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3" Watertigth flange

Hi to everyone, I am new here and happy since I just received my first batch of item from Blue Robotic. My first build will be a multiparameter probe. Implementing sensors and electronic should be easy but it is my first shot with underwater pressure / leaks so this part will be challenging for sure.

My first question is about the 3" watertigth acrylic cylinder and the flanges. When I unboxed my parts, I was surprise to see that the flange are push fit inside of the cylinder but that there is no screws to actually fix the flange on the cylinder! I plan to use the cylinder vertically with the sensor entering in the water and going down to the bottom of lakes and littoral zone. Will the flanges stay in place or there is a risk of them popping out of the cylnder if they are subjected to sudden shock? Will the vent plug be enough to prevent this? Should I imagine a way to hold the flange in place?

thank you
Charles

Hi Charles,

By the nature of the enclosure, once its sealed and goes into the water, the water pressure pushes against the housing and squeezes it causing the end caps to be pushed tighter into the housing. You can feel how tight the end cap is by trying to pull them off.If you pull a vacuum and then try to pull the end caps off.,Its almost impossible. Saying that, if you leave the vent plug in and then leave the housing in the sun for a while, the end caps do start push out of the housing a bit. Iv never used the housing vertically and im always run with the theory that if you think it might happen then it probably will happen. An easy way to lock them in place is to use some of the ‘L’ shaped pieces that lock the 4 inch electronics housing in the cradle, you can then pass some thread bar through them and lock the end caps in place.

Thank you for the reply. I took a look at the ‘‘L’’ shape part. It is a good straigthforward idea. Another option I have in mind is to drill holes in the cylinder. The flange and Endcap have holes in them and screws to assembled them together. Does someone tried to drill and tap holes in the acrylic wall of the cylinder just below the flange and endcap holes and then fix the endcap to the flange and the flange to the cylinder with longer screws?
More chance of leaks maybe? With the L shape parts, if I overtorque one side vs the other, I migth also unbalance the endcap and have more leaks correct?

any input and suggestions are welcome at this point!

I think the wall on the Acrylic cylinder is is a bit thin to drill and tap and it could certainly crack. Also with the screws having such i fine thread there a big chance of stripping the thread that was tapped in the Acrylic. i would normally use a helicoil or thread insert but again the wall is a bit thin for them.
With the L shaped parts and you should be torquing them down, they are just to top it popping off.

I found this on the forum :
Securing lid

Essentially, this is both option applied by other users. The option with drill and tap is on aluminium casing.
I agree that thread insert in acrylic may be hard on 1/4 inch wall. I already tried this in another application and it crack and was not stong . Another way would be to glue some more acrylic on the side of the tube and install a thread insert there or drill a big enough hole to install nut and bolt justr like a plumbing flange. It would also require a bigger acrylic end cap but Blue robotic could probably easily take the 3" drilling template and apply it to a 4 inch end cap leaving enough peripherical material to fix it while keeping the hability to screw the cap to the flange.

I will report my tests results for futur users.