Severn Tunnel - engineering improvements, events, incidents and history - merged posts

[whole diary]

[Chris from Nailsea]

From the BBC^» (British Broadcasting Corporation - home page):

Weeks of disruption for passengers on one of UK^▸ (United Kingdom)'s busiest rail lines

People travelling on one of the UK's busiest rail lines face weeks of disruption as engineers replace overhead power lines that corrode quicker than any other part of the network.

The Severn Tunnel, which connects south Wales with London and Bristol, will shut for 16 days from Saturday as workers fit a pioneering copper power line inside what was once the world's longest underwater rail tunnels.

Water that would fill 20 Olympic pools is pumped from the 140-year-old tunnel every day as saltwater from the River Severn constantly drips through its thick walls.

Direct GWR^▸ (Great Western Railway) services between London and south Wales will take longer on a revised timetable while buses replace some train services.

Passengers have been "strongly advised" to check their train times and allow extra travel time between south Wales and the south of England during the closure, between 23 May and 8 June.

Network Rail will also carry out track upgrade work around Bristol ready for the MetroWest project with a new station set to open on the former Filton airfield site later this year.

Rail bosses hope the £23m electrification upgrade project can ultimately improve train reliability and reduce the number of power failures and maintenance closures inside the Severn Tunnel .

About 200 trains normally travel through the 4.5 mile (7.2km) structure every day.

It has only once been shut for longer since it opened in 1886 - that was when electric wires were installed 10 years ago as part of the £2.8bn south Wales main line electrification project.

Network Rail has called the Victorian tunnel one of the most hostile environments on the UK rail network, where moisture, dripping saltwater and diesel soot accelerate wear on equipment.

(BBC article continues)

[Mark A]

The author of that article is clearly no fan of the rock group Big Big Train, who would have informed them that the water pumped from the Severn Tunnel is in the main, not salt water from the estuary, but ground water from the Great Spring.

Every night, their dreams were filled
With the fear of the river breaking in
But this was not a river god
This was something rising from the deep
From the depths of the mere

https://www.bigbigtrain.com/about-the-new-songs-the-first-rebreather/

Mark

[stuving]

Network Rail also have a page of information about this work:

Innovative Severn Tunnel upgrade to transform key rail link between South Wales and England

Region & Route:    Wales & Western: Wales & Borders

Passengers are advised to plan ahead as Network Rail carry out major upgrade in the Severn Tunnel and Bristol area, with replacement buses and diversionary routes in place to keep people moving from late May to early June.

This vital project will see Network Rail, and contractors ARQ, complete the transformation of the Severn Tunnel’s overhead power system, designed specifically to withstand the tunnel’s harsh, corrosive environment - making it more resilient, reducing the frequency of maintenance, and helping to minimise disruption for passengers.

The work will take place around the clock from Saturday 23 May until the early hours of Tuesday 9 June, with the railway closed between Newport and Bristol Parkway during this time.

The new system

Running beneath the Severn Estuary, the 4.35-mile Severn Tunnel is one of the toughest environments on the UK^▸ (United Kingdom) rail network, where moisture and saltwater accelerate wear on equipment.

Since electrification, the overhead power system has been prone to corrosion and electrical wear, leading to more frequent maintenance.

To address this, Network Rail’s Wales and Borders team has developed and successfully trialled an innovative new system. It uses a single 7km copper contact wire supported at regular intervals by modified bridge arms, to eliminate previous corrosion issues and improve performance.

Engineers will now install this system along the full length of the tunnel - using a world-first approach on this scale - to create a more resilient railway and reduce the need for frequent maintenance.

The programme of work involves:

    Replacing 838 bridge arms that support the overhead electric wires in the Severn Tunnel
    Renewing 9,000 metres of overhead wiring in the Severn Tunnel
    Carrying out track and infrastructure upgrades, and drainage works in the Bristol and Patchway areas.

Alongside the tunnel work, Network Rail will also carry out improvements in the Bristol area, including upgrades to the railway serving the new Bristol Brabazon station on the former Filton airfield site. The station is due to open in the autumn and will bring passenger services back to the Henbury line for the first time since 1964.

I think they are not "replacing 838 bridge arms", but installing them in place of what was put there in 2019. Unless there has been more going on in the interim, and I missed it, that is Furrer+Frey's ROCS^▸ (Rigid Overhead Conductor System) beam system but with aluminium contact wire clamped underneath it rather than the usual copper. That was meant to reduce the corrosion to manageable levels, with increased maintenance. But it looks as if they think having a third go at it will improve that further.

[Electric train]

Network Rail also have a page of information about this work:

Innovative Severn Tunnel upgrade to transform key rail link between South Wales and England

Region & Route:    Wales & Western: Wales & Borders

Passengers are advised to plan ahead as Network Rail carry out major upgrade in the Severn Tunnel and Bristol area, with replacement buses and diversionary routes in place to keep people moving from late May to early June.

This vital project will see Network Rail, and contractors ARQ, complete the transformation of the Severn Tunnel’s overhead power system, designed specifically to withstand the tunnel’s harsh, corrosive environment - making it more resilient, reducing the frequency of maintenance, and helping to minimise disruption for passengers.

The work will take place around the clock from Saturday 23 May until the early hours of Tuesday 9 June, with the railway closed between Newport and Bristol Parkway during this time.

The new system

Running beneath the Severn Estuary, the 4.35-mile Severn Tunnel is one of the toughest environments on the UK^▸ (United Kingdom) rail network, where moisture and saltwater accelerate wear on equipment.

Since electrification, the overhead power system has been prone to corrosion and electrical wear, leading to more frequent maintenance.

To address this, Network Rail’s Wales and Borders team has developed and successfully trialled an innovative new system. It uses a single 7km copper contact wire supported at regular intervals by modified bridge arms, to eliminate previous corrosion issues and improve performance.

Engineers will now install this system along the full length of the tunnel - using a world-first approach on this scale - to create a more resilient railway and reduce the need for frequent maintenance.

The programme of work involves:

    Replacing 838 bridge arms that support the overhead electric wires in the Severn Tunnel
    Renewing 9,000 metres of overhead wiring in the Severn Tunnel
    Carrying out track and infrastructure upgrades, and drainage works in the Bristol and Patchway areas.

Alongside the tunnel work, Network Rail will also carry out improvements in the Bristol area, including upgrades to the railway serving the new Bristol Brabazon station on the former Filton airfield site. The station is due to open in the autumn and will bring passenger services back to the Henbury line for the first time since 1964.

I think they are not "replacing 838 bridge arms", but installing them in place of what was put there in 2019. Unless there has been more going on in the interim, and I missed it, that is Furrer+Frey's ROCS^▸ (Rigid Overhead Conductor System) beam system but with aluminium contact wire clamped underneath it rather than the usual copper. That was meant to reduce the corrosion to manageable levels, with increased maintenance. But it looks as if they think having a third go at it will improve that further.

The contact wire is copper (standard OLE^▸ (Overhead Line Equipment, more often "OHLE") profile) it is clamped in an extruded aluminium beam; the beam is supported by "bridge arms".

It has always been know that Seven Tunnel is a hostile environment ie high humidity.  I know the Route electrification engineers have been looking for an improved conductor beam and support system