Hi,
I am thinking in buying the O-Ring Flange and dome end cap that are available on BR store in order to close my ROV tube which is in PVC.
So my first question is regarding the tolerance on the internal diameter of the PVC tube. For instance, with a 4" O-Ring Flange to work, what is the minimum and maximum diameter of the tube that can fit with the flange while preserving the watertight?
If you don’t have this number for the flange, I would be happy with the tolerance on the internal diameter of your acrylic tube! Looking at the technical details of the aluminium tube, I see that it has an internal diameter of 100.65 +0.15/-0.05 mm. Is it the same for acrylic? Does this tolerance can be relaxed? How does it compare to the tolerance on a standard PVC pipe?
My second question is regarding the quality of the internal suface of the tube. When I looked the documentation and videos about WTE assembly, I noticed that it is mentioned several times that the surfaces must be clean, without any scratch or dust, in order for the sealing to be waterproof. Although it was not clear to me if the surfaces that are mentioned were the surface of the tube, the surface of the o-ring or the surface of the flange, I am wondering if the internal surface of a standard PVC pipe bought in a classical store has the required quality in order for the sealing to be efficient?
The ID if the 4" acrylic tube is the same as the aluminum (or as close as it can be with cast acrylic). Because it is cast acylic, the ID sometimes goes in and out so we test fit the tubes. Our technicians are looking for a consistent 1-2 mm of o-ring mate all the way around. If there is a break in the seal, the tube is thrown out.
I think about the only way to really test that on PVC is to do a vacuum seal test and then if that works try lowering it down to your operational depth without electronics inside and see if it leaks.
We haven’t tested our flanges on PVC, so you are a bit into unknown territory.
Elliot, would you please look back in your company history and see if you tested 4" PVC pipe for use as a WTE? My current project is using just that, but of course my max working depth requirement is only 50 feet. With that in mind, and knowing that PVC pipe probably has wide inner diameter tolerance, any idea on how forgiving your end enclosure seal is for id tolerance? Right now, I am just using 1/4" plexiglass glued on plate flanges, but with 16 clamping bolts to deal with that is a real pain. I can afford to use your enclosure, but I like to be as innovative as possible wrt cost. Thanks.
I’ve moved your comment here because it’s on the same topic. I don’t expect we will have done testing with PVC pipes since Kevin’s initial response.
Note also that we’re currently changing our 3" and 4" enclosures to our locking series, which have a changed flange design, and precision machined ends on the tubes:
I imagine that will make it more challenging to use with a PVC pipe, particularly because the flange has a slightly wider diameter at the edge of the tube than the section with the o-rings in it.
The new locking design improves robustness and depth capacity, but does come at the loss of some generality / flexibility for mixing and matching with externally produced components.
We’ve been using the gen 1 flanges with PVC tubes. We switched over to using M4x92 o-rings to allow for less tolerance in the PVC diameters. (See https://www.amazon.com/gp/product/B00NJTYJLK)
We’ve only used ours down to about 50-75’, though so no idea if they hold up deeper than that.
will a 3 inch end cap work with 3 inch pvc? has this been tested? i’m trying to find a good way to have cable penetrators on a removable cap and this seems like the best way. operating depth is 100-200 feet.
Hi @bobo -
PVC pipe with Blue Robotics endcaps will definitely not work!
You may wonder why such an endcap isn’t available, as PVC pipe is so cheap and ubiquitous. While it may survive the 100-200 foot depth you target, it is manufactured with a very broad tolerance range - and this tolerance is only on the outside diameter, not the inside diameter! This means a custom machined end-cap made to seal to one pipe with o-rings could completely not work with another bit of PVC pipe! The seals made with this pipe rely on a glue solvent that literally melts the components together, to get around this tolerance issue.
Blue Robotics standard enclosures are your best bet for a robust solution - you get what you pay for!
