reitz general

Zuverlässigkeitskonzept_Hydro_BLA4_1 1

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Fans in the cement industry

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Topics1. Brief portrait of Konrad Reitz Ventilatoren GmbH & Co. KG

2. Design of fans

2.1 Volume flow and total pressure difference

2.2 The influence of density and temperature

2.3 Consideration of humidity

2.4 Consideration of installation or operational altitude

2.5 The interaction of fan and plant system

2.6 Lay-out design of fans

3. Fans in practice

3.1 Type overview

3.2 Cordier diagram

3.3 Structural design of impellers and inlet variants

4. Conveyance of solid matter with radial fans in the cement industry

4.1 Wear and sticking material on radial fans

4.2 Problem areas on impeller

4.3 Design features of fans for material transport


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Topics5. Vibrations on fans

5.1 Mechanical vibrations

5.2 Aerodynamic vibrations

5.3 Vibrations caused by variable speed operation

5.4 Reduction of vibrations - measures

6. Modernisation of existing fans in the cement industry

6.1 Factors that necessitate alterations

6.2 Requirements and effects

6.3 Examination of existing fans

6.4 Options to modifications

7. Fans working in the cement industry

7.1 Prehater fan

7.2 Raw mill fan

7.3 Separator fan

7.4 Primary air fan

7.5 Clinker cooler fan

7.6 Filter fan

7.7 Air slide fan

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Flow sheet production of cement


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2. Design of fans

2.1 Volume flow and total pressure difference

• Ideal gas rule

• p = System pressure

• V = Volume flow

• m = Mass flow

• R = Gas constant

• T = Absolute system temperature

� ρ = Density of flow medium

• Total pressure inlet

• Total pressure discharge

p * V = m * R * T

V = m * R * T / p p = m * R * T / V

p1 = p – pt1

p2 = p + pt2

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• Density with results in

equals

• Temperature• T0 = Absolute temperature = 273,15 K

• t= Temperature inlet or discharge

• Density inlet

• Density discharge

• pt1 = Total pressure inlet of fan

• pt2 = Total pressure discharge of fan

2. Design of fans2.2 Influence of density and temperature

ρ = m / V

ρ = p / R * Tp = m * R * T / V

ρ1 = (p-pt1) / R * T

ρ2 = (p+pt2) / R * T

T = T0 + t


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2. Design of fans2.3 Consideration of humidity

• relative humidity

• ϕ = relative humidity

• pD = saturation vapour pressure of dew point

• pStr = saturation vapour pressure of dry air temperature

Gas constant of humid air

• Rf = Gas constant humid gas

• Ri = Gas constant dry air in standard conditions 287 J kg-1 K-1

• RD = Gas constant of water vapour in standard cond. 461 J kg-1 K-

1

• pD = saturation vapour pressure of dew point

• p0 = atmospheric pressure

Reduced formula of Rf

ϕ = pD / pStr

Rf = Ri / 1-(1-(Ri / RD) * pD / p0)

Rf = 287 / 1-0,377* ϕ * pStr / p0)

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2. Design of fans2.4 Consideration of installation or operational altitude

Atmospheric pressure• Atmospheric pressure p0n in standard conditions 273,15 K (0 °C) for

air,

• 0 m amsl

• p0n = 10132,5 daPa

• Density of air in standard conditions (dry air) at 273,15 K (0 °C),

• ρLn = 1,293 kg m-3.

• Valid for the troposphere h <= 11 km installation height, that is to say

the temperature falls in accordance to height ~15 °C to –56 °C

Boltzmann barometric equation

• ph = atmospheric pressure of installation height [ daPa ]

• p0n = atmospheric pressure in standard conditions at 273,15 K and 0

m amsl for air,

• H = installation height [ m ]

• T0 = absolute temperature [ 273,15 K ]

• t = system temperature [ °C ]

ph = p0n * [1- (0,0065 * H) / (T0 + t ) ]5,256


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2. Design of fans2.5 The interaction of fan and plant system

∆pt/Pw

∆ptI

∆ptII

PwI

PwII

NP

BP/OP

VV1 I V1 II

∆pt

PW

• The interface point of the fan characteristic curve and the plant characteristic curve is the actual operating point OP

• The nominal point NP is the point of optimal range of efficiency.

