Wrong side signal wiring fault

[martin_wynne]

30 minutes ago, St. Simon said:

very few bits of it are truly 'fail safe',

 

Abermule was the classic case -- what's the use of a single-line tablet if it's the wrong one?

 

[Michael Hodgson]

10 hours ago, The Stationmaster said:

And you can't rely on axle counters to detect anything unless it physically  passes over one of the counters.

Of course it has to pass over the counters at both ends of the section to tell you the train has passed clear; even then, it can't know whether the section was clear to start with, so every time you switch it on you effectively have to tell it the section's clear. 

[roythebus1]

10 hours ago, The Stationmaster said:

And you can't rely on axle counters to detect anything unless it physically  passes over one of the counters.

Something no doubt local oiks may have discovered by jumping up and down on random axle counters.

 

[The Stationmaster]

10 hours ago, roythebus1 said:

Something no doubt local oiks may have discovered by jumping up and down on random axle counters.

 

As modern axle counters don't require physical contact between wheels and the counter head I doubt that would work (apart from possibly damaging the head?) but St Simon will know for definite.  A bit of pressure on a level crossing treadle might work but I suspect would need a lot of weight to do so

[Oldddudders]

41 minutes ago, The Stationmaster said:

  A bit of pressure on a level crossing treadle might work but I suspect would need a lot of weight to do so

ISTR on our Rules & Regs course in 1974 we had an outvisit to somewhere near Castle Donington, where some clown did indeed investigate the feasibility of such an action, with regrettable success. The instructor, a signalling inspector, had to eat humble pie on the phone with the controlling box....

[DY444]

52 minutes ago, The Stationmaster said:

As modern axle counters don't require physical contact between wheels and the counter head I doubt that would work (apart from possibly damaging the head?) but St Simon will know for definite.  A bit of pressure on a level crossing treadle might work but I suspect would need a lot of weight to do so

 

I don't know if this applies to modern axle counter heads but I believe some earlier variants were able to be confused by such things as shovel heads and other similar metallic objects being passed close by (usually by accident rather than malicious intent)

[St. Simon]

8 hours ago, The Stationmaster said:

As modern axle counters don't require physical contact between wheels and the counter head I doubt that would work (apart from possibly damaging the head?) but St Simon will know for definite.  A bit of pressure on a level crossing treadle might work but I suspect would need a lot of weight to do so

 

7 hours ago, DY444 said:

 

I don't know if this applies to modern axle counter heads but I believe some earlier variants were able to be confused by such things as shovel heads and other similar metallic objects being passed close by (usually by accident rather than malicious intent)

Hi,

 

No, modern Axle Counters aren’t affected by shovels or small hand tools (but larger hand tools can affect them, but they’ll fail rather than detect a train as the disturbance in the magnetic field won’t be correct for the system to recognise it as a wheel flange), nor will any youths jumping up and down on it.

 

There are now systems and logic in place to reduce a miscount and failure, particularly in Frauscher Counters. These include a system whereby a head doesn’t recognise any disturbances in the field unless there is a train on approach to the head. There is another new system that also reduces miscounts on Frauscher, but I can’t remember it now!

 

In terms of stuff (Trolley or RRV) entering ‘mid section’ and not having gone over an entry head, this should only be done under a line block or possession with the use of ‘Engineering Possession Reminder’ (EPR) within the evaluator and control system, that doesn’t require a reset, but does apply Aspect Restriction until a sweep train has gone through.

 

For stuff that might not trigger axle counters (certain OTP I think), then there is the ‘Special Train Reminder’ (STR) that works the same as an EPR.

 

Simon

Edited December 25, 2022 by St. Simon

[phil-b259]

23 hours ago, St. Simon said:

 

 

 

In terms of stuff (Trolley or RRV) entering ‘mid section’ and not having gone over an entry head, this should only be done under a line block or possession with the use of ‘Engineering Possession Reminder’ (EPR) within the evaluator and control system, that doesn’t require a reset, but does apply Aspect Restriction until a sweep train has gone through.

 

Ahem….

 

https://www.gov.uk/raib-reports/report-11-slash-2022-collision-between-a-passenger-train-and-a-hand-trolley-at-challow

 

[phil-b259]

On 23/12/2022 at 21:53, St. Simon said:

 

Hi,

 

Off Topic I know, but I think that is a myth, a broken rail can cause a track circuit failure in the right conditions, but it won't definitely cause a Track Circuit Fault. It is just as common, if not more common, that broken rails are detected via patrols or reports rather than a Track Circuit Failure. The reality is that it needs to be a clean 'wide' break in dry conditions to cause a track relay to drop. I think the 'rail break' argument taken out of any Track Circuit conversation

 

 

 

[TheSignalEngineer]

On 25/12/2022 at 11:12, DY444 said:

 

I don't know if this applies to modern axle counter heads but I believe some earlier variants were able to be confused by such things as shovel heads and other similar metallic objects being passed close by (usually by accident rather than malicious intent)

About 50 years ago we had a 'contactless wheel detector' mounted on the rail at an AHB crossing. It was wired to a pen recorder to along with the clearout treadle to check its reliability at detecting trains. We got a ghost reading several times each week. A site visit after working out the pattern discovered that it was the length walker's spanner coming close to it.

