Can someone please verify i have done this work correclty?

I have a Arc Welder - nameplate rating of 18.9 amps - 60% duty Cycle. 480v - 3 phase.

Overcurrent protection:

18.9 x 200% (per 630.12 (a)) = 37.8 = 30/3 (not more than 200%)

Conductor size:

18.9 x.78 (Table 630.11) = 14.7a = #14's.
Also can I ustilzie 14.7a in my panel calcs... or name plate rating?

I am not a welding man and do not understand the duty cycle thing....

Also... Anywhere does the NEC allow to diverisfy multipule welders. I am working on a welding lab with several welding booths.