Trackside cabinets

[Paul180]

On seeing what I thought were old cabinets I was wondering what they are for I always thought that they were for telecoms or something similar but on seeing them close up has changed that as they have a kn/m2 (kilonewtons/square meter) gauge on them I was wondering what there were for.

 

[dviner]

Greasers?

 

[najaB]

Does the railway pressurise cables?

 

[swt_passenger]

Similar cylindrical containers are fairly common on the DC network, I reckon they are pressurising oil filled cables.

 

[MrGrumpy]

If it's measuring pressure wouldn't it measure in lb/sq inch?

It's in kN which suggests force so I would guess an older Wheel Impact Load Detector (for flats and the like).

 

[Dai Corner]

If it's measuring pressure wouldn't it measure in lb/sq inch?

It's in kN which suggests force so I would guess an older Wheel Impact Load Detector (for flats and the like).

It's KN / M (possibly with a 2 superscript?) so maybe it is kilonewtons per square metre (i.e. pressure)?

 

[MrGrumpy]

Of course it is. I was scraping the bowels of my school education and forgot that it's also used to measure atmosphere/pressure.

 

[Tio Terry]

Probably oil filled high voltage power distribution cables. There's a lot of them on the former Southern Region.

 

[ainsworth74]

As I know very little about the subject could someone explain why you would fill a cable with pressurised oil?

 

[MrGrumpy]

Take from it what you will, but Wikipedia states:

Cables for power distribution of 10 kV or higher may be insulated with oil and paper, and are run in a rigid steel pipe, semi-rigid aluminum or lead sheath. For higher voltages the oil may be kept under pressure to prevent formation of voids that would allow partial discharges within the cable insulation.

 

[pdeaves]

As I know very little about the subject could someone explain why you would fill a cable with pressurised oil?

It acts as a combined insulator and cooler, I believe.

 

[najaB]

As I know very little about the subject could someone explain why you would fill a cable with pressurised oil?

As others have said, it keeps the water out. BT (well Openreach) pressurise their main cables, though with air rather than oil.

 

[macka]

NR uses an internal 33 kV distribution network to connect up the DC substations as they have to be situated quite close to each other to provide enough power for the 3rd rail.

 

[Joseph_Locke]

Probably oil filled high voltage power distribution cables. There's a lot of them on the former Southern Region.

There are still a few pressurised telecoms cables in the North ...

 

[Tio Terry]

There are still a few pressurised telecoms cables in the North ...

Really? I thought they were mainly out of use now. Do you still have 4Mhz FDM systems using them? Thought everything had changed over to PCM systems by now. I seem to remember a 4 Meg co-ax being used for PCM in amongst the London Linking Cable system, think it was Farringdon to Waterloo, that was pressurised, guess it's all long gone now!

 

[rebmcr]

Does the railway pressurise cables?

For pneumatic points machines, yes.

 

[Deepgreen]

Really? I thought they were mainly out of use now. Do you still have 4Mhz FDM systems using them? Thought everything had changed over to PCM systems by now. I seem to remember a 4 Meg co-ax being used for PCM in amongst the London Linking Cable system, think it was Farringdon to Waterloo, that was pressurised, guess it's all long gone now!

"A few remaining" and "mainly out of use" are compatible phrases.

 

[hwl]

NR uses an internal 33 kV distribution network to connect up the DC substations as they have to be situated quite close to each other to provide enough power for the 3rd rail.

The 33KV cables used to supply the 3rd rail substations are XLPE insulation the older 66KV network that is being removed used pressurised oil filled cables. Still some 66KV around New Cross area but that is being /has been removed.

 

[ainsworth74]

Thanks all!

 

[Paul180]

Thanks for the replys I would have never thought they would have used oil filled cables on the side of the railway. I suppose it was down to the technology of the day. Is it a bit of a headache to decommissioning and remove them these day.

 

[Signal Head]

There are still a few pressurised telecoms cables in the North ...

That brings back happy memories of visits to check on the temporary gas bottles (nitrogen, IIRC) put on when the pressure had dropped owing to a suspected leak. Nice easy job and a trip out.

 

[Tio Terry]

That brings back happy memories of visits to check on the temporary gas bottles (nitrogen, IIRC) put on when the pressure had dropped owing to a suspected leak. Nice easy job and a trip out.

Yes, and walking the track with a sniffer to find where the leak was! I'd like a £ for all the miles I walked.

 

[Tio Terry]

Thanks for the replys I would have never thought they would have used oil filled cables on the side of the railway. I suppose it was down to the technology of the day. Is it a bit of a headache to decommissioning and remove them these day.

An environmental nightmare! Very difficult to drain disused cables and a massive problem with the potential of oil leaks when recovering disused cables. They are often left in situ rather than risk the issues with recovery.