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Underwater Electrical Connection

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rvalente:
Hello mates,

a customer has a series of underwater clamshell, it takes iron oxide out of a tank with industrial water.

With the clamshell there is a underwater 3 phase 25HP hydraulic pump, the current is up to 25A. The pump is reversible, forward the oil feeds the clamshell opening and reversing the motor closes the shells.

In resting position cable length is around 3m and the deepest it can go is around 12m, being 5 underwater. The iron residue and water level changes a lot

Nowadays a standard IEC 60309, 4 poles, 32A is assembled inside a steel tube, sealed with an excess of screws and nuts.
Maintenance team try to improve the sealing by using a big amount of industrial silicone, it fails in just a few days
Dirty water gets in with iron chips, mixes with hydraulic oil damaging the pump, valves, pistons seals or gives the exposed motor windings low insulation tripping the VFD

The cable is a 4G4, the outside diameter varies from 12 to 18mm and is unwind from a spring cable reel

This improved version would still use a steel flange, with improved gasket and a locking nut for easy of maintenance.

The challenge is how to proper seal the cable? Cable glands have been used but they fail in one or two weeks.

I tried to locate underwater connectors but no source have been found.

Greetings

nfmax:
The magic word is “subsea”. Try searching for “subsea electrical power connectors“. This will get you products intended for the oil & gas industry

AlfBaz:
It looks like you need a metal cable gland with an IP68 rating.
However you will need to shop around as the definition of IPX8 is quite loose with regards to the amount of pressure (ie depth) it can withstand.
Each manufacturer will specify (hopefully) max pressure

I would also employ some kind of strain relief on the gland entry. A simple metal bracket that prevents the cable from moving at the entry to the gland.
Also, based on years of experience trying to keep water out of enclosures on decks of ships, don't use silicon! The metal rusts underneath rendering the stuff useless.

Either bolt a short tube around the gland and fill it with any tar like substance or wrap it with "Denzo" tape. The latter works well but I would replace it as part of periodic maintenance as a hard skin forms on it after a while making it inflexible. The strain relief should help with the loss of that flexibility

PS
There are other more robust glanding systems that I have seen where you pack an oil impregnated felt strip into a custom made tube but the ones that I have seen didn't look off the shelf, rather engineered and manufactured in a workshop

SmallCog:
There are also options for this in the world of bore/well pumps, I know Grundfos have submersible plug/socket sets for their pumps and other brands undoubtedly do too. Go speak to a local supplier/contractor that specialises in submersible pumps

Another term to search is wet mate connector which will lead you to products like this:

https://www.te.com/content/dam/te-com/documents/aerospace-defense-and-marine/SEACON/seacon-all-wet-brochure.pdf

I've used similar products on submerged 3ph equipment without issue, although I can't remember the specific part number / connector family I used.

rvalente:

--- Quote from: nfmax on November 16, 2022, 08:50:27 pm ---The magic word is “subsea”.

--- End quote ---
Worked like a charm, googled and a few O&G suppliers popped up! |


--- Quote from: AlfBaz on November 16, 2022, 11:07:52 pm ---It looks like you need a metal cable gland with an IP68 rating.

--- End quote ---
I was avoid using a cable gland because is basically the same approach currently place, however a electrical junction box cable gland is plance. I"ll reach to igus, lapp, murr and other high quality guys. Tks!


--- Quote from: SmallCog on November 16, 2022, 11:20:31 pm ---There are also options for this in the world of bore/well pumps, I know Grundfos have submersible plug/socket sets for their pumps and other brands undoubtedly do too. Go speak to a local supplier/contractor that specialises in submersible pumps

Another term to search is wet mate connector which will lead you to products like this:

https://www.te.com/content/dam/te-com/documents/aerospace-defense-and-marine/SEACON/seacon-all-wet-brochure.pdf

I've used similar products on submerged 3ph equipment without issue, although I can't remember the specific part number / connector family I used.

--- End quote ---

Great advice with Grundfos, they're easily reachable here, will definitely contact them

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