I bought a spare 6-inch O-ring flange so I can keep an alternative setup on hand for easy swapping on my 6-inch enclosure. Do you have a recommendation for how to protect the outside of the flange and the o-rings when it isn’t inserted into the enclosure? It seems like a very short section of the 6inch acrylic tube or something would do, but that would be a custom order from the plastics supplier. Is there any other hack that works well to keep the O-rings and edges nice and safe?
Hi @rangewider,
I don’t have any particular ideas for this, but I’m interested in the context surrounding it. Given the care required to avoid particles/dust/hair/etc getting on the flange and compromising the seal even just while installing the flange (particularly when it’s large), it may well be easier and quicker to replace just the end cap (and possibly the face-seal o-ring), and leave the flange in place.
Hmm. I’m very new to this. In fact, I’m just getting my first two setups together now. (The Blue Robotics parts arrive later this week.) I clearly have much to learn. Here’s what I have planned. Maybe I need to switch up. Please advise.
I am using the enclosure to house an audio recorder. I need to get in and out of the enclosure every day multiple times to turn the recorder on and off, change batteries, and retrieve recordings. I thought that you pulled the flange to do this, but from your response, I gather that’s not the case and I should unscrew the end cap. Is that right? Could you point me at the directions for how to install the flange super carefully and also how to best take off and put the end cap back on? This is an easy adjustment to my plan. One of my ends is blank, and I can use that for access.
Here’s the part that’s harder. The second end is tethered to a hydrophone array. I have three arrays and only two housings because I only need two in the water at a time and I hoped to save the money for a third complete setup. (Maybe penny wise, pound foolish.) The thing about these tetherings is that they are attached to the screws at the base of the flange using the predrilled holes there. (See diagram.) That means I can’t just swap out the end caps, I need to swap out the whole flange. Or at least that’s what I was thinking. Judging from your response, maybe I have to get an entire third enclosure. Is there any way around that?
Generally (particularly with vehicles) the idea is to avoid opening enclosures where possible, because it adds wear to the O-rings and increases the likelihood of the seal being compromised by things. That said, it’s still done quite regularly (particularly with battery enclosures, for example), but that’s easiest to do when the enclosure is small (there’s less area for dust/hair to land on, and a small flange is easier to shield from wind while it’s exposed to the air).
Given your actual use-case, my initial suggestion would be to consider whether it’s possible to do the required interactions without opening the enclosure - e.g. you could have an external switch for turning things on and off, and have some way of extracting recordings and charging batteries from the outside (wirelessly or via a connector), or potentially sending the audio signals out and supplying power externally via a tether that goes up to a small buoy/surface vessel or something, which then does the recording.
Waterproofing requirements for something at the surface are much less stringent than those for depth-rated components, which could simplify a decent chunk of the actual operations and maintenance while also reducing the required dive frequency (assuming it doesn’t need to be re-positioned daily). A surface component also leaves the door open to adding solar power in future, if that’s of interest, as well as potential remote data transmission, without impacting the depth-rated part of the setup.
Assuming the operating circumstances don’t permit such options, the main consideration when removing a water-tight seal is avoiding particulate matter getting onto either side of it before it gets replaced/restored. It’s also important to inspect the O-rings for nicks and scratches, and excessive flattening (in which case they’ll need to be replaced).
We have a guide on Watertight Enclosure Assembly which should cover most of the relevant information. That guide recommends removing the whole flange when opening the enclosure, but with a 6" enclosure it may be simpler to remove a blank end cap instead, because there’s less to inspect and maintain, and the hole should still be large enough to access the internals (depending on what’s in there and how it’s arranged).
Hopefully that’s clarifying/informative, but feel free to ask any follow-ups 
Very helpful. Thank you so much.
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