Classification of medical devices

I have a question which is bothering me regarding the classification of medical devices, and what would be regarded as a medical device. I have a client who assembles and sells X-Ray systems. All the parts, apart from some of the mechanical parts are imported from various suppliers and assembled into a single system here in South Africa. The mechanical parts (X-Ray table, Bucky stand and tube stand) are manufactured locally. Are they to be regarded as medical devices in themselves, or are they only components of the completed system? I am thinking that the X-Ray table has no medical device function before it is assembled into a X-Ray system. The same applies to locally built trailers which are used to install occupational health system and X-Ray systems into which are used as mobile units, especially in rural areas, Surely the trailer is not a medical device. My thinking is that the mechanical components do not need a separate medical device file, but can be included as component parts in the X-Ray system medical device file. Or am I seeing this completely wrong?