All O-ring seal applications are categorized in terms of relative motion. In situations involving little or no motion relative to the seal, the O-ring application is STATIC. In situations involving reciprocating, rotating, or oscillating motion relative to the seal, the O-ring application is DYNAMIC.
A dynamic seal application is best described as one where there is motion between a hardware component and the sealing element. Let's walk through everything you need to know about dynamic seals.