The reason why this is happening is due to the following problem:
as the electronics inside the tube are running, they generate heat that makes the air inside the tube expand. The same will happen if you leave it running out of the water for a while. At depth, the pressure on the outside keeps the endcaps in place, however, when you breach the surface (or the last couple of meters), the pressure on the inside becomes greater than the pressure on the outside, making the endcaps “pop”. This should not be a problem if you bring the ROV straight out of the water.
Another solution to the problem, and the one I always recommend, is the extract some of the air inside using a vacuum pump. We have successfully used the Mightvac MV7000 for some time now, but there are different models out there that can do the same thing; look for an automotive break fluid bleeding kit. Using a vacuum pump you achive 2 things:
- You get to test for leakages pre-dive; you generate a underpressure of say, 0,5 bars, and leave it like that for 5 minutes. If there is no change in the pressure then you have a tight container.
- You then replace the syringe plug before the e-tube has completeley refilled. This should leave sufficient room for the air to expand without creating an overpressure inside the tube.
Note that by doing this, you are creating a bigger pressure difference, so your MOD (maximum operating depth) should be reduced.