OHLE renewals.

[scotraildriver]

I was wondering if anyone on here knows how often overhead lines are renewed. The reason I ask is that as a driver I keep up to date with WONS/PONS etc. Now every week I read of track renewals, S & T work etc etc but never overhead line. So my question is how long does it last? Presumably only the contact wire requires renewal as the catenary/long track return etc has no wear. Anyone know? Just curious.

 

[swt_passenger]

I was wondering if anyone on here knows how often overhead lines are renewed. The reason I ask is that as a driver I keep up to date with WONS/PONS etc. Now every week I read of track renewals, S & T work etc etc but never overhead line. So my question is how long does it last? Presumably only the contact wire requires renewal as the catenary/long track return etc has no wear. Anyone know? Just curious.

Contact wire life is around 25 - 30 years, as mentioned in Gary Keenor’s OHLE book.

 

[furnessvale]

I was wondering if anyone on here knows how often overhead lines are renewed. The reason I ask is that as a driver I keep up to date with WONS/PONS etc. Now every week I read of track renewals, S & T work etc etc but never overhead line. So my question is how long does it last? Presumably only the contact wire requires renewal as the catenary/long track return etc has no wear. Anyone know? Just curious.

When I worked on the perway (years ago) other disciplines would often piggyback on long perway possessions taking advantage of the closure.

Does that still happen, or have things been tightened up?

 

[DidcotDickie]

Well, they're just getting round to renewing the OLE on the London, Tilbury & Southend line (C2C) and that was put up in 1959-62 and I don't think there have been any significant line renewals since then. Similarly the GE main line has recently been renewed between Liverpool St and Chelmsford/Southend Victoria. Whilst the electrification has been upgraded over the years (initially to 6.25kV and then to 25kV AC), I think that much of the actual wiring dated from 1949/1956 when it was energised at 1500V DC.

 

[swt_passenger]

Having rechecked the source, he does say that at the 25-30 year point “midlife” there’d only be 25-33% mechanical wear to the catenary, but the droppers and other components and fastenings would start failing. So I guess there’d be quite a few options before the contact wire runs themselves needed replacing.

So it seems there will be significant areas that wont actually be due contact wire change at all...

 

[thecrofter]

As with most things OLE (OCS), its not just one simple answer I'm afraid. Many variables will determine when a wire run is to be renewed. Age, the number of Pan passages, line speed, number of splices (repairs), side wear (if there is any), etc. Basically it should get renewed as and when it is required depending on the asset condition score determined by the inspection regime. There are some wire runs that see very little traffic and have never been renewed since they were first installed.

 

[Ploughman]

With the amount of times OHLE gets torn down, does it get renewed anyway?

 

[pdeaves]

The contact 'wire' (actually a beam) in the Severn Tunnel required replacement before its first use...

 

[swt_passenger]

The contact 'wire' (actually a beam) in the Severn Tunnel required replacement before its first use...

The contact wire is still present in the Furrer and Frey ‘beam’ though, it’s functionally the same as outside the beam area. I think this is done to make the transitions easier.

 

[hwl]

The contact wire is still present in the Furrer and Frey ‘beam’ though, it’s functionally the same as outside the beam area. I think this is done to make the transitions easier.

They swapped the copper wire for aluminium alloy matching beam extrusions to reduce corrosion issues. The beam wasn't replaced.

 

[LNW-GW Joint]

The WCML (fast lines at least) were rewired and upgraded for 125mph in the 2000s as part of WCRM.
NR bought a special train for the work, which has been used in recent electrification schemes.
The Liverpool Lime St area wiring has recently been renewed, after some 56 years of use.
I think some of the Glasgow south side wiring, of similar vintage, has also been replaced recently.
The GW wiring from Paddington to the Heathrow junction is being renewed and upgraded for 125mph, and the MML south of Bedford will follow.
There will also be work on the southern ECML to improve reliability.

 

[Bald Rick]

As with most things OLE (OCS), its not just one simple answer I'm afraid. Many variables will determine when a wire run is to be renewed. Age, the number of Pan passages, line speed, number of splices (repairs), side wear (if there is any), etc. Basically it should get renewed as and when it is required depending on the asset condition score determined by the inspection regime. There are some wire runs that see very little traffic and have never been renewed since they were first installed.

Good answer.

The OLE system is also much more capable of being renewed ‘piecemeal’. For example, just renewing the contact wire is quite straightforward, as are droppers, or registration arms, or tensioning kit, or insulators. Typically masts are good for 100 years at least, unless there is a fundamental change to the system design.

It only gets difficult when you have to renew it all at the same time.

 

[Bald Rick]

With the amount of times OHLE gets torn down, does it get renewed anyway?

Only damaged components - insulators, reg arms etc. Usually what comes down goes back up, and any breaks in the contact or catenary wires are spliced together.

 

[AM9]

Only damaged components - insulators, reg arms etc. Usually what comes down goes back up, and any breaks in the contact or catenary wires are spliced together.

Do insulators ever get replaced or cleaned because they are coated with contaminants that cause them to track? Similarly, do the glass/ceramic beads on the neutral isolators get cleaned?

 

[Bald Rick]

Do insulators ever get replaced or cleaned because they are coated with contaminants that cause them to track? Similarly, do the glass/ceramic beads on the neutral isolators get cleaned?

Yes neutral section beads, and section insulators, are cleaned - that’s in the standard cyclical maintenance schedules. Carbon from the pan heads builds up, and if they aren’t cleaned there will be, eventually, an arc dragged across by a passing pan. Quite a sight (and sound) if you see it.

Insulators aren’t routinely cleaned or replaced. Some individual examples might be, if faulted on inspection. Older types of insulators have been subject to ‘campaign’ replacements where they are all changed over a given stretch of line.

 

[thecrofter]

Yes neutral section beads, and section insulators, are cleaned - that’s in the standard cyclical maintenance schedules. Carbon from the pan heads builds up, and if they aren’t cleaned there will be, eventually, an arc dragged across by a passing pan. Quite a sight (and sound) if you see it.

Insulators aren’t routinely cleaned or replaced. Some individual examples might be, if faulted on inspection. Older types of insulators have been subject to ‘campaign’ replacements where they are all changed over a given stretch of line.

There are still many A26 type porcelain insulators that remain to be changed on WCML.

Even new polymeric types have to be cleaned particularly in heavily polluted areas such as stations and tunnels e.g Birmingham New St. which are subjected to diseasel fumes.