actuated valve running time

[EricZhao]

Dear friends:

I am in the process of selecting an eletric actuated globe valve. One of the specs I encountered is: Motor Running Time, 150sec. What does running time means?

thanks a lot,

 

[rmw]

Sounds like a reference to shift time, or time from full open to full closed or vice versa.

In other words, your actuator motor starts and it takes 150 seconds to move through the full stroke range.

rmw

 

[zdas04]

I've seen that spec and rmw guessed correctly.

A better question might be "why are you concerned about the running time on a valve designed for throttling?". An actuated globe valve typically is moving 1/8 turn at a time and if you slam it shut, chances are that it won't seal (throttling valves rarely give you a bubble-tight seal). If you slam it open it will still have some amount of pressure drop due to the changes in direction within the valve body.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The harder I work, the luckier I seem

 

[JimCasey]

David, he said a globe valve, not a throttling globe valve. He may, or may NOT, be using the valve for throttling. GLobe stop valves have wobbly stem-to-plug connections so the plug can nestle into the seatring and give tight shutoff. Globe control valves are rigidly guided so they give repeatable flow at intermediate positions and so the poeces don't wear against each other. But they, as you pointed out, don't shut off very well.

150 seconds is 2 1/2 minutes. Unless this valve is big enough to walk through it will stroke in much less time than that. My read on that rating is that the actuator is designed to run that long continuopusly without hitting its thermal rating value. If you are throttling with the valve, it is prudent to get an actuator with at least a 75% duty cycle, if not continuous. A throttling valve, as David pointed out, is almost continuously making small movements. These are rough on an electric actuator because each small motion comes with an initial inrush current. (Just like when your A/C compressor kicks in at home, and the lights dim for a second.) It's entirely possible to toast an actuator with frequent startups.