Question 443Steam Plants - Assistant Engineer

The correct answer is A) the amount of spring compression. The popping pressure of the safety valve is controlled by the amount of compression on the spring that holds the valve closed. Increasing the spring compression increases the pressure required to open the valve, while decreasing the compression lowers the opening pressure. This is the primary means of adjusting the valve's set pressure. The other options are not directly involved in controlling the popping pressure - the feather guide retaining ring, adjusting ring position, and seat bushing adjustment serve other functions in the valve design.