Brake continuity test on vacuum braked stock

[Compound2632]

On a slightly different but related tack, if you will excuse me? I've read that the standard coupling fitting for vacuum pipes was developed by S.W. Johnson and T.G. Clayton, the Locomotive and Carriage & Wagon Superintendents of the Midland Railway, at the time that line was standardising on the vacuum brake in the early 1880s. I got the impression that the design never changed (it would be difficult to adopt a new one on an already vacuum-fitted line) - did it become the subject of an RCH standard? Is their design essentially what was used until the end of vacuum brakes on BR, and remains in use to this day on preserved lines?

[The Stationmaster]

The GW was trying to achieve quicker release of vacuum brakes with it's 25psi, so it wasn't just about being different; as usual with the GW, it was about being 'better', even at the cost of the inconvenience of having to isolate the brakes and blow them off again every time a 25 inch loco was changed for a 21 inch on or vice versa.  You also have to pull the strings to isolate the applied brakes to release them for shunting when the train arrived at the destination yard, a lengthy enough process as you have to do each individual wagon on what might be a 60 wagon fitted freight, and no fun if it's belting down with rain!

 

The large ejector of a steam loco can blow a train's vacuum brakes pretty quickly, but early diesel and electric locos' compressors were not as capable, and this is probably one, though by no means the only, factor leading to the adoption of air brakes, originally with a twin pipe 'train' and 'reservoir' to facilitate quicker release.  There is no inherent superiority of air over vacuum; the efficiency of the braking system is down to the pressure of the brake block on the wheel or clasp on the disc, and a very good 'instant release' twin pipe vacuum system can be found on 1st generation dmus.  A quick release enables smoother and more accurate braking, and ensures that the brakes do not drag.

 

Not quite - the GWR developed the use of a higher level of vacuum in order to get a more powerful brake application and not to get a quicker brake release. The development followed a couple of serious collisions where it was estimated that the results might have been mitigated with a more powerful brake hence the adoption of the higher level of vacuum.

 

However going for 25" of vacuum poses a problem as the ejectors will consume more steam - the GWR got round this by using a crosshead driven vacuum pump to maintain the vacuum when running.  Compressors on a diesel or electric loco will of course have no effect whatsover on a vacuum brake system - it require exhausters to remove air pressure from the system rather than compressors to force air in at greater than atmospheric pressure.  The WR's diesels seem to have had no problems creating and maintaining a brake at 25" of mercury which suggest to me that they had ample exhauster capacity to do the job and they never seem to have had any problem blowing off the brakes.

[russ p]

With a diesel its simply a matter of adjusting a valve

[Wheatley]

Always 'bags' on the ER when I learnt them in 1988, and my instructor managed to find two wagons with brand new bags adjacent to each other for me to practice on. "If you can couple and uncouple these you'll be able to manage anything."

 

Cross the legs ...

Edited July 16, 2018 by Wheatley

[Siberian Snooper]

There was a problem on a steam special which was hauled by 6000 from Shrewsbury to Newport and Brush type 4 was the train engine from Newport to Exeter and the strings had not been pulled on one of the coaches, said coach developed flats on the journey through the Severn tunnel and had to be shunted out of the train at Bristol. I can't remember whether or not we were on air or vacuum behind the diseasal.

[roythebus]

Vacuum is measured in Hg, inches of mercury. Air is measured in pounds per square inch or bar.

 

As other have said, it is not possible to overcharge a vacuum system to allow for the 21"/25" difference between the GWR and standard BR vacuum systems. Strings usually have to be pulled!

 

We had a similar problem when BR went over from 70psi to 72.5psi for air brakes in the mid 1970's probably 1977 to make the pressure standard with European stock. I remember changing locos at York and having to pull the strings to release the air brake on a down express. 20 minutes delay! Converted locos had something like a yellow dot sticker in the cab near the brake valve to let the driver know it had been modified to 72.5 psi or 4 bar in metric. 

 

Someone above mention class 60 with vac brake? I doubt it, everything after and including the 56 and 87 had air brakes only.

[TravisM]

Slightly off topic but I never understood why vacuum braking lasted so long in this country when virtually the rest of the railway world went over to air brakes over a century ago? Is it because we’re a island and with very little interchange of traffic with the rest of Europe so the thinking was “it works, why change”.

