Thursday, May 14, 2020

CRANK HANDLE INTERLOCKING CIRCUITS (CHLR/CHR) - Part 25

CRANK HANDLE INTERLOCKING CIRCUITS (CHLR/CHR) 




Purpose of Crank Handle:

- Where point motors operate points, crank handles(CH) are provided to facilitate operation of points manually in case of point failure or maintenance.

It is not possible to provide CH interlocking for every point individually.  At the same time it is not proper to have only one crank handle common for all the points also.  Therefore, points are grouped to achieve optimum flexibility. 

Crank handle interlocking with signal and points 

      (a) Whenever a signalled movement has to take place over the points it will not be possible to release the concerned CH which is kept locked inside an electrical key transmitter (HKT/RKT/EKT).   

      (b) When the crank handle is OUT it shall not be possible to 
            − Operate the points from panel.  
            − Clear any signal concerned. 


      (c) It shall not be possible to insert the crank handle taken out from one group in any other group point machine. 


To achieve the above interlocking, the crank handle should be chained and welded to the EKT key. When the key is inserted in the EKT and turned to clockwise, and the SM acknowledge, thereby the crank handle IN indication light up and crank handle in proving relay CHLR picks up and sticks through its own front contact. 

- CH should be sealed and kept in Panel room.
- In some cases CH is provided at Location Box , In that case the Location will be locked and the key shall be kept in the personal custody of the SM on duty.


CRANK HANDLE ZONES AND WARDS

The points in yard are grouped in different zone for maintaining the yard flexibility.



- In this yard point no 52 and 53 are grouped under CH1.
- If CH1 is taken out , Sown movement signal alone are affected. 
- Up side signal can be taken for traffic.
- The point in the Yard are divided into groups and to distinguish a particular group , CH with different wards shall be used.


Crank handle free relay -CHFR

When all the concerned signal are in normal 
i.e. LRs dropped, 
then CH1FR will be in energized condition. 
Then crank handle free indication will be in lit condition in the CH box. 
There by it gives indication to SM that CH1 can be extracted if need arises. 

OR

When GN + UN -> Pressed and released simultaneously,
Then LR Picked up.
And Drops the Crank Handle Free Relay (CHFR)
Thereby the CH free indication is extinguished on the panel.
Thereby SM understands that CH1 can be not be extracted unless the signal is normalized. 















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