Penetrator solutions for tether/power cables with OD > 9.8mm rated for 250–300m depth?

General Discussion
1

Hi all,

I am working on an ROV build intended to operate at depths of 250m to 300m (~25–30 bar hydrostatic pressure) using a standard BlueRobotics 4" aluminum enclosure.

The Problem:

I need to pass a [power / hybrid tether] cable with an outer diameter (OD) of [X] mm into the enclosure. The jacket material is [PUR / Polyurethane].

Because the native WetLink Penetrator (WLP) system maxes out at ~9.8mm due to the M10 bulkheads, standard off-the-shelf options won’t fit.

Approaches currently considered:

  1. Custom CNC M14/M16 Penetrator + Potting: Machining a 316 SS or anodized 6061-T6 bolt with an integrated face seal O-ring groove, then potting the cable using 3M Scotchcast 2131 or DP420.

  2. Subsea Bulkhead Connector: Transitioning to a SubConn / Seacon MCBH micro-circular connector (requires re-tapping to 7/16-20 UNF).

  3. External Splice / Breakout Box: Breaking the large cable into multiple smaller AWG wires outside the hull, each entering via standard WLP penetrators.

Questions for the community:

  • Has anyone successfully modified a BlueRobotics aluminum end cap with an M14/M16 or 7/16"-20 port without compromising structural integrity at 300m?

  • For cables with PUR jackets at 30 bar, what surface preparation and potting compound have proven most reliable against water ingress along the jacket interface?

  • Are there any proven off-the-shelf compression glands or feedthroughs designed for 10–15mm cables at this pressure rating?

Looking forward to your insights and real-world recommendations!