Q & A

Fans in accordance directive ERP

Energy saving in the use of centrifugal fans

After focusing on improving the efficiency of electric motors, the European Union has defined the regulation 327/2011, on the energy efficiency of fans driven by electric motors with power between 125 W and 500 kW. They published the ErP Directive (Energy-related Product Directive 2009/125 / EC).

This issue is part of the Kyoto agreements, with the ambition to reduce fossil fuel consumption by 20%, to reduce greenhouse gas emissions by 20% and to reach 20% of the share with renewable energies by 2020.

This goal is to assign a level of efficiency “N” to each type of fan, applicable from 01 January 2013, which allows to define a target energy efficiency, knowing that this “N” value will be raised to a higher level from 1st  January 2015.

This efficiency objective will then go hand-in-hand with the IE3 efficiency motors commercialization requirement. This Directive applies to fans manufactured or imported and used into the EU, but does not include fans intended for export outside the EU.

From 01st January 2013, only ErP-compliant fans will carry CE marking, while non-compliant fans will not be marked and will be used only for non-EU applications.

Existing fans must not be replaced and only fans marketed after 01.01.2013 are concerned.

Timing of implementation of the ErP Directive

January 01 2013
1st phase

Target energy efficiency applicable for fans between 125 W and 500 kW
Motors between 0.75 and 375 kW: IE2 minimum

=> CE marking only for compliant fans

January 01 2015
2nd phase

Target energy efficiency enhancement for fans between 125 W and 500 kW
Motors between 7.5 and 375 kW: IE3 minimum, or IE2 if driven by frequency converter => CE marking only for compliant fans.

January 01 2017
3th phase

Target energy efficiency enhancement for fans between 125 W and 500 kW
Motors between 0,75 and 375 kW: IE3 minimum, or IE2 if driven by frequency converter => CE marking only for compliant fans.

In most of the cases, the fans from AIRVISION range already comply with these new regulations, and many applications are exempted from ErP-compliant fans, including:

– High power fans  > 500 kW at the maximum efficiency point of the fan.
– Fans designed to process gases over 100 °C.
– Fans designed to process corrosive, toxic or abrasive gases
– ATEX fans used in case of emergency (smoke extraction 400°C/2h, 300°/1h etc.)
– Etc.

AIR VISION is and remains your preferred contact for the definition of the fans necessary for your projects, by the guarantee offered in the respect of this directive.

Maintenance of an industrial fan

As every rotating machine, the fans requires serious monitoring to avoid characteristics deterioration, but also to avoid breakage, sometimes dangerous for the operator or user and likely to generate direct and indirect costs.

The impeller state should be often evaluated with eventual cleaning to avoid any unbalance. The lubrication of the house bearing should be done according the frequency, the quantity and the type of grease recommended by the manufacturer. Some fans, essential for the smooth operation of the production, should be continuously monitored on the house temperature bearings and vibrations. Belts and bearings should be regularly inspected and changed while planned shutdowns, according the lifetime recommended by the supplier.

Aeraulic check-list at fan start-up

Vibration status of the fans and balancing

Fan’s bearing lubrication


Noise industrial fans

Among the environmental matters to be evaluated while the installation of manufacturing equipment, the noise level before and after the commissioning is an important point.

A specialized company will be on charge for measurement of the background noise level existing before the installation and a specification note will be established figuring the noise level to be respected at the boundary property, even sometimes with the noise limits to be respected for each octave band.

The fans are noise generator and are often subject to these limitations. The manufacturer will give an important attention to offers fans with good efficiency, with moderate speed, with all necessary noiseless equipment: silencers, casing insulation, sound boxes, etc.

Noise, it is the empty barrels that are the noisiest

Benefit of the variable speed drive to an industrial fan

If the design values of a fan are rarely reached, it is interesting to use a variable speed drive to adapt the speed, as an alternative to the basic flow vein strangulation by a valve, a damper, a metal sheet or a diaphragm. Indeed, rather than to use all the pressure, even if not needed, through a strangulation device, it will be more profitable to regulate the speed to reach the operational flow-pressure point in order to save an important energy.

