Electrification contact wire height

[gsnedders]

One thing that's struck me recently is how it's decided what height to put the contact wire; obviously around many structures you don't have much choice, but on open lines is there a standard height they're put at? Are they put high enough for W12, even if the rest of the line doesn't have clearance? What about bridges that are replaced as part of electrification work, what clearances are provided around them?

It'd seem a shame if they weren't, given it means future gauge expansion work would potentially need to replace new structures and equipment.

 

[twpsaesneg]

One thing that's struck me recently is how it's decided what height to put the contact wire; obviously around many structures you don't have much choice, but on open lines is there a standard height they're put at? Are they put high enough for W12, even if the rest of the line doesn't have clearance? What about bridges that are replaced as part of electrification work, what clearances are provided around them?

It'd seem a shame if they weren't, given it means future gauge expansion work would potentially need to replace new structures and equipment.

W12 doesn't affect contact wire height, our absolute normal minimum is 4165mm and gauge height is 3990mm. W12 is more about the "shoulders" of the rolling stock.

For clearances, GL/RT1210 is your friend....

It's not the easiest subject to explain on a forum.

 

[3973EXL]

W12 gauge has the same maximum height as W6A, 3965mm above rail level.

Its purpose is to permit wider load units between 3080mm & 3965mm ARL where the permitted width of W6A decreases as height increases.

 

[gsnedders]

W12 gauge has the same maximum height as W6A, 3965mm above rail level.

Its purpose is to permit wider load units between 3080mm & 3965mm ARL where the permitted width of W6A decreases as height increases.

Bleh, for some reason I remembered W12 being very marginally higher.

 

[twpsaesneg]

W12 doesn't affect contact wire height, our absolute normal minimum is 4165mm and gauge height is 3990mm. W12 is more about the "shoulders" of the rolling stock.

For clearances, GL/RT1210 is your friend....

It's not the easiest subject to explain on a forum.

Just re-read this and realised you meant gauge clearance to the bridges!

Generally common sense prevails and rebuilt bridges are W12 cleared, however if there's a significant cost difference in getting OLE clear to W12 clear it would be likely not done - especially if not on a freight route.

For instance a track lower through an arch bridge, or the new arch jacking process would get OLE clear and not W12 (in general). Rebuilding the bridge in some way would be required in that case.

 

[Joseph_Locke]

Just re-read this and realised you meant gauge clearance to the bridges!

So in that case, it would be 600mm (reinforced insulation) from train to contact wire and the same from catenary to bridge - using all the normal numbers and allowances that gives you a deck soffit of nigh on 6.3m. To do anything else (for a new bridge) would need risk assessing ...

 

[gsnedders]

Just re-read this and realised you meant gauge clearance to the bridges!

There were two questions!

You implicitly answered one in your first post (is contact wire height high enough for W12? yes, because I'd forgotten that W12 didn't have further vertical clearance), and the other (are rebuilt bridges built to the largest loading gauge?) in your second.

Thanks all!

 

[twpsaesneg]

So in that case, it would be 600mm (reinforced insulation) from train to contact wire and the same from catenary to bridge - using all the normal numbers and allowances that gives you a deck soffit of nigh on 6.3m. To do anything else (for a new bridge) would need risk assessing ...

You'd think wouldn't you...

Somehow by wizardry 4780mm is the accepted rebuild height for some bridges.

There's various arguments about how the standard can be interpreted. Anything at "Basic " or above is generally considered ok, and there's a specific clause which can be interpreted as meaning "Functional" is acceptable without RA.

Compare though this to the "old" and still running on much of the network clearances down to 125mm passing in what was "Special Reduced " clearance

 

[HSTEd]

6.3m Clearance!

And we wonder why electrification is so expensive.

Those clearances would allow double stack containers!

 

[najaB]

Those clearances would allow double stack containers!

Not on an line with OHLE it won't.

 

[snowball]

That's probably HSTEd's point. He's probably imagining third rail.

 

[HSTEd]

Not on an line with OHLE it won't.

Obviously - but it does lend some context as to the enormous height requirement for OHLE under the new specification.

That's probably HSTEd's point. He's probably imagining third rail.

Well given the surprisingly low power-to-weight ratio of most freight trains (double stack or TOFC) in the US and elsewhere........