We are following time based change over philosophy for 2x100% and 3 x 100% redundancy equipment, furthermore we have Chinese plant so we don't have well designed reliable machines.
Few days back I heard from a reliability professional that modern approach is to declare one as duty pump and use it till a situation arise, and keep the standby as standby but have its periodic run tests time to time to ensure its health. Logic behind was that once the integrity of one pump is affected the other one would be like just new, with minimum running hours, while in time based changeover both will have almost same running hours.
Whats are your views and practices? If you support duty/standby philosophy can you please share some article/standard/reference etc, so I may convince my operations team