Flood from battery compartment to umbilical head

I had a recent flood - into the battery casing on my umbilical - due to a damaged o ring. The head also flooded, I am assuming it went through the cable. Does this sound right? If so - how do I stop it happening again?

I have toyed with the idea of potting the cable ends - but what with & how to make a secure pot in very little space?

What is best practice (other than keep the o rings good - so it does not flood to start with!)

Ta

Yes, if it is a complete flood with the battery compartment flooding to the ambient pressure then water will force its way through the cable into the head. This takes time so the longer you remain below the water the more water ingresses the head.

Regardless, multi strand copper cable is corroded by salt water and if there is current flowing through the cable (i.e. the circuit does not break immediately) then this accelerates the damage.

Be mindful how water can seep between the multi strands of the kern and the insulating layer of the mantle. You need to turn the multi-strands into a single strand and pass this through an insulating pressure resistant wall/bulkhead. For example in this photo the cable is soldered to a solid copper bolt, which passes through a plastic bulkhead and waterproofed;


In this case it is a single-body torch and not a canister-cable-head like yours however the idea is the same; waterproofing the separation between the battery compartment and the head. If one floods, at least the other compartment is salvageable

Yeah, once water gets to the cable it will wick in all the way in. There are some cables out there that are fused to prevent this but I have never used them. Salvo/Light Monkey lights have a cap in the lid with another gland that they say will prevent this, but I find it a bit flimsy so I am not sure if it will just delay water seepage or prevent it. Nice though though...

I seal the cable at both ends with lots of silicon before sealing the ends.
Not fool proof, but good enough

Codiak said:

I seal the cable at both ends with lots of silicon before sealing the ends.
Not fool proof, but good enough

Click to expand...

This is a good idea...as you say not perfect, but it will delay the amount of water getting through the cable for hopefully long enough to get to the surface and salvage as much as possible.

There are degrees of flooding (I know this from bitter experience! :mecry

Codiak said:

I seal the cable at both ends with lots of silicon before sealing the ends.
Not fool proof, but good enough

Click to expand...

Thanks all - least I am on the right track
Codiak - how do you mean? Do you just put a big blob of silicone on the cable end - with the 2 conductors passing through - a bit like an ice cream with flakes sticking out?


Sorry about the picture - its the best description I could think of!

Greenforce cables are supposedly gel-filled to stop this, not sure whether it works as I've never seen one flood at depth.

They sell the cables as a spare part I think but they're not cheap.

Couldn't you use a hydraulic oiler, like you would with a bike cable, to force some sort of gel or sealant down the cable? Maybe some kind of epoxy that would set afterwards?

demonic69 said:

Couldn't you use a hydraulic oiler, like you would with a bike cable, to force some sort of gel or sealant down the cable? Maybe some kind of epoxy that would set afterwards?

Click to expand...

Epoxy in a flexible cable would stretch the cable. Something would give - either you get crumbly (porous) epoxy bits in the cable liner, or you get cracks along the cable liner and the epoxy will still crackle off. Think of ice on a rope. A gel would do nicely. Dow-Corning sells VERY nice silicone-based gels that cure at reasonable temperatures. But they're expensive; I think the minimum order size is a 22-kg bucket.

Thanks for the ideas. I have put a big lump of silicone sealer on each end of the cable, which will hopefully slow down teh migtation along the cable.

It's a shame - you build these lights, knowing at some time they will flood............