method of calculating coupling thickness in pvelite

[MQ]

Hey!
Does any one know that how pvelite calculates the coupling thickness when using "coupling lookup" ?
it seems that it is a little different than what should actually be as per B16.11.
thanks

 

[JStephen]

I believe somewhere there in Section VIII, it gives an allowance for effective diameter of threaded fittings, but wasn't able to find it earlier.
Couplings do have a specified ID in the non-threaded part which is not normally shown in dimensional tables, and that could be used if the threads were beyond the area in question.
What I have commonly seen also is to assume the ID of the coupling is the OD of the pipe that would thread into it, which should be a little conservative.