A Unit can be in different modes, for example Producing, Maintenance, Manual, Clean, Calibration, etc. A Unit control mode is an ordered subset of states and commands that determines the strategy carried out by the Unit process, as shown in Figure 2. For example, the producing mode is used when the unit is producing, a manual mode may be used when the unit is being manually controlled for troubleshooting.
The states that a unit can be in depends on the mode. In the producing mode there is a state called SUSPENDED, where the equipment is not running due to an external event, but this state is not available in maintenance mode, neither is the COMPLETE state.
Figure 2 – Mode Management of States
PackML includes a standard manner of changing modes as well as displaying the current mode. For additional information please see the ISA-TR88.00.02-2015.