The presence of high pressure on an o-ring can jeopardize its ability to seal. For correct o-ring design in high pressure situations, see the Extrusion Limit chart below.
However, low pressure can present a problem as well. If the system pressure is below 100 psi, it is classified as low pressure. Because system pressure is not great enough to “activate” the seal, the design must rely solely on the resiliency of the elastomer to retain its original compressive force. Over time, the elastomer may not resist compression as much and take a compression “set,” resulting in possible seal failure. However, by proper component design which may include lowering the seal durometer or increasing the o-ring cross section, maximum seal utility is achieved. For an illustration of this relationship, see the Operating Environment Factors section.