A better airflow is achieved with round air ducts. In addition, less material is required for a same cross-section than with rectangular ducts. It is also easier to achieve a higher air tightness on round ducts. Please also refer to the document "Round vs Rectangular Air-ducts"
Where Leakages Mostly Occur
The highest leakages rates are usually found the connection areas, the folds and the seams. Welded seams and formed-on flanges minimize the occurrence of such problems.
State of the art technologies
With the technologies available today we can manufacture economically standard air-ducts with an airtightness exceeding the class D (DIN EN 12237) and fulfilling the requirements of the class ATC 1 (DIN EN 16798-3). Liquid and oil-tight air-ducts are also possible for certain applications (i.e. the process industry, machine hook-up's, the cleaning of air-ducts in commercial kitchens using liquid or foam detergents).
Smooth inner Surfaces
Air-ducts with smooth inner surfaces generate less friction, reduce turbulences, noise and pressure drops. They are also easier to clean and offer a higher energy efficiency grade.
The various parts should be easy to install without having to do any additional work or take additional sealing measures. Having to tighten only one screw per connection speeds up the assembly considerably and reduces the time spent on site. The properly engineered design ensures that the components are continuously rotatable and interchangeable (i.e. for the flexible retrofitting of CNC machine connections).
Pipe components should be light and sturdy at the same time. The formed-on flanges bring a lot of stability even when light gage steel is used. Having to carry around and install light air-ducts and fittings is a great advantage on the construction site, especially when the assembly has to take place several meters above the floor with a reduced crew.
The ventilation ducts should fit discreetly into the building. That way they do not necessarily have to be painted or hidden.
Air-ducts having the above-mentioned characteristics automatically fulfill the requirements of other applications. They would that way contribute to the energy savings, ensure an oil-mist free working environment in production sites, reduce the risk of contaminations in hospitals and laboratories, and simplify the cleaning operations in commercial kitchens for example.
Higher Standards Require Changes in our Fabrication Methods
Fully airtight ducts can only be achieved if no holes are drilled on the duct walls for mounting or hanging purposes. If a hole in the duct wall is unavoidable (see picture), the shaft joint must be of high quality fitted with an appropriate liner. This is especially important for oil-mist removal air-ducts.
The components should be well packed for transport and possible storage on site in order to reduce the risk of damages and save cleaning operations.