Trains
A train is a path that is contained within a process standby container in a PFS Diagram and operates in a standby redundancy configuration with other trains. Each train must have a Start block and an End block; these blocks cannot fail and have no operational properties of their own. Every train must use each input and each output defined for the process standby container.
To add a train to a process standby container, choose Process Flow >Blocks > Add [Active/Standby] Train.
The Train View will open in the same tab or window you are currently using, appearing to replace the current PFS diagram. You can now edit the train just as you would a diagram. When you are done working with the train, choose Process Flow >Blocks > End Editing Train, or simply close the tab or window. The PFS diagram will reappear.
To edit an existing train, you can select the train in the diagram and choose Process Flow >Blocks > Edit Train or click the Edit Train icon at the upper right corner of the train.
The train itself also has block properties. Double-clicking the train opens the Block Properties window for the train. In addition to the common block properties, you will need to specify the following:
- Operation
- Active/Standby allows you to specify whether the train is in an active or standby state at the beginning of the simulation.
Tip: You can quickly change a train's state by selecting or clearing the Process Flow > Blocks > Standby Settings > Set Block to Active (Not Standby) command.
- Reactivate after repair if selected, the train will return to the active state immediately after it has been repaired. Otherwise, the train will remain in the standby state after if has been repaired and will be switched back to the active state only if and when the train that was activated in the initial switch fails. This option is available only if the active state is selected.
- Throughput
- Units allows you to specify the units used for measuring input/output (mass) and time. For example, you might measure throughput in terms of kilograms per hour.
- Train failure flow rate threshold per output type is the level of flow capacity at which the train is considered to be failed. This is a measure of capacity, not of actual flow; that is, it considers whether, if all inputs were infinite, the train is currently capable of producing the required amount of output. If an active train drops to or below this threshold, the next standby train will be activated, provided that train is capable of processing its specified capacity. If no train can process its specified capacity, no switch will be executed at that time; the simulation will continue to check until a switch can be performed or there is no longer a switch needed. The order in which standby trains are checked is defined by selecting the process standby container and choosing Process Flow > Blocks > Standby Settings > Set Standby Order.
What's Changed? In previous versions, the train failure flow rate thresholds were called "minimum flow rate thresholds."