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Manufacturing Technology

Welding techniques

We utilize the most modern welding procedures available, and are certified according to EN ISO 9001-3834, ensuring that all our weld processes are according to specification. Among the techniques used are:

  • Fiber laser welding (single and/or dual spot)
  • CMT (Cold Metal Transfer)
  • TIG

All our welding processes are quality assured by WPQR, and we utilize the different techniques depending on cooling times and appropriate steel properties. The use of correct backing and shielding gases, in combination with continuous oxygen measurements in the heat-affected zone (HAZ) eliminates the need for cleaning the welds post-process.


Key process parameters

To avoid contamination of the stainless steel, our production facility handles only stainless steel. In addition, the use of oils during cutting / shearing is greatly reduced, due to our use of laser cutting, eliminating the need for most washing processes. Highly automated production lines greatly reduces the amount of manual handling and hence, contamination. To ensure the formation of the oxide layer, all our products are equipped with an initial protection anode, which requires no maintenance. This eliminates the process of pickling, which is a highly environmentally harmful process involving nitric acid.

Duplex stainless steel

OSO was an early adaptor of stainless Duplex steel for the production of water heaters. Duplex provides our products with lower weight, higher strength and better corrosion resistance. In terms of corrosion resistance, Duplex is equally good, and in most conditions, better than 316 steel grades and is the superior material quality being used for water heaters. Duplex also has a considerably higher strength than traditional, ferritic material qualities. This results in an increase in strength, a lower weight and a reduced material consumption which corresponds perfectly with OSO’s environmental approach.



Precision and repeatability in production processes from welding technology to final control ensure the quality for all of our products. With a steadily increasing demand for cost efficiency, this is crucial for maintaining production in a high cost country such as Norway. Circumference measurements, height measurements, roundness, flatness and straightness are only some of the factors which are continuously measured on each component before welding. Precision in all areas increases the quality of OSO’s products.

ECO Foam insulation

As one of the first water heater manufacturers, OSO introduced Polyurethane foam (PUR) as standard insulation for water heaters in 1996. Since then, more than 500.000 OSO water heaters with PUR insulation has been sold. OSO ECO Foam is a polyurethane based foam insulation based on environmentally friendly procedures. The insulation quality of PUR compared to traditional mineral wool or EPS is 25-30 % better. OSO ECO Foam entirely uses water power during the production process and in addition to the energy saving it is also environmentally friendly with a GWP of 1 and an ODP of 0. The foam insulation is 100 % recyclable and can be reused for a number of other products.