One of State-owned power utility Eskom’s main engineering contractors, Steinmüller Engineering Services, has reintroduced explosive welding technology for the refurbishment of high-pressure-feed water heaters, which are used in Eskom’s power plants, and held a seminar and demonstrated the process at its Bethal works for Eskom engineers.

Steinmüller’s business development consultant for feed heating plants, Jack Minto, says that, although the technology was used about 20 years ago at Eskom’s Kriel and Komati power stations, as well as the Rooiwal power station, local explosives manufacturers could not meet the requirements of the explosives specification so the process was abandoned.

However, after a gap of about 15 years, Steinmüller has now signed a technology agreement with UK-based engineering and maintenance company TEi/Yimpact, and has sourced the local explosive required for the process.

“Eskom was impressed by the demon- stration and Steinmüller is now waiting to receive word that the process is acceptable for all future heater refurbishment,” says Minto.

Explosive welding is used for the fusion of tubes to tube plates or headers in the manu- facture of high-pressure heaters in the workshop.

The explosive plugging of high-pressure heater tube leaks, which is performed on site, will reduce plant downtime, resulting in reduced costs of repairs and a reduction in the loss of revenue due to power outages.

With conventional welding technology, the call-out time for the staff on the plant is anything from one to three days, but, with explosive plugging, the process can be completed and leaking tubes repaired in a matter of hours.

During the explosive welding or plugging process, a controlled explosion creates interfacial pressure, which melts and forces the tube to be bonded to the tube plate or header, depending on the heater design. The process is suitable for most materials used in heat exchanger manu- facture, and enables dissimilar materials, such as carbon steel, stainless steel and titanium, to be used and welded in work- shop conditions.