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OS & Y valves
thread378- Forum Search FAQs Links MVPsForum
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(Civil/Environmental)
(OP)
4 Feb 02 19:14I 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.
(Mechanical)
4 Feb 02 21:33OS&Y means outside stem and yoke. The threaded part of the valve stem is exposed and the yoke (or bearing bracket) allows the stem to rise through. That is the stem is attached to the gate, but free to rotate, with the valve being opened or closed by the gate/stem assembly rising through the yoke.
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
(Mechanical)
6 Feb 02 05:00OS&Y stands for Outside Screw & Yoke which is basically a rising stem valve . While a NRS is a non rising stem in a valve . Hope ur query is resolved . regards
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Rising stem VS OS&Y valves
thread164- Forum Search FAQs Links MVPsForum
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(Mechanical)
(OP)
13 Apr 17 07:44Hi ,
is there any difference between the Non rising stem valve & OS&Y valves ? i see some time some ppl used rising stem description and others use OS&Y valve description
Thx
Ahmad
(Mechanical)
16 Apr 17 02:11In a Rising Stem (RS) the thrust bearing is inside the valve and the operating wheel rises as the valve opens, the bearing is lubricated by the fluid inside the valve.
Open Yoke and Stem (OS&Y) has the thrust bearing outside the valve so may require external lubrication, but it is very easy to see the valve position. This valve also takes more room to operate. The operating wheel does not change vertical position at the valve is operated.
Non rising stem (NRS) does not indicate the position of the valve and is typically buried, this valve remains the same size no mater what the position is nor does the operator wheel or nut move vertically. The thrust bearing is lubricated by the fluid.
Hydrae
(Petroleum)
16 Apr 17 08:50 http://www.eng-tips.com/viewthread.cfm?qid=Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
(Civil/Environmental)
17 Apr 17 14:45Yes, depends on the application.Non-rising stem valves are primarily used on gate and globe valves with cast-iron materials used in water applications with low pressure/temperature requirements. Non-rising stem valves cannot be lubricated externally and require a higher torque.
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