Where will the last semaphore signals be on the national network?

[Ken H]

problem is that power signalling seems to have a definite life after which its life expired. or obsolete, and parts are not available. So with increasing power signalling, much of it will be replaced every 30-40 years.

Mechanical signalling can generically be life extended indefinitely. Yes, I know that the skills are becoming scarce.

So resources for improvements will increasingly go to replacing power schemes, and mechanical signalling will have to soldier on.

 

[LNW-GW Joint]

Very unreliable - frequent issues with axle counter failures or non detection of the level crossings. Even though it's controlled all the way from Cardiff, the folks there often know what the weather is like in Shropshire. If it starts raining heavily, the level crossings stop working.
...
But apart from all that......

Would you have the same criticism of the later Connah's Quay-Llysfaen modular project?
I think it's the same Siemens system design.
I wonder how often the Flint reversible section has been used?

 

[PeterY]

I often wonder just how long the Shrewsbury area, will retain mechanical signals. I'm sure, I read that the box there has recently refurbished

 

[craigybagel]

Would you have the same criticism of the later Connah's Quay-Llysfaen modular project?
I think it's the same Siemens system design.
I wonder how often the Flint reversible section has been used?

I couldn't comment I'm afraid, I've not worked that line since the resignalling. I do recall the then ATW asked for the signal heads on that scheme to not be as bright as those used on Shrewsbury - Crewe, but I don't know if they were succesful or not.

 

[Deepgreen]

Is the Dudding Hill line the last part of London to have Semaphores? I know they were also replaced like-for-like not too long ago so don't think they're going anywhere anytime soon.

Does a fixed distant signal that is just a board showing a horizontal distant semaphore on it and linked with an AWS magnet count as a semaphore signal?

I would say that if the 'signal' cannot move it is not technically semaphore, which involves moving indicators (flags, arms, etc.) of some sort.

 

[Annetts key]

problem is that power signalling seems to have a definite life after which its life expired. or obsolete, and parts are not available. So with increasing power signalling, much of it will be replaced every 30-40 years.

Depends on which technology has been used. The biggest problem with relay interlocking is not the relays, but the insulation of the cables and wiring. Renewal is a large costly project, hence it’s often decided to renew the signalling system instead. The standard range of relays are still available at the moment. And this is not likely to change anytime soon.

With computer or electronic based systems, yes, the modules and the parts used to form the electronic circuitry does go obsolete. Semiconductor manufacturers and manufacturers of other electronic components will only produce older designs if there is sufficient demand. And the railways requirements for routine replacement under maintenance or for spares for fault rectification are nowhere near enough for this to happen unless the railway wants to pay large sums of money…

Mechanical systems have the advantage that small scale production is not too hard. Although I remember that not that long ago the railway was hunting high and low for channel rodding, no new supplies were available and some was needed somewhere. So all the depots on our ‘region’ had to checked to see if there were any useful lengths lying around…

 

[Ken H]

Sorry to bump an old thread but there is a semaphore distant approaching Hellifield from Gisburn. You can see it from the Gisburn -Hellifield road just by where the B road goes off to Hellifield. Its on the right coming from Gisburn.
No idea if it is a fixed one or not but it doesnt look like it.

 

[Western 52]

Working distants are unusual now, often replaced by colour lights to save a long wire run. Another rarity these days are motor worked semaphores- how many survive?

 

[Annetts key]

Working distants are unusual now, often replaced by colour lights to save a long wire run. Another rarity these days are motor worked semaphores- how many survive?

Five years ago there were still motor worked semaphores at Worcester. Don’t know about now though.

 

[MadMac]

Working distants are unusual now, often replaced by colour lights to save a long wire run. Another rarity these days are motor worked semaphores- how many survive?

A few motor operated signals still around in Scotland, including Glenwhilly’s Down Distant, which also happens to be the last working semaphore distant in Scotland.

 

[Sheridan]

Working distants are unusual now, often replaced by colour lights to save a long wire run. Another rarity these days are motor worked semaphores- how many survive?

In north Wales I believe there are two working distants, those being on the down at Tŷ Croes and the Up at Deganwy. Both have colour lights in the other direction.

