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PANTOGRAPH

Main requirement of a collection gear is that it should not leave the contact ofOHE under any circumstances. Contact wire in all practical installations is neverperfectly horizontal. It raises and falls depending upon the weight of the contactwire, the distance etween the droppers. !lso the contact wire comes very low

under ridges and tunnels and raises high over pulic crossings. "epending uponthe speed of the electric vehicle, collector gear has to rise and falls in order tomaintain the contact with OHE.

Main function of #antograph is to maintain a lin$ etween the overheadsystem and power circuit of the locomotive at varying speeds in di%erent climaticand wind conditions on varying sti%ness of OHE. &hese factors and di%ering ridingqualities of the locomotives at various speeds result in di%ering dynamic conditions,which a%ect the contact pressure etween the collector strip and contact wire.

! positive pressure has to e maintained at all times to avoid loss of contactand spar$ing. 'et this pressure must e as low as possile to ensure minimum wearof contact wire.

&here are ( types of #antographs). "iamond type pantographs are used for "C EM*s(. +ingle ended aiveley types are used for !C-"C locos and !C EM*s.

!gain, aiveley type pantographs are ( types

). !M )(for (/ 01 !C 2 single pan is used.(. !M )3 2for )/44 1 "C 2 two pans are used

In case of (/ 01 !C traction systems, the contact wire of OHE is of lightsection. &his would mean low contact pressure of 5./ to 6 0g as against averagepressure of )4 to )/ 0g for "C pantograph. !t higher speeds, aerodynamic pressuregets developed, which usually adds up to the static pressure. However it isadvisale to $eep this variation to the minimum y proper aerodynamic design ofthe locomotive ody and positioning of the pantograph suitaly on the roof.

#an e7tremities have special shape of inverted horn. &his prevents pan fromfouling with contact wire at crossings and also getting entangled with saggingcontact wire.

&here are ( pantographs mounted on the roof of an electric locomotive, eachone on four insulators. !t a time, one is raised and connects the locomotive withOHE contact wire. 8ormally the pantograph rear to the ca used for driving israised. i.e. rear to the direction of movement of the locomotive 9if rear is defectiveor damaged, front can e used to wor$ :

MAIN PARTS OF PANTOGRAPH

): ;ase 3: +pring o7(: Horizontal spindle 6: #ositioning lin$aising springs?: 'o$e )): +ervo motor/: *pper arm )(: Collector5: &hrust rod )

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CONSTRUCTION:

&he !M type pantograph comprises of ;ase and !rticulation system. ;ase isvery light and is made up of welded sections, carrying the articulated system on twoall earings.

!rticulation system is formed yB! horizontal spindle, which is turning inside two earings. ! lower arm is

welded with horizontal spindle. !n upper framewor$ is ointed to the e7tremity ofthe lower arm through 'o$e. !n upper frame consists of two tues one end D7ed toyo$e and at the other end raced across y &ransverse tue. ! thrust rod is pivotedat a D7ed point on the ase and other end is D7ed on the yo$e. &his rod ensures thepositioning of the upper frame, as the arm rotates. ! resilient suspension for thecollector is made on two spring o7es, which are carried at the end of transversetue. In each o7 there is a sliding plunger, which carries a for$, on which is D7edthe yo$e of collector. ! #ositioning lin$ is pivoted on a pin at the end of &hrust rodand other end is D7ed to transverse tue through a shan$ 9steady lin$:. &his lin$maintains the contact plane horizontal during vertical movements of collector. &hisarticulated system is designed to allow an e7tension of (.?54 meters. &wo raisingsprings alances the mass of the articulated system and at the same time, raisesthe pantograph and provides contact force. &hese springs are D7ed etween theends of a alancing memer and arms 9shac$les: on the horizontal spindle. ! #an isof light alloy frame and carries two olted collecting strips and un@insulated invertedhorns.

PNEUMATIC CONTROL MECHANISM

&he piston is held at the ottom of its stro$e y the group of < springs whoseforce overcomes that of the wor$ing springs causing the pantograph to lower and

e held in the down position even at high speeds. orce is transmitted y a pistoninside a cylinder and held ac$ y springs, the insulating lin$ which carries at oneend a slotted memer sliding on the pin of the horizontal spindle. !dmission andescape of air are regulated y the throttle valve, whose action permits raisingwithout shoc$ at the catenary and a rapid initial lowering followed y a slowingdown at the end of the movement, thus avoiding shoc$s on the ase. &he throttlevalve includes a arrel, its seat, nozzle connected to the feeding pipe and severalescape holes.

OPERATION

;asically, compressed air raises and the springs lower the pantograph. &hesole function of air is to cancel the lowering e%ort of the springs and it has no direct

e%ect on the pantograph. hen the pantograph is wor$ing and the air pressure ismaintained in the control cylinder, the piston is $ept still and the articulated systemis entirely free $ept raised only y the up@spring device. It therefore follows freely allthe oscillations of the contact wire. +hould lac$ of air occur, the equipmentcollapses y itself.

