The use of a flow meter for welding applications

16 September, 2021 José L. Velázquez

In a previous blog my colleague Koen van Bindsbergen and I explained how we were able to achieve superior welds in the assembling process of our Bronkhorst hygienic flow meters making them suitable for food and sanitary applications. In this blog, I want to highlight a completely different viewpoint to welding: how can gas flow meters and pressure controllers be applied to optimise your welding process?


Role of gas flow meters for welding processes

As a welding specialist at Bronkhorst, I can say that welding is a truly interesting application for our flow instruments. Not only for orbital welding, but all automatic and mechanized welding processes that require shielding gas, like plasma welding, laser beam welding, MIG, etc, can benefit from our flow meters.

flow meter in plasma welding

Most of these welding processes utilise gas to protect welds from oxidation and to ignite and maintain the welding arc. Manufacturers of welding equipment can capitalise on some of our flow meters’ features. Accurate flow and pressure control of shield- and backing gases used during your welding process will provide a constant and stable weld and thereby improve the quality of the welds.

Which gases need to be controlled in welding processes?

Welding involves using inert gases for shielding (externally) and backing welds (internally) to displace gases like nitrogen or oxygen that are detrimental for the quality of welds. Doing that prevents welds from oxidising when being welded and thus preserve chemical and mechanical properties.

flow meter for laser weld
Example of laser weld with a silverish glance due to perfect atmosphere protection

After welding, the colour of a weld is an indication of its quality. The lighter the colours, the better the quality of the weld, with no discolouration being the best. Orbital welding, for instance, often produces very high-quality welds since processing occurs in chambers filled up with inert gas. For austenitic stainless steels and nickel-based alloys, the most used gases are argon, mixtures of argon and helium and even a mixture of argon with hydrogen. This latter one is particularly interesting as its reducing properties binds oxygen from the weld. An additional advantage is that less energy is required to complete the weld.

Flow instruments are used to provide a constant and stable gas mixture resulting in an excellent welding quality with hardly any discolouration. Bronkhorst flow meters and pressure controllers can help with creating the right mixtures, at the right time with astonishing accuracy.

Which characteristics of a flow instruments are important in optimising the welding process?

Flow instruments can help the mechanised or robotised welding processes in three distinct ways:

  • To determine the flow rate of the purging gas; this way the right amount of gas can be regulated without excess use of expensive inert gas. One inert gas burst over a short period of time can remove all air inside those tubes and pipes resulting in better weld root protection and on a more efficient use of inert gas.
  • By helping create a perfect arc strike and its maintenance providing the right amount of gas at the right time (while ignition takes places and thereafter).
  • By offering a controllable internal pressure of the tubes and preventing operator/welding errors from happening. This pressure can be controlled as the weld is progressing with flow meters as flow rate and internal pressure relate to each other. It can be programmed, something extremely helpful with robotic or mechanized applications. Furthermore, it can control the mix of several gases to induce some special characteristics or control a specific aspect of a weld, by changing that mix as the weld progresses.
  • Setpoints for flow controllers used for controlling the backing and/or shielding gasses may be programmed via Bronkhorst or 3rd party software to synchronize with the applicable welding procedures. E.g. starting and stopping gas flow or changing flow rates and/or mixture composition can all be automated.
Using our flow meters and pressure controllers gives you the benefit of storing the flow- and pressure data from the instruments for quality control aspects.

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