How long could old DMU stock keep rolling?

[Plethora]

I came across a comment on Reddit by someone who said the 158s really only have about 5 years of use left in them due to their age. That felt wrong to me, so I thought I'd ask a more expert audience.

My thoughts had been that they could probably be kept running for as long as operators wanted, subject to a willingness to fund periodic refurbishments and perhaps a mechanical overhaul. There appears to be no shortage of parts, and I recall seeing a post by someone saying that parts are still widely available as there is nothing too unusual used in the construction.

Added to this, they seem to still be reliable (including when compared to newer stock) and we aren't seeing any being pulled out of use to cannibalise for parts.

Northern are keen to replace them and the 150s to simplify stock, but would it be feasible for certain Northern depots to run exclusively off the UK-wide stock of 158s (and 159s)? That strikes me as both an economical measure and one that would be quite popular with commuters.

Over to you, and thank you in advance for the input.

 

[swt_passenger]

I think it’s generally considered that the assumed life expectancy of that generation of DMU was about 35 years, with EMUs being a bit longer at 40 years. Of course that doesn’t mean they won’t or can’t stretch them out further.

There was a DfT/Rosco rolling stock summary quite a few years ago where those generalisations were published.

 

[Towers]

158s are constructed from aluminium, and so have an immediate lifespan advantage over earlier DMUs like the 150s, which are renowned for galloping rot. They also ride superbly - indeed, far better than most that has come since - and as with all BR-era units, they are extremely well known by the TOC depots who maintain them and comparatively simple to keep running.

The flip side to all of this is the growing obselescence of essential parts, in particular the oily bits, and the political agenda towards anything with a diesel engine being “bad” (despite also being absolutely essential for the forseeable).

With 150s we have seen how one TOC who has a replacement fleet (TfW) began withdrawals and ceased any further major exam or overhaul work, while others (Northern, GWR) continue to maintain theirs with a view to ongoing service for the medium term future. So it’s largely down to whether or not the powers-that-be want or need to keep them running, and the willingness to meet the costs of doing so. There is nothing about class 158s, or any other second generation DMU, which means they will suddenly become life expired in five years time, provided that parts can be obtained and bills paid to keep them going. In the case of 150s that also includes a constant battle to keep rust at bay, although some serious attention on previous major exams helps to a degree.

The similarly aged class 455s are a shining example of how an ageing fleet of trains can repeatedly see their withdrawal date and thus their lifespan extended, with the work necessary to keep them running having to be carried out regardless of the cost or how long they have left in service. The 701s were due to have wiped them out long ago, and yet they continue to soldier on and maintain some of the most intensive suburban commuter services on the network. The 769s are also worth a shout here, again similar ages and the same rot-prone steel bodyshells, but huge sums thrown at them to convert them into tri-mode stock expected to last another decade or so. It didn’t work, admittedly, but the money was spent - anything is possible!

 

[Discuss223]

I came across a comment on Reddit by someone who said the 158s really only have about 5 years of use left in them due to their age. That felt wrong to me, so I thought I'd ask a more expert audience.

My thoughts had been that they could probably be kept running for as long as operators wanted, subject to a willingness to fund periodic refurbishments and perhaps a mechanical overhaul. There appears to be no shortage of parts, and I recall seeing a post by someone saying that parts are still widely available as there is nothing too unusual used in the construction.

Added to this, they seem to still be reliable (including when compared to newer stock) and we aren't seeing any being pulled out of use to cannibalise for parts.

Northern are keen to replace them and the 150s to simplify stock, but would it be feasible for certain Northern depots to run exclusively off the UK-wide stock of 158s (and 159s)? That strikes me as both an economical measure and one that would be quite popular with commuters.

Over to you, and thank you in advance for the input.

Only the engineers who maintain and perform exams on 150s will know for definite how long they have left in operation. I would go as far as to say even drivers, and train crew wouldn't know for sure how long they have. That said, and my post here is of an enthusiast, not an engineer, the Class 150s utilise the MK3 body shell, some of which are still in service today, with prototypes dating back from 1972. So, in theory, they could be in service for another ten years or so. The Class 158s in my neck of the woods are currently being overhauled to provide many more years of Intercity service on the Norwich - Liverpool Lime Street route, so I would say atleast 10-11 years for those.


When Southern introduced their Turbostars, their CEO said they were planned to operate for atleast 40 years.

Ofcourse, components on DMUs are replaced intermittently and do become something of a Trigger's broomstick if you know what I mean. For example, the engines are reconditioned every 2 years on DMUs and I believe replaced around every 12 years, to my knowledge. Wheelsets etc will be replaced as part of overhauls. Wheel lathing helps wheel sets stay in service for longer.

