Underwater cable rubber seal casting

[Manul]

Hello,

looking for advice. Can not post picture of the actual cable, but it is similar to the one in the pictures attached. What is the best material to hand-cast the rubber seal where cable meets plug? Some type of polyurethane resin? Also, what important things and "traps for young players" I should know about?

Requirements:

1. Longevity at -30C to +50C at least 5-10 years
2. Depth of 300m (30 bar pressure)
3. Strong adhesion to the cable and plug surfaces
4. Slow curing to allow easy manual casting
5. Price does not matter

Thank you!

[Ian.M]

To get that sort of life, you'd have to know exactly which plastic or rubber the cable jacket and connector body are made of to select something that will chemically bond to both.  Surface cleanliness and preparation will be key to getting a good bond.  If the plug body is metal it gets far more complex, and you may need a special primer on the metal for the sealing compound to bond to.

[Manul]

To get that sort of life, you'd have to know exactly which plastic or rubber the cable jacket and connector body are made of to select something that will chemically bond to both.  Surface cleanliness and preparation will be key to getting a good bond.  If the plug body is metal it gets far more complex, and you may need a special primer on the metal for the sealing compound to bond to.

Thank you, I did not knew about surface priming. Added to my research list.

[Shiv]

Too specific requirements for me.


But for a well pump once I used this:



The only thing I can say about water resistance is that is in a well since 5 or 6 years ago... (about 10m depth)
And that I bought it in a marine shop...

[Haenk]

Maybe ask them:

http://www.reltekllc.com/

As money does not matter, they certainly have a way to do this (but I guess the chemicals are dangerous and not cheap...)

There are probably other offers as well.

(I think on the early cables they were using tar, which might be a good not-really-profesisonal DIY solution.)

[DeepLink]

We use 3M Scotchcast 2140U with very good results on subsea cables (PUR cables)

In the workshop we cast them in a mould (made of POM/Nylon)

On site we use heat shrink tube (Thick wall with glue), which we shrink in one end on the cable and pour the casting into the tube

This works down to 6000meters on sonar cables

On "shallow" water (down to a few hundred meters) you can use 3M Scotch tape model 23, which you wrap around the cable and finish with a heat shrink tube

The heat shrink tupe we are using is 3M MDT-A

[Manul]

We use 3M Scotchcast 2140U with very good results on subsea cables (PUR cables)

In the workshop we cast them in a mould (made of POM/Nylon)

Could you shortly describe, what preparation you use on a surfaces? How good 3M Scotchcast 2140U bond with metal surface?

[voltsandjolts]

If money no object, there are folks who do this for a living:

https://www.te.com/usa-en/products/brands/seacon.html?tab=pgp-story
https://www.eaton.com/us/en-us/catalog/industrial-connectors-assemblies/wet-mate-connectors.html
https://www.macartney.com/what-we-offer/systems-and-products/connectors/
https://www.hydrogroup-uk.com/cables/
http://cre-marine.com/

...etc, etc..

[DeepLink]

We use 3M Scotchcast 2140U with very good results on subsea cables (PUR cables)

In the workshop we cast them in a mould (made of POM/Nylon)

Could you shortly describe, what preparation you use on a surfaces? How good 3M Scotchcast 2140U bond with metal surface?

We clean the cable with solvent and I like to treat the surface with some sanding paper

No clue how it bonds to metal

We only bond to PUR cables and Subcon connectors (and Seacon) IL and OM types

[Renate]

I used to make underwater cables years ago.
One of the cable types we used was "sewer exploration cable".
It had a really tough jacket.

I don't have all the the details now, but...
We used to sandpaper the jacket and clean it.
I think we even applied some liquid coating then???
We had this rubber tape that wasn't adhesive, more like gummy, maybe 1/16" thick.
You'd wrap the tape around the splice.
We had aluminum molds and a heater.
You'd place the splice in the mold.
There was a vent at the top where you'd screw in a cylinder that you had stuffed with some rolled up rubber tape.
A screw at the top would compress the (now slightly liquid) tape into the mold.
You'd end up with a nice solid rubber lozenge around the splice.

Finally, when splicing coax, make sure you have some slack for differential shield/inner stretching.

[Manul]

Any experience/suggestion for the type of release agent to use with 3M Scotchcast 2140 (or other semi hard polyurethane resin) for plastic, 3D printed mold? It would be ideal if the mold would survive the release and stay usable.

[geggi1]

I can agree about that!
In the past I've done many sub sea umbilical and theathers for ROV and tooling.
Wen doing a umbilical we would normally have premade pigtails with plugs.
The issue when potting plugs is to ensure that all air is removed in the shell. Air in the shell will be compressed when submerged and expand when brought to the surface, this will cause a suction that over time will fill the void with seawater and can cause corrosion inside a plug.
If possible i would recommend to get pre-made pigtails and make a potted joint.