Construction features in conformity with the 2014/34/EU Directive (ATEX)

centrifugal fans, Series, to be used for extraction or compression of combustible gases, such as biological or natural gas, have been designed in order to fall within the Equipment-Group II as defined by the 2014/34/EU Directive, Category 2 both for the surrounding area conditions and for the internals of the machine. Their main construction features are the following:

• aluminium casted casing, impeller made of spark proof aluminium alloy with caulked vanes, bearings housing made in cast iron and with aluminium casted caps, shaft in carbon steel.
• casing impregnated with Loctite.
• casing halves sealed.
• shaft sealing by a pair of special double-lip seals whose lubrication is provided by an automatic lubricator..

The centrifugal fans are generally coupled to the electric motor via belt drive and the safety drive guard is made of spark-free material. We can also offer machines coupled to the electric motor via flexible shaft coupling and centrifugal fans manufactured in the so-called “CLOSE COUPLED” version – i.e. a flange mounted electric motor is bolted to the fan casing and the impeller, which is dynamically balanced, is fitted directly onto the motor shaft extension.

If the area surrounding the equipment is classified as Zone 1, the electric motors are flameproof, type of protection “d”, with specific marking Ex II 2 G, additional marking Ex-d IIB T3. If the area surrounding the equipment is classified as Zone 2, where, for the Group II, Category 3 equipment are accepted, the machine could be equipped with the type of protection “n” non-sparking motor, with specific marking Ex II 3 G, additional marking Ex-nA II T3. For particular duties and/or in function of the gas composition, fans with special construction features could be proposed; for example with the aluminium casted parts treated with anodic oxidation and the blades of the impeller in stainless steel; and it is also possible to fit the pair of double-lip seals on the shaft so that they are suitable for a barrier fluid in between.

centrifugal fans, series, can also be supplied for intake or compression of ambient air. In this case, their construction is simplified. For the air-handling version too, it’s available the execution for Zones 1 and 2, 21 and 22 of the 2014/34/EU ATEX European Directive

Advantages

The rotating parts are not in contact with the casing during rotation. There is therefore no friction during operation and thus no internal lubrication is necessary. The gas moving through the machine remains uncontaminated and completely oil-free.

The other main advantages of using the centrifugal fans are:

• easy installation.
• low noise level.
• no vibration.
• pulsation free gas flow and no surge, minimal maintenance.

Typical supply components

To prevent dust or other impurities from entering the machine, and in any case as a protection against accidental suction of any solid body, it must always be mounted, at the suction of the compressor, a filter of a large size for the expected flow rate and with design characteristics appropriate to the ambient environment and the particle size of potentially present dust or impurities. During compression, the air heat up considerably. In the case where, depending on the use, the air has to be cooled, it is installed at the delivery of the compressor a tube beam cooler, with a large exchange surface and minimum loss of load, suitable to reduce the compressed air temperature to even just a few degrees above the available water temperature.