O-ring Nibbling on Wetlink Penetrators

[Makenna (Makenna Reilly)]

Hello,

I have been successfully using an ROV with a 4" underwater enclosure with 6 T200s with the proper Wetlink connectors. Today, the vacuum test failed unexpectedly. I have been individually testing each penetrator to diagnose the problem, and found that the o-rings between the T200 wetlinks and the bulkhead looked like they had a bite taken out of them. I researched this problem a little, and found that it is very common. Should I just replace these o-rings? How can I prevent this issue from happening again?

Thanks,
Makenna Reilly

[EliotBR (Eliot)]

Hi @Makenna,

I asked about this internally, and was told

@WLP design engineers

They might have gotten damaged during initial installation - sometimes the o-ring will fall out of the gland right before you tighten it. Using Molykote [(silicone grease)] will help to prevent that issue, as the o-ring will stick into the gland.

If the o-ring is installed correctly then it shouldn’t have any visible nibbling, even after many cycles to high pressure. Nibbling like that is common on radial seals, but wouldn’t happen on face seals like this at low pressure unless it was damaged during install.

The installing penetrators section of our BlueROV2 assembly guide may be a helpful reference, especially from step 4.

@Makenna

I researched this problem a little, and found that it is very common.

We’d be interested to see the sources for this, as it doesn’t match our experience.

@Makenna

Should I just replace these o-rings?

Yep - if the o-rings are damaged they should be replaced.
We sell spares, if you don’t have any available.

[Makenna (Makenna Reilly)]

Thank you for the tips on install! I did further research since this post and found a resource comparing nibbling and installation issues and found that while the nibbling image looked similar to my issue, the installation issues made much more sense based on the application and placement of the problem I was facing. I will make sure to follow those instructions carefully as I replace the o-rings. Thanks again!

[Erlingns95 (Erling Nilsen)]

We have recently been experiencing similar issues. Is too much grease a possible root cause? We have had two of these and really wish to "never” see one again.

[tony-white]

Hi @Erlingns95 -
To me that looks like the o-ring wasn’t in place when the bolt was tightened down, cutting a section of it? Too much grease may have contributed to preventing it from staying put in the groove during assembly. Generally it’s good to check that things are seated and ready to tighten before doing so!

[tony-white]

To follow up @Erlingns95 -
We noticed that o-ring looks a bit smaller than it should - is it the standard size for WetLink penetrators? It should be. AS568-013 Buna-N 70A

[Erlingns95 (Erling Nilsen)]

I apologise for the uneven timeframe of my replies.

@tony-white

To me that looks like the o-ring wasn’t in place when the bolt was tightened down, cutting a section of it?

The O-ring was completely inside its track.

@tony-white

We noticed that o-ring looks a bit smaller than it should - is it the standard size for WetLink penetrators?

We only have original o-rings, if you think it looks smaller than usual I can only suggest an optical illusion!

[tony-white]

Hi @Erlingns95 -

No problem! That really doesn’t seem like an optical illusion - it looks like a backfill adapter o-ring to us…

Please reach out via the help center, report a problem with an order number so our support team can evaluate and potentially send replacements for the mis-pack. Thanks!