Piggyback pipeline (HPHT) with High Voltage power cable 1

[ek4putr4]

Has anyone ever design or install pipeline with piggybacked High voltage power cable? If yes, what is the limitation?

We have one HPHT pipeline (171 bars design pressure and 150 degC design temperature. And someone wanted it to have high voltage power cable to be installed piggyback with that pipeline.

 

[LittleInch]

It's all about the cable. Higher temperature is not good and can significantly increase your cable size and impact the type of insulation.

I find it difficult to believe that the od temperature of the pipe is 150c. A few more details would help.....

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[ek4putr4]

I did jot day the od temp of pipeline is 150degC. Pipeline design temp is 150 degC.

Is there any effect if the high voltage power cable to the pipeline as it is piggybacked to the pipeline. Like eddy current effect, interference to pipeline CP (sacrificial anode).

For the pipeline itself is not insulated, we need the pipeline temperature to drop as much as possible (reduce the lateral buckling issue).

 

[LittleInch]

Well you didn't tell us what it was so 150 seemed a good guess...

Especially with an armoured cable, there are no electrical effects on the pipe.

Your issue is the cable size. Cables don't like getting hot and need somewhere to dissipate heat. Strapping it to a hot pipeline whatever it is is not a good idea for the cable.

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[MikeHalloran]

Littleinch is right; extra heat is not good for cables.

Additionally, I'd worry about vandals.

Mike Halloran
Pembroke Pines, FL, USA

 

[bimr]

The limitation is that you need to have room for future maintenance. It is typical to provide at least 12-Inch clearance, side to side.

What do you mean by piggyback?

 

[LittleInch]

I think the op is referring to subsea pipelines. Piggyback means strapping the cable directly to the pipe so that pipe and cable can be laid in one go.

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[SPDL310]

If the pipe line is warming your cable that will also increase the cable's electrical resistance leading to decreased efficiency.

 

[rconner]

An uninsulated subsea pipeline at 300 degrees+ F. might be sizzling pretty good! While I have no idea exactly what is going on here, I think piggybacking of (hydro)power cables is also being considered up in the far North, as there are hydropower sources up there and not many folks to burn same. An apparent alternative in those areas is using the power at origin to produce hydrogen, then inject that into the product stream close by to enrich same, and send the merry mix it on its way through the pipeline to more population that can use same.
There are probably many technical issues, and also safety concerns, for both utilities in placing at least very high voltage cables very close to very hot, high pressure transmission mains. [I visited an ongoing pipe bursting installation last week, and all was going well until I understand a worker jobbed a post hole digger into a power cable (at a daylighting location) very close to the old line being burst and replaced with new pipe. While no one was hurt, that kind of put a damper on that pull until the cable could be repaired.]

 

[georgeverghese]

On high temp subsea pipelines, the design is sometimes made deliberately so that the pipeline will laterally buckle during operations at several locations to provide for expansion. Will this design requirement suit a piggyback HV power cable?

In the past, there are pipelines that now cannot be pigged because there were no provisions made for controlled lateral buckling.

Also, if both pipeline and HV cable are all wrapped up in concrete and HDPE, the cable could also reach 150degC - can the cable insulation handle this ? - the electrical engineer can tell you if this is permissible.

Both pipeline and electrical engineers need to be consulted for this one. There are many complications that a pipeline engineer has to work with when setting up lateral buckles on HPHT subsea pipelines, and piggybacking a HV power cable may make things more difficult.

 

[ek4putr4]

The pipeline has been designed for controlled lateral buckling. The things that im not sure is the effect if the cable to the pipeline (magnetic field, etc). Im searching tracj record worldwide and can only fiund DEH application.

 

[LittleInch]

As I said, that's because there isn't any effect. Especially as the cable will be armoured (faraday cage) there is no effect on the pipeline.

However because of the temperature issue and the difficulty in laying both together, most systems would lay the cable separately and then bury it as cable ships can run very long distances very quickly and the cost of your cable is a lot less because it is thinner as it is cooler. On a piggyback the cable will need to be in the top half and thus is exposed to potential for damage.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.