  High-power hadron accelerators have strict limits on fractional beam loss. In
principle, once a high-quality beam is set up in an acceptable state, beam loss
should remain steady. However, in practice, there are many trips in operational
machines, owing to excessive beam loss. This paper deals with monitoring
equipment health to identify precursor signals that indicate an issue with
equipment that will lead to unacceptable beam loss. To this end, a variety of
equipment and beam signal measurements are described. In particular, several
operational examples from the Spallation Neutron Source (SNS) of deteriorating
equipment functionality leading to beam loss are reported.
