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Level crossing operation when box is switched out

Discussion concerning level crossings

Level crossing operation when box is switched out

Unread postby AlanMR » Thu Apr 3, 2014 12:21 pm

I recently visited a small mechanical box using traditional AB which controls two standard lifting barrier crossings, both operated through the lever frame. One of the crossings is on-demand, with the barriers normally lowered, and opened only when a buzzer signal is received by the signaller.
Since the visit I have been informed that the box is switched out on a fairly regular basis. As some of the signals are semaphores, they can only be cleared through operation of the frame. As I understand it, for the box to be switched out, the running line signals have to be set in the clear position, effectively locking both level crossings. I am assuming that in the absence of a full signaller, a crossing attendant is provided to operate the barriers, as there does not appear to be any provision for remote operation. Is he/she authorised to operate the signal levers under instruction from the signaller at the box at the start of the (extended) section or will there be some form of switching to override the locking?
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Re: Level crossing operation when box is switched out

Unread postby JRB » Thu Apr 3, 2014 3:21 pm

I would expect it to work like a normal crossing G.F. when switched out with the keeper operating the signals & barriers as required. The barrier/signal interlocking would be maintained.
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Re: Level crossing operation when box is switched out

Unread postby Stuart Johnson » Thu Apr 3, 2014 5:39 pm

This was fairly common once, but I'm surprised to hear of it still taking place today. Modern block controls do not sit happily with signals that are operated while the box is switched out. Can you say where this box is?
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Re: Level crossing operation when box is switched out

Unread postby AlanMR » Thu Apr 3, 2014 6:50 pm

Stuart Johnson wrote:Can you say where this box is?


My visit was unofficial, so I prefer not to say so as to protect the identity of the signaller.

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Re: Level crossing operation when box is switched out

Unread postby Pete2320 » Fri Apr 4, 2014 12:03 pm

Stuart Johnson wrote:This was fairly common once, but I'm surprised to hear of it still taking place today. Modern block controls do not sit happily with signals that are operated while the box is switched out.

A box I worked forty years ago (Lowthorpe) had full block controls but could switch out and be worked as a gate box. There were only home and distant signals in each direction so the homes had line clear release. This still applied when the box was switched out, for one pull per "line clear" but was "remembered" by the equipment. I can't remember if this was simply one pull per LC or if it required the block to be at LC or TOL. Eastrington was similar but had no Welwyn or approach track.
Actually I suspect having a block switch at any box, gates or not, provides a means of overcoming Welwyn control.

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Re: Level crossing operation when box is switched out

Unread postby AlanMR » Fri Apr 4, 2014 11:12 pm

Thanks for the answers, which show that the circumstances can apply. However, I have now had information from a reliable source that while at least one other box in the vicinity is switched out from time to time, it is one without a level crossing, and the one I visited is definitely always operated as an AB box.
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Re: Level crossing operation when box is switched out

Unread postby John Hinson » Sat Apr 5, 2014 7:53 am

Pete2320 wrote:Actually I suspect having a block switch at any box, gates or not, provides a means of overcoming Welwyn control.

Not really. Most that I have come across have some sort of inbuilt circuitry (beyond my ken) to prevent this.

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Re: Level crossing operation when box is switched out

Unread postby Fast Line Floyd » Tue Apr 8, 2014 11:56 am

Pete2320 wrote:
Stuart Johnson wrote:This was fairly common once, but I'm surprised to hear of it still taking place today. Modern block controls do not sit happily with signals that are operated while the box is switched out.

A box I worked forty years ago (Lowthorpe) had full block controls but could switch out and be worked as a gate box. There were only home and distant signals in each direction so the homes had line clear release. This still applied when the box was switched out, for one pull per "line clear" but was "remembered" by the equipment. I can't remember if this was simply one pull per LC or if it required the block to be at LC or TOL. Eastrington was similar but had no Welwyn or approach track.
Actually I suspect having a block switch at any box, gates or not, provides a means of overcoming Welwyn control.

Pete

I can't imagine why Welwyn controls would have any relevance where a box switched out and became a gate box. Normally the switch would just bypass the line clear controls on the signals or the starter would be left off and just the home and distant levers worked (but this would mean there could be no mechanical rotation locking).

I have a feeling that I have identified the box that AlanMR was refering to, if so then if the box closes then so does the line as there is no facility to work the box as a gate box and the crossing which is opened in response to the request remains open by use of an absence switch on the block shelf.

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Re: Level crossing operation when box is switched out

Unread postby Late Turn » Wed Apr 9, 2014 6:20 pm

Indeed, the description of the box in question almost exactly fits that of one box that I occasionally work, apart from the fact that mine has no block switch! Given the relatively unusual nature of the crossing involved, I suspect misinformation at some stage.

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Re: Level crossing operation when box is switched out

Unread postby Richard Pike » Sat Apr 12, 2014 4:17 pm

Fast Line Floyd wrote:
Pete2320 wrote:
Stuart Johnson wrote:This was fairly common once, but I'm surprised to hear of it still taking place today. Modern block controls do not sit happily with signals that are operated while the box is switched out.

A box I worked forty years ago (Lowthorpe) had full block controls but could switch out and be worked as a gate box. There were only home and distant signals in each direction so the homes had line clear release. This still applied when the box was switched out, for one pull per "line clear" but was "remembered" by the equipment. I can't remember if this was simply one pull per LC or if it required the block to be at LC or TOL. Eastrington was similar but had no Welwyn or approach track.
Actually I suspect having a block switch at any box, gates or not, provides a means of overcoming Welwyn control.

Pete

I can't imagine why Welwyn controls would have any relevance where a box switched out and became a gate box. Normally the switch would just bypass the line clear controls on the signals or the starter would be left off and just the home and distant levers worked (but this would mean there could be no mechanical rotation locking).

I have a feeling that I have identified the box that AlanMR was refering to, if so then if the box closes then so does the line as there is no facility to work the box as a gate box and the crossing which is opened in response to the request remains open by use of an absence switch on the block shelf.

Graham


The controls i have circuitry evidence for uses a relay, BNSR, that is controlled over block switch out picks and sticks with both (all) distants off. BNSR down allows normal controls. BNSR up feeds the electric lock of the home/starter as required.
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