A Useful Tool: Mityvac


#1



One of the most important issues to monitor on an OpenROV dive is leakage. For obvious reasons, you don't want water seeping into the electronics tube. The o-rings on the end caps provide the seal, but it's nearly impossible to visually verify if the seal is sufficiently watertight, even with the clear, acrylic tube.


Of course, the best defense and leakage is preparation. Around the lab, we've started using a Mityvac to test the seals. We attach the suction-cup-type piece to the syringe valve (with the plunger removed) and pull out some air. If the gauge stays put at the new air pressure, we know we have a good seal.

I'll post a video of this being demonstrated in the next few days.

The Mityvac is available from Amazon.


#2

What pressure (vacuum) should be held, for how long, with how much loss? I am at the pressure testing stage. 11" bleeds down to 10" in about a minute. So I put one end (in this case the non-wire end, which looks like it has a great seal) in a bowl of water and sure enough about a teaspoon full of water leaked in over the course of about 60 seconds. I intend to put some tape over the syringe hole (on the inside) so hopefully I can determine if that is the source of entry of the water. If that is not the source, I will try re-doing the teflon, but I think I did a really good job so I am not optimistic about any improvement there. Probably my plan B is to try the latex balloon idea.

If water is is coming through the syringe hole, I would be tempted to epoxy the whole thing, since I can't understand why it is necessary to pressure relief valves on both sides. If I am missing something someone please let me know before I mess this up. By that token, I don't understand why one of the endcaps isn't epoxied to the tube. Why does the non-wire end cap have to be removable?


#3

I see the wisdom in leak testing. However, I agree one whole side of the tube should be sealed in and plastic welded to reduce points of failure.


#4

@Rick

My guess is that the non-wired end cap allows easy access for inspection and for draining in case of leakage... I get your point but I'm keeping mine removable... ;-)

Peter