hand valve control

im trying to write logic for a simple feature, i have an input for the hand valve. If the hand valve is closed your input is on if its is not your input is 0.

What im trying to do is when the hand valve makes a transition from closed to open and then closed trigger an output, how would i go about this in ladder logic??

I would use a 1-shot to set a latch bit when the input transitions from 1 to 0 to indicate "valve opened" status.

If "valve opened" latch bit == 1 and input == 1, then set your output and clear your latch bit.

What is the logical condition for de-energizing the output?

usually for valves you have 4 states
1. open
2. closed
3. transition from open to closed
4. transition from closed to open

As you say you have only one feedback so you have "closed" and "not closed" (or may be open, not open).
For the manually operated valve this isn't enough, as you could leave it in semi-opened/semi-close state.
For the motor operated valves usually there are limit switches for open and close.
For both of these types you could have position feedback, so you can regulate the percentage of opening, if needed.
The only valve I have seen with one feedback is the electromagnetic valve. When it works it opens/closes(depending of whether it is NO/NC) for very short interval of time, so in the PLC you can't catch it's transition.
It's the same as to catch transaction between states of an relay.
There should be other means to catch if the valve works.

@ bit bucket in my case the logical condition when the output denergizes is when a target weight is above set point and the only way it should come back on is when the hand valve is transitioned from its current position that is open then to close then to open when that happens the output will energize even if it's above weight set point, the output will denergizes again when the weight reading drops below set point and goes above Setpoint through which at that point the process repeats itself. Just to add their is a relay output firing from the weight scale to serve as an input telling me I'm above sp. If your wondering why it's programmed that way that's what the customer wanted and I'm just making edits to an existing program from hell that uses OTL and OTU everywhere

Thanks on the logic I think it will work that way just never had to program in that manner before