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[Harry Mitchell]

Hi! My project is a small-scale marine sensor housing; it needs to stay functional when briefly submerged (around 0.5 m depth) or exposed to heavy splashes on a boat deck. I’m using a machined aluminum cylindrical base and a clear polycarbonate cover — both have the same diameter (95 mm). The cover should be easy to remove for battery swaps, but I still need to keep a reliable seal when closed. Any advice on an effective O-ring groove design or alternative sealing approach that would allow repeated opening without losing waterproof integrity?

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[Daisy Spencer]

Since this is low-pressure sealing, you can keep it pretty simple, and just use a face seal, or, potentially, a radial seal. The radial might be better to use as the o-ring will stay in the channel, whereas with a face seal, the o-ring could fall out if you open the enclosure while on the water.

Select the groove depth so that it allows about 25% compression of the o-ring when closed. Good practice is to chamfer the edges of the groove so that there’s less risk of damaging the o-ring when opening, closing, re-seating, etc.

If you do go for a radial seal on the aluminum base, be aware of the movement of the o-ring when opening and closing the seal, that it doesn’t get caught in the clearance between the aluminum and the polycarbonate (an extrusion gap).

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[Henry]

The only alternative sealing arrangement to an o-ring that I can think of is a gasket, but I wouldn’t recommend that for your application here. Gaskets have to be seated correctly, and if you’re going to be opening the enclosure regularly, there’s a chance it won’t seat correctly each time.

Stick with the o-ring idea. Just be sure that whatever design you choose, that it fits a standard o-ring size that’s easily sourced. You don’t want to be stuck trying to replace it with a strange size in a few years’ time.

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