Aluminum XLPE conductors exposed to sea water
Aluminum XLPE conductors exposed to sea water
(OP)
An electrician ran 1000 ft of parallel 350 kcmil Aluminum XLPE cables in a PVC conduit underground. The run was from a non-fused disconnect to several large brine pumps on a platform. About 500 ft in to the run they put a non-wet proof splice kit in. About 7 months ago the customer noticed water boiling in the area of the splice kit and pull box. They then replaced the splice kits with the proper splice kit that was specified by me and is rated for the application. They also replaced the non-fused disconnect with a fused disconnect.
For about 6 months there doesn't seem to be any problems till I got called in today. It seems one of the 6 conductors on both ends of the conductor was dripping sea water out of the aluminum wire ends and of course dripped on the flow meter controls and damaged them. They created a make shift catch basin and it collected several pints of waters and then dried up. They are asking me for recommendations.
My thought is that the bad splice and the heat of the conductor sucked in water between the jacket and the individual strands of wire. The splice got fixed, but water was stuck in the conductor jacket. With the equipment now running, heat has finally cause the water to work its way out. It has since been evaporated. I have proposed an insulation test to make sure the conductor insulation wasn't damaged when the bad splice was in and a short was forming in the water without any fused protection. If it passes ok and we all agree it was water working its way out of the cable I am worried about one other problem. That is salt water working its way through the whole cable and leaving salt deposit in there for future corrosion. One thought says the aluminum oxide around the strands wouldn't be harmed by the salts and not to worry about it. Another thought says to replace all the conductors which would be a huge financial burden to the electrical contractor. Please give me your thoughts and anything else we can do to make sure we are OK from here on out.
For about 6 months there doesn't seem to be any problems till I got called in today. It seems one of the 6 conductors on both ends of the conductor was dripping sea water out of the aluminum wire ends and of course dripped on the flow meter controls and damaged them. They created a make shift catch basin and it collected several pints of waters and then dried up. They are asking me for recommendations.
My thought is that the bad splice and the heat of the conductor sucked in water between the jacket and the individual strands of wire. The splice got fixed, but water was stuck in the conductor jacket. With the equipment now running, heat has finally cause the water to work its way out. It has since been evaporated. I have proposed an insulation test to make sure the conductor insulation wasn't damaged when the bad splice was in and a short was forming in the water without any fused protection. If it passes ok and we all agree it was water working its way out of the cable I am worried about one other problem. That is salt water working its way through the whole cable and leaving salt deposit in there for future corrosion. One thought says the aluminum oxide around the strands wouldn't be harmed by the salts and not to worry about it. Another thought says to replace all the conductors which would be a huge financial burden to the electrical contractor. Please give me your thoughts and anything else we can do to make sure we are OK from here on out.






RE: Aluminum XLPE conductors exposed to sea water
The fact that water was boiling would mean it exceeded the temperature rating of the insulation which will probably be 90°C for XLPE. Did you identify the source of the heat?
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If we learn from our mistakes I'm getting a great education!
RE: Aluminum XLPE conductors exposed to sea water
Since I don't know the alloy in the aluminum I don't know how it stands up to salt water. There are many aluminum allows that handle salt water very well. Ust not sure about this type of aluminum.
RE: Aluminum XLPE conductors exposed to sea water
If this is a 480V installation and larger cables were used to keep the voltage from excessive voltage drop, I might not be so concerned as long as it passes and insulation test and the system isn't too critical. On the other hand, how hot must a cable get to force the water out of it?
Scotty has a good point about when it will fail. They always fail when you need them the most. If this is a critical system that cannot go down for very long, then you are probably best just replacing the cables.
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If it is broken, fix it. If it isn't broken, I'll soon fix that.
RE: Aluminum XLPE conductors exposed to sea water
It might be possible to purge first with de-ionized water to remove some of the salt and then later switch to the silicone fluid to provide long-term protection. These systems maintain a residual pressure on the fluid and so serve as a positive block against future water infiltration. Given the high ground water level, this might be a good long-term investment.
RE: Aluminum XLPE conductors exposed to sea water
Potteryshard, I am interested in knowing more about this process. Do you have any links on this or Florida company names?
RE: Aluminum XLPE conductors exposed to sea water
http://cbs-florida.com/field_service/index.htm
You will want to do a condition assessment test on your cable to find out what the extent of damage is, a Megger test is only pass/fail, you will need a more comprehensive test to determine if repair and injection or replacement is the best solution.
There are some pros and cons to this process, this thread covers them quite well. http://www.eng-tips.com/viewthread.cfm?qid=156645
RE: Aluminum XLPE conductors exposed to sea water
Most of this work is done at 15 - 25 kV which of course requires special MV splices to permit fluid flow. At secondary voltages, it should be much easier. It would probably be fairly easy to devise one's own system.
RE: Aluminum XLPE conductors exposed to sea water
RE: Aluminum XLPE conductors exposed to sea water
RE: Aluminum XLPE conductors exposed to sea water
RE: Aluminum XLPE conductors exposed to sea water
http://www.arcflashtraining.net
http://www.arc-flash-training.com
RE: Aluminum XLPE conductors exposed to sea water
RE: Aluminum XLPE conductors exposed to sea water
RE: Aluminum XLPE conductors exposed to sea water