Electrical box with knockouts

[safetyscott]

Is there an NEC requirement to prohibits the use of electrical boxes with knockouts from being installed on walls or machinery?

 

[triphase]

No. As long as the unused KO's are still intact or effectively closed. 110.12(A) 05' NEC

 

[celtic]

Is there an NEC requirement to prohibits the use of electrical boxes with knockouts from being installed on walls or machinery?

No, but their are restrictions if certain instances - wet areas require a 3R rating.

What is your application?