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Crossed linked Poly vs Thermoplastic Inuslation
2

Crossed linked Poly vs Thermoplastic Inuslation

Crossed linked Poly vs Thermoplastic Inuslation

(OP)
I've read the UL Standard test for these two types of inuslations. Both use tap water for the water test. I am looking for performance of these types of inuslation when exposed to saltwater. Anyone have any knowledge on the impact of salt water on these types of insulation?

I assume there must be a conductor rated for salt water use since we have miles of fiber cable under the ocean. And for use at marinas and boats.

Thanks.
Carl

RE: Crossed linked Poly vs Thermoplastic Inuslation

Fiber cable is not guaranteed to have any conductors in it, so your assumption may be fallacious.

There is almost certainly already a cable specialized for your application, but you haven't given us a clue what that might be.


Mike Halloran
Pembroke Pines, FL, USA

RE: Crossed linked Poly vs Thermoplastic Inuslation

(OP)
The applaication doesn't matter. Just interested in the performance of XLPE and thermoplastic insulation when exposed to seawater. But if you are interested, these are 600v feeders submerged in Sandy flood waters. we are relacing them but I would like to know what effect saltwater has on the conductor insulation. UL does not have that information. Nor a few cable manufacturers i talked with.

RE: Crossed linked Poly vs Thermoplastic Inuslation

Well, they're plastics, which are generally unaffected by seawater.
But to the extent that they're porous, or pinholed, or develop cracks, they don't protect the conductor from the seawater.

There's also the issue of ends and splices. The better grades of automotive wire include anti-wicking goo between the strands of wire, which limits intrusion of winter's salty water to just a cm or two. LV wires for submerged service are typically spliced with shrinktube overlay having sealant on the inside. Without the goo, the connections are doomed.

I should mention that 'thermoplastic' is a broad category that includes any plastic that melts when heated, as opposed to, e.g., Bakelite, a thermosetting plastic that chars when heated without melting first. XLPE is a thermoplastic, as is regular PE, as is PVC, as is acrylic, etc., etc.

Mike Halloran
Pembroke Pines, FL, USA

RE: Crossed linked Poly vs Thermoplastic Inuslation

Mike,

Older XLPE cable really doesn't like water, and eventually can cause failure over a long period. Modern stuff is a bit more tolerant. That's why cable has XLPE insulation but the outer sheath is PVC, which is largely unaffected by water.

Sorry I can't help with the original question.

RE: Crossed linked Poly vs Thermoplastic Inuslation

As MikeHalloran already said: “typically plastics are very resistant to saltwater corrosion. Some of them may also become brittle over time, but in general, the plastics like polyethylene, are very good.” See:
http://www.clihouston.com/knowledge-base/corrosion...
The usual underground listed cable is water penetration tested. See: UL 1072 and IEC 60502-2.
The problem could be, indeed, if the outer sheath is damaged. Then the salt water would corrode the armor.

RE: Crossed linked Poly vs Thermoplastic Inuslation

Thanks for the link zogzog.

RE: Crossed linked Poly vs Thermoplastic Inuslation

Very educational; thanks, ZZ.

Mike Halloran
Pembroke Pines, FL, USA

RE: Crossed linked Poly vs Thermoplastic Inuslation

(OP)
Thank you Z & Z.

RE: Crossed linked Poly vs Thermoplastic Inuslation

Thanks,Zogzog!

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