We had quite a few leaks trough our penetrators on our BR2, since we have it (around 4 years now), last one being trough tether cable (first version, not the revised one).
We more or less solved problems trough communication with BlueRobotics, but tether is not something we can deal like that, so we decided to do the potting ourselves, since there really isn’t any other solution.
Since we are based in Europe, there are lot of restrictions considering chemicals so we can not easily get products used in USA - recommended by BlueRobotics. I’ve searched trough all topics but did not find definitive solution to the potting problem, as what component to use that is relatively easily available to us in Europe.
I’ve found that material of “old” tehter cable that we use is polyethylene (different that other current BR product, harder to bond with epoxy).
Product that is easily avilable to us that I would like opinion of the community:
It was recommended to me by Loctite engineer, but with pressure testing prior to use because of no expertise in this particular field.
The tips I saw on the forum and BR video are:
very good surface cleaning
use of higher viscosity potting material
scouring on the cable that we want to pot
milling of the penetrator so bare aluminium is exposed
I’ve wanted to start this topic so potting problem (present in the community and at BlueRobotics) solution/help can be more available to community both in US and outside US. As far as I see 3M 2131 and Loctite epoxy marine are used in US and expiriences on this forum are good, altough not many expiriences are shared.
3M 2131 is somewhat available in EU (still researching the right supplier and options, part of the problem is only big size package) but there maybe are better options and expiriences.
I thank everyone in advance for input on this subject.
Hi mateov, maybe this is the right opportunity to share our experience!
We had the same issue and we have re-potted our penetrators with Loctite EA E-90FL. So far we had no leaks, but we haven’t tested extensively. This epoxy was recommended by the Nido Robotics.
Hi everyone, I hope every one is safe and well in Europe!
We are based in Australia where we have temperature ranging from 0c to 50c throughout our yearly season. One thing we have found out regarding potting compound is that is should be treated like an O ring. monthly checks and annual servicing’s. The potting compound is not designed to last years upon years, especially when it comes to subsea exposure like the BLUEROV gets.( wet, dry, wet, dry, sun etc…) we conduct monthly pull test/ vacuum test before a dive, this indicates any failures.
We also CARFEULLY heat our compound to 60c before mixing, we find this has better adhesion properties to the penetrators. ( be careful heating compound to 60c!!) The potting compound does go through undue stress due to its use. its not a forget and leave situation.
We are in a commercial industry and have opportunities to conduct these tests before use. We always conduct pre-deployment checks on our units so we don’t have leaks. We give our units a big over haul every year, (pots, o rings, electrical connections) to make sure all is right.
The BLUEROV is not a plug and play unit and does need some TLC.
We are happy to answer any further questions you may have. Happy flying!
@sample Thank you for your experience. What did you pot (tether, t200, etc.)? How deep did you go with that setup? Do you have any tips for using that compound? I know I am asking a lot, but would really like to find an optimal solution for this process.
@deepsupplies I agree that the environment that we use the ROVs in is harsh. We also check visually on regular basis and vacuum test multiple times before diving. But that showed some flaws since we had leaks multiple times during our dives, although everything looked good and vacuum test was more than satisfying. The more information about compounds and expiriences of others we have, the better we can react to prevent problems. With all that said, problems will always exist and it is a thing that we are used to and need to fix and improve
If you can give me insight on how do you check the pots? We perform only a weak “pull on the cable” test, visual inspection (new cracks, bubbles, etc.) and multiple vacuum tests.
We have completely re-potted a couple of T200s and back-potted everything else. Furthermore, we have used the same compound to pot the tether cable (new, more flexible edition) that we use to connect the external sensor. We had no super-deep dives after re-potting, but we were down to 70-80 meters with no problems. Actually, this was our first time to pot anything, so we have followed the BlueRobotics tutorial and used the sandpaper on the inside of the penetrator since we have read that should help with bonding. Regarding the tips and tricks, we can’t say much except that potting compound is quite thick, so count on that.
We have to note that our experience with this compound is limited to just a few dives, but we had no problems whatsoever.
@etienne
Thank you very much for your input. We are now really interested in complete transfer (in few steps/batches) to Cobalt connectors, so I have a few questions if you don’t mind answering
What did you connect with Cobalt connector? Our idea currently is to connect T200 (3-pin) and tether (8-pin), and in some time we would also make connectors for lumen, ping 1D, ping 360…
What material did you use to pot? Did you use primer on the connector (like in documentation from BlueTrail)?
Any other experience with potting this connectors? How do you check for leaks, do you just dive with it or did you found out some method to test?
Thanks in advance
@sample
That sounds great, thank you for sharing the info. Great info about potting thickness.
I assume by back-potted you mean you potted from the inside of the penetrator (method BlueRobotics used before), to stop potential leak from the black pot material from BlueRobotics?
I wish you best of luck and feel free to share experience about that potting set, when you have more dives
@SoSub hooked me up with GAM80 which I import from Australia but I am sure any king of 2 part epoxy that normal ROVs use will be fine. We 3d-print a mold and poor the mix in. Kelsey provided us with his mold step file as well. You can ask him, maybe he will give you.
We sand paper the inside of the shell and cable.
We use nail polish remover (acetone) to clean.
We connect everything.
3pins for thrusters and lights etc.
4pins for power
8pins for camera, signals etc
6pins can also be used to control multiple lights
For our surface power we use wetcom because of voltage ratings.
@mateov Our pool is set, and we are planning to take the full advantage of it
One thing to consider regarding the connectors is the maximum current through the connector, that is, can they handle operation of the ROV at 100% gain. The second thing is, although less important, the tools needed for the installation.
I’ve been using a polyurethane resin for several years without any problems ( for now anyway ! )
It’s an Electrolube product : UR5528 , the minimum pack is 250g and it’s easily availaible in Europe.
I generally test my potted products in my test tank, down to 500m for some of them, without any trouble.
My advices :
carrefully clean parts with isopropilic alcool ( avoid acetone ! )
avoid potting when humidity is high
ensure your part have no leaks because this product is rather fluid and will find each of them
It also work fine with Cobalt connectors ( which i distribute for France )
We use a 2 component PUR resin which we let sit in warm water for 10 minutes. We also ultrasonic our pots for 30 minutes at 50c.
We scuff the outer cable lightly to allow better adhesion and pour mixture in.
We use a small cable tie/tie wrap to push any bubbles out and to also smooth the resin over the lip of the pot.
Cure for 24 hours.
Vacuum and +ve pressure test, and also a reasonable pull test. (+ve test we do is small tube and attachment and blow into hose, we spray soapy water onto pots and look for any bubbles)
If you feel like the resin will pull out with a pull test, then the resin has not set correctly.
Hi all, I’ve made small animation on how to use the stand and I am attaching .stl files bellow, if anyone needs to pot BlueTrail Engineering Cobalt connectors
Works in PLA and PETG material, we use them at 20% infill and 0.35 mm layer height = less then 2 hours of print time per one set. Also, support needed for vertical part - see print orientations in the post above
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