Underwater Electrical Connection

[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]

The magic word is “subsea”.

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

It looks like you need a metal cable gland with an IP68 rating.

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!

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.

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

[Terry Bites]

I'd just dump a load of black mastic on there............

[DeepLink]

Search after connectors like
Subconn
Seacon

But You should consider a penetrator, a moulded cable entry, which is moulded directly around the cable and has "built in" strain relief in the outside end
The inside is mounted with a bulkhead, sealed with o-ring
Easy to service/replace

Penetrators are used at all subsea levels (personal experience down to 6000 meters)

Hans - DeepLink

[geggi1]

The simplest sollution might be to just use a lenght of steel pipe as a riser for the cable.
If you use a 4m lenght of pipe the cable entry will be way above the water level and you can use regular glands on top.

Another option is to use a potted entry for the cable, 3M had some good two component stuff that we used for ROV down to at least 350m.

[Poe]

[coppercone2]

can you make a restoration video where you scrub the rust off by hand? throw it in a creek first so you can garden hose the mud off

[rvalente]

The simplest sollution might be to just use a lenght of steel pipe as a riser for the cable.
If you use a 4m lenght of pipe the cable entry will be way above the water level and you can use regular glands on top.

Another option is to use a potted entry for the cable, 3M had some good two component stuff that we used for ROV down to at least 350m.

The steel tube would not last a day, the clamshell rolls over itself while closing while this is great because it sink itself in the residue the steel tube would crash with the tank walls.

These are the best cable glands I've found:

https://www.hummel.com/en/cable-glands/products/metal-cable-glands/hsk-mz/?filter_variant=Metric

https://www.hummel.com/en/cable-glands/products/plastic-cable-glands/hsk-k/?filter_variant=Metric
There are the best

[geggi1]

Look into Ex d potting glands.
Not the kind that is used with putty, but the kind used with two component resin.
You should also look into the kind of cable you are using. As far as i remember PUR cables are more waterthight than many other cables.

[aduinstat]

I used a connector from Birns on one project and it worked great.

[rvalente]

Look into Ex d potting glands.
Not the kind that is used with putty, but the kind used with two component resin.
You should also look into the kind of cable you are using. As far as i remember PUR cables are more waterthight than many other cables.

Agreed, I`ll be moving from PVC to PUR cables, mobile use and abrasion resistance.

I used a connector from Birns on one project and it worked great.

Do you recall the series or PN?