PRODUCT REVIEWS
Welding in the HVAC sector
Cemsa International Srl is an Italian specialist in the design and manufacture of resistance welding machines. It designs and produces custom-made solutions according to end user needs, either stand-alone machines or assembly lines. The company exports to more than 120 countries.
For the past six years, a U. S.-based multinational in the HVAC( heating, ventilation and air conditioning) sector, with five production plants( in California, North Carolina, Oklahoma, Florida and Pennsylvania) has relied on Cemsa to optimise the welding of its components.
The initial contact between the two companies goes back to 2018, facilitated through collaboration with another Italian company. This led to the supply of welding machines for stainless steel components for flue pipes, with thicknesses of 1mm and leak-proof welds tested with liquid penetrants. The first machine, delivered in 2019, prompted the American company to purchase ten additional machines over the next four years, with two machines deployed to each of its plants.
New welding requirements
“ In 2024, our customer faced a new challenge: its existing machines were unsuitable for welding a new type of galvanized or aluminised sheet metal whilst meeting strict quality standards,” it told ISMR.
Welding galvanized materials is difficult work: the main challenge relates to the layer of zinc on the surface of the sheet metal. This zinc layer with a fusion temperature lower than the base metal, as well as that of the copper, being heated by an electrode( spot or wheel) tends to react with the copper base. Because of this, the physical and mechanical properties of the copper( including its electrical conductivity) are modified consistently.
“ This means that, after a few spots or a few running rings of the wheels, the quality of the electrode surface changes dramatically, becoming impregnated by this zinc. Welding is no longer easy, the contact surface of the electrode( wheel) changes
HVAC pipes.
MRT F 2WR welding machine.
shape and the resistance increases, causing local overheating. The only way to continue with production is to clean and dress the surface by removing this unhealthy combination of elements,” explained Cemsa.
“ However, if a copper wire( running with the wheels) is interposed between the two electrodes( wheels), this wire( other than guaranteeing electrical continuity for the welding process) firstly presents a clean contact surface. This offsets wear of the wheels, whilst burning off and removing the first layer of zinc from the galvanized sheet metal. Once it is completely impregnated by zinc and therefore no longer usable, this running wire reaches the rear of the welding machine where it is wrapped on a winder,” continued Cemsa.
This wire coil can be removed by the operator and, from time to time, sent back to the wire producer who will process it for new bobbins. The customer therefore only pays for this regeneration process and not the basic material( copper).
A sustainable solution
Cemsa stepped up to this challenge with its latest innovation: the MRT F 2WR welding machine, specifically designed to process galvanized sheetmetal with thicknesses of 1mm. This technology enables the welding of segmented elbows made of zinc or aluminium-zinc with variable diameters ranging from 250-800mm( 10”-30”) and thicknesses from 0.5-1mm( 24G-18G).“ Using a system that employs two copper wires, in independent circuits, to protect the welding wheels from the zinc impregnation effect and reduce the risks of roller breakage,
The weld seam. means higher quality and higher productivity,” stated Cemsa.
“ The MRT F 2WR has also been used for automotive applications, such as welding fuel tanks. Liquid penetrant testing has certified perfectly sealed welds. Its integrated inverter enables energy savings of up to 50 %, compared to traditional solutions, making the production process more sustainable and eco-friendly,” concluded the manufacturer.
Negotiations are reportedly underway with Cemsa’ s U. S. customer for the supply of four more machines, which will enable all five of its facilities to leverage the advanced technologies. n
www. cemsa. it
72 | ismr. net | ISMR April 2025