The bodyshell on all trains undergo intense weather-proofing and crash endurability. Before entering service, each carriage is baked in a hot kiln to temperatures unbearable to human flesh and also frozen to temperatures below arctic level. They are coated in special paint to prevent rust and scratches etc. This makes them somewhat invincible.

I note your post is something of a Northern orientated one. Northern are currently planning on replacing their oldest DMU fleet with new ones in the next 10 years, with a tender for suppliers already being placed. So, therefore, Northern specifically will be replacing their 150s and 158s in the next 8 years or so but 158s will remain in the north of England with EMR operating them in Sheffield, Stockport, Manchester and Liverpool for many years to come.

All information is correct to the best of my knowledge as an enthusiast, not an engineer.*

 

[brad465]

The flip side to all of this is the growing obselescence of essential parts, in particular the oily bits, and the political agenda towards anything with a diesel engine being “bad” (despite also being absolutely essential for the forseeable).

This wouldn't be so bad if there was actually a plan behind the target. If we had a rolling electrification program the diesel abolition goal would be more achievable. Instead we had a bold electrification commitment suddenly rolled back on after costs got out of hand, which combined with battery tech seemingly reinventing itself repeatedly and not being deployed, have made DMUs a premium product. Therefore, many DMUs in service, will likely be made to stay in service for a long time beyond their initial design life.

 

[43096]

With 150s we have seen how one TOC who has a replacement fleet (TfW) began withdrawals and ceased any further major exam or overhaul work

The decision to cease overhauls and scrap those units is a ROSCO decision. The TOC don’t have a say on scrapping.

 

[Bletchleyite]

Trains are like houses. You can keep them going basically forever as long as you're content to keep replacing bits.

The thing that causes them to be retired is the economics of repair vs. replacement, which can vary depending on cost (in countries where labour is cheaper repair will tend to come out on top), and things like emissions and safety regulations (though again modifications are often possible).

 

[LowLevel]

Only the engineers who maintain and perform exams on 150s will know for definite how long they have left in operation. I would go as far as to say even drivers, and train crew wouldn't know for sure how long they have. That said, and my post here is of an enthusiast, not an engineer, the Class 150s utilise the MK3 body shell, some of which are still in service today, with prototypes dating back from 1972. So, in theory, they could be in service for another ten years or so. The Class 158s in my neck of the woods are currently being overhauled to provide many more years of Intercity service on the Norwich - Liverpool Lime Street route, so I would say atleast 10-11 years for those.


When Southern introduced their Turbostars, their CEO said they were planned to operate for atleast 40 years.

Ofcourse, components on DMUs are replaced intermittently and do become something of a Trigger's broomstick if you know what I mean. For example, the engines are reconditioned every 2 years on DMUs and I believe replaced around every 12 years, to my knowledge. Wheelsets etc will be replaced as part of overhauls. Wheel lathing helps wheel sets stay in service for longer.

The bodyshell on all trains undergo intense weather-proofing and crash endurability. Before entering service, each carriage is baked in a hot kiln to temperatures unbearable to human flesh and also frozen to temperatures below arctic level. They are coated in special paint to prevent rust and scratches etc. This makes them somewhat invincible.

I note your post is something of a Northern orientated one. Northern are currently planning on replacing their oldest DMU fleet with new ones in the next 10 years, with a tender for suppliers already being placed. So, therefore, Northern specifically will be replacing their 150s and 158s in the next 8 years or so but 158s will remain in the north of England with EMR operating them in Sheffield, Stockport, Manchester and Liverpool for many years to come.

All information is correct to the best of my knowledge as an enthusiast, not an engineer.*

The EMR class 158s are basically receiving cosmetic work and are slated for withdrawal in 2030, that's the current official internal line.

The main issue with 158s is the engine obsolescence (they're very old technology and getting hold of blocks etc isn't easy) and cracking of the bodyshells which has been a known issue since the 90s and has it's own maintenance regime.

The internal wiring and systems are also very elderly.

 

[Taunton]

The way the vehicle is kept is significant - you see this with people's cars, some get scrapped after 10 years, others of the same type last more than double that. Among other things for trains:

- Wiring. This does tend to have a limited life before the insulation breaks down, the connectors go, etc. You can rewire the vehicle but that is an expense, and it can depend on whether the heavy overhaul does it, or not.

