Let's say you have two pumps, one always running and the other in reserve. Maybe they're switched regularly, or maybe the other is only used when the first is broken/down for maintenance.
In a P&ID, drawn after ISO standards, will the reserve equiptment and/or the label of the reserve, equiptment be shown? I see a few different possibilities:
- Only one pump is shown, perhaps labelled with the label of the pump that was first installed. Nothing else.
- Only one pump is shown, but it is labeled "Pump x/x + 1/x + 2/..."
- All pumps are shown, with some kind of symbolization shown that the other pump(s) are not operating when one pump is operating. In the case of the reserve pumps only being used when the primary pump is down, this can easily be shown with normally-closed valves on the process lines going from the reserve pumps. In the case of periodic switching however, where there is no main pump, I have no idea how this is to be shown.