Expected waiting times at loading stations in discrete-space closed-loop conveyors

We present an analytical approach to approximate the expected waiting times for loads arriving at the loading stations in discrete-space, fixed-window, closed-loop conveyors. The expected waiting times are important for estimating the expected work-in-process (WIP) levels at individual loading stations (which can be used to facilitate buffer sizing) and to measure the overall performance of the conveyor loop. Derivation of the expected waiting times is complicated by our observation that the contents of adjacent windows on the conveyor are correlated under a range of conveyor speeds, and the expected waiting times are affected by this correlation. In fact, using analytical results and a numerical example based on simulation, we show that the above correlation has a significant impact on expected waiting times.