 

[SCDR_WMR]

Five years ago there were still motor worked semaphores at Worcester. Don’t know about now though.

Pretty sure they're still going strong there. I would say that Worcester may never get rid of theirs

 

[John Webb]

The biggest problem with motor-worked distants is to keep them working. The motors are no longer made, and there is a dearth of spare parts to keep them running! The Swanage Railway and other preserved railways are working on alternative methods using 'off-the-shelf' hydraulic power packs and actuators, according to an article in the Signalling Record Society's Autumn 2021 Newsletter.

 

[The Planner]

Pretty sure they're still going strong there. I would say that Worcester may never get rid of theirs

Re-signalling design has started.

 

[SCDR_WMR]

Re-signalling design has started.

Almost a shame really. I no longer work that route but I'm glad that did, not that many get to work semaphore signals these days. I don't miss attempting to see them in the dark, or against the backdrop of the shed lighting at Shrub Hill though!

 

[bramling]

Almost a shame really. I no longer work that route but I'm glad that did, not that many get to work semaphore signals these days. I don't miss attempting to see them in the dark, or against the backdrop of the shed lighting at Shrub Hill though!

Must admit there are some places which just won’t seem right without semaphores. Worcester and Shrewsbury for starters, and parts of the Cornish main line as well.

 

[plugwash]

Depends on which technology has been used. The biggest problem with relay interlocking is not the relays, but the insulation of the cables and wiring.

I don't know about the wiring used in railway signalling specifically but AIUI a big issue with old rubber wire insulation generally is that it goes hard and becomes prone to cracking but as long as it's not disturbed it does still insulate fine.

This means you get backed into a corner where modification or even repair work risks causing more problems than it solves.

 

[Annetts key]

I don't know about the wiring used in railway signalling specifically but AIUI a big issue with old rubber wire insulation generally is that it goes hard and becomes prone to cracking but as long as it's not disturbed it does still insulate fine.

This means you get backed into a corner where modification or even repair work risks causing more problems than it solves.

The railways like PCP type rubber cable, as it is robust and will not melt (like PVC) when wires are pulled over each other as they are run in.

Four problems:

For external cables, after fifteen to twenty-five years (typical if buried, lasts longer in surface concrete troughing), the sheath and insulation starts to become porous, letting in water. This causes earth leakage faults and eventually one or more cable cores will corrode and go open circuit.

For internal cables, especially in in a hot equipment enclosure or near/above a heat source, eventually the insulation goes brittle. Then any movement will cause cracks, then the insulation may literally flake off. This is called dry degradation.

Still with internal cables, sometimes the insulation goes mushy and wet. This is a reaction between the metal conductor and the insulation. This is known as wet type degradation.

For terminations and internal wiring, the past practice of using mineral oil to protect the terminals from corrosion has a side effect, it affects the PCP rubber. The insulation and sheath is affected, the sheath then splits.

And unfortunately, rather than dealing with it as soon as problems are noticed, it gets left, and then it becomes unpractical to work on…

 

[MarkyT]

I don't know about the wiring used in railway signalling specifically but AIUI a big issue with old rubber wire insulation generally is that it goes hard and becomes prone to cracking but as long as it's not disturbed it does still insulate fine.

This means you get backed into a corner where modification or even repair work risks causing more problems than it solves.

That is precisely the problem with some generations of relay interlockings. Insulation degradation seems to affect some manufacturers more than others, and particular batches of wire were worse than others. Certain GEC schemes from the late 1970 and early 80s caused major problems in this respect over the last two decades, while Westinghouse installations a decade or more older were still fine and capable of taking alterations. Sometimes, wired interlockings have been replaced by 'interfaced SSI' in the same equipment rooms to overcome the problem while keeping all the external lineside cabling and equipment from the original scheme.

And unfortunately, rather than dealing with it as soon as problems are noticed, it gets left, and then it becomes unpractical to work on…

Unfortunately, it's also often difficult to accurately determine how widespread the problem is once some signs are first identified in a large, complex interlocking, as the precautionary principle means you have to be very careful pulling wires out of well-packed trunking (often laced tightly together in early schemes) to investigate, as that risks further damage to the wires. While insulation degradation can cause short circuits, blowing fuses and disabling functionality, it can also potentially set up random 'false feeds' between unrelated circuits that just happen to run alongside each other in a particular raceway. That could instigate 'wrong side' false aspect clearance or unexpected point movement in a worst-case scenario, putting moving traffic at great risk. When I was at RT/NR until just over a decade ago there were a fair number of installations still in service on the former Southern patch that had embargoes on any alterations in force, while awaiting schemes to solve the degradation.

