Question 254General Subjects - Assistant Engineer

The correct answer is A) Safety valves are designed to open wide when lifted by excessive pressure and only reseat when the pressure has dropped significantly. This is the correct answer because safety valves are designed to fully open when the pressure exceeds the set relieving pressure, in order to rapidly release the excess pressure and prevent system damage. They are not designed to throttle or modulate the flow, but rather to open fully and only reseat once the pressure has decreased significantly, typically to around 90-95% of the set pressure. The other options are incorrect because B) safety valves are not always set to relieve at a pressure exceeding the maximum allowable working pressure, C) they are not designed to throttle the flow, and D) they do not immediately reseat when the pressure drops by a small amount.