PBOF Systems

Time and time again I keep seeing people being paranoid about flooding etc. There is a solution to this if you are willing to go the extra mile. Instead of leaving your systems full of air you can fill your containers up with a high dielectric oil. If you want to understand more of what I am talking about look up “Pressure Balanced Oil Filled”.

I have built cables with pretty much Tygon tubing and connectors filled and equalized … and vacuum degassed … with oil that have went to the bottom of the ocean and back. PBOF systems are used in a lot of your SONAR towed cables and other systems that have electronics and require acoustic transparency. It is nothing new but it is basically messy and you have to deal with a fill system etc.

Using the WTE sold on here, you can make a PBOF system so you don’t have to be worried about your little ROV going to a 1000 feet and dying.

Just wanted to toss out that suggestion in case anyone wanted to go a little deeper in protection schemes for their systems.


I agree with that. When going especially deep. It’s just a mess. I use mineral oil from CVS, LOL, for my battery boxes on some of my kits.

Jim, another thing the fluid helps to do is bleed the heat off too. Air is not that well at conducting the heat away from battery packs etc. Anything that can help transfer the heat to the water etc. helps a lot.


Ditto what Harold and Jim said. Years back, I built thrusters using brushless inrunner motors. The housings were designed to be fluid filled and I experimented with a number of different fluids. Mineral oil is cheap, non-toxic but was a bit too viscous for my application, so I used radiator coolant (the non-toxic type).

Most electronics and wiring work well in fluids. The problem I see with filling the main WTE with fluid would be what to do about the camera? I suppose you could move the camera outside of the WTE but then you’d have to come up with a way to protect it separately. Potting is probably one of the better options but then how would you tilt the camera? A water tight servo? Again, another potential issue that filling with fluid might not resolve.

Very interesting. Thank you both for the insights. I think with the camera, you should keep it separate and in a pressure vessel. If it fails, not a big issue, as everything else should be ok.


Another option for the camera is to encase it in optical doming epoxy. You can get stuff up to 85D for hardness. Basically the stuff will be as hard as a bowling ball. That is about 85 Shore D in hardness.

The resin itself can be used to cover the optics so you have an absolutely clear waterproof cast over that area and then you could use polyurethane or other types of compounds to encapsulate the rest of the camera etc.

Considering the pressures that most of the hobby stuff is going to you would have no problem. If the camera and mount system were seal in one end of the WTE perhaps to the end cap itself … since it should bond to it, you could then fill the rest of the area with some other fluid that you don’t have to worry about clarity etc.