Cylinder-type actuator
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The position of the valve in the event of a failure of the instrument air (or other actuating medium) should be determined. If a cylinder-type actuator is chosen, the valve should be of positive action. Question: How should this sentence be understood? Does it mean that the entire valve operates in positive action mode? Is the cylinder actuator of positive action? If the entire valve is of positive action, what happens if there is a conflict with the fault location? Can’t it then be used with a cylinder type?
The solenoid valve is used to achieve fault on, fault hold, and fault off.
It’s hard to understand what you’re saying. A cylinder combined with a spring can be used to achieve FO or FC (fault open, or fault closed) operation; without a spring, air can be introduced on both sides of the cylinder, allowing for FL fault mode. Generally, cylinders aren’t classified as positive-acting or negative-acting. The control method employs positive and negative feedback.
If it weren’t me, the first sentence is the exact wording from the guidelines, and it’s hard to understand