Study on Safety Assessment Methods of the Penstock of the High Head Hydropower Station Using the China Standard GB/T 19624-2004

Abstract

Based on the finite element analysis, the general mechanical property tests and the CTOD (crack tip opening displacement) test of the penstock in the third deviated hole, the GB/T19624-2004, that is the criterion of safety assessment for in-service pressure vessels containing defects suggested by China, is applied to assess the five weld defects in the penstock, which experienced the failure of the pressure test. The assessment results indicate that 1# defect and 5# defect could be accepted, while the other defects should be repaired. According to the assessment results, the defects over criterion in the penstock must be repaired. After the penstock was repaired, it was checked by the ultrasonic flaw detection again. And the results indicate that all weld joints including circumferential and longitudinal weld joints in the penstock around the pipe close in the third deviated hole are acceptable, what provides a scientific basis for the second pressure test and the safe operation of the High head hydropower station.