• The plant characteristic curve follows a quadratic equation p = c * V2

• As the fan can operate on any point of its characteristic curvedepending on the plant resistance, the actual working point in theplant is called the operating point OP.

• Should the plant resistance be lower than calculated,

fort example in new plants or when the safetyresistance is calculated too high, there will bea stronger volume flow V1II at the operating point OP.

• As a result the mounted motor will be

overloaded to PWII and will be damaged.

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• Pressure variations of fans

• Pressure operation

� ∆pt2 = total pressure increase discharge

• pst2= static pressure discharge

• Pdy2=dynamic pressure discharge

• Vacuum operation

� ∆pt1 = total pressure increase inlet

• pst1= static pressure inlet (-)

• Pdy1=dynamic pressure inlet

• Mixed operation

2. Design of fans2.6 Lay-out design of fans

�pt2

V = V =

0 1

0 1� �

pd2

pst2

∆ ∆pt = pt2

pd1pst1

p ; 0 0ρ

pd2

V0

0�

V ; pst ; pd

1 1

1 1

�

Anlagenwiderstand /plant resistance

pd2

∆ ∆pt = pt1pt1

pd1

pst1

p ; 0 0ρ

pstpd

2

2

pstpd

1

1

pd2

pst2

∆pt pt2

pd1

pt1pst1

p ; 0 0ρ

∆pt2 = pst2 + pdy2

∆pt1 = pst1 + pdy2 - pdy1

∆pt = pst2 +pst1 + pdy2 - pdy1


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Structural design MXE

directly driven by the motor shaft on which the impeller is mounted

Structural design KXE (overhung design)

Power transmission from motor shaft to fan shaft by flexible

coupling, the fan shaft runs in two antifriction bearings

Structural design RGE

Power transmission from motor shaft to fan shaft by V-belt,the fan shaft runs in two antifriction bearings

3. Fans in practice3.1 Type overview

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Strucural design MSE directly driven by the motor shaft on

which the impeller is mounted, hinged drive unit

Structural design, KBA, KXZ (SISW, DIDW)

Power transmission from motor shaft to fan shaft by flexible coupling, the fan shaft runs in two antifriction bearings

mounted on concrete foundation

Structural design RBEPower transmission from motor shaft to fan shaft by V-belt,the fan shaft runs in two antifriction bearings,

mounted on concrete foundation

3. Fans in practice3.1 Type overview, further designs


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3. Fans in practice3.2 Cordier diagramm, characteristic field

Aerodynamic model rules

The aerodynamic characteristic functions (model rules) are to be differentiated by the type of analysis. It differs in its correspondence to the types: type-related

and not-to-type related analysis. For the type-related analysis the following rule

applies to the complete range of characteristic curve of a fan: (λλλλi, ψψψψ, ηηηηi, δδδδ,

σσσσ) = f (ϕϕϕϕ, Re)

The figure shows the non-dimensional characteristic field of a radial fan with

high efficiency in correspondence to the latest relation of a defined Re-number-

range.

Cordierdiagramm

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3. Fans in practice3.3 Structural design of impellers and inlet variants

• Impeller design

The impeller design provides for an ideal layout of theimpellers in dependence on the impeller geometry. The fieldsthat influence the impeller design are:

- Fluid technology

- Acoustics

- Manufactering techniques

- Strength of material

- Costs

- and operational needs


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3. Fans in practice3.3 Structural design of impellers and inlet variants

Bauart Beschreibung Bild / Skizze

DN1 Normlaufrad mit Düse nur für den Kennzahlbereich AKZ1.0 und AKZ1.1. Bei anderen Kennzahlbereichen muß das Rad modifiziert werden.

DN2 DN3

Laufrad in schmaler Ausführung und mit vergrößertem Außendurchmesser. Für dynamisch beanspruchte Räder. Einsatz für alle Kennzahlenbereiche möglich.

