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Entire 800/801/802 fleet stood down for safety checks

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Steve Harris

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I'm no materials expert but if the metal that the hoop is fabricated from is stronger than what it is secured to, that might explain the location of the crack in the scenario mentioned.

EDIT
Not sure that I buy the misaligned jack theory. Much more credible (and worrying) is the under specified metal referred to up thread - seems like someone got their sums wrong :rolleyes:
IF the hoop is made out of steel and the bolster is out of Aluminium and the hoop is bolted to the Ally bearing the steel is stronger BUT a lot less of it than the ally at best it would probably have about the same strength at best. Plus you haven't taken into account that the bolts haven't stripped the threads in the holes !!
And of course the cracking would be because a jack was being lowered (rather than raised), as a jack wouldn't try to peel away the bolster from the body if it was being raised. If it was being lowered and could exert enough force then it might be possible to cause the issue.

Screws for the anvil support bracket too long & bottomed out?
If bolts are steel and the bolster is Aluminium I would expect the threads in the holes to strip before the force of them bottoming out starts to crack the welds (of course that is dependent on how much weld there actually is)!

You have to remember Aluminium is normally not as strong as Steel (although there are a few ally grades that come very dam close). Everything depends on how much there physically is (ie width, depth, thickness) of each material and how it is physically fixed (welded, bolted (pitch of thread) etc) to each other.
As all of us are going off pictures which tend not to show scale very well and only show limited detail, so therefore we are just making assumptions which are more than likely wrong.

Until we actually know more I don't see any point in anyone speculating further as it just makes us look even bigger armchair experts than we already are !

Yes I have my own assumption but I'm keeping it to myself as I could be wrong (however, it wouldn't surprise me if the yaw damper crack isn't completely seperate to the jacking bracket crack). But I'm just going to sit back and see what comes out in the wash.
 
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Clarence Yard

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Can we park the theories about the hoop, please? The fault in this component lies with the metal in the jacking plate itself, it's suitability for the application and whether the specification for it's construction (including a lack of stress relieving around the weld) was adequate.

The metal appears to be suffering from Stress Corrosion Cracking, a condition that will worsen over time as environmental conditions and duty cycle both contribute to the propagation rate. Every 80x unit will require remedial attention when the SCC reaches a certain point, either in the jacking plate and/or in the yaw bolster assembly.

As at this morning, 63 out of the 93 GWR IET sets are available for traffic. The full service requirement for the pre-Covid timetable is 80.
 

Nottingham59

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Thank you for that information. If it is indeed Stress Corrosion Cracking, would that be stresses from on-going operations and maintenance activity? Or residual stresses created in the metal during manufacture that were never relieved by, say, annealing? Or is it too early to say?
 

swt_passenger

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What's the purpose of the "hoop" anyway?
I’m glad someone else wondered about that as well. I’m sure many of the jacking points of other stock don't have anything similar, it doesn’t seem to have an obvious purpose.
 

Clarence Yard

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Thank you for that information. If it is indeed Stress Corrosion Cracking, would that be stresses from on-going operations and maintenance activity? Or residual stresses created in the metal during manufacture that were never relieved by, say, annealing? Or is it too early to say?

The stress is created during manufacture and is exacerbated by operating the trains, rather than their maintenance which really doesn't have any role to play in this fault.

The specific grade of aluminum used is quite tricky to deal with and has certain properties which may, or may not, be entirely suitable for it's application in this part.
 

Domh245

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I’m glad someone else wondered about that as well. I’m sure many of the jacking points of other stock don't have anything similar, it doesn’t seem to have an obvious purpose.

Would be to ensure that the jack is properly located I'd think? Seems that some jacks are pads which locate under the point, but others go into a recess in the body and lift there. The lifting arrangement for these units can be seen in this picture - more 'pin' type than pad
 

coppercapped

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The stress is created during manufacture and is exacerbated by operating the trains, rather than their maintenance which really doesn't have any role to play in this fault.

The specific grade of aluminum used is quite tricky to deal with and has certain properties which may, or may not, be entirely suitable for it's application in this part.
I looked up some research papers for the type of alloy mentioned earlier. I notice that there are a few papers reporting on stress corrosion cracking (which is quite common - both rear coils springs on my Golf broke after about 10 years use) so it is obviously an issue. But I hasten to add not only with this particular alloy.

What may be significant is that a couple of the papers mentioned the accelerating effects of some pollutants in the air, such as sulphur and chlorine.

