Hitachi trains grounded

[Titan]

That's pretty much it, stray currents on 25Kv are negligible.  However Class 92 has insulated buffers and couplings to ensure that when working on DC all the return current went via the brushes on the axles, and not via the bearings on the wagons it was hauling!

[Hobby]

4 hours ago, adb968008 said:

Or 47/37’s, or castles, kings, saints…

 

If design life isnt 40 years, then 66’s are doomed as we speak, and 59’s are almost passed it…. Even pacers made 35 years !

 

Yes, but that is just the length of time they've been around, modern stock is used far more intensively and clocks up far higher mileages than HSTs and the diesels. They are also expected to work much harder whilst out there than the older stuff was as well. Gawd knows how many miles the Voyagers have clocked up in the twenty years we've been using them, we did used to keep an eye on the Km counter on TMS but CZ kept zero-ing them so we don't know!

[rodent279]

3 hours ago, roythebus1 said:

There was a problem with bearings overheating and failing on the southern's DMU fleet. The same units didn't have problems elsewhere in the country. IIRC part of the problem was the earth return current of the 750v DC electric system was going through the bearings and causing premature failure. Simple answer was to fit carbon brush in the bearing caps to carry stray return currents from the bogie frame to the axle end. Could this be the same for new units running under 25kv AC?

 

Why would traction return currents be passing through a diesel train's wheel bearings?

I could understand return currents from an electric train would have to pass from the traction motors to the wheelsets somehow, but a diesel train would not be connected to the traction supply.

[Titan]

In the last days of BR, contracted design life was 35 years for diesel, and 40 for electric.  Always thought it was a bit of a pointless figure, as so many factors could affect it - not least of which the likelihood of the respective manufacturer still being around to make a claim from!

[Dunsignalling]

1 hour ago, Hobby said:

 

Yes, but that is just the length of time they've been around, modern stock is used far more intensively and clocks up far higher mileages than HSTs and the diesels. They are also expected to work much harder whilst out there than the older stuff was as well. Gawd knows how many miles the Voyagers have clocked up in the twenty years we've been using them, we did used to keep an eye on the Km counter on TMS but CZ kept zero-ing them so we don't know!

Some Western Region HST rosters involved up to around 800 miles in a day, though it would be unlikely that an individual set would be on the longest one for more than a couple of days per week. Freight locos running at half the speed wouldn't normally get close to matching that.

 

Even more mundane stock could clock up the distance surprisingly quickly. When they were new and there were fewer of them, the daily roster of the first trio of SWT's 159 sets to leave the depot in the morning reached 500+. The first one to cover a million miles did so, IIRC, in the same number of months as a typical Bulleid Pacific did in years.

 

John

 

Edited November 15, 2022 by Dunsignalling

[Davexoc]

11 hours ago, Mike_Walker said:

Hitachi are a very secretive organisation so it's not clear whether or not the more recent builds and those currently in build are to a modified design and/or incorporate different, correct, grades of aluminium.  One would hope so but only time will tell.  If they too start visiting Eastleigh or Newton Aycliffe...

 

Are they covering up for others? There has been alot of falsification of data relating to metals produced in Japan, and it seems to have been going on for some time.... One article;

 

https://www.ft.com/content/13779d58-bb69-48ad-a8ee-8400ba6457d2

[Reorte]

4 hours ago, Hobby said:

 

Yes, but that is just the length of time they've been around, modern stock is used far more intensively and clocks up far higher mileages than HSTs and the diesels. They are also expected to work much harder whilst out there than the older stuff was as well. Gawd knows how many miles the Voyagers have clocked up in the twenty years we've been using them, we did used to keep an eye on the Km counter on TMS but CZ kept zero-ing them so we don't know!

Gawd, another one that makes time seem to have gone past alarmingly quickly. I still think of them as fairly new.

[BernardTPM]

4 hours ago, Hobby said:

Gawd knows how many miles the Voyagers have clocked up in the twenty years we've been using them

 

23 minutes ago, Reorte said:

Gawd, another one that makes time seem to have gone past alarmingly quickly. I still think of them as fairly new.

 

They've had almost a decade longer in service than the Blue Pullman sets already and have been much more intensively used.

[roythebus1]

4 hours ago, rodent279 said:

Why would traction return currents be passing through a diesel train's wheel bearings?

I could understand return currents from an electric train would have to pass from the traction motors to the wheelsets somehow, but a diesel train would not be connected to the traction supply.

Apparently it was something to do with return current from electric trains and track circuits. My son, as assistant fleet engineer for the Southern diesel fleet had to deal with it. Maybe a signal engineer could explain better than I can.

[roythebus1]

2 hours ago, Davexoc said:

 

Are they covering up for others? There has been alot of falsification of data relating to metals produced in Japan, and it seems to have been going on for some time.... One article;

 

https://www.ft.com/content/13779d58-bb69-48ad-a8ee-8400ba6457d2

A bit like the mazak pest we have to put up with on certain Chinese models like the Hornby class 31 I have.

