I keep reading that oil compensation would allow for most housings, even PVC pipes, be (theoretically) rated for full-ocean depth. But I’ve seen notes that some components would not function at these pressures inside of an oil-filled housing. Naturally, I could see how some capacitor types, relays, and batteries, components that are hollow but sealed, and cannot be oil-filled, would fail. And that eventually, some integrated circuits would crack, or that the solder joints on the PCBs would shrink and snap. What I’ve yet to see is a “straight” answer on when any of this would happen.
To those who have used oil-compensated housings in the past, what has your millage been? How deep could they go, what components were housed in them, and what components had to be housed in non-compensated 1-atm housings?
This topic isn’t one I have much experience with, so am unfortunately not able to go into depth about specific details and expectations. That said, from a theoretical standpoint component failures in an oil-filled component would be dependent on the crushing strength of the materials and structures involved.
I imagine many of those who have used oil-filled components won’t have had reason (or the necessary equipment) to test them to failure, so you may find limited information as to what doesn’t work. I would at least expect integrated circuits and solder joints to withstand much higher pressures than “can” capacitors, or other hollow components. That kind of thinking can perhaps guide you as to which information is most important/relevant to what you want to achieve (i.e. only the weakest component matters, and validation beyond a particular point stops providing useful results).
Do you have a use-case or some limitations in mind (e.g. can X components withstand Y pressure), or are you mostly putting out feelers for gotchas/limitations that others have found that you’ll need to look out for if pursuing an oil compensation approach?
My experience is with work class ROVs and oil filled electronic boxes is very common with PCB and control electronics immersed in the oil for intelligent hydraulic valve operation. Have a look at this link:
I know that crystal oscillators can fail under pressure. I have built some oil-filled servos (commercial R/C servos in my own waterproof case) that had crystal oscillators that failed at about 400 meters. You may be able to fix that by putting a blob of hard epoxy over the oscillator to protect it from the pressure. Of course, that technique requires careful surface preparation and a sufficiently hard epoxy.
All the other components in these servos did fine up to 600 meters. If your device needs a motor, try to use a brushless motor instead of a brushed motor.