DZ Zylindrisches Laufrad Einsatz nur für den Kennzahlbereich AKZ1.0. Einsatzbereich siehe Tabelle �

ZD1/ZD2 ZD3

Laufräder DN1 bis DN3 in ein- bzw. zweiflutiger Ausführung mit durchgehender Welle. Einsatzbereich für die Ausführungskennzahl AKZ1.0 und AKZ1.1.

TR Transportlaufräder offene Ausführung (ohne Deckscheibe). Einsatz für direkte Förderung. Transporträder müssen auftragsbezogen den jeweiligen Anwendungen entsprechend modifiziert werden wie z.B.:

a) mit oder ohne Transportkonus

b) mit oder ohne modifizierte Einströmvarianten

Transport-konus

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3. Fans in practice3.3 Structural design of impellers and inlet variants, continuation

• Inlet variants

The inlet configurations that depend on the operational conditionsresult in the different inlet variants


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3. Fans in practice3.3 Structural design of impellers and inlet variants, continuation

• Type of blades

In general, radial fans are classified bytheir

type of blade:

- backward curved blades orbackward inclined straightblades

- straight blades radial tipped

- foreward curved blades

There is a variety of blade designs in order to

meet the different operational requirements in

practice.

The types of blades are subdivided in series of

blade design.

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4. Conveyance of solid matterwith radial fans

4.1 Wear and sticking material on radial fansIn the case of fans that handle air with certain dust content, the degree of dust charge or the

mixing ratio µµµµ is of decisive importance. The degree of dust charge µµµµ is the ratio of the mass

flow of solid to the mass flow of the handled air. With a mixing ratio of µµµµ ≤≤≤≤ 0.5 we speak of hydraulic transport, in the case of which the particle floats in the current of air; basically, this

is what should be striven for. In the case of closed impeller, the limit of the handling capacity

is reached with µµµµ=0.5. For the correct dimensioning of the impeller, knowledge of the dust that is to be handled is an important precondition, such as the dust type, composition, grain

size distribution and its abrasive, adhesive, sticking or hygroscopic features.Tendency of the impellers to build up sticking material or to wear, depending on the blade

angle ß1 and ß2 or type of blades


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4.1 Wear and sticking material, continuationWear and building-up of sticking material in the case of fans

The tendency towards building-up of sticking material or to wear of the individual blade

form can be shown by means of the different impeller designs, particularly with the different blade angles ß1 and ß2.

Tendency of the impellers to build up sticking material or to wear, depending on the blade

angle ß1 and ß2 or type of blades

0 20 40 60 80 100 120angle ß2

15 bis 35° 30 bis 90° 30 bis 90°angle ß1

backward curved blade

increasing built-up of stickingmaterial underside of the blade

backward inclined straight blade

with optimum angle of inclinationself-cleaning to some extent

foreward curved blade

increasing wear on the rear side ofthe blade

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4.2 Problem areas on impellerProblem zones on the impeller that tend to build up sticking materialSticking material occurs on the underside of the blade and to some extent, in the area of the

impeller inlet nozzle. Fig. 2 shows the possibility on the underside of the blade with the zones

inner – middle – outer; Fig. 3 with sticking material across the entire underside of the blade.

Fig. 4 shows the sticking material in the area of the impeller inlet nozzle .

Fig. 2 Sticking material

in partial zones

Fig.3 Sticking material

on the underside of the

blade

Fig. 4 Sticking material in

the nozzle area


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4.2 Problem areas on impeller, representations

Sticking material on the

hub side and on the

underside of the blade

Sticking material on

the underside of the

blade

Sticking

material on the

impeller and in

the nozzle area

Sticking material on

the inlet guide vane

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4.3 Design features of fans for material transportPhysical factors can be influenced by the shaping of the impeller (impeller configuration and type of blades). Important design features that can be controlled, the shroud angle and the

blade angle, are depicted in Figures 5 and 6. The angle of repose is depicted in Fig. 7. The

angle of repose ßS is a measure of the flowing ability of a granular material. This can also

be viewed as the friction angle of the material used. Knowledge of these values is greatly

important for the selection of the impeller, since the angle of repose ßS should be less than the blade angle ß.

