Welding solutions company Applied Welding Technology (AWT) – a member company of professional welding organisation the South African Institute of Welding – has recently localised the manufacturing of high-pressure bypass system flow control components for State-owned power utility Eskom’s Tutuka power station units.

The project, alongside its 12-year record of maintaining ISO 3834-2 certification, further cements the company's role as a trusted welding solutions provider, says AWT GM and CEO designate Thulani Mngomezulu.

“The components were manufactured [to] . . . cost-effectively improve delivery lead times ahead of scheduled outages. The older parts, which were in service for several years, had started to fail while in service in recent times, necessitating replacement.”

The delivery of these components involved various work processes, including design improvements, the design of detailed manufacturing method statements and reverse engineering activities, retrofitting and quickly incorporating insights gained from interim testing to produce the finished products. It also included knowledge sharing between AWT and the end-users of components.

Computer numerical control turning and milling, assembly, welding, post-weld heat treatment, non-destructive testing (NDT), hardening processes and oversight of certain activities by the approved inspection authority were used during the manufacturing processes.

ASTM A182 Gr F91 grade material was also used to manufacture the components. The final product conforms to approved engineering drawings, as well as client-approved quality processes that incorporate AWT procedures, testing and adaptation, Mngomezulu adds.

Supplementing the Welding Processes

AWT and NDT sister company Integrity NDT (INDT) are “paving the way for the future of welding efficiency” says INDT GM Luke de Beer.

NDT processes ensure that welding components meet quality requirements stipulated by international codes and standards regarding the design and fabrication of welded components.

“NDT detects lack of fusion, porosity, cracks, incomplete penetration and other discontinuities that can initiate in-service failure. When applied at fabrication and during service, it provides objective evidence that the weldment will perform safely for its intended life and directly influences the longevity and reliability of the asset,” he elaborates.

The company’s latest deployment of NDT technologies involved phased array ultrasonic testing (PAUT) and time-of-flight diffraction (TOFD) testing technologies for the inspection of a hot-reheat safety-valve bypass pipe for a client that required a solution to “detect and characterise internal flaws”.

De Beer says the combination of PAUT and TOFD testing technologies enabled the client to not only replace and remove the affected pipe but also carry out predictive maintenance to avoid operational failure.

“We first applied PAUT to obtain full volumetric coverage of the weld. When a significant indication was identified, TOFD was used as a complementary technique to independently confirm the indication, its location and its through-wall extent,” explains INDT operations manager Ridwaan Patel.

This ensured that the client received “early, high-confidence characterisation of a defect in a critical high-energy piping system”.  He adds that PAUT also reduced downtime – compared with conventional radiography, which requires plant area evacuation – while allowing for inspection of the asset's condition in a difficult-to-reach area.

“These techniques allowed for a condition-based decision, rather than a conservative or time-based one, improving plant safety, reliability and availability”, says INDT responsible Level 3 Tyson Makhura.

While acknowledging the persistent need for additional investment in local welding capacity and skills development, Mngomezulu and De Beer believe that the future of the welding industry will be driven by new welding equipment and technologies, as well as the NDT industry's increased adoption of robotics, digital twins, AI-powered solutions and permanent or semi-permanent monitoring systems.

De Beer adds that computed radiography will play an important role in reaching restricted-access areas and confined-space drone inspection will identify safety risks while alternating current field measurement will reduce the need to strip and repaint components when testing through coatings, complementing magnetic-particle inspection.

“Technology is evolving rapidly. INDT is committed to staying ahead by introducing new approaches to asset integrity and continuous monitoring as they become available,” he notes.

“This industry remains key to industrialisation projects and positively impacting [on] . . . livelihoods. AWT is favourably positioned to support the greater regional industry efforts, based on the technical progress we have achieved so far, and sectoral developments . . . taking place around the region where construction work involves welding as one of the fundamental processes,” Mngomezulu concludes.