Sink Blocks

A sink block is where a fluid exits the PFS diagram. A sink block has one type of input (but may have multiple instances of that one type) and zero outputs.

To configure a sink block, in addition to the common block properties, you will need to specify the following:

• Throughput
  • Units allows you to specify the units used for measuring input (mass) and time. For example, you might measure throughput in terms of kilograms per hour.
  • Throughput defines the amount of input that can be accepted by the block in a given period of time. This can be a constant numeric value, a variable or a throughput profile.
  • Flow Revenue allows you to choose or create a cost model to represent the amount of revenue per unit of input accepted by the block.
  • Demand allocation allows you to specify how input is accepted if there are multiple incoming paths to the block and the amount of input that they deliver exceeds the block’s capacity, either as defined by the Throughput value or as limited by downstream capacities. If all input can be handled by the block, the selection here is ignored. To understand the demand allocation types, consider a block with a capacity of 10 units, receiving inputs A - 5 units, B - 3 units and C - 2 units. Now assume that downstream issues have limited the block’s capacity to 5 units.
    • If Allocate according to connection priorities is selected, the input will be allocated according to the priorities specified for each connection (i.e., all input will be taken from the highest priority connector until its capacity is reached, then all input will be taken from the next highest priority connector and so on, until the block’s capacity is filled). When this option is selected, you will be able to set priorities by selecting each connector that carries input to the block and using the commands at Process Flow > Selection > Input Priority. The input priority for each connector is shown at the end of the connector caption. In our example, if path A has the top priority, then input will be accepted only from A, because the 5 units it provides fill the block’s capacity. However, if B has the top priority, followed by A, then 3 units will be accepted from B and the remaining 2 units to fill the block’s capacity will be accepted from A.
    • If Weighted allocation across paths is selected, the amount of input refused when the block’s capacity is filled will be weighted according to the capacity of each incoming path. The software calculates the total capacity of all paths and then determines the percentage of the total capacity represented by each path. An equal percentage of each path’s capacity will be refused, thereby maintaining the weights of the paths. In our example, the block’s capacity has decreased by 50%, so 50% of each path’s input will be refused. The following amounts will be accepted: A – 2.5 units, B – 1.5 units and C - 1 unit.
    • If Allocate equal share to all paths is selected, an equal amount of input will be refused from each of the paths when the block’s capacity is filled. In our example, the block’s capacity has decreased by 5 units, so 5/3 = 1.67 units will be refused from each path. The following amounts will be accepted: A – 3.33 units, B – 1.33 units and  C – 0.33 units.