- Corrosion control. This is noticeable on the current DLR fleet. The bulk were built in 1991-95 and are up for replacement. Despite being 30 years old, until a couple of years ago the bodysides were perfect. Once the replacements were ordered then however this was ensured seems to have been given up; suddenly, within a year or two, many are showing substantial corrosion along the bottom of the windows. However this was prevented before has just been stopped.

 

[Towers]

The decision to cease overhauls and scrap those units is a ROSCO decision. The TOC don’t have a say on scrapping.

I’m sure if TfW hadn’t had a replacement fleet entering service their 150s wouldn’t be going for scrap!

But yes, obviously the ROSCO are the owners, and replaced 150s coming off lease as overhauls are due are unlikely to find any further use.

 

[Invincible]

Trains are like houses. You can keep them going basically forever as long as you're content to keep replacing bits.

The thing that causes them to be retired is the economics of repair vs. replacement, which can vary depending on cost (in countries where labour is cheaper repair will tend to come out on top), and things like emissions and safety regulations (though again modifications are often possible).

The target for withdrawal of Diesel trains is 2040, some DMUs will be unviable to maintain before this.
But from

Diesel trains are still here for now – but data modelling could help cut emissions

www.imeche.org

...The test deployment between Middlesbrough and Whitby – selected because of the number of bends and speed restrictions over the roughly two-hour journey – used fuel pumps with fitted sensors to measure the flow of fuel throughout, which could then be fed back into the algorithm to make the engines as efficient as possible.

“If we understand how the train is using fuel to the second, to the metre hopefully, then you can understand and make a plot of the network,” said Rutter. “If we know we’ve got to get between A and B within a certain amount of time, actually, what is the most fuel efficient way of doing it?”...

There are options for reducing emissions.

 

[778]

158s are constructed from aluminium, and so have an immediate lifespan advantage over earlier DMUs like the 150s, which are renowned for galloping rot. They also ride superbly - indeed, far better than most that has come since - and as with all BR-era units, they are extremely well known by the TOC depots who maintain them and comparatively simple to keep running.

The flip side to all of this is the growing obselescence of essential parts, in particular the oily bits, and the political agenda towards anything with a diesel engine being “bad” (despite also being absolutely essential for the forseeable).

With 150s we have seen how one TOC who has a replacement fleet (TfW) began withdrawals and ceased any further major exam or overhaul work, while others (Northern, GWR) continue to maintain theirs with a view to ongoing service for the medium term future. So it’s largely down to whether or not the powers-that-be want or need to keep them running, and the willingness to meet the costs of doing so. There is nothing about class 158s, or any other second generation DMU, which means they will suddenly become life expired in five years time, provided that parts can be obtained and bills paid to keep them going. In the case of 150s that also includes a constant battle to keep rust at bay, although some serious attention on previous major exams helps to a degree.

Are the 15x and 16x DMUs in better condition now than what the 1950s built DMUs were in the 1990s?

 

[LiftFan]

Are the 15x and 16x DMUs in better condition now than what the 1950s built DMUs were in the 1990s?

They certainly have the advantage of not being riddled with Asbestos

 

[Mikey C]

They certainly have the advantage of not being riddled with Asbestos

Asbestos and then slam doors killed off much stock before it was "worn out". Net Zero will eventually kill off all diesels, but that's not imminent, and there's been no low floor revolution in trains that happened in buses, where high floor buses left service prematurely due to legislation.

 

[Russel]

Trains are like houses. You can keep them going basically forever as long as you're content to keep replacing bits.

The thing that causes them to be retired is the economics of repair vs. replacement, which can vary depending on cost (in countries where labour is cheaper repair will tend to come out on top), and things like emissions and safety regulations (though again modifications are often possible).

Beat me to it, they will keep going for as long as someone is willing to throw money at them.

 

[Invincible]

The industry will be watching the class 230 Ealing, Merseyside, the Dublin Alstom X'Trapolis low level and other battery running trains if more battery power (and low level doors) will be viable in the new UK tenders.
Hydrogen/battery is still a possibility with Porterbrook still testing it.

No doubt SWR will do tests fitting batteries to 450s to see if they could replace 158s, but the 158s still have several years left.

 

[Tetragon213]

Trains are like houses. You can keep them going basically forever as long as you're content to keep replacing bits.

The thing that causes them to be retired is the economics of repair vs. replacement, which can vary depending on cost (in countries where labour is cheaper repair will tend to come out on top), and things like emissions and safety regulations (though again modifications are often possible).

How many parts of a train can you replace, before it's no longer the same train?
In all seriousness, I think the 158s and 159s can continue on for many more years to come. We used bubblecars for nearly 60 years, after all!

