Ensure that for same block instrument, batteries for Indication & bell circuit are separate.

Indication battery for two block instruments of adjacent section at a station should also be separate.


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Ensure that wire connection at the terminals are firm.

Check and ensure that earth and earth connections are effective and in good condition.

Ensure that common earth is not used for indication circuit because in case of leakage or breakage of one earth, both the instruments will come in series.

In case of “Train On Line” position +ve will on line & -ve on earth from the line battery. At that time for another line clear the -ve will be on line & + ve on earth, during this period if earth breaks PR (Polarised relay) may attract to Train On Line position & a PD (potential drop) is created. If the value of PD is more than 5 volts, PR will attract to line closed position when a train is in the section. This enables the Last stop signal to be off for 2nd train which is unsafe hence common earth should not be provided.


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DIRECTOR, 01/03/-1,


PERIODICITY OF OVERHAULING

A thorough periodical overhauling in Workshop is necessary and the period shall not exceed 7 years.

10. RECOMMENDED TOOLS

Tension Gauge of 0-500 grams range. Multimeter Hydrometer Cutting Plier 8 inch Nose Plier Screw driver (small) Megger

11. PRECAUTIONS TO BE TAKEN IN RE AREA

The following precautions shall be taken for block instruments on AC traction:

A block filter of an approved design shall be used between the block instrument and line wire. It is essential that the line & block instrument terminals of the filters are never interchanged. The Block filter is a low pass filter consisting of series choke coils S1 & S2 in each line & the shunt condenser C1 (see Fig. no.5). The condensers adopted are 4-terminal condensers to prove the continuity of conductors forming the condenser. Also two gaseous type Lightening Arrestors with a flash voltage


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of 150 V are provided on the line side for high voltage protection.

WHEREC1 - 4 TERMINAL CONDENSER C=10F TEST VOLTAGE = 1000 VOLTST1 - TRANSFORMER INSULATED INSIDE

P&T BOXS1 - PROTECTIVE CHOKE R= 50 OHM

‘Z’ AT 50 HZ =40,000 OHMTEST VOLTAGE = 600 VOLTS

S2 - PROTECTIVE CHOKE R= 40 OHM‘Z’ AT 50 HZ =20,000 OHMTEST VOLTAGa:\seminarE = 50 VOLTS

P - LIGHTENING ARRESTER GASEOUS TYPE, FLASH VOLTAGE 150 VOLTS


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LINE V2

TO BLOCK INSTRU -MENT

BLOCK EARTH

BLOCK EARTH

LINE V 1

BELL

TELEGRAPH

w

w

S 1 S 2

S 1 S2

EARTH

V 1

V2

LINE SIDE

T1

T2

C1

C2

P&T BOX

P

P

Fig No. 5


The block telephone shall be worked on separate pair of conductors.

Block telephone is connected across the line through a condenser when the bell relay is normal. When the bell relay picks up the block telephone is cut off.


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Notes on SGE block instrument

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