Penetrator Wire Sealing (take 2)?

Blue Robotics Products Potting
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On my ROV setup, we have 8 penetrators (with the 16/2 BR cable) connected to 8 bilge pumps (Tsunami 1200GPH). The team has noticed that it did leak air slowly when a mild vacuum was applied to the tube, but after discussing it on this forum concluded that it probably wouldn’t be an issue (see: https://discuss.bluerobotics.com/t/waterproofing-penetrators/ ). Today we ran a simulated test to 40ft for 15 minutes and found one of our two tubes to be nearly filled with water :frowning: .

All of the o-rings are in place and were covered with dielectric grease before being fastened to the 1/2" acrylic plate. Submersion testing while applying a vacuum to the setup confirmed that the leaks were through the cables/wires and not through the o-ring seals. The wire seals were made by soldering the individual wires in line, then applying two layers of liquid electrical tape to the joint, followed by covering that with adhesive lined heat shrink.

Are there any other recommendations for sealing these wires off?

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Hi Seth,

Bummer that you’re having issues with this! Sounds like you’re doing everything appropriately. Can you send some pictures of your setup including close-ups of the penetrators and the cable splices? I think that will help.

-Rusty

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Hey Rusty,

I created an imgur album with some basic descriptions of what’s going on with our setup: Leaky Penetrator - Album on Imgur

If you have any suggestions for resolving this, we’re open to anything. In the meantime, I think we’ll be switching that endcap over to using the more bulky and heavier SubConn bulkheads we have on hand. They are without a doubt overkill for our needs, but they’ve always seemed to perform flawlessly.

-Seth

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Seth,

Based on the photos I think there are a few possible failure points.

  1. Did you add another layer of heat shrink and liquid electrical tape over the red heatshrink? From the last picture, near the bottom, it looks like no. The end of the urethane jacket is exposed so if there any minor nicks in the conductors inside the water could leak in and enter the enclosure. See attached picture. I would recommend sealing that area well.

  2. Where are the red and black wires going? To a bilge pump motor? Are you 100% sure that the ends of those wires are sealed and water cannot leak through the conductors?

For further diagnosis, you can replace each penetrators with a “blank” penetrator and see if that solves the vacuum test issue.

Let me know what you think!

-Rusty


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Rusty,

Thanks for taking the time to review the photos.

  1. The last photo that you attached shows the internal heat shrink
  2. The wires are going to a tsunami 1200 gph bilge pump motor. I suppose I'm not 100% confident that it isnt leaking. I'll verify that.
 

We’ll be taking a more detailed (investigating some of your suggestions) look at the setup next week, and we’ll see where we get.

-Seth