A calculation can be made in order to evaluate the depreciation period time for the cost of a variable speed drive.

Regulation of the fan working with a variable speed drive

What choose material for the manufacture of an industrial fan?

In the case of quite clean industrial air, non-corrosive, for a temperature up to 400°C, we use carbon steel. The nuance to be used (yield stress from 37 kg/mm² up to 70 kg/mm²) will depend on the mechanical stresses appearing in the impeller because of the centrifugal forces et will be calculated by the fan manufacturer.

For high temperatures, we will use stainless steel or even refractory. Several nuances of stainless steel or plastic material (PP, PVDF, polyester) will be used if the gases are corrosive. Hard steel or even steel with carbide protection or with tungsten will be recommended if the gases are loaded with abrasive dust (clinker, metallic oxides, sand…)

What motor power choose to drive the fan?

A fast calculation gives :

Power absorbed by the fan :

Pabs.  = Q x H / (100 x η),


  • Pabs in kW
  • Q in m³/s
  • H in daPa
  • The efficiency of the fan ρ = 0.75 as middle value.


To this value a factor of 15% should be add, then we choose the first standard power motor higher than the calculated value.

How to Calculate the loss of a circuit?

The pressure loss of a circuit is the addition of the pressure loss of each device in the circuit and all the obstacles met by the air.

Devices & equipment: the value of the pressure loss should be given by the supplier/manufacturer (ex: filter, heat exchanger, scrubber, recovery boiler…)

Obstacles: elbows, bifurcation, reduction, enlargement of the pipe section are brakes to the air move, represented by a pressure drop expressed in Pa, mmH2O, mbar, etc.


-∆p is the pressure drop in daPa

-v  is the speed of the air in m/s, with v = Q/S (Q is the flow in m³/s and S the section of the pipe in m²)

-ρ  is the density of the air in kg/m³,

We have:

∆p  = K x v² x ρ / 20, K, is the factor of the pressure drop of the considered item (ex: elbow K=0.1 to 0.5 according the design)

Energy saving in the use of centrifugal fans

How to calculate the flow of an industrial fan?

For the industrial process, the flow value to be processed is generally subsequent to a calculation, for example, the gas volume from combustion, the cooling air quantity for dilution, the necessary speed air for avoiding any dust deposit on the side walls… in the case of building ventilation, according the application, it’s the number of air renewal per hour multiplied by the volume of the building giving the necessary flow.



How to Select an Industrial fan?

The user should be able to give at least the following data:


  • The flow
  • The pressure drop of the system
  • The air temperature to be processed

This information will allow the supplier to choose in the range product the fan whose flow/pressure curve crosses by the wished point “flow/pressure drop”.

Numerous other parameters will help to refine the selection, for example:

  • Gas composition, is different than air
  • Type of fan function: combustion air, exhaust, fluidization, building ventilation…
  • Particularity of the gas: abrasion risk, corrosion, explosion risk…
  • Requested rotational speed and/or the noise level allowance.
  • etc…
What type of industrial fans choose?

An axial fan is recommended for high flow comparing the pressure loss.

In opposite, we will use centrifugal fan when the pressure loss is quite important in regard to flow.

Different transmissions modes of the power electrical motor to the fan exist.

  • Impeller directly mounted on the motor shaft (arrangement 4)
  • Impeller mounted on a shaft and house bearings, the transmission is done by belt between the motor and the fan (arrangement 9 and 12)
  • Impeller mounted on a shaft and bearings,  the transmission is done via a semi-elastic coupling between the motor and fan shaft (arrangement 8)

In the case of a centrifugal fan, it is also possible to choose the orientation of the outlet duct according the position of the pipe. These orientations are standardized according the rotational direction (LG or RD) and the radius between the outlet axis in regards to the vertical (0°, 45°, 90°…)