Facing Point Locks

[Nearholmer]

Dear Eminences Gris

 

I seek your guidance in the matter of FPLs and locking bars.

 

In some places, a locking bar actuated by the train wheels to operate FPL.

 

in some places an FPL operated by a lever at the 'box or GF.

 

MoT Regs & Recommendations 1950 addition has a section entitled FPLs, which then seems to talk only about locking bars, not about FPLs operated by a lever (I admit that I may have misunderstood what it is trying to say!).

 

Why the differences in practice?

 

And, was there a change in thinking or legislation away from locking bars at some date, and if so, why?

 

This is not an IRSE exam practice question, I'm just more curious about the topic than is really healthy for a grown man.

 

Kevin

[micknich2003]

Here is a picture of a mechanical Facing Point Lock. There is no "Lock Bar" because a Track Circuit is run through the switches. With the TC occupied the FPL lever is electicaly locked and therefore the FPL can't be withdrawn, and the switches remain locked.

 

[Grovenor]

Dear Eminences Gris

 

I seek your guidance in the matter of FPLs and locking bars.

 

In some places, a locking bar actuated by the train wheels to operate FPL.

I am not aware of any such locking bars in UK practice, when the wheels are above the locking bar they prevent the bar from being moved by the lever.

in some places an FPL operated by a lever at the 'box or GF.

Yes, that is standard, in installations without track circuits the lever will work the facing point lock and the locking bar. Where there are track circuits over the points then the facing point lock lever will be electrically locked to give the same effect as the locking bar, ie the facing point lock cannot be unbolted when a train is present.

MoT Regs & Recommendations 1950 addition has a section entitled FPLs, which then seems to talk only about locking bars, not about FPLs operated by a lever (I admit that I may have misunderstood what it is trying to say!).

 

Why the differences in practice?

I assume you are referring to this section

21. Facing point equipment. Facing points on passenger lines, and all points regularly used in the facing

direction by passenger trains to have:—-(a) A bolt-lock through a third stretcher bar, with its

bolt either worked through a locking bar or controlled by track circuit. Locking bars, if used, to be longer than the greatest inter-axle

dimension of vehicles likely to pass over them.

This clause requires a facing point lock (called a bolt-lock) and for this to be locked in place by a locking bar or by a track circuit just as I said above. It does not mention levers as the lever is not the safety precaution and not all points are operated by levers.

And, was there a change in thinking or legislation away from locking bars at some date, and if so, why?

No there has not been any change in this requirement but the mechanical locking bars have beengradually replaced by track circuits as signalling has been modernised. Where points are operated by machine the facing point lock bolt is incorporated in the machine. And some alternative designs have been accepted that achieve the same objective with a different mechanical arrangement, eg Clamp locks.

 

 

Regards

Edited August 28, 2015 by Grovenor

[Siberian Snooper]

Another method of FPL is one where you need a key on the token to unlock the FPL lever and reverse it before reversing the turnout, used a lot on single lines or remote sidings.

[The Stationmaster]

I think you will find in all cases as far as mechanical points are concerned that the FPL is operated by a lever in the signalbox which controls that point.  But there the 'common' situation ends - in the modern situation with track circuiting through the point the FPL is usually directly operated by the lever and there is an electric lock, controlled by the track circuit, on that lever.  The usual arrangement in theh past was for the signalbox lever to actuate the facing pint lock  (or locking) bar and for the actual facing point lock (as illustrated by Micknich) to be driven in turn by the lock bar.  thus in both cases, but in different ways, the presence of wheels in the vicinity of, or on, a facing point prevented the lock from being unlocked.  The other situation is where an economical facing point lock was employed (much favoured by the Midland Railway and latterly on parts of the LMS in which case a single lever worked the lot, including the point switches.

[RailWest]

>>>Another method of FPL is one where you need a key on the token to unlock the FPL lever and reverse it before reversing the turnout....

That is simply a variation in how the FPL lever is controlled, unrelated to the actual mechanism at the FPL itself. However, in such cases. it tended to be the practice that NO lock-bar would be provided at the point because the person working the GF would be stood very close to the point and therefore could see whether or not the train was stood over it.