Dawlish - I'm looking at you... :(
 

Irascible

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I looked up some research papers for the type of alloy mentioned earlier. I notice that there are a few papers reporting on stress corrosion cracking (which is quite common - both rear coils springs on my Golf broke after about 10 years use) so it is obviously an issue. But I hasten to add not only with this particular alloy.

What may be significant is that a couple of the papers mentioned the accelerating effects of some pollutants in the air, such as sulphur and chlorine.

Dawlish - I'm looking at you... :(

Or Longrock. What do GWR use in the carriage wash plants?
 

Wilts Wanderer

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If Dawlish was an issue then there would be a significant difference between the impact seen on the GWR Class 802 fleet compared to the 800s, which have far less work in the south west. AFAIK this isn’t the case?
 

coppercapped

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If Dawlish was an issue then there would be a significant difference between the impact seen on the GWR Class 802 fleet compared to the 800s, which have far less work in the south west. AFAIK this isn’t the case?
Quite possibly. But there are clearly a number of variables at work. A Chinese-American paper from 2015[1] has the following abstract:
Humidity is a key factor affecting the quality of welded joints for high-speed trains. Welded joints made of A7N01S-T5 aluminum alloy were fabricated under five relative environmental humidity conditions: 50%, 60%, 70%, 80%, and 90%. The microstructures of the welded joints were examined using an optical microscope and porosity quantities were calculated from macrographs using image analysis software. The fatigue strength of the welded joints was measured with high-cycle fatigue testing. It was determined that the microstructures and grain sizes in the weld zone and heat-affected zone (HAZ) were similar under different humidity conditions; however, porosity distribution varied significantly. Porosity quantity increased as humidity increased. The weld joint made under the 90% humidity condition had the highest quantity of porosity, while the weld joint made under the 70% humidity condition had the maximum diameter and area of porosity. The weld joint made under the 70% humidity condition also had the lowest fatigue strength. Fracture morphology of fatigue samples showed that the weld joint made under the 70% humidity condition had brittle fracture, while others showed ductile fracture. Therefore, 70% humidity was determined to be the critical humidity level for welding joints in high humidity environment.

There are many other papers on this and similar topics. A Chinese-Canadian paper in the journal Corrosion[2] has this to say in the preamble:

The A7N01S-T5 alloy contains, in addition to Zn and Mg, various alloying elements such as Cu, Si, and Cr. It has been reported that when the Zn and Mg content was increased to the limit of Zn + Mg = 7.5% for solid solution strengthening, the sensitivity of the alloy to stress corrosion cracking (SCC) would increase considerably. Increased temperature and humidity would also influence the SCC behavior of A7N01, especially when the concentration of chlorine ions in the atmosphere is relatively high and the pH value is low.

There are many other papers covering various topics in this area so identifying the root cause for the cracking and a repair programme will obviously take some time. Especially when the second paper also states:

SCC is considered to be a very dangerous form of failure to the safety of high-speed train structures. A number of A7N01 Al alloy components such as traction beams, bumper beams, and cross beams, as well as many other aluminum alloy structures manufactured with A7N01 aluminum alloys, experience fracture from time to time.

There are a lot of questions to be answered.



[1] Materials & Design Volume 85, 15 November 2015, Pages 309-317
[2] Corrosion Volume 72, No. 9, 2016, pp1133-1145
 

Grumpy Git

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This article has been published today on the Modern railways website, (19th May):
‘Stress corrosion’ could be the cause


Industry insiders told Modern Railways that while investigations into the cause of the cracks on Hitachi trains continue, initial thoughts are that they are a form of stress corrosion cracking – a combination of stress and a chemical reaction. Substantial samples were cut from No 800026 and more severely damaged No 802205 and taken for metallurgical analysis by The Welding Institute and in Japan, while No 800013 was used as a testbed for a full repair programme. Nos 800013/026 were two of the four trains involved in the earlier issue where cracks were discovered around the yaw damper bracket bolsters during April.


The design authority in Japan responsible for the Class 80x product provided the train operators and Office of Rail and Road with a better understanding of the role of the lifting pockets and what risks may or may not follow should one become completely detached. This situation, whilst possible, is thought to be extremely unlikely given the equipment is secured at several points. Initial conclusions by engineers were that the small number of yaw damper-related cracks found in late April could be related to the weight of the diesel engines on those vehicles, but that the more numerous jacking point cracks are ‘definitely not related to vehicle weights’. It is noted that vehicles fitted with diesel engines have a different yaw damper setup to those without.


