HEP (high energy piping) in power plants are at risk of flaw accumulation. This is of great concern for plant safety, and for unexpected outages and plant damage. Margan offers the trend monitoring inspection service that removes these concerns by performing periodical tests on the lines. A network of sensors is installed in the plant at the first inspection. As usual there is no need for a shutdown or scaffolding erection. The plant is then regularly monitored in order to detect any trends of concern with intervals of typically 24 months apart, except for the first interval is of 6 months. The baseline level and plant specific acoustic patterns are scrutinized in the first inspection at installation. Dangerous problems can be already be pointed out at baseline. The next trending inspections can detect even smaller flaws and accumulating damage.