Underwater Electrical Connection - Page 1
Forum section: electronics / projects

author: rvalente
author_rank: Frequent Contributor
timestamp: November 16, 2022, 08:26:56 pm
content: 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 lotNowadays 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 daysDirty 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 VFDThe cable is a 4G4, the outside diameter varies from 12 to 18mm and is unwind from a spring cable reelThis 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

author: nfmax
author_rank: Super Contributor
timestamp: November 16, 2022, 08:50:27 pm
content: The magic word is “subsea”. Try searching for “subsea electrical power connectors“. This will get you products intended for the oil & gas industry

author: AlfBaz
author_rank: Super Contributor
timestamp: November 16, 2022, 11:07:52 pm
content: 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 pressureI 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 flexibilityPSThere 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

author: SmallCog
author_rank: Frequent Contributor
timestamp: November 16, 2022, 11:20:31 pm
content: 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 pumpsAnother 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.pdfI've used similar products on submerged 3ph equipment without issue, although I can't remember the specific part number / connector family I used.

author: rvalente
author_rank: Frequent Contributor
timestamp: November 17, 2022, 11:15:52 am
content: Quote from: nfmax on November 16, 2022, 08:50:27 pmWorked like a charm, googled and a few O&G suppliers popped up! |Quote from: AlfBaz on November 16, 2022, 11:07:52 pmI 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 pmGreat advice with Grundfos, they're easily reachable here, will definitely contact them

author: Terry Bites
author_rank: Super Contributor
timestamp: November 21, 2022, 10:36:13 pm
content: I'd just dump a load of black mastic on there............

author: DeepLink
author_rank: Regular Contributor
timestamp: November 22, 2022, 12:52:33 pm
content: Search after connectors likeSubconnSeaconBut 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 endThe inside is mounted with a bulkhead, sealed with o-ringEasy to service/replacePenetrators are used at all subsea levels (personal experience down to 6000 meters)Hans - DeepLink

author: geggi1
author_rank: Frequent Contributor
timestamp: November 22, 2022, 05:09:16 pm
content: 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.

author: coppercone2
author_rank: Super Contributor
timestamp: November 23, 2022, 04:09:32 pm
content: 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

author: rvalente
author_rank: Frequent Contributor
timestamp: November 28, 2022, 12:00:33 pm
content: Quote from: geggi1 on November 22, 2022, 05:09:16 pmThe 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=Metrichttps://www.hummel.com/en/cable-glands/products/plastic-cable-glands/hsk-k/?filter_variant=MetricThere are the best

author: geggi1
author_rank: Frequent Contributor
timestamp: November 29, 2022, 10:54:51 pm
content: 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.

author: aduinstat
author_rank: Contributor
timestamp: November 30, 2022, 01:30:37 am
content: I used a connector from Birns on one project and it worked great.

author: rvalente
author_rank: Frequent Contributor
timestamp: December 01, 2022, 12:08:03 pm
content: Quote from: geggi1 on November 29, 2022, 10:54:51 pmAgreed, I`ll be moving from PVC to PUR cables, mobile use and abrasion resistance.Quote from: aduinstat on November 30, 2022, 01:30:37 amDo you recall the series or PN?