That’s not something we’ve tried, but it could potentially be possible by using a 3D-printed mould to ensure a consistent diameter.
Smaller cable sizes have been asked about and discussed previously here, where the suggestion was to use heat-shrink to increase the cable jacket diameter.
It may be worth considering an adhesive-lined heat shrink for waterproofing and avoiding pull-out and push through, but given your non load-bearing use-case and the radial pressure of the WetLink penetrator’s compression seal I don’t expect they would be particularly significant issues.
thanks eliot - yep missed that post in my forum search - confusing title.
i’m sla printing a mould and will try this out, will give an update if it works.
For adhering to a cable/instruments under pressure eg. like potting a cable. Is it better to use flexible resins (eg. silicone/polyeurethane) or hard epoxies?
I’m a little uncertain about what’s going on/what deforms under pressure. My guess is that a hard resin would have a greater pressure rating, limited only by the deformation of the cable jacket. With flexible resins if it’s softer then the cable, then that will deform to allow water to penetrate first?
I don’t have a heap of experience with potting, but I’d assume that rigid potting makes sense where it’s desirable to protect the internals from external pressure, whereas flexible potting likely makes more sense for situations where the potting is expected to deform. By that logic, potting around a device should likely be rigid, while potting a cable should be flexible, to allow the cable to flex (and to avoid stress concentrations at the edge of the potting).
That seems particularly relevant for a compression-gland seal, where the compression plug is expected to compress both the seal and the cable jacket. Rigid epoxy may prevent the seal from being as strong, and could provide a protective shell that holds back the seal pressure and allows water to slide through by compressing the cable jacket underneath the epoxy. That’s purely conjecture though (I don’t have test data or specific experience to back it up), so take it with a grain of salt.
I realise that this thread is quite old, but I was hoping that I could still get answers for some concerns I have.
I develop AUVs with my team and we require the use of hydrophones for our purposes. The hydrophone cables are potted to a penetrator on the hull for waterproofing. Unfortunately, this is rather poor as the potting gets worn out and the penetrator turns into a leak point, so we were considering switching over to the WetLink Penetrators to bypass the need for potting.
Unfortunately, the hydrophone (Teledyne Reson’s TC4013) cables are also only 2mm in diameter, so I we may need to spam some heat shrinks to thicken it to work with the WetLink Penetrators too. This, however, has me thinking of another potential issue: would a stack of heat shrinks being clamped upon by the WetLink Penetrator be any better than just a typical potted penetrator? That is, would there be improved waterproof-ness and sturdiness relative to the potted penetrator?
Hi @Violet -
Welcome to the forums!
That’s quite a thin cable - is it coaxial? I would agree with what Eliot mentioned above, my intuition says a compliant layering of heatshrink with glue will interface better with the compressed Wetlink plug compared to a rigid potting making the cable a larger diameter. That interface between potting and cable is always a tricky one!
The pressure “in the seal” is what keeps water out - unless the water is at a higher pressure. If you’re able to add 3-5 layers (?) of heatshrink, maybe of two sizes, and it is the type that has internal glue (great for marine appplications) I imagine you’ll get a good seal once you tighten the plug down completely. You’ll want the heatshrinkg up against the internal geomery of the bolt, so the material is pinched by the seal into the bolt head.
It is easy to test with a vacuum pump! I wouldn’t expect this approach to work at the typical 950m max depth other larger cables have, but for pool depths you’ll likely be fine. Let us know how it goes!
Hi @Violet -
Cool - does that connector fit through the WetLink or are you re-terminating the cable?
Yes, any heat-shrink with internal glue lining would be ideal, I’ve never see ones with epoxy?
Best of luck!
