We ship a small dosing skid, CompactLogix 5069-L306ER, V33. Last month I converted the fill and dose sequence from ladder state bits over to an SFC.

Now valve XV101 stays open after the fill step exits, right through the dose step, until the drain step writes it off. Two valves overlap for about 4 seconds and the customer spotted it on the flow trend. Each step has one action with the valve OTE inside it, and I can watch the fill step go inactive online while the OTE sits there on.

I tried an OTU on XV101 in the first rung of the dose action and that does work, but then every step needs an OTU for every other valve, which can't be how anyone does this.

Is SFC just not suited to valves, or am I missing something?