Quick O-ring Groove Design Guide

During the last couple of years I developed several mechanical designs involving o-ring grooves. O-ring grooves are used to seal removable sections in a design which are at different pressures and/or in contact with different fluids. If designed correctly, o-rings can provide a very effective seal. There is a lot of information scattered in many places about how to properly design an o-ring groove. I have gathered some of this information to make a quick design guide to be used to design o-ring grooves that fit standard o-ring sizes and that can be machined easily. This guide should work for most common o-ring groove designs as it has worked for me on several applications including moderate pressure and vacuum. For special types of seals and  applications, I recommend a more in-depth investigation on design requirements for the specific application.

Here is a diagram (crossectional view of an o-ring groove with the o-ring in it) of the important dimensions of an o-ring groove followed by the corresponding nomenclature and important relationships:

 

Here are the steps to follow:

1. Estimate the length of an appropriate inner perimeter for your groove (IP)
2. From the AS568A O-Ring Dash Number comparison chart provided by McMaster here, select an o-ring with a slightly smaller inner perimeter (OIP) than the groove inner perimeter (IP) and the desired o-ring width or Crossectional Diameter (W)
3. Note down the selected o-ring Dash No., Width (W), and inner diameter (ID)
4. Based on the Width or Crossectional Diameter (W) of the selected o-ring, use Table 1 to find the appropriate Gland Depth (F)Table taken from:Oberg, E., Jones, F., D., Horton, H., L., Ryffel, H., 2000, Machinery’s Handbook, Twenty-Sixth Edition, Industrial Press INC., New York, NY.
5. Based on the Dash No., use Table 2 to find the necessary Diametrical Clearance (D) and the Groove Width (G) Table taken from:Oberg, E., Jones, F., D., Horton, H., L., Ryffel, H., 2000, Machinery’s Handbook, Twenty-Sixth Edition, Industrial Press INC., New York, NY.
6. Used the  formulas to calculate the O-ring Inner Perimeter (OIP), the  compression or squeeze amount (S), the groove depth (H), and the percent stretch (% stretch)
7. Check that the percent stretch is between 1% and 5 % (2 % is recommended)
8. If the percent stretch is not within the limits or if the selected o-ring does not work, go back to step 1 and iterate changing the estimated groove inner perimeter and/or selected o-ring

For square o-ring groove shapes, keep a radius corner of at least three times the width of the o-ring (3W). To chose the appropriate o-ring material, consider the chemicals that will contact the o-ring, the operating pressure and temperature.