Is a vent required in a watertight enclosure?

Hi there!

We are currently building an ROV and have an inquiry on the watertight enclosure, specifically in closing it. Is the enclosure vent and plug required to be used in the watertight enclosures? Or would it be okay if we just simply unscrew the end caps every time we need to open and close it? We are unsure if we could use another hole for a vent since most of our holes are already dedicated for wiring.

Any response to this question would be highly appreciated. Thanks!

It’s possible to use an enclosure without a vent, but the vent is useful for the following purposes, which are worth considering when determining whether to remove it:

  • The vent is a simple way of equalising pressure when wanting to open or close the enclosure, or just avoiding pressure differentials while the vehicle is being transported to/through areas with different temperature/pressure
  • The vent o-rings are more cheaply and easily replaceable than the face-seal o-ring from the flange cap, which would be getting more wear and be at higher risk of getting dust/dirt in it than is expected from normal operation, so you would need to be extra vigilant to ensure a good seal, and regularly check the o-ring state
  • The vent provides an easy way of doing vacuum-testing, to check if the enclosure has any leak points, which isn’t possible to do if you don’t have a vent

If you definitely need more space for wires, but decide it’s worth keeping the vent, have you considered using an end-cap with more holes? We sell end-caps for our 4" enclosures with up to 18 holes :slight_smile:

Thanks for your answer!

This makes a lot of sense. Unfortunately, when we ordered our parts, we have not included any spare vents in our purchase, and considering the amount of customs fees that we have to pay in case we order again, it would be difficult considering that we have a limited budget.

I see. We have another question on this. When we bought our 4" enclosure from blue robotics, we thought that the vent in itself could be used to perform a vacuum-testing. However, we did not know that it would need a separately purchased vacuum plug in order to perform vacuum-testing. Is there another way to perform vacuum-testing without this plug? Do you have any ways other than this to ensure that the enclosure is fully sealed without any leak points?

Yes, we have actually bought the end cap with 18 holes, however, the number of external sensors that we have included have used up the available holes :sweat_smile:. On that note, is there another place where we could externally purchase blue robotics penetrators and end caps? We are keen on having extras but ordering from the US does not seem like a viable option for now.

The vacuum plug is intended as a useful interfacing part that can form a seal with the vent and a tube so that vacuum testing is possible. It includes a rubber stop that allows testing the vacuum equipment prior to testing the enclosure. If you’re able to make a similarly robust seal by some other means then you don’t need the plug - we just provide it because it makes setting up vacuum testing simpler, and you don’t need to design/manufacture/find your own equivalent parts from elsewhere.

We apply the same reasoning to things like our penetrator wrenches - they’re not a requirement for installing a penetrator but they’ve been designed to make the job easier, so if it’s something you’re doing multiple times then it can be worth having :slight_smile:

The only other way I’m aware of is that some people apply slight positive pressure, but that’s not something we recommend (read that post for more info), and if anything it’s more difficult to set up than a vacuum test because you still need a similar plug, but also a way of keeping it from sliding out of the enclosure.

Fair enough. In cases like that it can be worth considering having some cables with multiple wires, which you make a waterproof splice on to cater to multiple sensors. That increases the risk of water getting into the cable, but can at least reduce the number of penetrators you need.

Alternatively you may be able to use a larger enclosure, or you can use an additional small enclosure that takes in a few cables on one end, and either connects the wires into fewer wires on the other end (acting like a splice), or you can have a board in the enclosure that takes in multiple sensors and sends the data over a single connection to the main enclosure (although that can get a bit expensive).

I’m not sure where you’re based, but we have an awesome network of distributors all around the world, so it’s very likely you can find someone closer to you and/or more convenient for you to purchase from than directly from us :slight_smile:

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I see. Hopefully we could find a way to achieve an alternative seal. It’s really unfortunate that we have not included the vacuum plug before.

Thanks for the info. We’ll read into this.

This is what we have also thought of. Hopefully the epoxy should provide a good enough seal on the penetrators.

This may be a viable workaround for us. We’ll see what we could do with it.

We are located in the Philippines and blue robotics actually has a distributor here called Delta ROV Inc. Unfortunately, their products are quite limited, and ordering overseas incurs us ridiculous customs fees which would be difficult for us students. Hopefully we could get by with what we have bought.

All your answers are really helpful to us, @EliotBR. Thanks once again!

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Their website has a note at the bottom which says

I’m not sure if they sell any Blue Robotics products beyond the ones listed on their website, but it likely wouldn’t hurt to send an email asking the question, just in case :slight_smile:

Glad to hear it - I’m happy to help where I can :slight_smile:

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Hi yvesyves.
If you have a switch in one of the holes, it is easy to modify it to give it both uses by making a small hole in it. Can be used as a switch and an enclosure vent at the same time


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