TABLE OF CONTENTS One common problem that must be addressed in any process cell with more than one unit is handling material transfers between units. When the S88 recipe/equipment pattern is followed, material transfers require coordination across units. The upstream unit must be ready to send the material and the downstream unit must be ready to receive the material. The transfer can not occur until both sides are ready.
Material transfers can be further complicated by alternate paths between units. Transfer paths may be one-to-one, one-to-many, many-to-one, and many-to-many, as illustrated in Figure 5-37.
These paths can be handled by two patterns a simple transfer pattern for one-to-one, one-to-many, and many-to-one transfers, and a header transfer pattern for many-to-many transfers.
The simple transfer pattern has a transfer-out phase on each of the upstream units and a transfer-in phase on each of the downstream units. The recipes execute the transfer-in and transfer-out phases for the appropriate units at the correct point in the process.
The equipment (valves, pumps, motors, etc.) used for the transfer can be associated with either the upstream or the downstream unit, but should be handled consistently.
The recipe view of transfers is shown in Figure 5-38. Transfers, however, require synchronization across phases. This can be handled in two different ways through the recipe-execution system, or through equipment module to equipment module communication.
When possible, it is better to use a recipe-execution system...