[david.hill64]

18 hours ago, TomScrut said:

The industry should conduct further work to identify the reasons for the higher levels of fatigue loading experienced by rolling stock. Since the Hitachi Rail design complied with the applicable industry standards, the industry as a whole should evaluate whether the applicable standards take into account the loads arising from operation on the rail network in Great Britain. This industry collaboration will require the involvement of those parties responsible for design, manufacture and maintenance of rolling stock including, but not limited to, Hitachi Rail. 

 

Reading between the lines that means to me that there is a possibility of the specification not being correct, with the trains encountering greater loads than what was required of them in the tender.

 

Two issues here:

 

First: there are no applicable standards relating to Stress Corrosion Cracking in rail vehicles. I expect one will be developed.

 

Second: there is a Technical Standard for Interoperability and supporting Euronorms relating to fatigue loading of rolling stock components. These standards are mandatory and it is illegal (at least until, and if, the relevant EU legislation is removed from UK law) to specify any stricter (or more lax) requirement. Unfortunately it appears that vehicles running on UK track are likely to experience higher loadings than the standard mandates. When assessing vehicle compliance, the Notified Body responsible for certification can only confirm compliance with the standard. Having said that, Hitachi were provided with sufficient information on track geometry for them to have worked out that mere compliance with the standard was likely to be insufficient to prevent fatigue. They could have designed according to the likely actual loads and then submitted for assessment evidence that the vehicles complied with the standard.

[david.hill64]

10 hours ago, rodent279 said:

Why would traction return currents be passing through a diesel train's wheel bearings?

I could understand return currents from an electric train would have to pass from the traction motors to the wheelsets somehow, but a diesel train would not be connected to the traction supply.

Traction return currents in electrified areas pass along rails and will seek the path of least resistance. If this happens to be from one rail to another via the wheelset and bogie frame of a passing DMU it will do so. Fitting brushes to prevent electrical damage to bearings is good practice.

[Hobby]

11 hours ago, Dunsignalling said:

Some Western Region HST rosters involved up to around 800 miles in a day,

 

Going slightly OT, many years ago I was speaking to one of the fitters and a control bod and it seems that pre covid the Voyagers were knocking up between 800/1000 miles per day and would go in for a "service" every 10 days, that's one heck of a mileage per year! The diagram for the Aberdeen to Penzance was over 960miles. I found that once people realised just how intensively we used them they tended to be a little more tolerant of the odd failure, most were comparing them to their car until they realised that the train could knock up a "car years" mileage in a couple of weeks!

[jjb1970]

At the moment it is speculation, notwithstanding the fact that the ORR has given a heavy hint that it is not just a case of Hitachi dropping the ball.

 

There are all sorts of things that influence machinery and failure modes, design basis, duty cycle, material properties, workmanship and QA/QC for example. Modern equipment is being pushed to deliver more efficiency and lower emissions which basically means reduced weight with improved aerodynamics and more efficient power packages. More and more design work depends on modelling which means sensitivity to the underpinning assumptions used for modelling and the veracity of the math routine (I had a friend and colleague whose hobby was identifying issues with such routines, he was a bit bonkers and turned out to be a Chinese spy but despite that he was a bit of a mad genius). Things aren't over engineered as they once were because they can't be, not for regulatory reasons, performance reasons and cost reasons.

 

I'm sure we'll find out what went wrong in time.

[jjb1970]

I still get a lot of complaints from people about why-oh-why is such and such a piece of equipment saddled with all that electronic nonsense when the old stuff worked forever, and we could buy spares anywhere. Because, commercial aspects aside (let's be honest, locking customers into OEM product support is very lucrative, much more so than the initial sale in many cases) it just isn't possible to deliver the sort of performance needed to survive in the market and be regulatory compliant without all the trick technology in many fields.

[rodent279]

Going back to an earlier post, I don't think 190 years of experience has been lost or disregarded at all. Rather, boundaries are being pushed, new materials introduced, and performance levels expected which the "old technology" just wouldn't be able to deliver.

[The Stationmaster]

13 hours ago, Dunsignalling said:

Some Western Region HST rosters involved up to around 800 miles in a day, though it would be unlikely that an individual set would be on the longest one for more than a couple of days per week. Freight locos running at half the speed wouldn't normally get close to matching that.

 

Even more mundane stock could clock up the distance surprisingly quickly. When they were new and there were fewer of them, the daily roster of the first trio of SWT's 159 sets to leave the depot in the morning reached 500+. The first one to cover a million miles did so, IIRC, in the same number of months as a typical Bulleid Pacific did in years.

