Centrifugal fan

What are centrifugal fans?

Radial fans or centrifugal fans are a type of fan that uses centrifugal force to create a pressure increase and a volume flow.
This type consists of a fan wheel that rotates in a snail-shaped cover.
The flow enters the fan through an inlet placed axially with the fan wheel shaft and motor, and is then thrown out radially with the help of the force from the fan wheel.
Unlike axial fans, the motor is not in the volume flow of radial fans.

To change the performance and characteristics of centrifugal fans, different designs are used on the fan wheel.

The strength of the centrifugal fan is its versatility. A radial fan can be designed to transport a variety of volume flows at a wide range of pressures.

At higher flows and relatively low pressures, an axial fan may be a better option.

Centrifugal fans are available in single and double suction versions.
Single suction radial fans have the inlet on one side and drive on the other.
Double-suction radial fans have inlets on both sides, which enables larger flows into the fan, with the disadvantage that the drive ends up to a certain extent in the volume flow.
Centrifugal fans can be connected in series in two or more stages, this gives acceptable sound levels even at very high pressures.

A centrifugal fan usually has a higher overall efficiency than an axial fan.

The flow of centrifugal fans is mainly regulated with speed control, it is also not unusual for centrifugal fans to run towards a fixed operating point.
As an alternative, the flow can also be regulated with dampers that have variable opening. A third option is through a guide rail device that creates a co-rotation of the volume flow before the fan.

To choose the right centrifugal fan, you should start from the area of ​​use, how the fan is to be controlled and whether there are any special requirements.
Contact us at FläktComp for support.

Where are centrifugal fans used?

A centrifugal fan is a versatile fan that is suitable in many different systems and can, for example, be used as process fans in industry or as a material conveyor in sawmills.
Centrifugal fans can be adapted to most operating situations, everything from corrosive gases, high pressures, high temperatures, gas mixtures to material transport fans.

Depending on requirements, the design of the centrifugal fans is completely adapted to the customer’s needs.

Correctly dimensioned, a centrifugal fan provides problem-free operation and high performance over many years.

Volume flow:	100 – 300.000 m3/h
Pressure:	100 – 50,000 Pa
Inlet size:	from 63 to 2500 mm
Casing thickness:	from 1,5 to 20 mm
Models:	RNZ (Low Pressure), LRZ (Low Pressure), PRZ (Medium Pressure), MRZ (Medium Pressure), HRZ (High Pressure), SRZ (Ultra High Pressure)
Motor size:	0,1 kW to 800 kW (Motor frame 63 till 450)
Drive:	Coupling, belt drive or direct drive
Outlet:	RD/LD 0 - 315 acc. Eurovent
Casing design:	Single-, double-suction or with split hood.
Coating:	Primer, finish, hot-dip galvanizing or as desired.
Material:
Impeller	Steel (carbon steel, stainless, acid-proof, Duplex, etc.), corrosion-resistant cast aluminum
Fan casing	Steel, aluminium, special alloys
Specia ldesign:	Sparkproof, high temperature, gastight, decontaminable, shockproof, for material transport or according to special requirements
Standard accessories:	Shaped inlet, Fire damper, Safety net, Mounting feet, Vibration damper, Jet cover, Flexible spigots, Counter flange, Silencer, Variable inlet vanes, Back damper, Insulation, Sound enclosures, monitoring sensors, etc.

Design

The range of our radial fans is adapted to meet most combinations of volume flow and pressure using direct-driven fans.
As the fan range is based on a modular system, the majority of fans can be manufactured from standard components.
In addition to standard fans, we also manufacture a large number of special designs, according to your needs.

Below is an overview of our standard range of radial fans.

Design 1 (3d and 6d)

It is often beneficial to aim for a direct drive fan. It is more compact, has fewer parts and is in most cases cheaper than other designs.
We offer 3 different designs with direct drive. Designs 3d and 6d differ from design 1 in that they are pivotable and that the impeller can be removed from both sides.
A flange-mounted motor makes the 6d design lighter and more compact.

Design 2

At higher speeds that cannot be achieved with a direct drive motor is required, or if there are other installation-specific requirements, a fan with belt drive is used.
Assembly of the engine takes place in a number of different ways.

For design 2, the fan and motor are mounted on a common base.
Design 2a is the same construction but with a rotatable casing and a fan wheel that can be dismantled on both sides.
Design 2b has the engine mounted on the side of the pedestal to achieve a more compact design.
Design 2c is for small engines.
Here the motor is mounted inside the pedestal with an external junction box. Although this design is more difficult to service, it is the most compact belt drive and less expensive than the other belt drive options.

Design 4

Design 4 is a complete unit where the motor with belt drive is mounted directly on the fan cover. When a compact design is needed, design 4 offers an interesting alternative. However, relatively extensive reinforcements of the fan cover are often required.

Design 5

Today, it is relatively common for fans to be equipped with an elastic coupling. It can e.g. be in applications with high temperatures.
An elastic coupling also makes it possible to dampen and protect the motor in tougher applications that require high starting torques or variable torques such as in e.g. material transport.

Impeller

As standard, our fan wheels are manufactured in steel or aluminium. Aluminum has the advantage of being light, which results in lower moments of inertia and lower starting currents.
We also have extensive experience with other materials such as e.g. various stainless and acid-resistant steels.

