OS & Y valves
OS & Y valves
(OP)
I have general question related to valves on water service lines. For domestic water supply I am required to supply NRS gate valves. O.k., that means non-rising stem, right? For fire protection supply I am required to provide OS&Y gate valves. What is an OS&Y gate valve? What is the main difference between NRS and OS&Y gate valves? What else can you tell. Thank you in advance.





RE: OS & Y valves
A NRS valve on the other hand has a stem fixed at the yoke. but free to rotate with the movement of the gate being effected by the stem screwing in or out of the gate.
Relatives features of each -
NRS cheaper.
NRS valves require clean fluid which will not clog the internal stem/ gate threaded connection.
OSY valves are higher temperature tolerant due to the mechanical threaded connection being out of the process fluid and able to obtain some cooling to the environment.
NRS valves require the fluid to have some lubricating properties while OS&Y valves require external lubrication.
OS&Y threads may be clogged from external factors such as dust, but may be cleaned in service.
The most important difference is that the position of the gate (i.e open or closed) is readily determinable with the OS&Y valve. When the valve is fully opened, the stem will be protruding through the handwheel and flush (or nearly) when closed. The NRS valve does not have this advantage.
Hope this helps,
Bill Birch
RE: OS & Y valves