Improving the Productivity and Reliability of Non-Destructive Testing on Welds for Hong Kong Construction Industry

提高香港建築業焊縫的無損檢測生產力和可靠性

Student thesis: Doctoral Thesis

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Author(s)

  • Sajeesh Kumar BABU

Detail(s)

Awarding Institution
Supervisors/Advisors
Award date26 Jul 2018

Abstract

Non-destructive testing (NDT) has emerged as a highly relevant area in Hong Kong industries related to construction work. NDT techniques are indeed of paramount importance in the safety of human lives as they determine the quality of materials. They help in ensuring safety and improving profitability by guaranteeing the integrity of infrastructure. A remarkable growth has been observed in the Hong Kong construction industry. However, the industry is still not free from serious incidents due to the lack of techniques for testing the defects in welds. Thus, this study was performed to reduce the risk factors due to welding discontinuities, which have not been reliably identified by previously implemented NDT techniques, and to improve overall productivity.

This study aimed to find the most reliable and productive combination of NDT techniques for detecting defects in structural welds within the Hong Kong construction industry. These NDT techniques include manual ultrasonic testing (UT), radiographic testing (RT), phased array ultrasonic testing (PAUT), magnetic particle testing (MT) and eddy current testing (ET). All the tests were conducted using three accredited testing laboratories. The main study was performed in three phases. The initial phase involved a comparison of the productivity and reliability of gamma and X-ray RT, manual UT and PAUT in examining weld defects on structural steel. The result of this phase revealed that PAUT is the most productive and reliable among all three techniques.

In the second phase, the productivity and reliability of surface NDTs, such as MT and ET, were compared. The results of this phase showed that MT is more productive than ET. In terms of reliability, MT and ET showed similar results. However, MT was observed to have false call issues. In the comparison, a t-test was performed to measure any differences in the mean values of reliability and productivity for all tests.

In the third phase, the results of all manual UT, PAUT, MT and ET were examined. The results of this phase showed that PAUT, together with MT, is the most productive testing technique in terms of the time consumed to complete an inspection task. PAUT was found to be the most reliable NDT. In this phase, human factors were analysed, and the results indicated that qualifications, skills and training play the most significant role in improving the productivity and reliability of NDT. The measures used to reduce the hazards of radiation due to NDT were explained in the context of the Hong Kong construction industry.

In sum, this thesis determined the variations in the productivity and reliability of conventional NDTs and concluded the innovative application of advanced NDT for structural welds by measuring individual test and combined performances.

    Research areas

  • construction industry, eddy current testing, magnetic particle testing, manual ultrasonic testing, non-destructive testing, productivity, reliability, radiographic testing