 

[35B]

How many parts of a train can you replace, before it's no longer the same train?
In all seriousness, I think the 158s and 159s can continue on for many more years to come. We used bubblecars for nearly 60 years, after all!

Are there any considerations about aluminium fatigue life

 

[The exile]

Asbestos and then slam doors killed off much stock before it was "worn out". Net Zero will eventually kill off all diesels, but that's not imminent, and there's been no low floor revolution in trains that happened in buses, where high floor buses left service prematurely due to legislation.

Pacer withdrawal was by “diktat”, albeit then subject to external factors (COVID) - so akin to the demise of high floor buses.

 

[Tetragon213]

Pacer withdrawal was by “diktat”, albeit then subject to external factors (COVID) - so akin to the demise of high floor buses.

Tbf, the vast majority of the travelling public shed few tears to see the backs of the Pacers...

Iirc, Pacers weren't PRM compliant at all.

 

[Invincible]

Are there any considerations about aluminium fatigue life

Think the aluminium on trains and say land rovers last a lot longer than the lighter aircraft structures.

Tbf, the vast majority of the travelling public shed few tears to see the backs of the Pacers...

Iirc, Pacers weren't PRM compliant at all.

But Pacers originally were to last not more than 20 years, some operators made them last longer.

 

[Sun Chariot]

Off Topic I know -
I had to smile when I saw the title "Old DMU stock" and then read it's in reference to class 158s.
Old DMU stock, to me, was everything from the latter 1950s and early 1960s,.that was still going at the end of the 1980s and start of the 1990s.
I still recall the 140, 141s, Pacers, 151s, prototype Sprinters and production 150s coming into service, let alone the Super Sprinters, 158s and 159s.

 

[Clarence Yard]

Pacer full life at 20? That’s incorrect - it’s an urban myth that they were only for short term use. Pacers were supposed to last as long as a 150.

All BR DMU stock of that era were booked to last at least 25 years.

 

[The exile]

Tbf, the vast majority of the travelling public shed few tears to see the backs of the Pacers...

Iirc, Pacers weren't PRM compliant at all.

Indeed - all I meant was that their withdrawal was not entirely due to a natural process of becoming surplus to requirements.

 

[Towers]

Tbf, the vast majority of the travelling public shed few tears to see the backs of the Pacers...

Iirc, Pacers weren't PRM compliant at all.

I imagine plenty of users in South Wales, crammed into short formed TfW trains - comedically plastered with “Keep apart” signage during Covid - would have prefered not to see a mass culling of perfectly useable rolling stock for no valid reason other than politics!

 

[VioletEclipse]

I suspect that a number of 158s will have to stay in service upwards of 40 years, or even 45, due to a combination of increasing demand for more services while many even older trains will need replaced first, and there aren't exactly hundreds of new regional DMUs on order anywhere. Another big factor is the lack of electrification which ideally should have made the sprinters almost obsolete by now.

 

[Backroom_boy]

I suspect that a number of 158s will have to stay in service upwards of 40 years, or even 45, due to a combination of increasing demand for more services while many even older trains will need replaced first, and there aren't exactly hundreds of new regional DMUs on order anywhere. Another big factor is the lack of electrification which ideally should have made the sprinters almost obsolete by now.

With them hitting 35 years and nothing ordered to replace them, I would say that's a certainty

 

[JonathanH]

Another big factor is the lack of electrification which ideally should have made the sprinters almost obsolete by now.

Trains with batteries seem to be the only likely electrification for most Sprinter replacement now. From other postings, it seems that the cost of continuous electrification can't be justified for secondary routes with half hourly services. I guess that the DMUs have to continue until the replacement fleets can be afforded.

 

[philthetube]

If the fleet was to remain at its current size then they would last a long time.

The fleet is big enough to make it worth while producing parts, however as units are scrapped and less are around the economics change.

I know that the first sentence sounds odd but I could not think of a better way of putting it and I am sure you understand.

 

[stevieinselby]

Pacer withdrawal was by “diktat”, albeit then subject to external factors (COVID) - so akin to the demise of high floor buses.

Whereas the Pacers were pretty much universally reviled, with only a few contrarians wanting to see them retained, and even the 150/155s feeling very much past it and overdue for retirement, my experience of the 158/159s is that they are still providing a good passenger experience on secondary routes and they feel much more modern than the Sprinter family even though there's only a few years in it.

They won't be killed off because of public opinion, and it's extremely unlikely they will be killed off because they no longer meet the current standards given how many newer trains are running to the same standards (whether that's being diesel or high floor), so it's almost certain they will keep on going until they are no longer cost effective to maintain.