In a PID diagram, what does the horizontal line on a on/off valve mean?
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On the process flow diagram, what does a small horizontal line next to a switch valve mean?
Oh, can it switch between automatic and manual?
Switching is one aspect; mainly, it enables manual emergency operation in the event of actuator failure modes. (Manual mode is for emergency use only and is not one of the main operation methods.) “The figure of 8,000 or 80,000 cycles in “Heroes of the Flames” is a bit exaggerated, but it does illustrate that the manual mode of the actuator is intended only for use in emergency situations.
I didn’t watch the movie. The 8,000 or 80,000 turns you mentioned – we encountered that situation as well. It was a design by a foreigner, which specified how many turns the valve needed to be turned in order to open completely. In practice, however, it opened fully after less than ten turns. The foreigner said that the manufacturer’s instructions had deceived him, as the time required to turn the valve was taken into account and factored into the cost; fortunately, things were resolved in the end.
Hello! This indicates the mechanical position of the valve in the event of a power outage, with options including open, in place, closed, and unpositioned. This is likely due to an energy interruption and the valve not being in the correct position.
Judging from the diagram alone, it should be considered that the entire set of valves comes with a manual mechanism, allowing for emergency operation by hand when the actuator is not in a functional state
If only a few valves with HV are drawn this way, then they are handwheels; you can check on site to see if any such ones exist. If that’s the case, and the valve on-site also doesn’t have a handwheel, then in the drawings, the lower part represents the valve body while the upper part represents the actuator.
It should be a handwheel, not FO, FO, FLO, or FLC. But usually, the handwheel is located on the side. First, take a look at the PID diagram; the legend at the beginning should provide an explanation.