Pressure

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 in Section 5 under Critical Operating Environmental Factors.

However, low pressure can be 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 profile under compression. Over time, the elastomer will 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 cross section, maximum seal utility is achieved. By lowering the durometer and/or cross section, the force required to compress a given cross section decreases, resulting in an effective seal at lower applied force per unit length of seal. For an illustration of this relationship, see Section 5.