29-03-2010, 05:53 PM
(29-03-2010, 08:23 AM)Archie Wrote: Can somebody explain to me the process of points detection?
Not really sure what you are asking. Detection is the name given to the proving that the point switches have really moved to the position which the interlocking has requested- i.e. that the closed switch is sufficiently tightly closed to the stock rail on one side and that at the other side there is a sufficiently wide gap between the open swich and the other stock rail so that there is no risk of the back of the wheel flange contacting it. Also detection will (almost always) prove that the points are physically held in position by a facing point lock (or alternaive means of achieving the same aim).
Detection of mechanically operated points is sometimes still achieved mechanically, bit in general is achieved electrically and therefore there are NKR and RKR repeat relays that are energised when the points are proved fully in one position or the other. It can get a bit more complicated than that where there are multiple detection elements, there is a subtle difference between pure "neat detection" and "correspondence", but this gives the overview. Fundamentally it is the feedback in the control system so that we know the site equipment has truly responded to the command to move. Does that answer what you were meaning?
I must admit when I first started to read this, the first thought that I had was that I thought the difference between detection and correspondence was quite important. If the points are in "closed and locked" position, they will be legitimately detected there irrespective of what the interlocking had asked them to do meaning that they are only in correspondence when the state of the detection and the state of the interlocking call agree.
Another area that my thoughts differed slightly was on "open switch detection" because on the UK mainline, we have not normally proved this consistently. OK, the Clamplock has had this feature but until recently, no other operating mechanism has - we have relied on the integrity of the stretcher bars and assumed that if the switch that should be closed is detected, the switch that should be open is open.