The reason has a long explanation...but I would say its a very clever work by power controller.
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This shunter becomes the main power of Gour express (sometimes 12987)
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•Previously,every day, a diesel loco...
more... used to come to SDAH from BWN by Gour Exp./went back from SDAH to BWN by SDAH RPH Pass (hence they had 20 mins stop at BWN). The locos used to come for Pass duty for about 10 trains as well as to perform freight duty. Now 5 of the 10 trains are operated Electric. The "link bringing" trains are also electric. Now the "link bringing" train from BWN to SDAH is DN BSB SDAH Exp. (Hence double alco comes from BWN to SDAH,as it has +30 mins stop time at BWN) •A loss of freight duty BWN Locos is also observed,as the link DN BSB SDAH brings is used to operate rest of 5 diesel trains...so seperate locos are not readily available from BWN. As a result,the intra-divisional freights are being operated by HWH ALCo & BGA Shunters. [HWH is now sending its passenger unfit ALCo (marked as NP) to SDAH div for freight duty,due to lack of locos from BWN]
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💠Hence i have explained the unavailability of enough shunters at SDAH stn.
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Now,why an Electric P/class shunter?
As the no of electric trains have increased, the ETS/pooling point at NKG outdoor is not enough to keep so many locos. (Capacity hardly 8-9). So a new pooling point (capacity 5-6 as appears) has been made just beside coaching yard. Now,this "new pooling point" has a "common electrified entry/exit point" with the busy yard, i.e.,if any express train blocks the exit of yard...the locos will also become unable to come out of the pooling point.
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Hence SDAH is doing a unique practice....they are taking the Loco out of the pooling point just after rake of Hate Bazare clears the exit point➡️attaches the loco to Kanchankanya Express➡️shunts it to platform➡️attaches the same loco to Gour Express just after Kanchankanya departs and Gour is shunted to platform
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💠I hope u understood that the shunter WAP7 is the main power of Gour Express at last (or 12987 sometimes). This is followed because,if they made delay in taking out this WAP7,it would get stuck at the exit point of yard as at that point of time, Darjeeling mail,gour Express,ajmer express, Padatik express back-to-back blocks the yard exit point.
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💠One may have another question...Why they can't bring locos from pooling point just beside NKG outdoor?
...The answer...That place receives the Dn locos of Kanchanjungha,maa tara, ajmer sealdah,etc which have their checking...the space is very small with 2 bays only. So bringing a loco from that point will be hectic.