The impellers of the fan series have been developed modularly, which gives the advantage that a number of impellers fit the same casing. This means that if an installation needs to be changed, this can often be achieved by replacing the impeller.
This without having to replace the entire fan.

Low pressure fans RNN

This is a model series with fan wheels that have the same external dimensions, and thus fit into the RNN cover. The cover can be made with a cut-off (eg type RNZ) or without a cut-off (eg type RNN).

Technical data RNN:
Inlet size:                            180 – 2000 mm
Fan wheel diameter:                   224 – 2500 mm
Pressure: 100 – 5000 Pa
Flow: 100 – 300,000 m3/h

Impellers for the RNN series

RNZ9

This impeller wheel type with 9 backward curved blades and pressed induction nozzles has high efficiency, very good sound performance and a very stable characteristic curve.
With increasing volume flow, only a slightly increasing power is required.

RSZ10 and RSZ12

These types are similar to the type above, but have 10 or 12 backward-sloping, S-shaped blades with a steeper pitch. Which enables higher pressure and is also less affected by particles in the flow, with a slightly lower efficiency.

VPZ

The fan wheel type is designed in a classic scirocco design and fits into the same cover as the above mentioned types.
The wheel type provides the opportunity to extract relatively high performance in a small format.
However, the efficiencies compared to other RNN impellers are relatively low, where the shaft power is highly dependent on the operating point.

Low pressure fans LRZ

The LRZ models are designed to cover the need between the RNN series and the medium pressure fans PRZ/MRZ.

The LRZ fan wheels are designed with 9 backward curved fan blades.
The impeller series consists of 4 different impellers LRZ9, LRZ9A, LRZ9B and LRZ9C. Where the letters A, B and C indicate shortened blades.

The fan wheel LQZ11 is adapted for flows with a lot of particles.

The LRZ series is very suitable for use in e.g. fuel burners as they can be controlled in principle over their entire volume flow volumes without problems.

Technical data LRZ
Inlet size:                            180 – 1400 mm
Fan wheel diameter:                   280 – 2240 mm
Pressure: 800 – 8000 Pa
Flow: 100 – 200,000 m3/h

Medium pressure fans PRZ

The PRZ fan wheels are designed with 9 backward inclined fan blades.
The fan wheel series consists of 4 different fan wheels PRZ9, PRZ9A, PRZ9B and PRZ9C. Where the letters A, B and C indicate shortened blades.

The series is a classic medium pressure fan that achieves an efficiency of up to 85%.
In this assortment, the fan wheel PQZ11 can be used for material transport.

Technical data PRZ
Inlet size:                            125 – 1400 mm
Fan wheel diameter:                   250 – 3000 mm
Pressure: 1,600 – 10,000 Pa
Flow: 1000 – 250,000 m3/h

Medium pressure fans MRZ

The MRZ series can handle a slightly higher pressure than the PRZ series.

There are a total of 6 fan wheels, MRZ9, MRZ9A, MRZ9B, MRZ9C, MRZ9D, MRZ9E. Where the letters A, B and C indicate shortened blades.
In addition, a particle (dust) wheel with the designation MQZ11 is offered.

Technical data MRZ
Inlet size:                            90 – 560 mm
Fan wheel diameter:                   280 – 1800 mm
Pressure: 2,000 – 15,000 Pa
Flow: 500 – 100,000 m3/h

High pressure fans HRZ

The HRZ high-pressure fan with 10 backward-sloping shaped blades can reach an efficiency of up to 81%.
The fan wheel series consists of 7 different impellers: HRZ10, HRZ10A, HRZ10B, HRZ10C, HRZ10D, HRZ10E, HRZ10F. Where the letters A, B, C, etc. indicate shortened blades.

Also for the HRZ series there is a particle (dust) wheel with the designation HQZ11.

Technical data HRZ
Inlet size:                            63 – 400 mm
Fan wheel diameter:                   280 – 1800 mm
Pressure: 2,500 – 25,000 Pa
Flow: 500 – 50,000 m3/h

(Ultra)High pressure fans SRZ

For ultra-high pressures and small volume flows, we use the types SRZ12, SRZ12A, SRZ12B, SRZ12C, SRZ12D and the particle (dust) wheel SQZ12.
Where the letters A, B, C, etc. indicate shortened blades.

Technical data SRZ
Inlet Size:                            63 – 355mm
Fan wheel diameter:                   400 – 2240 mm
Pressure: 5,000 – 30,000 Pa
Flow: 100 – 50,000 m3/h

Other radial fans / Special fans

Particle (Dust) fans

We offer fan wheels that can handle particles/material transport in all our radial fan series.
Their designations are RSZ, LQZ, PQZ, MQZ, HQZ and SQZ.

Freely rotating impellers RLN

RLN is the designation for RNN fan wheels that are used without a cover, e.g. for air conditioning boxes or filter boxes. These fan wheels achieve a high degree of efficiency in a compact design.
The fan wheel range goes from 6 blades to 12 blades with the type names RLN6, RLN8, RLN10 and RLN12.

Dual intake fans

All our low- and medium-pressure fans can be delivered in double-suction versions.
Normally, a protective net is then mounted in both inlet openings and that both bearings and belt drive will be in the volume flow.
This causes a pressure drop that must be taken into account.

Multistage fans

Our high pressure fans can be supplied with two or more stages to achieve reasonable noise levels even at very high pressures.