Fig. 5 blade angle Fig. 6 shroud angle Fig. 7 angle of the

respective material


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4.3 Design features of fans for material transport,

continuation

Figures 8 to 9 show impeller construction types that depict the inclination to build up sticking

of the dust in the impeller, depending on the shroud angle [ ϕ ] and the nozzle radius [ ρ ].

Fig. 8 Broad impeller with

tendency to build up high D1/D2

strong sticking material

Fig. 9 Impeller with a D1/D2>0,6<0,7 with smallshroud angle

tendency to build up sticking

material present

Fig. 10 Impeller with aD1/D2<0,6 and a pronouncedshroud angle, and small nozzle

radius, low tendency to build

up sticking material

bad better good

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4. Conveynance of solid matterwith radial fans

4.3 Design features of fans for material transportAn optimal anti-sticking design is illustrated in Figures 11 and 12. Often, however, the local

installation dimensions are not conducive for such a design. In addition, the rotational

speeds sometimes have to be reduced to such an extent that the prices become unacceptable. Therefore, it is advisable to discuss all the advantages and disadvantages in

advance .

Caution ! If the impeller tends to build up sticking material, the use of inlet guide vanes is

not recommended. The impeller then has an even higher inclination to build up sticking

material on the undersides of the blades and at the impeller inlet. Particular attention must be paid to the respective operating points on the fan characteristic curve and the damper

valve position. Intense damping must be avoided without fail.

Fig.11 Optimum impeller

configuration matched to the be-

havior of the dust type

Fig. 12 Optimum blade angle βmatched to the angle of respons βSof the dust type


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5. Vibrations on fans5.1 Mechanical vibrations

Fans are besides pumps the turbo-machines that are mainly employed in industry. They

have a broad operative range and are often applied for ventilation purposes in a complex

process. Characteristic features of fans are a high variety of structural designs and a broad diversity of size. They are basically defined by the volume flow that is to be generated and

the total pressure increase.

When working with fans we are repeatedly confronted with the problem of vibration. The

vibrations are, however, often difficult to classify due to the variant diversity and the different structural designs as well as the various appliances. Nonetheless, an exact analysis of the

vibrations is the decisive factor for their elimination. We distinguish two types of vibrations,

these are

mechanical vibrations

aerodynamic vibrations.

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Mechanical vibrations are most frequently caused by out-of-balances at the rotating parts. Unbalances result from uneven wear and / or sticking material at the impeller blades.

Alignment errors of shafting produce mechanical vibrations as well; they are visible in the

frequency spectrum as 2. and 3. harmonic of the speed. Other mechanical vibrations, that

often occur, originate from alignment results and resonance effects of fan parts in dependence

of their arrangement and installation. Furthermore, damages to the antifriction bearings also excite mechanical vibrations in the form of shock pulses.

Representation of design parameter that influence vibration

5. Vibrations on fans5.1 Mechanical vibrations, continuation

no. event effecting part 1 out-of-balance forces • unbalance impeller

• unbalance – keyway, coupling

• belt flutter

2 impeller rigidity • natural resonance

3 running and positional tolerance of the impeller

• in axial (wobble) and radial (vertical impacts) direction

4 alignment errors • motor, coupling, bearing housing, belt pulley

5 rigidities • bearing rigidity

• rigidity of the sub-structure (base frame, elastic mounting, etc.)

6 fit tolerance • fit clearance bearing

• fit clearance hub / shaft (eccentricity)

7 deflexion of the shaft

• f1, f2, f3 = deflexion of the shaft

observe the gyroscopic effect and the critical lateral speed

8 constitutional resonances • housing, pedestal and impeller

9 torsional vibration, pulsatory torques • excited by electrical errors of the drive motor or in the mains and the transmitting devices


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Mechanical vibrations, whatever, can be easily measured, located and analysed.

