Breakaway torque for Trunnion Ball valve, different seat
Breakaway torque for Trunnion Ball valve, different seat
(OP)
Good morning dear all,
I am new to valve industry, our sales threw a question to me regarding if they are changing seat material from, how much torque will added to actuate the valve.
1.) NPS 16, class 600, Trunnion ball valve, seat material changing from Nylon to Peek, what might be the approximate breakaway torque increase? (I assume as 15%)
2.) What will be the approximate breakaway torque increase changing from resilient seat to metal seat for trunnion? What about floaters?
Can anyone give some lights on it? Any help will be greatly appreciate
Xun
I am new to valve industry, our sales threw a question to me regarding if they are changing seat material from, how much torque will added to actuate the valve.
1.) NPS 16, class 600, Trunnion ball valve, seat material changing from Nylon to Peek, what might be the approximate breakaway torque increase? (I assume as 15%)
2.) What will be the approximate breakaway torque increase changing from resilient seat to metal seat for trunnion? What about floaters?
Can anyone give some lights on it? Any help will be greatly appreciate
Xun





RE: Breakaway torque for Trunnion Ball valve, different seat
You can calculate or test the torque.
Regards
Bao
RE: Breakaway torque for Trunnion Ball valve, different seat
What size does the valve have? Actuation type?
Following link on other properties than torque could be interesting for you http://www.curbellplastics.com/technical-resources... The link shows the materials to be fairly close in properties, and perhaps not too far from eachother in loosening torque.
As a reminder: Necessary torque for operation (to dimension actuators) is a result of actual experience and measurements from the factorys side, and for given fluids (the most common for apllications for the valve) and with a reasonable safety factor. This factor could be anywhere from (say) 20 to 50 up to 100%.
If the valves sticks dry for a longer periode the necessary loosening torque could be much higer than this, up to 2-5-10(?) times.
The torque is also depending on how thight it is necessary to close the valve to get a dropthight sealing. Wrong closing torque or adjustment of limiting devices could also give a much higher torque than calculated.
Following remarks/personal advice: I would have selected the softclosing PEEK as most equal to existing, whereas a metal to metal seating requieres a high accuracy and undamaged seat over time to close properly. In some cases a metal sealing could be the best choice, but not knowing the application one has to assume that soft-sealing, as existing, is ok.
I would have selected an actuation with gear (either for hand operation or electrical operation). This will both make it easier to get the correct limitation for the closing position and the necessary opening force. In addition the gear could easily be changed or given a 2:1 additional stage if the torque proves to be too low.
RE: Breakaway torque for Trunnion Ball valve, different seat
For floating ball valves there is considerable clearance between the ball and the seats so I would not expect any change in torque if you changed the seats from teflon to emery cloth.
David Simpson, PE
MuleShoe Engineering
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"
RE: Breakaway torque for Trunnion Ball valve, different seat
gerhardl,
Your information is supportive and helpful. Thanks a lot.
David,
You answer is what I want exactly, but could you illustrate why floaters does not change, what I think is dP pushes ball to seat hardly that breakaway torque highly depends on the seat material to get friction.
Sincerely,
Xun
RE: Breakaway torque for Trunnion Ball valve, different seat
David Simpson, PE
MuleShoe Engineering
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"