API 6D 6.17.3 question

[MuShoe]

Hello,

API 6D section 6.17.3 states:

6.17.3 Allowable deflections
For ball valves, the total torsional deflection of the extended drive train when delivering the design torque shall not exceed the overlap contact angle between the seat and obturator.
Deflections of the extended drive train shall not prevent the obturator from reaching the fully closed position

My question is simple. What is "the overlap contact angle between the seat and obturator" (ball)?

Thanks.

Jeff

 

[prex]

I guess it is the angle between the fully closed position and the position where the obturator starts to leak.

prex

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[MuShoe]

Interesting thought. I was also thinking that it might be the width of the sealing face of the seal against the valve. The problem is that these are only guesses... I think that the width of the sealing face (in deg) will be less than the angle between the fully closed position and the position when the ball starts to leak. I'll check that and perhaps take the more conservative of the two.

Thanks!

Any other ideas?