[LMS2968]

One reason was that you either came up with your own design of air brake system or paid royalties to Westinghouse, something which was always anathema to the railways.

A second reason was that, with a steam loco, a vacuum system was easy and reliable, involving an ejector with no moving parts to create the vacuum; air brakes required a pump of some sort, and maintenance costs.

Third, yes, it worked, so why change? It was the diesels which required an exhauster, so removing one of vacuum's main advantages.

[EddieK]

When I was involved at a well known steam railway, the vac brake continuity test required the train guard to jump down at the rear of the train once the loco was attached at the front and pull the vac hose off the dummy. Certainly proved continuity but more risk to the Guard in jumping off and onto platforms, also an increased risk of dirt, debris etc being drawn into the brake system. I believe they changed the rules such that this test applied first thing in the morning, also if the train had been shunted to add or remove a vehicle, but if the train was untouched apart from a loco run-round then operating the handle in the brake van was sufficient.

Every brake van had a little sign in it "Last Loco GWR" so the Guard could apply it to the parking brake as a reminder to pull the strings if the next loco was not GWR.

[LMS2968]

We didn't do that, even on BR. If opening the setter dropped the vacuum to zero, then the driver was able to rebuild it back to 21", that was it. You can hear the brakes going on and then back off without getting on the floor to see.

[russ p]

When I was involved at a well known steam railway, the vac brake continuity test required the train guard to jump down at the rear of the train once the loco was attached at the front and pull the vac hose off the dummy. Certainly proved continuity but more risk to the Guard in jumping off and onto platforms, also an increased risk of dirt, debris etc being drawn into the brake system. I believe they changed the rules such that this test applied first thing in the morning, also if the train had been shunted to add or remove a vehicle, but if the train was untouched apart from a loco run-round then operating the handle in the brake van was sufficient.

Every brake van had a little sign in it "Last Loco GWR" so the Guard could apply it to the parking brake as a reminder to pull the strings if the next loco was not GWR.

Sorry but thats Typical preserved railway rubbish, the reason a test is undertaken every time the continuity of the pipe has been disturbed is to check that the rear is working and not having the brakes held off falsely by a rag stuck somewhere that had been sucked into a pipe.

When it was BR where I was a test was ALWAYS carried out.

I'm afraid with preserved railways altering rules and other long standing instructions its only a matter of time before there is a big accident on a UK one. I hope I'm wrong but quite frankly I'm surprised it hasn't happened by now.

Some of These amateur outfits always seem to know best.

The rule book was based on incidents that had happened in the past and was to prevent these happening again, thing is the idiots they also employ as management on mainline railways its also starting to happen here too

[The Johnster]

As the guard's inspector that passed me out on Rules very colourfully put it, 'never forget, each one of these rules came out of a bucket of blood'.  If Heritage railways are not doing things properly, then this is a very serious matter and a failure not only of their own managements but the authorities to ensure that proper practices are carried out.  

[russ p]

I really hope that this stupid amended working isn't on the NYMR, because with a gradient like that and running over the national network things could be very serious

[Mike Storey]

Sorry but thats Typical preserved railway rubbish, the reason a test is undertaken every time the continuity of the pipe has been disturbed is to check that the rear is working and not having the brakes held off falsely by a rag stuck somewhere that had been sucked into a pipe.

When it was BR where I was a test was ALWAYS carried out.

I'm afraid with preserved railways altering rules and other long standing instructions its only a matter of time before there is a big accident on a UK one. I hope I'm wrong but quite frankly I'm surprised it hasn't happened by now.

Some of These amateur outfits always seem to know best.

The rule book was based on incidents that had happened in the past and was to prevent these happening again, thing is the idiots they also employ as management on mainline railways its also starting to happen here too

 

Interesting, emotional response, which I would guess is based on some experience or other.

 

I can only further comment by saying the issue over preserved ( and all) railways cannot be anything other than that approved by HMRI (ORR), whom I believe are still highly respected in the area of operations. Light Railway Orders can often result in relaxation of some rules, deemed heretical on the big railway. My only direct involvement as a member of mainline preservation was at the NYMR, whose COO at the time was an ex-BR director, who had a very long operations career and was highly respected in his R&R knowledge.

