(599b) Estimating the Capacity of Simple Batch Processes

Batch processes often arise in small-scale production of high value products. The batch process consists of a series of ?steps? in sequence. If a particular step is not the bottleneck in the sequence of steps, then some of the equipment units within the step might be idle during operation. Good process design calls for matching in some way step cycle time, or what we will later define as the ?equivalent? cycle time of each step so that no one step in the sequence is a bottleneck.

We examine a process that consists of a sequence of batch steps in which each of the steps is composed of a number of individual units which can be of differing cycle times. We suggest a simple means of estimating:

a. equivalent cycle time of a step. b. the bottleneck step from (a). c. an upper bound of capacity of the overall batch operation from (b). d. the fraction of product produced by a given unit of the bottleneck step.

Itis assumed: 1. batches are all the same size. 2. 100% availability of equipment

Also, we distinguish between ?process cycle time?, ?step equivalent cycle time? and ?cycle time of a unit?.