Achieving superior welds in hygienic flow meters

Instruments, like flow meters, that are used in the food processing industry are subject to demanding regulatory requirements. Authorities like FDA (Food and Drug Administration), 3-A, EHEDG (European Hygienic Engineering and Design Group) and AWS (American Welding Association) have set standards and regulations for equipment and processes to mitigate public health risks as much as possible.

For example, health risks in food production processes can be caused by bacteria accumulating in rough, less accessible areas of equipment or by cross-contamination of inedible substance with food products. This must be avoided at all cost.

Welding of liquid flow meters in Bronkhorst workshop

When manufacturing equipment in compliance with voluntary industry standards like 3-A or EHEDG, very high-quality standards must be adopted for hygienic design, materials used and fabrication processes. One special process that we have implemented and that we are focusing on is this blog is welding of joints.

Welding of joints for hygienic design

One of the aspects described in the 3-A Sanitary Standards is the welding of joints for hygienic use. A perfect weld joint must be strong, leak-tight and smooth, free of cracks and voids and with a minimum of soot contamination, oxides or other foreign matter if they are to be used in food production processes.

Weld of a liquid flow meter

Welds are used instead of gasketed joints for a variety of reasons, e.g.:

there is limited space
the geometry doesn’t allow for alternative permanent connection methods
a smooth, full metal transition between two metal parts is preferred

Quality framework for hygienic welds

In order to achieve consistent welding quality, it is imperative that, besides proper materials and welding equipment, there is a quality framework in place. This framework contains training of personnel, standardized validation & verification processes, well established inspection methods and continuous improvements. All elements contribute to a consistent and top-level weld quality. The requirements for such welding quality framework are all standardized by decades of experience from the industries, therefore standards like 3-A rely heavily on specifications set by the American Welding Association (AWS).

Hygienic requirements & pressure equipment directive

In the food processing industry, flow meters are often part of a pressurized system. This means that besides the hygienic requirements to be met, it is also mandatory to comply with the Pressure Equipment Directive. Luckily, the welding standards for hygienic use and pressure equipment largely overlap, so a single welding quality framework can be implemented to cover both requirements.

Welding processes in flow meter products

There are numerous welding processes including TIG, MIG, MAG, all having their own characteristics and pros and cons. Processes are selected on the characteristics of the job like material type and thickness, reachability, required speed, quality requirements etc. Bronkhorst typically applies two of these processes. We weld process connections to flow meters using orbital arc welding, which is a mechanized variant of TIG welding. Next to this, we weld capillary tubes in sensors using laser welding. Our suppliers utilize laser welding as well for some other parts for us. These two processes result in very high quality levels and they are the perfect choice.

How did we apply a welding quality system at Bronkhorst?

Welding process parameters and equipment were optimized for best results. Welds from each operator have been tested destructively and non-destructively and the process has been endorsed by Lloyd’s Register third party verification.
Our welding operators are certified to AWS B2.1/2.1M standards. Every six months qualifications are prolonged based on performance.
All welding procedures are documented meeting ISO standards
Continuous monitoring of weld quality by both destructive and non-destructive testing are part of standard operating procedures.

3-A Sanitary Standard

Our new generation of ultrasonic flow meters, the ES-FLOW series, has been launched recently. By implementing all the processes mentioned above, this series of liquid flow meters meets 3-A Sanitary Standards (equipment type 28-06 Flow Meters). Voluntary use of the 3-A Symbol on dairy and food equipment conveys assurance that equipment meets sanitary standards, provides accepted criteria to equipment manufacturers for sanitary design, and establishes guidelines for uniform evaluation and compliance by sanitarians. Bronkhorst is now authorized to use the 3-A Symbol on this flow meter series, which opens up many hygienic applications.

Ultrasonic ES-FLOW liquid flow meter in a installation used for confectionery manufacturing

Ultrasonic ES-FLOW liquid flow meter in a Haas Mondomix installation used for confectionery manufacturing

What’s next?

Driving on the experiences gained with the 3-A certification, Bronkhorst is now aiming to expand its hygienic welding capabilities to other products and processes, to offer a complete product portfolio for the food processing industry. Bronkhorst may also provide hygienic welding documentation and certificates upon request.