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Wrong sided failures

Discussion concerning level crossings

Re: Wrong sided failures

Unread postby edwin_m » Sat Mar 12, 2011 9:50 pm

Is it simply a question of providing failure alarms similar to an AHB for loss of mains power and possibly other detectable problems, while retaining the confirmation of correct operation to approaching trains? If so then it seems sensible, though more costly, to alert the signaller immediately rather than waiting for the crossing to fail completely and be reported by a driver.
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Re: Wrong sided failures

Unread postby Keith » Sun Mar 13, 2011 7:52 am

John wrote:
Keith wrote:I was told that on one occasion, the chief constable of the area arrived at a certain AHB on one occasion to find the barriers up, no lights flashing, and a train thundering by. There was no collision and no formal report, but ever since then location cases at AHBs have had heaters in them... :roll:


Most events are due to local control when the respective parties 'come to a complete misunderstanding' but very rare - wrthat is why bidi controls are mandated!
This incident was long before bidi controls came in (on normally unidi lines). My comment about heaters was related to moisture inside a relay case turning to ice which kept the relay up with no power applied.
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Re: Wrong sided failures

Unread postby Fay Singpoint » Mon Mar 14, 2011 9:59 pm

Keith wrote:
I wrote:Barriers at automatic crossings need power to stay up
Chris Bellett wrote:ABCL crossings keep the barriers up when the power fails.
Oops! :oops:

That shows how long ago I was working on level crossings - ABCLs hadn't been invented then!


Things may have moved on a bit but we seem to be forgetting that AHB's, ABCL's etc are worked off batteries. You may get a mains power failure (and an alarm to the signaller or lack of DWL to the driver) but the crossing keeps working until the batteries give out.

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Re: Wrong sided failures

Unread postby Keith » Mon Mar 14, 2011 10:47 pm

Fay Singpoint wrote:Things may have moved on a bit but we seem to be forgetting that AHB's, ABCL's etc are worked off batteries. You may get a mains power failure (and an alarm to the signaller or lack of DWL to the driver) but the crossing keeps working until the batteries give out.
Good point - that is certainly relevant to avoiding the wrong-side failure of the road lights not flashing, even if the related barrier failure is (sort-of) right side.
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Re: Wrong sided failures

Unread postby edwin_m » Tue Mar 15, 2011 10:49 am

In an AOCL with remote monitoring as mentioned above, you would presumably alarm the loss of mains supply remotely but would you keep the crossing and driver indicator working normally on battery until the battery charge fell to some critical level?
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Re: Wrong sided failures

Unread postby Fay Singpoint » Tue Mar 15, 2011 12:42 pm

edwin_m wrote:In an AOCL with remote monitoring as mentioned above, you would presumably alarm the loss of mains supply remotely but would you keep the crossing and driver indicator working normally on battery until the battery charge fell to some critical level?


The first thing with an AOCL is the letter L which means locally monitored. As above, someone has come up with an AOCRL which seems to have caused its own problems because who is now in charge?

For a "proper" AOCL the following applies;

With a locally monitored crossing the Drivers White Light (DWL) tells him/her that everything is working normally and the crossing is closed to road traffic. A power failure prevents the DWL from being illuminated but the crossing may still be correctly closed to road traffic. In any case the driver proceeds at caution in accordance with the rules. The driver will contact the signaller, by which ever means available, to report the lack of DWL (which means any number of things may have failed). The arriving technician then goes on a fault finding mission and subsequent trains will continue cautioning themselves over the crossing until the fault is fixed.

The DWL does indeed monitor battery level (amongst many other things) because the charger/inverter could go sick with the mains supply working.

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