Experimental validation of non-contacting measurement method using LED-optical displacement sensors for vibration stress of small-bore piping

• A proposed non-contacting measurement method for piping vibration was verified.
• The applicable conditions of the proposed method were clarified.
• The influential factors on the application of the proposed method were shown.
• The applicability of the method was discussed from the viewpoints of S/N ratio.
• The practical use of the proposed method was experimentally demonstrated.

There have been many reports of fatigue failures of small-bore piping systems such as drain piping, vent piping and instrumentation piping in nuclear power plants that arise from vibration sources such as pumps. To prevent the failures, integrity evaluation of piping is conducted by measuring and analyzing vibration stress in the piping. But, a more efficient and economical measurement method is desirable to evaluate the vibration fatigue in small-bore piping. In this study, a non-contacting measurement method was proposed that is based on optical displacement sensors using light emission diodes (LEDs) to measure the vibration stress. The applicability of the method was discussed based on the vibration experiments using pipe elements and a mock-up piping system. From the experimental results, the proposed method was clarified to be sufficiently applicable and practically useful for the vibration measurement and stress evaluation in small-bore piping systems.