Study of loading policies for unequal strength shared-load system

This paper presents three policies for load assignment among unequal streng th units based on: (1) maximizing the mean time between failure (MTBF) of t he system (Policy A); (2) requiring all active units to fail simultaneously (Policy B); and (3) simply taking the same load for all active units (Poli cy C). The traditional shared-load k-out-of-n: G system performs satisfacto rily if at least k of the total n units are up, with load being shared amon g the surviving units. One of the advantages in such a system is that the a ctive units play the role of both an actuator and a sensor. Thus we have en ough time to make corrective replacement of failed units while the system i s still kept on duty. We use examples to show that policies A and B have al most the same MTBF (the difference is within 1%), which is much more superi or than Policy C. Two indices are used for the selection of valve k, with g iven number of total units. One is called the effectiveness factor, while t he other is the tolerance factor. The former concerns with the effectivenes s of load assignments among the surviving units. The tatter deals with the time buffer when one more unit fails. (C) 2000 Elsevier Science Ltd. All ri ghts reserved.