Example for mechanical vibrations

Unbalance Alignment errors at coupling

speed 17,8 Hz

1. Harmonic

35,6 Hz

2. Harmonic

Spektren Spektrum KXE063-063030 177932 3H 1K [1] 28.04.2003 16:45:39 49,883 Hz

177932 3H 1K [1]

Speed 49,8 Hz

1. Harmonic

2. Harmonic

99,6 Hz

3. Harmonic

149,4 Hz, higher than

1. Harmonic


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Example for mechanical vibrations

Mechanically detached connections (e.g. shaft-hub) anti-friction bearing damage,

e.g. inner ring

5. Harmonic and the

following

Damage frequency anti

friction bearing inner ring

fi=181 Hz

Modulation with speed

fn=16,25 Hz

2. Harmonic of the

inner ring frequency

2*fi=362 Hz



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5. Vibrations on fans5.2 Aerodynamic vibrations

Aerodynamic vibrations manifest themselves in air vibrations with pressure or flow deviations, they produce excessive noise and they may come up to strongly distinctive pumping, which could

even influence the volume flow to change its direction in the fan or in parts of the system. The

origins of aerodynamic vibrations can be very manifold. In many cases, the fan is not solely

responsible for the vibrations but they result from the interaction of plant system or of its

component parts to the fan.

We have to examine the complete plant system and not only the fan exclusively to find out how to

eliminate the undesired vibrations. We need therefore profound knowledge about the physical

processes that prevail in the system and the interactions and reciprocities of all system components. The design engineering of the plant system has to include all necessary steps to

avoid in the first place potential problems in the field of aerodynamic, acoustics, physical

properties and vibration technique as well as monitoring of the system.

The following pages show typical vibration problems that have been found in praxis and systematically explain their different symptoms and their origins and give examples.

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fig. 1.1 Outline of a ventilation system, the numbers refer to vibration phenomenon acc. to table 1.2

AK suction box

AKM vent stack

AKO system component

DF diffusor (duct piece)

DJ damper

DR inlet guide vane

KP flexible connection

LB chute

SD silencer

Table 1.21 vortex caused by stall at system components2 stationary waves in the duct work (air column vibrations)3 vortex caused by stall due to lacking chutes4 vortex caused by stall at the silencer baffles (inlet and outlet of silencer)5 + 6 vortex caused by stall at vent stack that is not optimally designed with

resulting air column vibration, stationary waves7 vortex caused by stall at the vanes of the nearly closed damper 8 air column vibrations caused by flow whirls /vortex in the dead area of the

suction boxes (areas where no flow is present) when the inlet flow is disturbed9 vortex/whirl caused by stall at the guiding blades of the inlet guide vane

when the flow is too strongly reduced 10 rotating stall at fan impeller 11 main residual frequency12 swirled stall caused by misarranged components; possible to occur

in all system areas13 vibrations due to pumping

5. Vibrations on fans5.2 Aerodynamic vibrations, continuation


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Stalls

Technical flows often vary from the ideal of controlled flow because they feature the so-called

stalls

For example, the flow does no longer stream closely to the components (the flow burbles), when it flows in the area of sharply bended surfaces or edged protruding or recessing parts

(fig. 3.1 – 3.2). Also, stalls can occur in duct or parts of it, in which the flow streams, if the flow

direction is changed considerably (e.g. in duct bend) or where strong constant or suddenly

occurring cross section alterations or obstacles (“thinks built-in”) exist (fig. 3.3).

Stalls result from the fact that so-called dead areas are formed between the wall that is no

longer in the flow due to stalls and the definitely directed duct flow. These dead areas are filled

with eddy water. Energy has to be provided for keeping up the vortex, which has to be taken

away from the flow energy of the handled gas. This leads on the one hand to a loss of effective

energy in the form of pressure loss. On the other hand, vibrations of the flow speed and the pressure in the flow field arise since the flow in the eddy water is always more or less

unsteady. These local vibrations could also excite vibrations in the complete system (as well

as in the fan).



