I am looking how to calculate the thread size for a threaded ring closure, as described in ASME UG34, type n.

I have a channel size of 1630mm, the needed thickness is 150mm
I was thinking to use a channel cover of diameter 1700mm.
This cover is fixated by a threaded ring.

What type of thread is used for this type of ring? ACME? Trapezoid? Metric? ...

How do I calculate the pitch and other thread parameters needed to produce this thread?

Thanks in advance!
Jeroen.