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Durgo Air admittance Valve

The Durgo Air admittance valve

Bengt Arne Persson the inventor of Nonair had worked as a plumber and teacher on a vocational school for plumbers. After having finished the studies to engineer in the HVAC field he started working as a consulting engineer.

Bengt Arne had through his working life come across many different problems that he tried to work out solutions for. On a seminar about how fire could be spread in a stack pipe for sewage water the conclusion was that if the flow of air through the stack pipe could be blocked the prevention of fire would be increased. As the stack pipe has to be vented he realised that if he could find a solution for the problem that the stack must be both open for venting and closed for odours perhaps a business opportunity was in sight.

He went home and got an idea and made one simple prototype that he tested and found working. The day after he took his prototype and went to the company Durgo and presented his invention, the Air admittance valve and after that day millions and millions Durgo valves has been sold.

Nonair Micro bubbles Separator Standard

The Nonair® Micro bubbles Separator

In his work as a consulting engineer Bengt Arne had regular contact with distributors for all kind of equipment that the representant was kean on being prescribed in the design documentation for the installation.

One representant was distributor for the first and sole Micro bubbles Separator on the Swedish market. He wondered why the company that Bengt Arne worked for didn't prescribed that separator and got the answer that it would be irresponsible against the client to prescribe a product that was sole on the market and consequently rather expensive. The representant that knew about Bengt Arnes earlier invention skills proposed that he being an "inventor" should design his own Micro bubbles Separator.

With the experience from the Durgo Air admittance valve he started to think how he could design a Micro bubbles Separator with an unique design. His intention was to create a unit with a minimum of pressure drop and shortly he knew how to do it. He made a prototype and tested it and found it not working. After some days he had redesigned it and made a new prototype and tested it and found it again not working.

Bengt Arne didn't resign but had to do over two hundreds of redesigned prototypes before he was satisfied with the performance.

In the year 1991 the company Avonni AB was started for the development and later on production and marketing of the Nonair Micro bubbles Separator.

The first distributor that 1993 adopted Nonair was the company in Sweden that later on became Beulco Armatur AB and which representant was the one that proposed Bengt Arne to invent his own Micro bubbles Separator.

From start the Nonair was manufactured in brass for the small dimensions and ordinary Carbon Steel for the greater dimensions. As we would like to take a further step to a unique design we decided to manufacture the Nonair in Stainless Steel, acid proof, 316L material. Thanks to this decision we got a product with much reduced weight that will simplify all phases of the product from manufacturing and transport to mounting and recycling.

Nonair Air separator with built in Strainer


The Nonair® Micro bubbles Separator with built-in Strainer

Traditional Strainer is mostly built as a cylindric formed plain strainer mesh in a narrow housing. It's more or less the surface of the strainer towards the outlet end that is acitve. Very soon the strainer gets clogged creating an increasing pressure drop with reduced flow through the system as result.

We started to think how to develop a strainer with a new principle and had a number of features as our goal.

  • The first was that the strainer mesh should have a relative great area in comparision to the inlet area.
  • The second was that the whole strainer surface should be active.
  • The third was that the material should be in Stainless Steel to reduce the weight.

We found that if the strainer mesh was crinkled we could increase the area of the mesh. In our Strainer the area of the mesh is 8 times the inlet area of the connecting pipe.

We made the strainer insert as a vertical cylinder with inlet both at the top and at the bottom. The strainer is placed in a spheric housing that allows the flow to find a new and clean way round an eventual clogg in the strainer.

We also made all parts of the strainer of Stainless Steel and that gives a product with low weight.

The benefit with our Strainer is that it is effective and thanks to the great area of the strainer mesh it will take long before it has to be cleaned.

The final result was so good so we decided to build it combined with a Nonair. With this Nonair Strainer model we separates the air at the inlet end and all types of particles at the outlet end.