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Plugs for WetLink Penetrator

I saw where there are WetLink blanks available. Wouldn’t it be better to simply have plugs to block off WetLink Penetrator so that it is ready to install a cable without have deal with replacing blank and dealing with nut assembly on back side?

Hi @dtrail,

Unfortunately this would not be possible. Though it technically would be feasible to have a modified blank plug with a radial o-ring seal to block off a bulkhead, the plug torque required to install a cable into a bulkhead would overwhelm the plug mating to the end cap, and would spin it out. The plugs need to be torqued to a specific value, 14 Nm in the case of the WLP 6.5 MM, and the bulkhead/nut would torque out and spin on the end cap before this point.

Though you could theoretically use an open ended wrench or some other tool to hold the flats of the bulkhead and keep it from torqueing out on the end cap while torqueing down the plug, at this point it would be so awkward its just easer to take it off altogether and assemble it separately as we recommend.

Furthermore, a WLP bulkhead with solid plug would weigh about 14 g, over double the blank at 6.6 g. This may not seem like a lot, but the weight can add up quickly with lots of holes, and together with the previously mentioned drawbacks we think just having a separate blank make more sense, while also being more cost effective and flexible in most cases.

-Adam

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Thanks Adam.

By plug I simply meant a dummy made of Acetal or solid rubber inserted in place of the cable.

Doug

You could try that, but the same caveats above would apply. The torque on the plug necessary to seal around the dummy or cable would overwhelm the bulkhead/end cap connection.

-Adam

@adam, I think @dtrail is suggesting something like this:


so installation would be basically the same as normal.

That said, the reasons I can think of against doing that are basically:

  • the WLP seals aren’t reusable, so doing this would waste a seal per penetrator
  • while the plug+bulkhead are reusable, we recommend not reusing them more than 3 times, and installing around a solid dummy cable would still use up one of those uses
  • there’s more than one size of M10 WLP (and there are about to be several more), so using a dummy-cable approach would require that we decide ahead of time on which cable size people are going to use, or alternatively offer blanks for every size and allow selecting each blank’s cable-size when buying an ROV enclosure (which is logistically impractical, likely at both ends)
  • a dummy cable means the water pressure is applied directly towards the hole, which would require additional validation on our part, and may not be sufficiently leak-proof to meet our requirements (not sure if this is what Adam was referring to with high(er) torque requirements)

@Eliot - You are correct on concept.

Use of Nylon rod .250” would be perfect for 6.5mm and 3/16” for 4.5mm.

Even if I had to replace seal when I need to put cable in, it’s much preferred to trying to get these new nuts installed in a populated bulkhead plate. Old round nuts I prefer as wires don’t allow to fall off when trying to start threading with a couple fingers or needle nose pliers in the rats nest.

I would think solid nylon would make torque requirement much less critical and can’t imagine problem with pressure at through hole.

Yes would have to validate but should be simple and cheap to try.

I could do for myself but think you and your customers might benefit too.

Thanks for considering.

Doug

@dtrail,
I spoke more about this with @adam and he explained more about why he doesn’t think this is a feasible approach. In particular, the bit that I wasn’t understanding initially was what he meant by the bulkhead/nut torquing out and spinning.

To rephrase Adam’s original comment, the torque required for the plugs to form an effective seal around a cable is significantly larger than the torque required to install the bulkhead+nut through an endcap hole. This means that the bulkhead+seal+plug must be installed and tightened onto the cable first, before the penetrator can be installed into an endcap. To do them in the reverse order would put much more torque on the bulkhead+nut than is intended, and would likely fail because the bulkhead+nut would lock together and just spin on the face of the endcap (likely causing damage) rather than holding still for the plug to be screwed in.

Accordingly, if a dummy cable was used the full WLP would still need to be removed before a new cable could be installed, which means you would still need to “deal with the nut assembly on the back side” (which is precisely what you were hoping to avoid).

The only way to install a cable through an already-installed bulkhead would be to

which Adam has said

While it may be less awkward with a tool setup like the following, it may be difficult to cost-effectively make a bulkhead holder like that without a decent economy of scale, which would likely require a large interest in it before it would be feasible for us to decide to make (e.g. to pay for a mould and casting, or a stamping die, or multi-axis machining with quite large waste). That’s compounded by there being multiple bulkhead sizes, which would need to be served by various sizes of the tool.

Perhaps there could be a niche market for say a small batch of 3D printed metal ones, but I’m unsure how cheap a tool like that would need to be in order for it to be of interest to people.

Regardless, thanks for the suggestion! :slight_smile:
At worst it’s an interesting idea, and at best may even be something for us to look into trying/making down the track :slight_smile:

I see said the blind man.

Outside ring of penetrators might not be a big issue but inside would as a back up wrench would be custom. Also probably not a problem with threaded hole bulkhead plate.

Thanks for looking into anyway.

Doug

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