Point to Point Locking
Content
Point –Point Locking:-
3.10.
INTERLOCKING BETWEEN POINT LEVERS (point to point locking): As per the sub-para (iv) of para 7.82 of SEM (1988) the interlocking between point levers shall be provided to the extent feasible to avoid the conflicting movements. Here conflicting movement broadly shall refer to the movement, which is (i) unsafe for the rolling stocks and (ii) unsafe for the permanent way. However the interlocking between point levers shall be considered only when the points are in close vicinity to each other such that a train before it clears the first set of points negotiates the other points.
3.10.1. Interlocking between points is mainly provided to achieve i) Safety of the unsignalled movement and ii) Safety of the ground gear during unsignalled movement.
10 R.by 7 For example in the figs. (a) & (b) the interlocking between 7 & 10 has to be, 10 R.by 7. If such locking is not given then point No.10 can be reversed without reversing 7, at that time an un-signalled movement initiated from siding may get derailed, so it is unsafe for the movement.
7 locks 9 In some other cases as shown above, if 7 locks 9 locking is not given then, at the time of performing a movement with 7 reverse, point No.9 is free and if 9 also is reversed this will give an access to another movement encroaching in the route of the first movement. It is unsafe and dangerous. So 7 locks 9 isolates the moves and shall be provided to the extent it is feasible. 3.10.2
Points and crossovers are the important structures of permanent way, usually they are protected by the signals. But some time when there has to be an unsignalled move over the points there may be a possibility of the points connections getting damaged if the correct position of points are not ensured by the pointsman.
(a) 10 locks 12
(b) 10 locks 12
(c) 10 X 12
(d) 10 R.by 12
In the case of figure (a), (b) & (c) above, there has to be an interlocking between 10 & 12 as 10 locks 12. If such locking is not provided then there may be a possibility of keeping both 10 & 12 in the reverse position, at that time a movement initiated from line I will damage the point No.12 while trailing through. Similarly in fig (d) the interlocking between 10 & 12 has to be preferably 10 R.by 12. If such locking is not provided then 10 can be reversed keeping point No.12 normal, at that time a movement initiated from line 11, will damage point No.12 while trailing through (when one point is released by another point has to be considered, then "less important point is released by the more important point" may be preferred, to protect the more important point or as preferred in the yard). The importance of the points is decided by the speed of train over the points. 3.10.3
To sum up, the following are the advantages of point to point interlocking: i) It prevents damage to the points during unsignalled move ii) It is for safety of unsignalled movement iii) It isolates the moves iv) It economises the interlocking
3.10.4. However in situations when one point is reversed for a movement the position of other points can be normal or reverse for the same movement or other parallel movements, the interlocking between such points is not considered necessary.
In all the examples shown above, there should not be any interlocking relation between 8 and 10. If we provide any locking between them, then this will curb the flexibility of the yard to which it is designed.
3.10.
INTERLOCKING BETWEEN POINT LEVERS (point to point locking): As per the sub-para (iv) of para 7.82 of SEM (1988) the interlocking between point levers shall be provided to the extent feasible to avoid the conflicting movements. Here conflicting movement broadly shall refer to the movement, which is (i) unsafe for the rolling stocks and (ii) unsafe for the permanent way. However the interlocking between point levers shall be considered only when the points are in close vicinity to each other such that a train before it clears the first set of points negotiates the other points.
3.10.1. Interlocking between points is mainly provided to achieve i) Safety of the unsignalled movement and ii) Safety of the ground gear during unsignalled movement.
10 R.by 7 For example in the figs. (a) & (b) the interlocking between 7 & 10 has to be, 10 R.by 7. If such locking is not given then point No.10 can be reversed without reversing 7, at that time an un-signalled movement initiated from siding may get derailed, so it is unsafe for the movement.
7 locks 9 In some other cases as shown above, if 7 locks 9 locking is not given then, at the time of performing a movement with 7 reverse, point No.9 is free and if 9 also is reversed this will give an access to another movement encroaching in the route of the first movement. It is unsafe and dangerous. So 7 locks 9 isolates the moves and shall be provided to the extent it is feasible. 3.10.2
Points and crossovers are the important structures of permanent way, usually they are protected by the signals. But some time when there has to be an unsignalled move over the points there may be a possibility of the points connections getting damaged if the correct position of points are not ensured by the pointsman.
(a) 10 locks 12
(b) 10 locks 12
(c) 10 X 12
(d) 10 R.by 12
In the case of figure (a), (b) & (c) above, there has to be an interlocking between 10 & 12 as 10 locks 12. If such locking is not provided then there may be a possibility of keeping both 10 & 12 in the reverse position, at that time a movement initiated from line I will damage the point No.12 while trailing through. Similarly in fig (d) the interlocking between 10 & 12 has to be preferably 10 R.by 12. If such locking is not provided then 10 can be reversed keeping point No.12 normal, at that time a movement initiated from line 11, will damage point No.12 while trailing through (when one point is released by another point has to be considered, then "less important point is released by the more important point" may be preferred, to protect the more important point or as preferred in the yard). The importance of the points is decided by the speed of train over the points. 3.10.3
To sum up, the following are the advantages of point to point interlocking: i) It prevents damage to the points during unsignalled move ii) It is for safety of unsignalled movement iii) It isolates the moves iv) It economises the interlocking
3.10.4. However in situations when one point is reversed for a movement the position of other points can be normal or reverse for the same movement or other parallel movements, the interlocking between such points is not considered necessary.
In all the examples shown above, there should not be any interlocking relation between 8 and 10. If we provide any locking between them, then this will curb the flexibility of the yard to which it is designed.
