The shape of the gland may be modified to suit the project’s requirements, but typical rectangular grooves with straight sides help prevent O-ring extrusion and nibbling. Provided the seal pressure will not exceed 1,500 psi, a five-degree slope may be added to the sides of the groove to facilitate the machining process. Radiusing (rounding off) the internal recesses and top corners of the groove will eliminate sharp edges and further reduce the chances of damaging the O-ring during installation of the seal, assembly of the gland, or actual service (see Figure 91).

Bear in mind that the O-ring will likely undergo changes (such as swell) during the course of its service life. For this reason, the minimum volume of the groove should exceed the maximum expected volume of the O-ring by at least 10%. This builds in a safety factor so the O-ring doesn’t ever overfill the groove.

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