Maintenance:1. Servomotor:

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"rain the cylinder and overhaul

Chec$ the piston for wear, luricate the cylinder walls and chec$ for airlea$ages.

*se multipurpose grease egal starfa$ special 9shell:2. A!"#tment#:

+tatic contact pressure of A $g. >aising time and lowering time

Horizontality of pan y spirit level

&ransverse Fe7iility$. L"%rication:

Graphite grease 9grade (: lurication on panto pan

&hrottle valve lurication y 1aseline

Oiling of spring plungers with *>+! oil - &!=#! ?4 9+hell:-Moil oil "&E +-&>O supervisors.

Complete oint report shall e sent +r."EE9&>": N +r."EE9&>+: for furtheraction.

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Format:

#!8&OG>!#H 2 I&EM+ O CHEC0

+r.8o.

I&EM+ O CHEC0

O;+E>1!&IO8

+&!8"!>" !C&*!=

) ( < ?) earing strips astening ): #roper astening

(: 8o loose fastener

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+r.8o.

I&EM+ O CHEC0

O;+E>1!&IO8

STANDARD

!C&*!=

) Contact wire height 2 main line ?.3 M to 9/.54 4.4(:M( Contact wire height @ turn out-cross

over/4 mm aove main line

< Contact wire stagger@ main line9&angent - Curve trac$:

#ush o% 2 (44-epresentative >epresentative >epresentative

PANTOGRAPH OHE ENTANGELMENT

DTC 13

1.6 INTRO;UCTION

).) Entanglement of pantograph with OHE normally ta$es place due tomechanical prolems either in the OHE or with the pantograph. Entanglementcan also ta$es place during an accident. >ecently, a numer of cases of pantoentanglement have een reported y >ailways. ! study was underta$en y>"+O to analyse them and suggest measures to avoid their recurrence.

2.6 EUIPMENT

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(.) &he maority of pantographs presently in use on (/ 01 !C Electric=ocomotives, EM*s are of aiveley type !M)( or simialr design. ! limitednumer of aively type =1(544 and !M6(, and +MC type ;>(ailways with 5/ mm sq. catneryand )4A mm sq. hard@drawn grooved contact wire is simple polygonal typeregulated OHE with )444 0g tension for catnery and )444 0g tension forcontact wire. &he stager of the contact wire on streight trac$s in (44 mm andon curves, it is

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$.2 &he proale reasons for the loosening-rea$age of pantograph componentsare inadequate maintenance, delay-not carrying out timely lurication ofmoving components, use of improper luricant, water entry in thelongitudinal tue etc. &he remedial measures for these have een advised tosheds and shops for compliance.

$.$ It has also een oserved that on some of the >ailways, grease pan asdesigned y the original equipment manufacturer has een replaced y aplate olted elow panto pan and e7tending on either side for carryinggrease. *sage of this plate results in increase in the upward force on thepanto pan particularly at higher speeds which may lead to the panto panhitting the stay arm. >ailways have een advised to use the grease pan asper the design of the original equipment manufacturer only and not adoptany local modiDcation on the same.

$.& Cases of pantograph coming in the unwired section and e7tending eyondma7imum limit resulting in entanglement have also een reported. #rovisionof stopper arrangement to prevent the pantograph e7tending eyondma7imum limit has already een introduced vide >"+O modiDcation sheet

8o. !M?-)/4 dated ().4/.35.

&.6 REME;IAL MEASURES A;OPTE;

&he remedial measures adopted for ensuring satisfactory performance of thepantograph in service and avoid entanglement with the OHE are detailed asunderB@

&1 SMI No. R;SO5ELRS5SMI5132 ate 12.6,.3/ Covering generalmaintenance chec$ to e carried out on the pantograph. &hese instructionscover proper alancing of the pantograph, chec$ing correctness of thehorizontality of the pan, chec$ing the current collector strip material-proDle

and D7ation etc.

&.2 Moi8cation Seet No. @AG(523 ate 3.$.3 for provision of a ruerush inside the open end of the longitudinal tue to prevent seepage of waterentry into the tue resulting in rusting and consequent rea$age.

&.$ SMI No. R;SO ELRS5SMI513 ate 2&.$.133 giving luricationschedule for critical components of the pantograph such as plunger o7,servo motor throttle valve, articulation system etc. =uricants to e used andperiodicity of lurication so as to arrest crac$s and sometimes rea$age of

the components.

&.& SMI No. R;SO5ELRS5SMI5261 t. 23.6&.133 giving details of theGrease #an to e used with the pantograph.

(.6 CONCLUSION

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ith the implementation of the aove remedial measures, instances ofpantograph OHE entanglement are e7pected to e minimised.

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