Official Answer
Answer
In reciprocating pumps, the rapid reversal of axial loads can cause the spiral ring to 'chatter' in the groove. This creates a hammered effect, where the ring repeatedly impacts the groove walls. This dynamic loading can lead to fatigue of the groove land even if the static load is well within limits. Furthermore, if the frequency of the pump matches the natural frequency of the ring, resonance can occur, causing the ring to vibrate out of its seat. Increasing the ring's thickness $t$ to increase its natural frequency and using a 'Tight Fit' groove are the standard mitigations.