>>> In some places, a locking bar actuated by the train wheels to operate FPL.....

 

AIUI it was the case on the 'Mumbles Railway' that trains leaving a passing-loop depressed a fouling bar in order to unlock the facing point so that it could be trailed. I wonder if similar was used elsewhere?

[phil-b259]

 

AIUI it was the case on the 'Mumbles Railway' that trains leaving a passing-loop depressed a fouling bar in order to unlock the facing point so that it could be trailed. I wonder if similar was used elsewhere?

 

I believe that a similar-ish arrangement (in respect of the principles, not the actual equipment) was / is employed on RETB lines where passing loops are installed. Basically it ensures the points are locked for trains entering a loop from the single line, yet said points can still be trailed through by a train heading in the opposite direction on to the single line.

[Grovenor]

Trailable facing point locks are fairly common elsewhere in Europe but have not been accepted for UK mainline use. The clamp lock was developed from a German trailable design and was modified to remove the trailable feature so that it met the UK requirements.

Regards

[The Stationmaster]

I believe that a similar-ish arrangement (in respect of the principles, not the actual equipment) was / is employed on RETB lines where passing loops are installed. Basically it ensures the points are locked for trains entering a loop from the single line, yet said points can still be trailed through by a train heading in the opposite direction on to the single line.

Not quite Phil - there is nothing to 'unlock' (other than in the mechanism itself) when the points are trailed.  My two pics below, taken on an IRSE visit some years ago, show the mechanism - at Churston in the case but absolutely standard BR kit - (including one with the emergency pump handle in position) and they are basically held in the facing position by ram pressure.

 

 

 

As some people may know there have long been considerable problems sourcing spare parts for this equipment and in a  number of cases (e.g the Central Wales Line) they have been replaced by ordinary electric point machines (which are not trailable as far as I'm aware).

Edited August 30, 2015 by The Stationmaster

[Nearholmer]

Many thanks Gentlemen.

 

Somehow, I overlooked these very useful replies, and pestered StationMaster into a long explanation on another thread.

 

I now feel able to talk about this topic without confusing myself and others in the process!

 

Kevin

[rob brown]

anyone know when should FPL testing be carried out and how often thanks

[Merfyn Jones]

anyone know when should FPL testing be carried out and how often thanks

 

After any alterations or renewals, otherwise every 12 weeks when I retired. Is it still the same ?

[rob brown]

After any alterations or renewals, otherwise every 12 weeks when I retired. Is it still the same ?

Thanks for the help Merfyn

[mike hughes]

When I first started it used to be every 6 weeks, don't know what it is now as all our mechanical FPLs went a few years ago

[timbowilts]

After any alterations or renewals, otherwise every 12 weeks when I retired. Is it still the same ?

IIRC In my time on the WR we expected the Signalman to do a self test of the frame on Sundays

 

Tim T

[The Stationmaster]

IIRC In my time on the WR we expected the Signalman to do a self test of the frame on Sundays

 

Tim T

 

While something very different from check gauging FPL tolerances the S&T locking tests were a regular feature on the WR and were carried out by experienced S&T staff as they knew what to look for when testing locking - the K2 notice regularly contained entries about Sunday locking tests.  The only 'locking test' a Signalman was required to carry out was a test of the electric locks on signal levers released by 'Line Clear' and that was on all occasions immediately after taking duty - quite why it lasted so long in the regulations I really don't know but presumably it was in the SGIs as a consequence of somebody's past naughtiness which had caught out the Signalman who relieved him?

[TheSignalEngineer]

At New Street when I started the FPL tests were monthly. Mechanical trailing points with shunt moves had detection tested 3-monthly.

[phil-b259]

FPL tests are required to be carried out by S&T staff every 12 weeks as a minimum.

 

There is nothing which means various S&T chief engineers cannot reduce this for reliability reasons - but they cannot extend it beyond 12 weeks.

 

Before the introduction if condition monitoring / data loggers to each set of points down our way, it was quite common for points on the fast lines to have a check every 6 weeks so adjustments could be made more frequently to avoid failures (these days condition monitoring data tells us about potential problems which we need to investigate between 12 weekly visits).