First, you should be sure that you have a proper saturation curve to establish initial process parameters. Then, every 8 hours of machine operation you need to verify peening intensity. You should also verify the quality of the shot size (by sieve analysis) and shape (by microscope analysis). To verify coverage you should use 10-30X magnification of a sample item peened only long enough to achieve 98% denting. Then, double the peening time for production. There is no method to inspect directly for 200% coverage.
