Delhi Metro Rail Corporation Training Institute ISO 9001:2008

Delhi Metro Rail CorporationTraining InstituteISO 9001:2008ESSENTIALS OF INTERLOCKING

ISO 9001:2008ISO 9001:2008INTERLOCKINGINTERLOCKING means an arrangement of signals, points and other appliances, operated from a panel or lever frame, so interconnected by mechanical locking or electrical locking or both that their operation must take place in proper sequence to ensure safety.ISO 9001:2008Essentials of InterlockingIt shall not be possible to take off a running signal, unless all points including isolation are correctly set, all facing points are locked and all interlocked level crossings are closed and locked against public road for the line on which the train will travel, including the overlap.

ISO 9001:2008After the signal has been taken off, it shall not be possible to move any points or lock on the route, including overlap and isolation, nor to release any interlocked gates until the signal is replaced to the on position.

ISO 9001:2008It shall not be possible to take off at the same time, any two fixed signals which can lead to any conflicting movements.ISO 9001:2008Where feasible points shall be so interlocked as to avoid any conflicting movement.

ISO 9001:2008ISOLATION means an arrangement, secured by the setting of points or other approved means, to protect the line so isolated from the danger of obstruction from other connected line or lines. OVERLAP means the length of track in advance of a stop signal, which must be kept clear, either for clearing the stop signal next in rear or for the purpose of granting permission to approach.

ISO 9001:2008PrinciplesofSignallingSD of aSignal to beZeroNormal DangerSystem, One Operation One Clearing of the SignalMinimumNo. of Signals On a RouteRAMSVisibility of Signal from the Place ofOperationOne AspectOne IndicationFailSafeFeatureContinuousVisibility of Signal to DriverOverlapsUniformity

OperationFriendly Block & Yard Signalling to be independentFailure in any of the components or sub-system shall result in safe side failure of the system Second clearing would require Normalising of preceding operationDictum of Minimum Signals in a Route enables smooth flow of Traffic with minimum exertion & strain to the Driver The two should be insulated from each other to the extent possible to provide flexibility in operationUniformity of Signalling on a section is important from Drivers view point. It means, he knows what to come next & when Includes facilities of Shorts Shunts, Simultaneous Moves & Standby Modes of workingDetermines the Location of the Signal. Should remain continuously visible after it is picked up by the DriverDriver should be able to react to the Aspect of the Signal from the foot of the Signal. This is so in case of MA Signalling. Aspects shall be Distinctive & un-ambiguous. Action required on Indication shall be definite & capable of easy implementationIf not visible, Repeating Indications are to be provided. Repeaters also required at the place of Operation of Block InstrumentsHigh Reliability & Availability. Easy & Quick to Maintain & Service Plus built-in Redundancies for Fall-back option Overlap must be included in the SIP. Overlap, being a function of Aspects, should reduce with increase in the number of Aspects in a Signalling systemISO 9001:2008