 

John

 

Some WR HST diagrams were covering the same daily mileage as IETs do now so I don't see how an IET does more miles than an HST.  And there were some (non WR) HST diagrams at one time knocking up over 1,000 miles in a day - I wonder how many IET diagrams have that sort of mileage (there probably will be some).

 

Simple fact is that unit daily mileages will only increase if more trains are run.  IET joyurney time savings compared with HSTs are relatively small so ina given working day the limit will be set by what the service is and by the fuel mileage capacity (where the IET is running on non-electrified railway).

 

and of course whatever the mileage on any particular day in well regulated circles the sets will be working round a cycle of diagrams in order to equalkise mileafe across the fleet which allows for simpler planning of exams and the use of balanced exams.

[Reorte]

11 hours ago, BernardTPM said:

 

 

They've had almost a decade longer in service than the Blue Pullman sets already and have been much more intensively used.

Well the Blue Pullman sets were gone by the time I was born, so they seem suitably old in my mind.

 

I think I find that I subconsciously divide everything in to "appeared later than when I was a fairly small child == new, gone before I was born == old, everything else normal." Which gets increasingly ridiculous as time goes by of course.

[Reorte]

1 hour ago, jjb1970 said:

I still get a lot of complaints from people about why-oh-why is such and such a piece of equipment saddled with all that electronic nonsense when the old stuff worked forever, and we could buy spares anywhere. Because, commercial aspects aside (let's be honest, locking customers into OEM product support is very lucrative, much more so than the initial sale in many cases) it just isn't possible to deliver the sort of performance needed to survive in the market and be regulatory compliant without all the trick technology in many fields.

 

I think it's possible to both raise an eyebrow at the electronics etc. whilst also understanding the reasons they're there. I get this quite often whenever I express a rather negative opinion on the way something is now (I'm talking very generally here, not trying to pin this on the particular issue under discussion - it's never an all or nothing). Someone inevitably tries to explain the reasons for it, apparently assuming that I don't know and would have a less negative opinion if I did.

[rodent279]

And lest we forget, they didn't always get the "old technology" right. There were a spate of failures of Britannia driving axles during the 1950's, which was tied up I think with the axle centres being hollow.

[Dunsignalling]

2 minutes ago, Reorte said:

 

I think it's possible to both raise an eyebrow at the electronics etc. whilst also understanding the reasons they're there. I get this quite often whenever I express a rather negative opinion on the way something is now (I'm talking very generally here, not trying to pin this on the particular issue under discussion - it's never an all or nothing). Someone inevitably tries to explain the reasons for it, apparently assuming that I don't know and would have a less negative opinion if I did.

I think there is an assumption these days that if something can be done using "new tech", then it should, rather than critically examining what (if any) real advantage it offers over established methods.

 

A truism often ignored is that a high proportion of innovative methodology proves to be transitory, either because it fails to pass muster over the longer term or because something better comes along that displaces it.  

 

John

[Mike_Walker]

2 minutes ago, Dunsignalling said:

I think there is an assumption these days that if something can be done using "new tech", then it should, rather than critically examining what (if any) real advantage it offers over established methods.

 

A truism often ignored is that a high proportion of innovative methodology proves to be transitory, either because it fails to pass muster over the longer term or because something better comes along that displaces it.  

 

John

I agree.  Is it really necessary to have all that complicated electronics working the loo door on an IET for example, which regularly seems to fail stopping the whole train, rather than a good old fashioned bolt?  The latter is simple, reliable and costs peanuts.

[Oldddudders]

Many years ago ISTR an article in Modern Railways that identified just how many 'bright ideas' from BR's Research hub were cheerfully using APT as their test-bed, thus diverting some attention from the need to prove and fine-tune the base concept. Where complexity increases incrementally it may be contained, where exponentially is another matter, at least to this non-engineer. 

 

 

 

 

Edited November 16, 2022 by Oldddudders

[jamie92208]

10 minutes ago, Mike_Walker said:

I agree.  Is it really necessary to have all that complicated electronics working the loo door on an IET for example, which regularly seems to fail stopping the whole train, rather than a good old fashioned bolt?  The latter is simple, reliable and costs peanuts.

As far as I onow the various disabilty groups have been asking for a simpke mevganical lock on accessible loos for years.

 

Jamie

[TomScrut]

9 minutes ago, Mike_Walker said:

Is it really necessary to have all that complicated electronics working the loo door on an IET for example, which regularly seems to fail stopping the whole train, rather than a good old fashioned bolt?

 

In fairness that has been a thing way before IETs came on the scene. I believe it was the case on the refurbished mk4s on the disabled loos for example. Saying that there is a practical advantage on a disabled loo in my opinion as the buttons can be more accessible.

 

The other aspect of this is what the legals are on it. I don't design trains so I don't know the rules but heights and positions of stuff like door handles/locks/buttons will be set by the regs.