Aluminium enclosure

Hi guys,

I’m having a lot of pain putting the flange in position in a 4’’ alu tube. The difference between the flange and the tube seems not to be enough to put the o-ring in place. I’ve actually damaged the first o-ring :rage: by trying to put the flange in position. The o-ring has been cut because of the lack of space between flange and tube. Tube was empty and no endcap on it. Unable to push the flange with 40/45kg of pressure, which is incredibly too much. Either the tube diameter is too small, the flange is to big or o-rings aren’t compressible enough. There was grease everywhere, even inside the tube…

Is there any solution (I can’t see one) or I have to ship back everythink? :frowning:

Flange diameter: 100.52mm
Flange with o-ring diameter: 102.40mm
Tube inner diameter: 100.58mm

Thank you

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Does the ID of the tube have a good chamfer? Hopefully BR or other experts will chime in, but I wonder if using Quad-Rings/X-Rings might be an acceptable solution…

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Dear Tim,
thank you for your support. I’ve never seen Quad rings underwater. I’m an experienced diver and even on torches (they use the same sealing idea - working on diameter) never seen quad rings, might be only because of cost constraint.

Yes the alu tube has a good chamfer, this shouldn’t be the problem. It’s most likely to be the internal diameter of the tube.

I’ll definetly wait for someone form BR to step in.

We only use round Buna-N O-rings for 99% of the stuff that I mess with. Quad O-rings are thing that I see in hydraulic cylinders … all special use places.

It should be noted that the clearance between the inner ID of the tube and the flange is going to be pretty tight because of how the race would be designed. You have to make sure you are getting a straight on push. If it is slanted … well things don’t work right.

I can confirm that I have the same problem with my 4" alutube from may month.
If You check the BR technical drawings, the 4" alu tubes have less space for O rings compared to acrylic tubes.
Alu ID:100,65mm, Acryl ID: 101,6
On the 3" tube, diameters is the same, with enough o ring space.
ID 76,2 on both

Hi Bo,

have you been able to insert the flange into the alu tube with a “normal” amount of pressure? What I can’t find is the diameter of the flange (the side that fit the tube)…

Pressure! I remember a discussion … are you venting the flange? Please remember the O-ring clearance is REAL tight and it won’t allow air to escape when you are trying to push the flange on. I believe they have “vent” plugs that you can put in your flange and if you don’t have one I would highly recommend that you install one and use it or it can be extremely difficult … to the point that you can’t mate it even if you were standing on it.

I have made O-ring seals before that might has well been gas shocks because it was so blasted hard to get a seat with a radial seal because of trapped air inside of the shape I was sealing.

As states, there is no endcap at all, I can’t even put the first flange on
it, plenty of way for the air to escape.
I ended to damage the oring because of the pressure, this can’t be related
to vent plugs (which I have btw), it’s just there is not enough space for
the oring to go in position…

What are the dimensions again? I don’t own one of the caps but I can run the race calculations for the ID on the tube and the OD on the flange … and the depth of the O-ring race.

Like I have said, there should be little room because of the tolerances for a standard 1500 psi race.

And I think I saw that there was a lead in chamfer on the tube … correct?

Flange diameter: 100.52mm
Flange with o-ring diameter: 102.40mm
Tube inner diameter: 100.58mm

There is several ways to solve this issue. You could try to heat up the tube in a food owen to 60-70 degrees celcius. It will expand sufficient and It will not harm the o-rings. You can also try to use the vacum pump and suck both endcap in place. It is important to lube the o-rings.

I am getting a little confused. I have up the drawing for a BR 4" flange and the diameter that is on the drawing is 100.4 mm for the diameter that has the O-Ring races cut into it. What are you measuring?

Heck I am confused at the drawings the BR has online for the AL O-Ring Flange and the AL Tube

The Tube drawing has the ID being 3.962" … I am using English measurements since I happen to have that O-Ring book and for the denoted O-Ring size of “238”, the ID on the tube should be 3.762. Either someone has a typo or the tube and the end caps are cut to some other calculation.

According to the Parker O-Ring handbook for a 238 size O-Ring I would have the ID on the tube at 3.762" and the Flange would have an OD of 3.747 with an O-ring race depth of .111 to .113"

Again, I am confused as all heck! It is not my design so I can’t speak to the calculations that the parts are cut to. The maximum tested depth on the AL tube is 2000 feet so I would assume that everything is supposed to be using a Industrial Static O-Ring race design.

HI @mau792
I heated the tube combined with a hydraulic press to keep it aligned.
It works if You dont open often, but i do not like that the o rings is so compressed and cant move with pressure.

Hi all,

We’ve had a few people report this in the last week or so and I think there might be an issue with the tubes. They are normally a little more difficult to close than the acrylic tubes, but not to the point of requiring any special tools!

We’ll investigate our stock here today and if anyone has tubes with this issue, please send us an email at and we’ll get it fixed as quickly as we can!


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Hi Rusty,

thank you for your support. There’s usualy a bit of pressure to push orings in this situations, but not at the point to slice an oring…

Just sent you an email regarding support.

THank you all