[TheSignalEngineer]

On 23/12/2022 at 21:53, St. Simon said:

 

Hi,

 

 a broken rail can cause a track circuit failure in the right conditions, but it won't definitely cause a Track Circuit Fault. It is just as common, if not more common, that broken rails are detected via patrols or reports rather than a Track Circuit Failure. 

Thread Drift Warning.

Especially in electrified areas. In AC electrification bridges and structures are bonded to the traction rail so it is inherently a big earth rod. A broken rail in the traction return rail can be bypassed by earth leakage and also cross bonding between parallel tracks. I had an interesting case when doing immunisation tests on the original Thameslink job. When we joined the running  rails through near what is now City Thameslink station the pattern of DC traction leakage from the Southern 3rd rail network at Farringdon was not as predicted. I followed the track towards Barbican checking the current flowing in the structure bonds attached to the rail. About three bonds into Smithfield Tunnel there was a much greater current than anywhere else. I looked up and saw it was all bonded to the roof girders above me,  which were part of the structure of Smithfield Market. Upstairs this carried a spiders web of conduit which was in turn connected to the local electricity board earth in the substation.

On 23/12/2022 at 21:53, St. Simon said:

Not all trains operate Track Circuits reliably, On Track Plant being one such type, and there are conditions (where the vehicle axle does not present the least resistive circuit) that allow the relay to be picked whilst a train is on the circuit.

Added signalling details to an accident inquiry plan for a PW machine wedged under the front of a Class 47 at Lapworth many years ago. Route had been set out from a siding at Hatton. Signalmen changed over whilst it was running towards Dorridge and it was forgotten about. New signalman saw routes set but no tracks showing occupied, pulled the route and buttoned up for an express. Oh $**T.

 

On 24/12/2022 at 20:05, St. Simon said:

The more you delve into signalling, the more you realise that very few bits of it are truly 'fail safe', instead the key is that it is the system as a whole that is fail safe.

In the days of us Dinosaurs, our understanding was that in any working system faults are inevitable. Many will be protected as the system will cease to function when the fault occurs. Occasionally the subsystem affected will continue to operate incorrectly causing a potential hazard. Sometimes the overall system will recognize this and protect against it. Sometimes it will be noticed by the signalman, train driver or other person and they will take action to stop 'The Machine'. On a very few occasions it will get through all of the checks and cause an accident. Our job was to reduce this to as near to zero as possible. 

[2251]

I take it this was the report in question:

 

https://www.railwaysarchive.co.uk/documents/MoT_Lapworth1969.pdf

[jim.snowdon]

11 hours ago, TheSignalEngineer said:

Especially in electrified areas. In AC electrification bridges and structures are bonded to the traction rail so it is inherently a big earth rod. A broken rail in the traction return rail can be bypassed by earth leakage and also cross bonding between parallel tracks. I had an interesting case when doing immunisation tests on the original Thameslink job. When we joined the running  rails through near what is now City Thameslink station the pattern of DC traction leakage from the Southern 3rd rail network at Farringdon was not as predicted. I followed the track towards Barbican checking the current flowing in the structure bonds attached to the rail. About three bonds into Smithfield Tunnel there was a much greater current than anywhere else. I looked up and saw it was all bonded to the roof girders above me,  which were part of the structure of Smithfield Market. Upstairs this carried a spiders web of conduit which was in turn connected to the local electricity board earth in the substation.

Thank you for reminding me of the detail of that. One of the occasional aspects of my day job is teaching people about the perils inherent in the way that 3rd Rail DC electrification (including tramways) is not earthed, as well as why it is not earthed.

[TheSignalEngineer]

10 minutes ago, jim.snowdon said:

Thank you for reminding me of the detail of that. One of the occasional aspects of my day job is teaching people about the perils inherent in the way that 3rd Rail DC electrification (including tramways) is not earthed, as well as why it is not earthed.

We got some strange results when we took measurements on the Midland line from Farringdon. Track had been laid in the tunnel but not joined through. We had already taken some measurements and had found quite a large amount of background DC which matched in with train movements on London Underground and around Blackfriars. One Sunday night we clamped big traction bonds across the gap in the running rails. We had arranged for the last DC  substation on the way into Blackfriars to be disconnected so that the feed was coming from south of the river to increase the length of the return path and maximise the amount of local leakage. We calculated that the highest load we could get would be  two Class 455 units coupled and starting away from Blackfriars into Holborn Viaduct. We connected pen reorders to measure the volt drop along the return rail at the Moorgate and Kings Cross legs of the junction at Farringdon, St Pancras Main Line station, Kentish Town, West Hampstead and Hendon. Besides the unexpected result at Farringdon we managed to measure a change in the DC level in the rails at Hendon. The strange thing was that the DC out there was suppressed by the train at Blackfriars. When the results were all viewed together we surmised that there must have been some very interesting effects in the West Hampstead area where you have the Metropoliotan/Bakerloo and the North London (still 3rd rail at that time). The MML sits half way between the two other lines and they seemed to be working in opposition.  Another place we got an unexpected drop was around Kings Cross were the Fleet River (Sewer) goes across the roof of the Widened Lines tunnel. As the area is AC with a Return Conductor and Earth wire bonded to the structures in the roof it is also connected to the sewer pipe.