 

[Ken H]

Working distants are unusual now, often replaced by colour lights to save a long wire run. Another rarity these days are motor worked semaphores- how many survive?

There is one approaching hellifield from clitheroe

 

[Annetts key]

Unfortunately, it's also often difficult to accurately determine how widespread the problem is once some signs are first identified in a large, complex interlocking <SNIP>

BR had discovered many of these problems by 1988, some of them a lot earlier. They also discovered that some supplied (new) wire had insulation that was not satisfactory even a short amount of time after having been installed.

There was an inspection done around this time on Western, and the notices that were installed in the affected equipment stated after the warning about wiring with fragile and defective insulation being present, that this wiring would be replaced. But this did not happen and instead the privatised railways instigated inspection. One installation carried on until 2019. That’s over 30 years. It’s possible that some of this defective 1986 batch is still in use elsewhere.

In my area, as long as the insulation was still there, mostly no specific renewal work went on to replace it (*). That is until the insulation could no longer be patched up with insulation tape. And then it was mostly maintenance staff that very carefully replaced individual wires (just the worst examples).

* unless other project work was taking place.

Back when maintenance was allowed to renew lineside cables, when renewing the lineside cable in an equipment location cupboard, my team among others regularly took the opportunity to replace the internal wiring between the cable terminations and wherever else it was going. We often renewed the other wiring that was in the same cable tree as well. But this was a local initiative rather than an official policy.

Oh, and it needs to be pointed out that defective/degraded insulation can no longer withstand the rated insulation test voltage. Especially if condensation forms or the wiring gets wet by other means. This can cause earth leakage faults and stray voltage faults. Both of which may contribute to a unsafe wrong side signalling failure. One member of staff with wet hands touched some dry wiring that had defective/degraded insulation and was rewarded with an electric shock. Luckily it was minor.

 

[MarkyT]

BR had discovered many of these problems by 1988, some of them a lot earlier. They also discovered that some supplied (new) wire had insulation that was not satisfactory even a short amount of time after having been installed.

There was an inspection done around this time on Western, and the notices that were installed in the affected equipment stated after the warning about wiring with fragile and defective insulation being present, that this wiring would be replaced. But this did not happen and instead the privatised railways instigated inspection. One installation carried on until 2019. That’s over 30 years. It’s possible that some of this defective 1986 batch is still in use elsewhere.

In my area, as long as the insulation was still there, mostly no specific renewal work went on to replace it (*). That is until the insulation could no longer be patched up with insulation tape. And then it was mostly maintenance staff that very carefully replaced individual wires (just the worst examples).

* unless other project work was taking place.

Back when maintenance was allowed to renew lineside cables, when renewing the lineside cable in an equipment location cupboard, my team among others regularly took the opportunity to replace the internal wiring between the cable terminations and wherever else it was going. We often renewed the other wiring that was in the same cable tree as well. But this was a local initiative rather than an official policy.

Oh, and it needs to be pointed out that defective/degraded insulation can no longer withstand the rated insulation test voltage. Especially if condensation forms or the wiring gets wet by other means. This can cause earth leakage faults and stray voltage faults. Both of which may contribute to a unsafe wrong side signalling failure. One member of staff with wet hands touched some dry wiring that had defective/degraded insulation and was rewarded with an electric shock. Luckily it was minor.