 

As for present-day on the main line, I fail to see your reason for such a comment. UK Rail safety has continued to improve despite all expectations, over the last 10 or more years (since Potters Bar at least). The continuing debate surrounds the difference between the long-standing ALARP basis of UK safety legislation and regulations, and that of codifying all rules, regardless of localised or specific risk assessment, favoured by most regimes across the western world (not just the EU as is often implied). You clearly favour the latter, as is your right - a rigid, unalterable set of processes and rules, based on the worst possible case regardless of likelihood. There is no criticism of that  - it has many experienced supporters. But it is also of note that the safety record of those administrations with a continuing record of poor safety, such as Germany, France, Spain and Italy, who apply rules in this way, have a very significantly worse record than that of the UK, over the past 18 years or so anyway. Those regimes are stuffed full of "experienced" railway peeps.

[EddieK]

Not speaking as a railway operator, but if the continuity of a set of coaches has been proven at the start of the day - all the way from the loco to the far end of the rake - and that brake pipe is then not disturbed except by taking the loco off one end of the coaches and putting it on the other end, is it not less risky to test the continuity between the coaches and the newly attached loco by operating the red handle in the Guard's office? Less chance of a blockage being sucked into the pipe there than on the track. 

In my own BR experience, everything we had at the carriage depot was air braked, and eventually we even had clever TDM that could vent the brake at the far end of the train as I recall....

[russ p]

Not necessarily, there was an incident in the last twenty years where a thread protector had not been removed correctly on an air braked set of coaches I believe on the WCML and somehow ended up in the brake pipe and as the result of an incorrect brake test possibly TDM ,trapped some air somewhere it shouldn't meaning that a full application wasn't available and some incident or spad occurred

Just better to be safe than sorry a brake test every time.

[The Stationmaster]

An interesting debate has emerged and I'm writing as someone who has actually framed a set of Rules for a leisure sector railway which only require a Vacuum Brake Continuity Test (apart from one in each direction on the first two workings of the day) if something affects the continuity of the brake such as adding or removing vehicles.   When preparing Rules for the leisure and heritage sector you are in a rather different situation from both the 'big railway' of today and the 'big railway' of yesteryear.

 

For a start my inclination is to condemn on sight any heritage type railway which is using, say, the BR 'black' Rule book or even the current monster RAIB Rule Book because either of those approaches suggests to me they have taken an easy way out.  You cannot prepare Rules and procedures or any of these railways without considering wider safety legislation and the need to present whatever you are writing in a clear and consider manner - including risk assessing where required - plus obviously the nature of that particular railway.  And the latter is a key point, for example I would not adopt the same attitude to brake tests on the NYMR as in the unnamed instance I mentioned (a relatively short line with mainly level track throughout its length) because the potential risks are different, the short line as it happens also frequently attaches and removes strengthening vehicles so Brake Continuity Tests are in reality frequently required anyway.  I certainly wouldn't drop 100% Continuity Tests on air brake trains because of what can happen to the brake pipe cocks on intermediate vehicles, and so on.

 

Imposing seemingly pointless checks and work doesn't necessarily work on heritage railways - because many volunteers simply don't understand the need and can simply not bother.  But on the other hand you do have to add, emphasise, or expand various personal safety procedures and these are hammered home repeatedly (and would if they had applied there have avoided the fatality involving a Guard on the NYMR).    Always better in my view to be informed by current procedures but also legislation (often it isn't directly railway legislation) but then consider application in the context of the railway you are looking at.

 

Incidentally while HMRI have an Inspecting remit they do not necessarily need to see or approve a heritage/leisure sector railway's Rules & Regulations although they can comment on them and require changes if anything untoward comes to light as a result of an incident or Inspection.  Their major interest nowadays centres on SMS (Safety Management Systems) although the railway's Rules & Regs etc are of course part of that.  In one case a book I wrote did go to HMRI for them to have a look at (no comment other than 'very good, very clear') whereas back in pre-ROGS days a book sent to the Inspectorate would be thoroughly studied from the opening page to the end and changes might be required  (as opposed to 'suggested')

[Boris]

Interestingly for many years the NYMR did NOT require a full brake test every morning on its Whitby sets as they had a valid mainline FTR and therefore only required a continuity test from the rear every morning.  Thankfully a full brake test is now required on all sets every 24 hours before they enter service.