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Examples for aerodynamic vibrations

Fig. 3.1 stall behind a protruding part

Fig. 3. 2 stall at objects in the flow stream;Kármán’sche Wirbelstrasse

Fig. 3. 3 stall at an aerofoiled wing that is set too steep


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Fig. 3.4 stalls in duct work, duct bend

Fig. 3.5 stall when the duct is considerable widend,

bad diffusorFig. 3.6 stall at obstacles

Ablösungen


Examples for aerodynamic vibrations


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Inlet guide vanes

Upstream installation of inlet guide vanes to the fan can lead to low-frequent and more often

than not comparatively broadband air vibrations, especially when the inlet guide vane strongly

reduces the volume flow. The frequencies observed have nothing in common with the rotary frequency of the fan. Frequently, the installation performance curve also deviates from the

characteristic curve of the test bench. The reason for this is a considerably disturbed inlet flow

to the fan impeller..

Stall at the guiding blades of the inlet guide vane. Under specific conditions, excessive reduction of flow by an inlet guide vane will result in a critical stall at its guiding blades, which

impede a defined vortex (fig. 3.8). The mentioned specific conditions are: unfavourable inlet

flow conditions and a small range of angle setting, when the guiding vanes are strongly to

almost closed. We can avoid the stall at the inlet guide vane by optimally designing the inlet

flow and avoiding the special critical angle setting. Preconditions for this are the ideal specific fan size definition and a secured realisation of the calculated operating point. In addition, we

have to choose a control range in the top 2/3 of the inlet guide vane position. If “0°”

corresponds to a closed damper and 90° to an open one, setting of the vanes at angles of

more than 60°should be avoided at all events.


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Fig. 3. 7 fan with inlet guide vanecharacteristic curve

Fig. 3. 8 inlet guide vane, unfavourable flowwith vortex



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DampersIt is common practice to mount dampers on top of the suction box for double inlet as well as

single inlet application with a separate upstream suction box, fig. 3.9.

The valves of the damper can be adjusted in parallel or in opposite direction depending on the

customer’s specification and the required load conditions.

Bild 3. 9 production of whirl by spin forwardarrangement of a damper at a suction boxwith valves adjusted in parallel line

Bild 3. 10 asymmetric inlet flow from distribution

duct

SKA

V/2 V/2

V

KP1

DJ1

AKA B


Ventilator

Stellklappen

Ansaugkasten

Drallerzeugungdurch Mitdrall

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Vent stackAn unfavourable design of the branch point leads to stalls with swirls when the flow enters the

vent stack (fig. 3.11). A “smooth” design of the branching, possibly with chutes (fig. 3.12) will

guarantee a constant flow that is low in vibration.

Fig 3.11 flow stall on vent stack entering,

WH = vortex height, WB = vortex widthFig. 3.12 favourable design of duct at branch pointof vent stack: on the left an angle of 30°to 60°With chutes (LB) to prevent stall vortexon the right alternative design

WH

WB

LB

LB

AKM

AKM

LB



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5. Vibrations on fans5.3 Vibrations caused by variable speed operation

The operation of fans by drive motors with variable speed operation may result in additional vibration excitations by the variable speed control. There are primarily upper harmonic waves that occur from the rotating field (e.g.

1., 5., 7., 11. and 13. harmonic for a 6-pulse converter connection), the rotor current generate the so-called rotor remanence field. The difference of the stator current harmonic and the feed current harmonic results in an alternating torque which is zero-point transient in timely regard. This alternating torque is also called oscillating torque which has a synchronous moment impact on the stator lamination steel. The resulting forces are transmitted to the motor housing and the foundation (pedestal). The height of the oscillating torques amplitudes

depends on varying types of the variable speed control (current (I-) or tension (U-) controlled). Hence, the excitability of systems varies in dependence of the variable speed drive employed. It is most likely that the critical torsional speed of the shafting is excited (the shafting consists of impeller, coupling and motor stator). In addition, the variable speed control operation can excite natural frequencies of fan parts like housing or impeller and even the natural frequency of anti-vibration mounts could be animated in case the fan is mounted on

vibration damping elements.

