Rising vs Non rising stem 1

[pdp123]

Hi
Is there any basis for selection between rising and non rising stem for valve.

Thanks...

Hard Work with Smartness is the key to success

 

[pennpiper]

Normally rising vs non-rising stem only applies to Gate Valves.
Non Rising stem Gate Valves are normally cheaper than the Rising stem versions.
Why are you asking this question?
What is your potential use (purpose for this valve)?

Sometimes its possible to do all the right things and still get bad results

 

[MickMc]

Rising stem is normally with Outside Screw & Yoke with the stem threads being isolated from the medium by stem packing whilst in non rising the thread is exposed to the medium therefore could be subject to erosion, corrosion etc depending on the medium therefore should be of more corrosion resistant material hence more expensive. The only advantage I can think of with non rising stem is where space is limited and both non-rising and rising can apply also to globe valves as well as gate. On a recent project our contractor stipulated rising stem as per data sheets but vendor offered non rising in small bore globe valves which was accepted as stem material was suitable for the medium.

 

[LittleInch]

Often this is no more than custom and practice, not technical. Many operators prefer rising stem as it is much easier to rapidly see from a long way away which valves are open or closed. On a big manifold or complex pipe system this can be very important.

Rising stems are exposed to the elements and can become corroded, painted and require greasing on a regular basis.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[gerhardl]

Be also reminded that knife-gate valves normally have the knives rising to free air (past body/knife sealings) on a non-rising stem. Also: some fluids (gas, steam, toxic, surrounding harming) will require all parts closed in, and a nonrising stem and closed bonnet is required.

In general, for harmless fluids, I agree with all above: it is mostly a practical and pricing question, if quality and lifetime els is about equal.