Figure 52 shows a valve that is operated by a worm gear and motor. Each turn of the worm gear moves the stem by 0.18 cm, and the total range of stem travel is 4.0 cm. The worm gear motor has three states: A TTL high to the up terminal causes rotation at 15 rpm that moves the valve stem up, a TTL high to the down terminal causes rotation to reverse, moving the valve stem down (closing the valve), and with TTL low to both terminals the motor is off. The valve body is equal percentage with a rangeability of 20 and a maximum flow of 0.6 m3/min.
a. How many rotations of the worm gear are required for the full stem travel?
b. How long does it take to move the stem over the full range of travel? What is the minimum flow rate?
c. What is the stem position for flow at 90% of the maximum?
