O-Ring Sizing
O-Ring Sizing
(OP)
Could anyone tell me how to select the proper O-Ring size necessary to hold back a specfic pressure? There are formulae everywhere telling the dimensions of the gland, the dimensions of the clearance, the material to be used etc. but all the calculations I have found assume that you have already selected the proper O-Ring size.
I have an axial, externally sealing O-Ring application, I know the pressure which I want to seal, but I don't know what O-Ring diameter (thickness) I need to do the job. I know that this will depend upon durometer and clearance as well, but I can't find a formula anywhere to calculate this with.
I have an axial, externally sealing O-Ring application, I know the pressure which I want to seal, but I don't know what O-Ring diameter (thickness) I need to do the job. I know that this will depend upon durometer and clearance as well, but I can't find a formula anywhere to calculate this with.





RE: O-Ring Sizing
http://www.marcorubber.com/clearance_gap.htm
I like to remind everyone that an O-ring is compound and as such that all are not created equal in terms of fluid compatibility. If your find a specific O-ring that is compatible with your process fluid don’t change to another compound of the same family without checking compatibility.
RE: O-Ring Sizing
I was thinking that the diameter of the O-Ring material would also be important seeing as larger diameter O-Rings would have a longer contact surface than smaller diameters.
If I have a 1/8" diameter O-Ring in a current application could I replace it with a 1/16" diameter ring as long as I modify the gland so as to have the same clearance?
RE: O-Ring Sizing
Remember this is just a guide and if there is any doubt contact the manufacturer.
RE: O-Ring Sizing
If, for example, you look at the chart on this page ht
O-Rings with a diameter of 0.07" have a recommended diametrical clearance of 0.002" - 0.005". From the same chart, O-Rings with a diameter of 0.275" have a recommended clearance of 0.004" - 0.007". What I'm wondering is if I determine (from the graph you posted) that I need a clearance of 0.005" can I use either a 0.07" or a 0.275" diameter O-Ring (of the same material) and achieve the same allowable pressure?
RE: O-Ring Sizing
http://www.parker.com/ead/cm2.asp?cmid=2973 they have an Americam and a Europien versions
RE: O-Ring Sizing
RE: O-Ring Sizing
I would typically give you the equations that govern stretch and compression, but the Parker reference pretty much covers this and much, much more.
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: O-Ring Sizing