Primary air fan with variable speed drive

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5. Vibrations on fans

5.4 Reduction of vibrations - measures

Mechanical vibrationsIn principle, regular and expert servicing and maintenance considerably contribute to a high operational quality and reliability of fans. Even the first stage of system planning can considerably influence the

thorough and exact design of the necessary equipment. Fans have to be laid out and designed meeting the

individual requirements and specifications in order to achieve the maximum operational reliability in

practice. This is particularly important for fans that have to transport abrasive or sticking material within the

handled gas. The fan manufacturer has hence necessarily to be informed about all relevant parameter to

choose the correct fan. The most important parameter besides volume flow and pressure are temperature,

handled gas, humidity, inlet flow conditions and the use of dampers, if foreseen.

List of measures event measure

out-of balances caused by sticking material or wear

choose appropriate impeller type and material in the planning stage

servicing of fans in operation at regular intervals, remove sticking material, timely repair of damaged parts

take measures for reduction of stickings and/or wear; e.g. fan after separator

vibrations due to alignment errors check of coupling alignment, align if necessary, timely replace worn coupling parts

vibrations due to damage of shafting replace damaged parts


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Aerodynamic vibrationsThe reasons for aerodynamic vibrations in systems can be manifold. It is recommended to pay particular attention to the design of the duct work conduit and the system’s process when planning a new system or

remodelling an existing one. A basic principle is: the better the system components are designed in

consideration of the flow guidance, the smaller is the probability of exciting aerodynamic vibrations.

List of measures


5.4 Reduction of vibrations - measures , continuation

event measure

aerodynamic vibrations cause analysis, change the duct work, if necessary, by built-ins like chutes etc., avoid discontinuous duct parts

consider the effects of changes of individual system parts on other, depending parts and the fans concerned (change in the charateristic curves, operational point of fan e.g. to the left of the ideal design point)

additional dampers in the duct work, if possible, to change the system characteristic curve and adapt the curve of the damper

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Vibrations caused by variable speed controlAgain, all relevant operational parameter have to be made known to the fan manufacturer to the avoid vibrations that are caused by the variable speed control operation. The said parameter are speed range

and possible speed changes per time unit, type of variable speed control (current (I-) or tension (U-)

controlled) and the installation condition of the fan.

List of measures


5.4 Reduction of vibrations - measures , continuation

event measure

vibrations caused by variable speed control tune the unit consisting of fan, motor and variable speed control to a resonance-free operation

choose suitable machine parts like coupling, shaft and impeller type

choose proper way of vibration-absorbing fan installation: foundation, suitable arrangement of anti-vibration mount


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6. Modernisation of existing fansin the cement industry

6.1 Factors that necessitate alterationsThe motivation to modernise fans in existing systems can have

numerous reasons.

In the first place, these can be demands of economic nature.

On the other hand, the operating companies of plant systems

more and more focus on environmental compatibility and ecology. The most important factors for the modernisation of

system parts and fans are the reliability of a system and its

availability, which greatly influence its profitability.

At first, the requirements have to be defined that are necessary to achieve acertain objective.

The following parameter can influence the decision on modernisation of fans.1. change of operational parameter, e.g. by improving the production processes

2. installation of additional filter,

3. installation of big heat exchanger or rotary kilns

4. increase of capacity of the raw mill or separator,

5. extension and modernisation of the clinker cooler,

6. expansion of storage capacities for finished products

7. change in the system plant’s lay-out

8. exchange of used-up fans or parts of them

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6.2 Requirements and effects

6.2 Requirements and effects When the list of parameter is drawn

up, we have to consider how to

achieve the required aims. Based on

the parameter list, the requirements and the actions to achieve them are

listed below.

ref no. demand action / requirement to be achieved by

1. adaptation of volume flow and pressure increase

exchange of impeller, observe motor capacity

exchange of fan

2. adaptation of pressure increase exchange of impeller, observe motor capacity,

exchange of fan,

3. adaptation of flow volume and pressure increase, alteration of working temperature


exchange of fan,

other measures

4. adaptation of flow volume and pressure increase, modified residual dust content in the handled gas

exchange of impeller, observe motor capacity,

echange of fan

5. adaptation of flow volume and pressure increase, perhaps change of working temperature

exchange of impeller

exchange of fan

6. additional duct work, adaptation of pressure increase

additional fans

7. adaptation of all operating parameter


exchange of fan

8. worn or used-up fan components like impeller, shaft, bearings, coupling etc.

exchange the defective parts, check remaining components for suitability and use technical innovations if possible, include all fan components in the tests if fan parts have been exchanged


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6.3 Examination of existing fans

6.3 Examination of existing fansWe have to determine all practicable improvements and

modifications for the existing fan when the new

operational parameters for the fan operation are defined.

