The fischer Group SA, which invested R60-million in facilities and machinery in order to manufacture a small, highly-specialised tube and housing for an exhaust gas return (EGR) heat-exchange unit, was named Runner-Up in the Project category at the 2006 Stainless Steel Awards, hosted by the Southern Africa Stainless Steel Development Association (Sassda).
The aim of the unit is to substantially reduce the nitrogen-oxide emissions in diesel engines. The investment included one of only two five-axis laser-cutting systems in South Africa, which also features two loading stations to boost productivity.
“This investment in complex, hi-tech equipment demonstrates the fischer Group SA’s confidence in the stainless steel produced locally, and the ability of our employees to turn this into a reliable product of international quality,” says fischer Group SA MD Eric Kotzenmacher.
“The final product is 100% exported, and therefore contributes to the growing reputation of South Africa, providing value adding services from raw materials to completed product that compete well in terms of the global-sourcing policy employed in our industry,”
The EGR heat-exchange unit, designed by Behr Engine Cooling, allows part of the exhaust gas produced by the combustion process to be cooled and mixed with fresh air. This reduces the oxygen concentration in the combustion chamber, and subsequently the combustion temperature. The end result is a reduction in exhaust emissions.
Stainless steel grades 1.4301 and 1.4404 were used for the tube and housing. The small tube acts as the intermediary between the water and gas, and is the main interface in exchanging heat between the two. To ensure even heat distribution and rigidity in the assembly, the tube has indentations on the inside and outside in accordance with strict dimensional requirements.
The tube mill installed by the fischer Group SA for this project has been designed to run continuously by using an accumulator to create a time period for the next coil to be welded before the previous one runs out.
The tube is monitored continuously for any breakage or holes during the winglet pressing stage, with the mill automatically marking any area that is cause for concern. If the problem is repeated, the mill switches off and an alarm is sounded. Micro sections are assessed regularly to ensure that the minimum thickness is maintained.
After tube-forming, the section is laser welded and calibrated. The welding operation is monitored continuously to ensure integrity. Thereafter the long tubes are cut to length according to customer specifications, and are loaded automatically into packs designed especially to ensure direction and compatibility with the customer’s production line.
The housing is produced by hydro-forming, which allows shapes to be produced in tubes that would be extremely difficult to form by normal pressing, as well as considerably reducing subsequent pressing. The process uses a fluid pumped into the tube at extremely high pressures.
The tube lies in a die, and the fluid forms the tube from the inside into the shape of the die. The hydro-formed tube is processed further by the five-axis laser-cutting system. Due to the nature of the product, both items are cleaned to ensure that further laser welding is carried out with dirt- and oil-free components.
Erich Kotzenmacher
fischer Group SA
Tel : (012) 653 1142
Fax : (012) 653 1146
