We have a lot of machines located in many places in our site, and we need to define the activity that inspecting the machine running status regularly by plan in field, does the "spot inspection" a nice word to define this activity?
Consider calling it a regular inspection. The dictionary entry has an example that includes the usage you describe.
Regular adjective 2 Recurring at uniform intervals: a regular monthly check - ODO
As Phil Sweet comments, spot checks are not scheduled inspections. As its definition suggests, spot check is not an appropriate term for planned inspections.
Spot check noun A test made without warning on a randomly selected subject - ODO