 

Guards are allowed to test from the setter in a very specific circumstance - when the train formation has not been altered between the van and the rear of the train, basically when a loco change occurs at the same the end guard tests from the van, running round they should test from the back.

[russ p]

I would have thought ANY train travelling over network rail metals must have to comply with the current vac brake regs which as far as I know have never changed and a continuity test from the rear is required every run round.

When I was a shunter at grosmont in the early 80s every train had a brake continuity test on every run round

[Boris]

I would have thought ANY train travelling over network rail metals must have to comply with the current vac brake regs which as far as I know have never changed and a continuity test from the rear is required every run round.

When I was a shunter at grosmont in the early 80s every train had a brake continuity test on every run round

Yes, I agree entirely, but I am talking where you do a loco change when a different loco goes on the same end of the train as the previous loco in those circumstances (on the NYMR NEVER on the Network) we allow guards to use the setter in the van.  Its my name on the Guards paperwork and we aren't having any unsafe lazy ######!

 

The current RSSB rulebook isn't the clearest when it comes to vacuum brake continuity tests, so we have interpreted it as vacuum continuity tests must be done from the rear of the train.

Edited July 20, 2018 by Boris

[roythebus]

On the KESR (vac braked) the brake test is done from the rearmost vehicle first thing. During the day it is done from the guard's office every time there's a run-round.

 

The iWSR (air-braked) is the same. Both instances providing there's been no attachments or detachments during the day.

[russ p]

I took a loco from work to a preserved railway and they weren't happy that I insisted on brake test every run round.

Our companies instructions demands this and as we were using a dual braked loco as a brake translator I though it best.

I'm not keen on translating except in an emergency which is how the instructions were originally set out for.

The problem is with it the driver of the air braked loco has no indication of the state of braking on the train and therefore no way of knowing if the pass comm has been activated.

I really fail to see why guards on preserved railways can't walk to the back of the train for a brake test. Its about 7 or 8 coaches at most not a bloody two mile long UP double stack!

[The Stationmaster]

It does seem to me a bit odd that some of the above posts imply that Brake Continuity Test is carried out from other than the rearmost vehicle (or am I misreading things?).  if you test from other than the rearmost vehicle you aren't testing continuity and I'm not at all re what is being tested apart from the action of the brake setter.  Incidentally there is no way on any sort of railway that I would countenance a failure to test brake continuity at the start of the operating day before the first trip in each direction (or when an engine is changed) becuase you don't otherwise know if the brake really is continuous.

 

The current 'monster' book is indeed no sort of guide and it is in my opinion, and experiemn ce, far better to use the procedures set out in the old BR General Appendix as the guide in compiling  Regulations for any other railways

[The Johnster]

Agreed 100% Mike.  A brake continuity test should be, and normally is, carried out every time the vacuum or air pressure is destroyed; the fact that the same vehicles are re-made into the same train which worked fine earlier in the day has no bearing on this, as the continuity test is to confirm that nothing has got into the pipes and compromised the system by giving false indication on the gauges aboard the loco and in the guard's van.  Detritus, ice, or anything that blocks the pipe will enable the brakes to remain off despite applications from the loco or the guard's setter, and the 'isolated' brakes will eventually leak on and drag, causing more trouble.  The loco and van gauges should only be relied on when the system has been proved by the continuity test; note it is a test of continuity as well as brake function.  As foreign matter in the pipe is most likely to enter it when the system is open to atmosphere, this must be done every time the system pressure is lost to atmosphere by uncoupling.

 

Any deviation from this suggests a generally lax attitude, and one can more or less guarantee unpleasant results even if they are not directly related to the continuity test, but that's about attitude and a different subject.  Railway equipment is usually designed to fail safe, so the brake system's pressure holds the brake off, but only if the pipe is continuous, so it must be proved to be continuous before the train moves off anywhere.

[johnb]

As a non-railway person I would have thought that if the brake setter is in the last vehicle, then all that is not being tested is the last bit of vac pipe between setter and the end of the vehicle. So to me if there is a setter on the last vehicle at EACH end on the set, then that could be usable to prove the continuity during a days operation. So if the setter or setters are somewhere else within the set then surely an end of train test ought to be compulsory at each runround/loco change.

 

OR .... am I missing something?

 

John