There is very limited market for freelance industrial equipment design.
The most of the industries who are making these equipment have in house design setup.
There are other industries too but they don't want to give design fee. They just go to fabricator and get the things made. For them proper design is not important.
There are another kind of people too who will discuss the details with you and tell the fabricator based on your discussions. in that case too they don't pay you any consultancy fee. Freelance means Free.....