Although the Hitachi fleets were withdrawn en masse, there was an emerging view within the industry that that the discovery of further cracks in any significant numbers is unlikely. One senior insider told Modern Railways: ‘I don't think we will find any more cracks because we've been through the whole fleet now with a very thorough examination. The view of the engineers is that the cracks we were finding had been there a while because they weren’t showing any fresh metal. It appears that these cracks don’t develop “overnight” and whilst there might be one or two that possibly creep over the line, we're not expecting to find that many more units have developed cracks suddenly.’ Another source added that the cracks had not become visible on painted vehicles as the new paint was sufficiently flexible to remain intact, hiding the cracks beneath.





Repairs will be complex


There is widespread acceptance that an extensive repair programme will now be needed, covering all Hitachi’s Class 80x and Class 385 fleets and taking many months. Modern Railways understands that although the cracks aren’t in a weld, they will be repaired with a weld.


An insider explained ‘Although we think that Hitachi can demonstrate that the vehicles can run, it is clear that they will, in the medium to longer term, have to be repaired. There are a number of options being looked at for the long-term solution. One is whether a weld would solve the problem to everyone’s satisfaction. Hitachi might have to look at a slightly different assembly and look at whether they bolt it on and not weld it. The other option is whether to just cut that piece of the vehicle out and weld something new in.’ Engineers are also considering whether the fact that there is a connection via the bracket between the anti-roll bar, yaw damper and the lifting bracket might mean that a replacement should be designed in a different way.


When a plan is agreed, all electrical equipment must be disconnected to avoid damage during welding. Past experience with other fleets suggests it is more efficient to modify all vehicles in a set at the same time rather than take individual vehicles out of service. Early industry estimates are that it could take until the end of 2022 to complete repairs to all affected vehicles.


The repair process is complicated further by the fact it will require dedicated facilities with appropriately trained engineers. As one insider commented: ‘There are a limited number of people who have the right skills for welding railway vehicles and there are a limited number of places where you can take the vehicles, support them in the right place and do the welding itself’. The aluminium alloy used on the trains means the work must be overseen by The Welding Institute to ensure it is completed correctly. The work by Hitachi is being independently validated by consultancy Ricardo to ensure full compliance. At the time of writing, no definitive cause had been identified by Hitachi, nor any fix proved.
https://www.keymodernrailways.com/article/stress-corrosion-cause-series-800-cracks


Edit: there is also a further article from today on the roll out of repairs on the same website:
Jacking point cracks prompt mass withdrawal from service





Repair of all Hitachi 800 Series trains affected by an issue with underframe cracks is expected to take at least 18 months, it was reported as Modern Railways went to press.


Hitachi withdrew the entire Class 800, 801 and 802 Intercity Express Train (IET) fleets operated by Great Western Railway, Hull Trains, LNER and TransPennine Express overnight on 7/8 May after severe cracks were discovered in jacking points. Ten Hitachi-built ScotRail Class 385 EMUs were also withdrawn after cracks were found in the same component. The issue followed the discovery of cracks in yaw damper mountings on some of GWR’s Intercity Express Train (IET) Class 800/802 fleet during April, prior to the discovery of the jacking point issues.


All Class 80x operators were forced to suspend services using the trains, with very few long-distance services running for GWR and LNER over the weekend of 8-9 May, and TPE forced to amend its timetable. The Hull Trains units resumed operation on 8 May. A reduced LNER service operated throughout the following week, with no services north of Edinburgh, although these were expected to be restored in mid-May.





Services cut


GWR was operating a skeleton service on long-distance routes, supported by hourly CrossCountry services between Swindon and Bristol, and Class 387s were rapidly cleared to run in passenger service as far west as Swindon with DMUs filling in elsewhere.


Initially the Office of Rail and Road refused permission to return some sets to service under strict conditions on 12 May, but on 13 May Hitachi announced that some trains would be able to return to service on GWR and LNER. ‘Based on the work undertaken to understand the issue, and after extensive engagement, Hitachi Rail and train operators, working with the rail regulator, have put in place suitable criteria for the trains to meet before they can re-enter service’ a statement said.


GWR expected to reintroduce a significant number of IETs by 17 May to operate close to its full planned timetable, albeit making use of stock drafted in from other operators and with some services short-formed at five-car length instead of 10-car. This timetable was expected to include half-hourly services from London to Bristol and South Wales, and hourly to Plymouth, the South Cotswolds and North Cotswolds.





Rigorous inspection


The IET sets returning to service with GWR were to have three checks carried out every day, covering the lift pockets and yaw damper brackets; all three checks were required to be passed every 24 hours for a set to remain in service.


As of mid-May, further sets were still being x-rayed amid concern that paint defects may be hiding cracks underneath. Engineers confirmed the rectification programme will take at least 18 months and the maximum number of sets available throughout will be in the region of 70; from its 93 Class 800/802 sets, GWR has 85 diagrams to cover on an average day.