Proceed as follows:

Ascertain the current performance data like1.1 volume flow

1.2 pressure increase,

1.3 working temperature,

1.4 max. working temperature,

1.5 speed,

1.6 max. speed

from the technical documentation or nameplate. If necessary,

carry out measurements to determine the data.

Measuring in the dust system

RADIAL – VENTILATOR / Radial fan

Typ Type

Fabr. - Nr. / Baujahr Serial – No. / year of construction

Kom. - Nr. com. – No.

Ventilatordaten bei einer Dichte von / Fan dates at a density of ρρρρ1 = 1,2 kg/m³

Eintrittstemperatur Inlet temperature υ1 °C

Volumenstrom Volume flow V1 m³/min

Totaldruckerhöhung Total pressure increase ∆pt2 daPa

Totaldruckerhöhung Total pressure increase ∆pt1 daPa

Wellenleistung Shaft rating PW kW

Drehzahl Speed n 1/min

Betriebstemperatur Operating temperature υ °C

Nameplate of fan

46

Ascertain the maximum loads that have to be observed for the mechanical design

of the fan; e.g. for the

- impeller material as to strength, temperature resistance etc.

- bearing sizes and design, e.g. limiting speed, grease or oil lubrication, etc.- critical lateral and critical torsional speeds,

- load on coupling or belt drive,

- housing dimensions,

- design of inlet and discharge,

- FEM analysis of the impeller,

- natural frequency of the impeller,

- natural frequency of the type of mounting,

e.g. rigid or flexible mounting

- structural details of housing,

pedestal and base frame.

Ventilation performance test

fan data sheet


6.3 Examination of existing fans, continuation


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6.4 Options of modifications

6.4 Options of modifications1. replace the exisiting impeller by a new one that offers suitable blade

form, impeller design and inlet nozzle

2. provide anti-wear layer at impeller and housing3. increase of speed by using variable speed operation or,

in case of V-belt drive, by modification of the transmission ratio

as long as the machine-dynamic limiting values are not exceeded,

4. replace fan components like bearings, shaft,

coupling and V-belt drive or

5. replace complete fan

In case the existing fan is modernised, compare the new technical data

with the maximum allowable data.

Wear protection repair on the

impellerWear protection on the inlet

box and inlet nozzle

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7. Fans working in thecement industry

7.1 Preheater fan

Double inlet fan with silencer, resilientlymounted

KZB125-1120010-00


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7.2 Raw mill fan

Wear protected impeller

KAE125-500010-00

Arrangement of fan for raw mill

KAE125-500010-00

V1 = 5000 m3 min-1 ∆pt2 = 1250 daPa

50


7.3 Separator fans

Impeller SFV 6.1.4 wear protectedSeparator fan with damper and suction

box

KXA080-224010-00

V1 = 2240 m3 min-1 ∆pt2 = 800 daPa


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7.4 Primary air fan

Primary air fan KXE355-080030-00

V1 = 800 m3 min-1, ∆pt2 = 3550 daPa

Primary air fan KXE315-016030-00

V1 = 160 m3 min-1, ∆pt2 = 3150 daPa

52


7.5 Clinker cooler fans

Arrangement of fan with suction

box, silencer and inlet guide vane

Fan with suction box and inlet guide

vane

KXE050-056030-00

V1 = 560 m3 min-1, ∆pt2 = 500 daPa


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7.6 Filter fans

Filter fan KZB100-1600010-00

V1 = 16000 m3 min-1 ∆pt2 = 1000 daPa

High efficency double inlet impeller

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7.7 Air slide fan

Fan with inlet air filter

MXE080-002830-00

V1 = 28 m3 min-1, ∆pt2 = 800 daPa


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End of presentation

Thank you for your kind attention

reitz general

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