 

Happy Days probing the mysteries of how electricity gets back to source after it has been used to drive things. Makes the black art of signalling seem simple stuff.

[Oldddudders]

13 hours ago, TheSignalEngineer said:

Happy Days probing the mysteries of how electricity gets back to source after it has been used to drive things. Makes the black art of signalling seem simple stuff.

ISTR the Class 92s were the subject of some engineering concerns on DC, delaying route approval, not least because one of the suppliers was distinctly coy about the characteristics of his kit. 

[The Stationmaster]

1 hour ago, Oldddudders said:

ISTR the Class 92s were the subject of some engineering concerns on DC, delaying route approval, not least because one of the suppliers was distinctly coy about the characteristics of his kit. 

The Class 92s, effectively half a Class 373 in many respects as far as the electrical kit was concerned.  caused considerable concern over much of the rail network but 3rd rail land suffered first.  One observer described them as having an emissions signature similar to the explosion of a nuclear bomb - but testing basically disproved that although their current draw was restricted at first and then gradually increased (as had been the case with Class 373s).  The big worry was interference with various types  jointless track circuits and some types were not permitted to be used (and had to be replaced) on routes where Class 373s and 92s were intended to operate.

 

It got even more entertaining on the WCML where all tests had to be initially conducted north of, I think either Carnforth or possibly Lancaster, but it was then relaxed to allow working on test trains only north of Crewe provided they ran in their booked path.  But the real amusement came up day when the train was sitting in a loop and the emissions monitoring equipment went berserk with some of the worst figures the test team had ever seen.  They tried to work out what was going on and then realised that the information had been recorded as a normal ECML passenger train - probably worked by a Class 87 - had been passing.  So they looked out for a further opportunity to see what happened if a Class 87 passed while the 92 was stationary and sure enough they got similar readings.  The tests were then curtailed and 92s were rapidly officially cleared for various parts of the BR 25kv network with no more questions asked.

[TheSignalEngineer]

I remember some tests with an 87, I think 87101. It put out so much electrical noise it dropped off the radar in Kilsby Tunnel.

 

When we were doing testing on the DC Lines SSI scheme in 1988 we had a lot of problems at Harrow & Wealdstone. We had an oscilloscope on the Data Link and signalling power supply to look at the interference. Within a couple of hours I could tell 100% accurately what type of loco or unit was coming just by what rubbish it was putting out.

[martin_wynne]

RAIB report published today:

 

 https://www.gov.uk/raib-reports/report-11-slash-2023-two-trains-in-the-same-signal-section-at-south-wingfield

 

Martin.

[ess1uk]

I thought IRSE licensing was supposed to stop this?

[Michael Hodgson]

16 minutes ago, ess1uk said:

I thought IRSE licensing was supposed to stop this?

 

Only one of the three testers at Wingfield was licensed and Network Rail wasn't checking the qualifications of contractors' staff.

However people can make mistakes even when they are qualified.

[Vanfit]

Having an IRSE Licence does not in itself mean the holder is at all times and in all situations competent.

 

To quote from the IRSE web site:-

‘The IRSE Licensing Scheme provides assurance about the competence of individuals to carry out technical safety-critical or safety-related work on signalling and railway telecommunications equipment and systems.

It provides an accepted cross-industry benchmark of competence for personnel carrying out a range of activities from maintenance through design, installation, testing, project engineering and senior technical management. All licence holders must abide by the Obligations of Licence Holders, which set out the professional standards expected.’

 

The licence scheme was developed after the Clapham tragedy as a means of (for instance) increasing professionalism, setting consistent standards of working and giving assurance that the person has reached a certain level of competence set against defined standards.

 

A licence on its own has benefit in assessing an individual’s suitability to carry out certain tasks, however the licence must be complemented with that persons Authority to Work (ATW - an agreement between the employee and employer as to exactly what tasks may be undertaken and at what level of complexity). For instance, holding an IRSE Principle Designers licence will not necessarily mean the holder is competent on all types of interlocking from Mechanical through RRI to SSI, that information is contained within the ATW.

 

The licence is held and owned by the individual and not the company, the ATW is the associated company document.

 

But perhaps the most important safeguard that ensures these authorities are suitable and sufficient for each individual is that those who manage IRSE licence holders should undertake regular checks in person. For a licence holder whose duties are mainly outside/practical this could mean management ‘by walking about’ seeing the work actually being carried out. If in an office environment then perhaps the G J Churchward technique of sitting with a designer and talking over the work. These can be carried out by managers in a supportive and professional manner, it is basically the cement that holds all the pieces of competence documentation together

Edited January 2 by Vanfit