While a few individual wires could be replaced expediently by local techs, running them on top of the trees and definitely not pulling the old ones out (but clearly cutting them back from terminals and properly insulating them!), the risks and costs of wholesale replacement was a major issue, and practically the industry probably didn't have the capacity without abandoning pretty much all other renewal and enhancement works, especially after the Clapham Jn recommendations came into force, limiting extreme overtime working. Risk analysis was definitely carried out for affected installations and the consensus generally was that as long as the wiring wasn't disturbed (by alterations for example), in most cases the risk was tolerable pending full renewal at some time in the future. Some kinds of alterations were possible in the meantime, such as the abandoning of selected operational facilities where the redundant wires could all be left in the wiring trees. Major layout changes usually triggered complete renewal. An example was Stoke Gifford (Bristol Parkway), renewed in full as a WR E10K relay interlocking in the mid-1990s for the shiny new Royal Mail terminal that was abandoned shortly afterwards. Fortunately, the equipment room there was large enough that complete replacement racks were able to be wired and tested alongside the old ones and the commissioning simply changed over from the old interlocking to the new one.

 

[Annetts key]

An example was Stoke Gifford (Bristol Parkway), renewed in full as a WR E10K relay interlocking in the mid-1990s for the shiny new Royal Mail terminal that was abandoned shortly afterwards.

Funnily enough, before BR was killed off, this interlocking was supposed to be modified for SIMBIDS (simplified bi-directional signalling). But after the overruns with the North Somerset Junction to Thingley Junction SIMBIDS scheme, operations declined four day weekend blockades and not enough money was available apparently for replacement with SSI…
Hence there were never any more SIMBIDS signalling schemes on this part of Western.

The full replacement of Stoke Gifford interlocking as part of the Royal Mail scheme was in part funded by external funding as I understand it.

Now the complete interlocking is redundant, having been replaced by the TVSC SSI scheme.

Sorry, this has gone a bit off topic

To try to get it back on topic, in mechanical signal box areas, a type of wiring that went by the nick name ‘flameproof’ was often used. I can’t for the life of me remember it’s official name though. It appeared to survive for longer than the normal PCP rubber insulation.

 

[MarkyT]

To try to get it back on topic, in mechanical signal box areas, a type of wiring that went by the nick name ‘flameproof’ was often used. I can’t for the life of me remember it’s official name though. It appeared to survive for longer than the normal PCP rubber insulation.

'Flameproof' has a strong shiny textile sheath over the rubber insulation of each individual wire. I assume the textile is treated with some fireproofing chemical but it also provides considerable mechanical strength to prevent damage to the insulation if it comes into contact with the metalwork of lever frames etc.

 

[snowball]

(but clearly cutting them back from terminals and properly insulating them!)

Failure to do which caused the Clapham crash, of course.

 

[MarkyT]

Failure to do which caused the Clapham crash, of course.

I think prior to Clapham most good installers who were not overtired or impaired by sleep deprivation knew the importance of that measure very well and usually at least applied a fold of insulation tape over the ends of cut-back wires. Post Clapham, instructions required a crimped insulated terminal on each redundant wire end and proper labelling. It was a particular issue with the old shelf-type relays as at Clapham with big exposed terminal posts (there are plastic covers available to protect these but they're not always present). More modern plug-in relays with hidden 'spade' type terminals were much less prone to this kind of thing, although the risk was still present at exposed fuse terminals and cable termination links.

 

[Steve050462]

New to this thread, but I would have thought that the remaining semaphores on the Boston to Skegness line would be amongst the last to remain in situ. I'm not aware of any planned re signalling scheme for East Lincolnshire unless of course, anybody knows differently..

 

[HSTEd]

I suppose modern signalling mitigates against those sorts of false feeds simply by reducing the number of cables in which erroneous connections can cause an undetected false feed dramatically.

If a couple of digital signal cables touch they are unlikely to do anything but cause an error to be generated on the bus.

 

[TheBigD]

Working distants are unusual now, often replaced by colour lights to save a long wire run. Another rarity these days are motor worked semaphores- how many survive?

M21 signal on the up line at Manea is a motor worked semaphore signal.

 

[High Dyke]

New to this thread, but I would have thought that the remaining semaphores on the Boston to Skegness line would be amongst the last to remain in situ. I'm not aware of any planned re signalling scheme for East Lincolnshire unless of course, anybody knows differently..

Not aware of anything either. There are always suggestions circulating about projects, but nothing seems to materialise. The closure of Swinderby seems to have gone back yet again (now believed to be 2024).

In respect of motor worked signals. Currently Lincolnshire has:

• Ancaster - Up Distant
• Hubberts Bridge - Down Distant
• Boston West Street - Up Starter