O-ring Flange Installation

I’m having a bear of a time installing the aluminum flanges with the double radial O-rings into the 2" acrylic tube from the watertight enclosures kit. The first O-ring goes in relatively easily, possibly because at this point the flange can go in at a slight angle. I haven’t yet been able to get the second O-ring to go in on either side – can’t get it past the tube lip. I’ve put about 120lbs on it, which started to feel wrong, so I figured I’d go to the forum.

Are there any installation tips for this step? The O-rings are both lubed. Thanks!

Do you have an open vent in one of the endcaps? You do need to be pretty firm and committed sometimes to get the endcaps all the way in. If you can get the first O-ring in, I think you should be able to get the second. Can you share a picture of how much the first O-ring is compressed after fitting into the tube?


I’m using some custom endcaps, but I’ve left them off during installation so both ends are open.

I actually was able to get them to go. I think I had to just post about it and try again … by applying some force offset from the center axis, I was able to start a seal on a small patch of the second O-ring and then by varying the applied force, was able to slowly walk the sealing patch around the whole way.

No Vent Valve in either custom end cap?

Hi @skcolb - Sometimes it’s helpful to lightly sand the inside edge of the tube to help the O-rings squeeze into place. The size of the acrylic tubes varies slightly so some are tighter than others.

If I understand, he was pushing only the flange on, so it’s still a hollow tube at this point.

@rjehangir, thanks for the tip. I will probably chamfer the inside edge a little next time I’ve got it apart.

@jwalser, correct, I was pushing only the flange on, sorry that I wasn’t so clear in my description.

@tciii, no vent valves in either custom end cap. My typical installation is to install the end caps last, so the only air that doesn’t have anywhere to go is the swept volume of the cap when compressing the small face seal O-ring. It’ll be difficult to disassemble on a cold day; hopefully that won’t come back to bite me later. The “end caps” are actually a rotary seal with a bearing and gearmotor behind it inside the tube, so there’s not much area on the ends left for anything else.