API 620 shell thickness calculation

[alienitmeca]

hello,


API 620 uses computed values for meridonal and latidunal unit forces T1 an T2 in order to determine shelle thickness,
the formula used for the calculation contains many factors such as W and F,

questions:

-segnificance of W

-segnificance of F,

any insights on the subject could be helpful because i think this needs an experiented engineer point of view.

thanks in advance