Application Of Radiography In Evaluating Quality Of Welds: Case Of Selected Jua Kali Fabricated Products In Kenya
Radiography is an effective Non Destructive Testing (NDT) method for inspecting internal and surface defects in engineering materials. It has been applied in this study to establish the integrity of welded joints in Jua Kali fabricated products. The welds were evaluated and classified based on type and size of defects observed as per ISO 5817 standard. Specifically, welded Pull type of hoes and Tee type hinges were the Jua Kali products investigated. Hoe specimens were sourced from Shauri moyo Jua Kali open air market in Nairobi along Jogoo road. While hinge specimens were sourced from Nyeri Jua Kali shades next to Nyeri Municipal Hall. Thirty samples of each were analyzed for defects at the Kenya Bureau of Standards (KEBS). For comparison purposes, standard based welded specimens were also evaluated. These specimens were obtained from Kenya Bureau of Standards NDT laboratory where radiography test was carried out. Radiographic exposure was done in accordance to ISO 17636 standard, while evaluation and classification of defects was done in accordance to ISO 5817 standard. Key instruments used include x ray machine of model 300, Kodak industrex AA400 films, lead intensifying screens of 0.1 mm thick, 10FE EN wire penetrameter and DDS2 digital type of a densitometer. X-ray star type of developer and Primax PT-F type of fixer were used in film processing. Lack of fusion was found to be the widely spread defect in Jua Kali welds inspected. Of the sixty Jua Kali welds inspected, 52 or 83% were observed to have lack of fusion defect. Second in occurrence was underfill, with a 70% representation. Other observed defects include; porosity, undercut, burn through, slag and crack. The study showed that 86% to 100% of the Jua Kali welds were defective hence non compliant to ISO 5817 standard. On the contrary, standard based welded joints failed to comply with only 10% defective welds. The quality welds have been attributed to application of welding standard by qualified welders. The results show that at α = 0.5 level of significance, the three types of welds tested are significantly different. Jua Kali hinges are heavily defective, followed by Jua Kali hoes, whereas standard based welds were found to have very minimal defects. Key recommendations include application of welding standards, use of Non Destructive Testing (NDT) techniques for quality control and revision ofapplicable product standards to accommodate Jua Kali innovations. Further study to correlate weld quality and product application has also been recommended.