"Hunt Thermal Engineering can rightly claim to be one of the leading designers and manufacturers of heat exchangers in Europe and has an unrivalled depth of expertise with half a century's experience in the specialised area of heat transfer.
This is allied with a commitment to the highest standards of quality which is assessed and approved by Lloyds Register Quality Assurance Limited to ISO 9001 for the Design, manufacture and repair.
With such a commitment to quality there is only one choice of welding equipment and consumables for them – Lincoln Electric.
Our first collaboration with Hunt Thermal involved the welding of half round header pipes onto header plates, required for the manufacture of extended surface heat exchangers. Previously this type of weld had been made using a TIG root run which was filled and capped using a basic (E7018) type stick electrode.
In order to improve welding productivity and reduce welding costs, trials were undertaken using the Lincoln Electric Surface Tension Transfer (STT) process for depositing the root weld. The STT process delivers very precise amounts of current to the welding arc depending on the instantaneous requirements of the arc. In this way the STT process can deposit TIG quality welds at MIG welding speeds and is particularly suited for open root welding or situations where the fit up of the base materials is variable.
Trials with the STT process using SupraMIG Ultra wire and 100% CO2 shielding gas were an instant success leading to significant reductions in welding time. However, the success did not stop there! Rather than filling out the remaining joint using a stick electrode, Hunt Thermal opted to use Outershield MC710-H, which is one of Lincoln Electric’s best selling metal cored wires.
Since Outershield MC710-H can be operated at high current densities, the weld metal deposition rate is much faster compared to stick electrode welding, thus significantly reducing the welding time. Moreover, Outershield MC710-H produces virtually no slag thereby eliminating the need for chipping, cleaning and disposal of slag.
Success with this first project encouraged Hunt Thermal to look for other welding applications where the STT process could be used. One particular job that they had involved the welding of over 3,600 tubes, this has been traditionally done with TIG with two passes. Yet again this application was well suited for use with STT process.
Two days were spent evaluating and accessing the partial nature of this job. The results of which were that by using the STT process with 0.8mm wire and 100% CO2 gave them increased productivity and quality. Yet another success!
Overall the STT process has been a complete success at Hunt Thermal with many applications suited for the welding with this process. Lincoln Electric and Hunt Thermal continue to make progress in partnership together.
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