To help cover the shortfall, three Class 387s transferred on loan to GWR from c2c, and after replacement of pantograph heads and a software update were due to be available to provide additional Thames Valley capacity. As we went to press it is understood GWR was looking to make ‘387s’ available to operate services to Bristol Parkway and Cardiff to cover for shortfalls in IET availability, while ‘387s’ were also due to work services to Newbury with a connecting DMU shuttle to Bedwyn. The retention by Govia Thameslink Railway of its Class 365 EMUs on Great Northern services to allow Class 387s to move temporarily to GWR was another possibility; the ‘365s’ were due to be withdrawn at the May timetable change.


In other contingency moves, a set of former East Midlands Railway Mk 3 coaches owned by Locomotive Services Ltd was transferred from Crewe to Plymouth Laira depot on 10 May, although at the time of writing its planned usage was unclear. A Riviera Trains rake of Mk 2s top-and-tailed by Class 67s was also a possibility to strengthen services – as was the loan of three TransPennine Express Class 802s. LNER, meanwhile, reinstated stored Class 91s and Mk 4 coaches into traffic earlier than planned; it had intended to reintroduce the sets following the conclusion of remodelling work at King's Cross in early June.
https://www.keymodernrailways.com/article/hitachi-800-series-trains-cracks
 
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LNW-GW Joint

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Just to observe that the MR article seems to be the same as the one originally published on 13 May in Railway Gazette (at least some of the text is identical), which I posted at the time.
So it might not be "new" news.
Class 80x recovery plan takes shape | Rail Business UK | Railway Gazette International

eg the following:
Substantial samples have been cut from sets 800026 and more severely damaged 802205 for metallurgical analysis, both in Japan and at The Welding Institute. These include one of the two Class 800 units where cracks were first discovered in early April. The second is being used as a testbed for repairs.
 

fgwrich

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Just to observe that the MR article seems to be the same as the one originally published on 13 May in Railway Gazette (at least some of the text is identical), which I posted at the time.
So it might not be "new" news.
Class 80x recovery plan takes shape | Rail Business UK | Railway Gazette International

eg the following: Substantial samples have been cut from sets 800026 and more severely damaged 802205 for metallurgical analysis, both in Japan and at The Welding Institute. These include one of the two Class 800 units where cracks were first discovered in early April. The second is being used as a testbed for repairs.

Is 802205 a typo for 800025 or is TPE's 802205 suffering badly? If it is the 802 - then that has to potentially be the worst of the Italian batch.
 

Trainer2

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Are they changing the jacking point design? Modifying it so it fails in a different way if it fails at all?
 

Apedlar12

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Reported elsewhere that from Monday GWR will be operating class 387s in passenger service between London Paddington and Bristol Parkway...
 

yorkie

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Just a reminder this thread is specifically to discuss the issues with the 800 series units

Alternative provision can be discussed elsewhere, thanks:)
 

JonathanH

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Surely a typo for 802005? Pretty sure it isn't one of the TPX ones.
Definitely not TPE unit 802205 as that has been reported in service in the last few days (as has 800025) and the report suggests that the actual unit involved is the worst affected unit. Guess it must be 802005 (which hasn't been reported in service)
 

Ianno87

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The impression I had was that LNER had it far less bad and were able to quickly reinstate an ok service, whilst GWR had more problems with their bi-modes

And LNER are running a slightly reduced timetable anyway due to the King's Cross works.
 

father_jack

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Couple of cancellations this evening ex Paddington, fleet availability has now dropped below the basic service. The 5 cars are keeping the service going but are way fuller than the socially distanced aspiration of "window seats only". Everyone's favourite Friday evening train 1848 Paddington to Swansea is a sole 5 car.....
 

43096

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They have enough to run the service at present.
That Class 91s have been needed this week on an unplanned basis would suggest either there aren't enough to run the service or Detachi aren't getting the availability that they should.
 

Emaharg

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The 1604 Paddington - Penzance (16 late) which I travelled on this evening, had to wait for the unit that was supposed to do the 1630 Paddington - Cheltenham, which was cancelled at the last minute.
I travelled to Doncaster earlier on one of loco hauled sets 91106, you can tell they have been warm stored, and possibly been rushed back. Basics like the flush not working in the toilet etc.
 

Bald Rick

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That Class 91s have been needed this week on an unplanned basis would suggest either there aren't enough to run the service or Detachi aren't getting the availability that they should.

Yes sorry, I should have said enough units... with a little help.
 
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