Derailing switches
Derailing switches are provided on loop lines to isolate it from main line, so that if a vehicle standing on loop line escapes from loop and rolls down it will not infringe the main line, where train operation at full speed is going on. It consists of two stock rails and one tongue rail. It may also be noted that as per RDSO T/5836, RDSO T/6068 derailing switch is a part of turn in curve. One of the stock rail and the only tongue rail is provided a pre-curvature of radius 232.260m. At most of the places turn in curve is provided with a radius of 441m, whereas radius of tongue rail of derailing switch is 232m. So there is a need to provide derailing switch as symmetrical split if these designs are to be used. By providing it as symmetrical split, radius of tongue rail of derailing switch will almost match with turn in curve radius. RDSO have also issued drawings for laying derailing switch as symmetrical split. Drawing number RDSO/T-8077 have been issued for 60kg, 6400mm over-riding curved derailing RH switch on BG on PSC sleepers. Similarly a drawing RDSO/T-8153 have been issued for 52kg, 6400mm over-riding curved derailing RH switch on BG on PSC sleepers. However if some other radius of turn in curve is selected, radius of derailing switch may be modified accordingly. A bend is also required at TTS, the angle for which is to be decided depending on required radius of tongue rail.
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| Derailing switches |
Recently 2 new drawings for derailing switch has been issued by RDSO
1) RDSO/T-7008, in which tongue rail as well as one stock rail is straight and the other stock rail have been given radius of 232m. Such derailing switches can be laid on straight after end of turn in curve. This design has an advantage that turn in curve is less disturbed, but length of loop line gets reduced by this design. Hence these cannot be used at all the places. The basic sketch of this design is shown in fig.
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| Derailing switch as per RDSO/T-7078 |
2) RDSO/T-8089, in which tongue rail is made curved and a normal 60kg tongue rail of 1:12 curved switch of 10125mm switch length have been used. In this derailing switch tongue rail will be a part of turn in curve and radius will be of the order of 441m. So it will suit more to the turn in curve radius.
Hence selection of design of derailing switch to be used will depend on whether enough space for accommodation of derailing switch on straight is available or not. If sufficient space is not available derailing switch of RDSO/T-8089, RDSO/T-5836 or RDSO/T-6068 should be utilized.
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