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Custom Penetrators

hi all

I am about to get a custom ROV body machined with the motor penetrators positioned just to the rear of the motor. This will be the latest in an increasingly long line of iterations and I had included holes for a type of penetrator I wanted to incorporate in this design. As you can see by the attached pic, the penetrator is something of a miniaturised flange with two radial o rings and a face o ring (possibly redundant). in theory it should work no less well than the normal flanges that go into the wtc but I would very much welcome any input from anyone with more knowledge before I spend $4k on a body that may start leaking as soon as any real pressure comes on.

This goes on the 4inch end cap?

How do you secure it?

Hi John,

Cool idea. I definitely think the face seal is unnecessary and if you don’t have a way to secure this then that seal would not be engaged until you are at pressure.

The other glands look a little narrow. How did you size the gland depth/width?


Hi Rusty

good to know the face seal is indeed redundant. The choice of 2.62 mm cs o rings was just a guesstimate of what might work and was wondering if 3.53 mm cs o rings might be better. I took the gland depth and width sizing off a table I found on an o ring suppliers website - https://www.allorings.com/o-ring-groove-design-metric

Do you think I should go with 3.53 mm if the 2.62 looks too narrow?

I hadn’t planned on having to secure the penetrators to the wtc because I had taken the fact that the normal BR o ring flanges stay in place without securing as an indicator that the same would work here even at low pressure. Your thoughts on that?


Hi John,

Alright. The smaller O-rings are probably just fine for this size. Small is fine if you can ensure pretty tight tolerances. I’m glad you used an O-ring table. That should work great. My comment about it being too narrow was just based on the visual appearance of the width versus depth of the gland.

The flanges stay pretty secure because they have a large total O-ring area to provide a friction force. Since this part has a very small diameter I would expect the force to be much smaller. It would probably work but you’d have to be careful not to yank the cables out accidentally.


your input much appreciated as I am sure you did some serious research on the matter before you designed the o ring flanges for the different wtc options you have come up with. on the basis of that I will run with a design omitting the face o ring and staying with the 2.62 mm radial rings.