What is the difference between NRS and OS&Y gate valves?
NRS means Non-Rising Stem. OS&Y means Outside Stem and Yoke. In an NRS valve, the stem will turn to open and close the gate, but the stem does not move up or down as it turns. With a OS&Y valve, as the stem turns, it moves into or out of the valve, which also moves the gate to open or seal the valve.