Breakaway torque for ball valve

[Newbie]

Hi everyone!

Can somebody explain to me how to calculate the breakaway torque for ball valve particularly for 2 inch - class 150 ball valves. The material for seat is PTFE and the ball is made up of ASTM A105. Thanks!

 

[gerhardl]

Hello jethrolawing!

I would recommend you to check previous discussions on the topic in this forum and others. I believe the answer is already given there.

Torque is normally measured (not calculated) under (simulated) operating conditions, and will vary with a factor of at least 1:3, others will say 1:5 or 1:10 in 'real life.'

So: what is the purpose of your calculation? Giving the normal torque in continious operation by a 'nice' fluid, for instance pure, thin oil without impurities, or selecting the construction details for the spindle top when applying a 10-times normal force?