A METHOD FOR MEASURING COMBINED STRESS OF SMALL BORE PIPING AROUND WELD IN FIELD USING STRAIN GAUGE HOLDER

摘要

This paper proposes using the strain gauge holder which has 12 elements of strain gauge in order to measure the 2 directional bending stresses and the torsional stress synchronously around the weld in small bore piping. The paper also provides the actual measured dynamic stresses around the welds in real fields including combined stress by the strain gauge holder. The measured stresses are shown on a time axis, on a frequency axis, on an X-Y display like Lissajous figure, and on an X- Y-Z 3D display. It was confirmed that the strain gauge holder was able to be installed within 20 minutes, to be used on 180°C piping, and to be reused in real fields because it was not necessary to adhere the strain gauges on the piping. The measured strains obtained by using the strain gauge holder can provide useful information of the piping system to decide whether the reinforcements are necessary, to enhance the accuracy of the design and calculation, and to improve the validity of fatigue evaluation. It is planned in future to develop a methodology of fatigue evaluation based on the measured stresses obtained by using the strain gauge holder.