Why might a machine with a rise in low-frequency vibrations require immediate attention?

A rise in low-frequency vibrations is significant because it often suggests underlying mechanical issues within the machine. Low-frequency vibrations are typically associated with conditions such as unbalance or misalignment. When a machine is unbalanced, it can cause excessive vibration at lower frequencies as the rotating parts exert uneven forces on the bearings and structure. Similarly, misalignment can lead to similar symptoms, as components that are not properly aligned will create additional stresses and vibrations during operation.

Addressing these problems promptly is critical because they can lead to further mechanical failure, increased wear and tear, or even catastrophic breakdowns if left unattended. Monitoring low-frequency vibrations allows for early detection of such issues, enabling timely interventions that can prevent extended downtime and costly repairs. Thus, option C accurately identifies the concern that a rise in low-frequency vibrations indicates potential unbalance or misalignment issues, necessitating immediate attention to maintain machine health and operational efficiency.