•  FAN TEST

Fan tests aim to determine airflow and pressure, as well as all electrical data and sound levels in order to establish characteristic curves.

2.1 Airflow/pressure test

Airflow/pressure tests for SODECA fans are carried out at our fluid mechanics laboratory, in accordance with ANSI/AMCA STANDARD 210-85 and its equivalent, UNE 100-212-90.

Fig. 1 shows the ANSI/AMCA test chamber, with exit nozzles and variable air extraction system, used for testing and measuring axial fans.

For testing centrifugal fans, section 7 of said ANSI/AMCA standards is used.

2.2 Sound level test

Air displacement and the movement of the impeller or turbine at a specific velocity cause the fan to make a certain noise which is measured in our laboratory according to ISO-3744 and ISO-3745 standards.

Values are determined according to free field measurements of pressure and sound levels. They are expressed in dB (A).

•  GRAPHIC REPRESENTATION OF TESTS

A fan's characteristics curve is a graphic representation bringing together, on coordinate axes, all the values resulting from the tests.

This curve will represent all the fan's possible working points.

Looking at any characteristics curve in this catalogue, we can see how the Airflow Q, plotted on the abscissa axis, is reduced on the ordinate axis as static pressure (Sp) increases, with airflow being at its maximum when static pressure is 0. This is called free airflow. Hence the fan's curve shows us, in graphic form, the airflow which the fan can develop according to pressure demanded from it.

Data given on our characteristics curves correspond to:

- Temperature 20ºC.

- Air density 1.2046 kg/m3.

- Atmospheric pressure 760 mm.Hg.

•  OPERATING LAWS

The operating of a fan is governed by three fundamental variables: specific weight of the circulating air d, angular velocity n and diameter of the impeller D. When these vary, so do the fan characteristics. Next we will consider cases of variation of one of the variables, with the other two being constants:

4.1. Variation of d, with n and D being constants. The fan characteristics are expressed for a specific weight d = 1.2 Kg/m3. Variations in this produce a directly proportional variation in pressure and energy absorbed by the impeller. Airflow remains constant. With d' being the new specific weight the following will apply:

4.2. Variation of n, with d and D being constants. When the impeller rotation velocity varies, the characteristics vary as follows:

n' is the value of the new velocity. 4.3. Variation of D, with d and n being constants. This ratio only applies to geometrically similar fans. For a new value D' you would have:

•  FAN COUPLING

5.1. Parallel fan coupling

5.2. Standard fan coupling