Intrinsic Circuits Receptacle and Plug

[altacleets]

I'm looking at an application where I need to have about 3 buttons and a scale on a cart that is used in a Class 1, Div1, Group C,D area. I've found a battery operated intrinsically safe scale, and all the other devices would be 504.2 "Simple Apparatus" so that part is no problem. The cart is used to unload product in batch a process. They have about 20 machines that each run similar batches, but only need a few carts to cover the unloading part of the process (the machines don't all finish a batch at the same time). They would like to be able to pull the cart up to a machine, plug it in and then use the buttons and scale on the cart to control the unloading process for the machine it is attached to.

The plug and receptacle has got me concerned.
504.20 says I can use any wiring methods suitable in the rest of the code, (A listed plug and receptacle would be fine as a standard wiring method).
504.10 says everything must be installed in accordance with the control drawing. Would the control drawing from the intrinsic barrier manufacturer need to show the plug and receptacle for it to be allowed, or does 504.20 allow me to use any basic wiring method, including plugs and receptacles to "connect the dots" on the manufacturers control drawing?

Finally if you think all the rest checks out, what about 504.30(B) " The clearance between two terminals for connection of field wiring of different intrinsically safe circuits shall be at least 6mm(0.25 in.) Would I need a plug and receptacle that had at least 6mm clear between pins of different intrinsic circuits, or is this article specific to terminal strips in a panel or junction box? I think I can avoid this issue entirely by using a multichannel intrinsic barrier whose interactions between channels have been investigated so the circuits in any one plug would not be "Different Intrinsically Safe Circuits" as defined in 504.2

Thanks in advance for your help.

 

[altacleets]

Still struggling with this one, I've reduced the application so I've only got one intrinsic circuit that needs to go to the cart, a serial Current Loop. Both the scale and the interface device have been FM approved and have control drawings with Entity parameters. The control drawing shows the two devices connected schematically with a simple line, and a max distance, and calls out sealing between classified and non hazardous areas. It doesn't specify a wire type or wiring method. So am I only allowed to directly connect the two devices, or can I insert a UL listed plug and receptacle between them?