Open Tolerance Bore - How to Seal

[ella0509]

Hello,

I have an aluminium extruded tube that is 150mm ID. The diameter tolerance is +0.7mm / - 1.3mm. This is a stock component used in our standard product and cannot be modified. For some prototype testing, we want to seal a new filter cartridge into this tube, sealed on the internal diameter. I'm struggling to find a suitable sealing method due to the large tolerance band and wondered if any of you guys had came across any similar issues. The seal mechanism will be static and operating temperatures will be 20C - 100C. The operating pressure will be 1 Bar.G maximum. Compressed air is the medium.

Was thinking of using a large section o-ring with a low shore hardness with back up rings to prevent too much extrusion into the gap. Is this a viable option?

Thanks in advance.

 

[israelkk]

Select the largest and thickest O-Ring that can get inside the tube. Use two circular plates. The first is just flat uniform thickness plate with blind threads. the second circular plate has a gland to support the O-ring but with only one side wall for the O-Ring. This plate needs to have matched holes to the blind threads in the first plate. The first flat plate will be use as the second wall of the gland for the O-Ring. Now, loosely connect the two plated using bolts, and install the O-Ring in the formed gland. Inserts the assembly into the tube and tighten the bolts to compress the O-Ring between the two plates. This will expand the outside diameter of the O-Ring and seal against the tube while the inside is supported on the gland of the second circular plate. The gland width has to be smaller than the O-Ring thickness to allow compression of the O-Ring.

Hope it is clear without a drawing.

 

[ella0509]

Thanks for your reply israelkk.

Yes, I do understand your solution - you described it very well. I had actually sketched up something very similar to your description, but rather than using a "square" gland profile, I made the lower plate with a large 45 degree chamfer around the upper outside edge. The o-ring sits in this chamfer and is compressed outwards when the top plate is tightened to the lower plate....something akin to this crush seal arrangement:

http://www.rlhudson.com/O-Ring Book/Gland Dimensions/table46.html

I will sketch up your solution and see how we look.

Thanks.

 

[israelkk]

The 45 degree solution is inferior because the o-ring radial expansion will be smaller than with square gland.