Interpretation ANSI B1.20.1

[Nukie]

My question is regarding ANSI B1.20.1, article 4 ''SPECIFICATIONS FOR INTERNAL STRAIGHT THREADS IN PIPE COUPLING' NPSC.''

- Does that means coupling internal threads are straight threads (NPSC)?

- Or that means it can be possible for some applications?

- If it is used on some applications I would appreciate to have some examples and the pros & cons about it.

- Does coupling stands for all fittings (el, tee,couplings etc...)?

- When internal NPT taper threads are used if so ?

Thanks

Marc