Centrifugal Pump Design

Centrifugal Pump Design

pump&) valves

Contents

1 Symbols, Units and Designations

2 Design

2.1 Pump Capacity 2.2 Pump Head 2.3 Svstem Head 2.4 ~ b e e d 2.5 Selectina the PumD Size 2.6 calculating the power Consumption 2.6.1 Pump Power lnput 2.6.2 Calculating the Drive Rating 2.7 Pump Characteristic Curve

2.8 System Characteristic (Piping Characteristic) 2.9 Operating Point 2.1 0 Parallel Operation of Centrifugal Pumps

3 Suction Characteristics

3.1 NPSH Required 3.2 NPSH Available

4 Pressure Losses

p,

4.1 Head Losses H, in Straight Pipes 4.2 head Losses H, In p~ast-c P pes 4 3 Head Losses H, lor VISCOUS Llqulds

in Straight Pipes 4.4 Head Losses H, in Valves and Fittings

5 Changing the Pump Performance

5.1 Changing the Speed 5.2 Trimming the Impellers

6 Handling Viscous Liquids

7 Typical Selection Examples

7.1 Selecting the Pump Size 7.2 Calculating the Power Consumption 7.2.1 Pump Power lnput 7.2.2 Calculating the Drive Rating 7.3 Calculating the NPSH, 7.3.1 Suction Lift from OpenfClosed Tank 7.3.2 Positive Suction Operation from OpenlCiosed

Tank 7.3.3 Positive Suction Operation from Closed Tank

at Vapour Pressure 7.4 Changing the Speed 7.5 Trimming the Impeller 7.6 Handling Viscous Liquids 7.6.1 Calcuiating the Operating Point 7.6.2 Establishing the Pump Size

Page

4 General

National and International Standards for Centrifugal Pumps Shaft Deflection Improving the NPSH Requirement impeller Types Pump Types Pump Installation Arrangements Pump Sump Configuration Suction Pipe Layout Shaft Couplings

9 Technical Data

9.1 Vapour pressure p, and Density p of Water 9.2 Vapour pressure p, of Various Liquids 9.3 Density p of Various Liquids at Atmospheric

Pressure 9.4 Extract of Main Legal Units for Centrifugal

Pumps 9.5 Conversion of British and U.S. Units 9.6 Graph for Calculating Flow Velocity v 9.7 Graph for Calcuiating Velocity Head v212g 9.8 Graph for Calculating Velocity Head

Differential A v212 g 9.9 Graph for Calculating Head Losses H, 9.10 Graph for Calcuiating Conversion Factors

fern, ~ H , W and f,,,~ for Viscous Liquids 9.1 1 Graph for Calculating Conversion Factors for

and f~~ for Viscous Liquids 9.12 Graph for Calculating Specific Speed n, - Schedule for Calculating the Operating Point

or Pump Size for Viscous Liquids

Page

22

1 Symbols, Units and Designations

A m2 Area a mm Width b2 m Impeller outlet width D mm (m) impeller diameter,

pipe diameter DN (mm) Nominal bore of pipe d mm Smallest inner diametel

2 Design

2.1 Pump Capacity The capacity Q is the external volume flow per unit of time in ms/s (I/s and m3/h are also commonly used). Balance water, leakage water etc. do not count as part of the capacity.

F N Force - Conversion factor for head 2.2 Pump Head f~

fa - Conversion factor for flow rate The head H of a pump is the useful mechanical energy trans-

f? - Conversion factor for efficiency mitted by the pump to the medium handled, related to the

9 mIs2 Gravitational constant = 9.81 mlsz weight of the medium, expressed in m. It is independent of H m Head the density p of the medium handled, i.e. a centrifugal pump HA m System head H.... m Static head ~ o ' " Hs ,,, Hz ,en

H" H",, AH K k L n NPSHreq NPSH, nq P P Pb Po P" AQ Q Q,," R Re U v Y z G.d

i '1 a IJ. " P

w 1P

Indices

a B d e G gee K S

opt R sch W z 1,2,3

m m m m m m 1 mm m llmin m m llmin kW bar (N/m2) bar (N/m2) bar (NIm2) bar (Nlm2) I/s (mVh) Ils (m31h) Ils (m3/h) mm 1 m mls mm l / h m

- - - 1 m21s kg/m3 (kg/dm3) 1 0

Shut-off head Static suction lift Static positive suction head Head loss Head loss - suction side Differential head Coefficient Absolute roughness Length of pipe Speed NPSH required NPSH available Specific speed Pump power input Pressure Barometric pressure Vapour pressure of liquid Pressure loss Differential capacity Capacity/Flow rate Minimum flow rate Radius Reynolds number Circumference Flow velocity Stroke Switching frequency Height differential between pump suction and discharge nozzles Loss coefficient Pump efficiency Pipe friction coefficient Correction coefficient Kinematic viscosity Density

Temperature fact01 Opening angle

at outlet cross section of the systemlbranching off at operating point at discharge nozzle of pump/flowing through at inlet cross section of planVbranching off for cast iron geodetic for plastic suction side, at suction nozzle of pump at best efficiency point radial for sulphuric acid for water for viscous liquids consecutive numbers, items

will generate the same head H for all fluids irrespective of the density p. The density p determines the pressure within the pump p = p . g . H

and influences the pump power input P.

2.3 System Head The total head of the system H, is made up of the following (see Figs. 1 and 2): . H,,., Static head = height difference between the suction

and discharge fluid levels. If the discharge pipe emerges above the liquid level, then H,,, is referred to the centreline of the outflow section.

.-, the pressure head difference between the suction P'S

and discharge fluid levels in closed tanks.

.ZH,, the sum of all pressure head losses (pipe friction, friction in valves, fittings etc. in suction and discharge pipes). va2 - ve2 .-- ,the difference in velocity heads in the tanks.

29

The system head HA is thus:

In practice the difference between the velocity heads can be ignored, leaving for closed tanks

HA = H,,, + + ZH,, P'S

for open tanks

HA - Hseo + ZHV

2.4 Speed With three-phase motor drives (asynchronous squirrel cage motor) the approximate pump speeds are as follows:

In practice, however, motors usually run at slightly higher speeds which - upon consent of the customer - are taken into account by the pump manufacturer at the design stage (see section 7.4). Different speeds are possible using a speed adjustment device, gearbox or belt drive.

12

llmin

480 580

No. of poles Frequenw 14

415 500

4 2 6

at 50 Hz at 60 Hz

in curve

960 1160

8

~eterence speeds

10

documentation 725 875

2900 3500

in

580 700

1450 1750

Fig 1 Pumping system with suction lin

Flg. 2 Pumping system with p ~ i t i v e suction

II KSB - 2.5 Selecting the Pump Size (see 7.1) The data needed for selecting the pump size - capacity Q and head H at the required duty point - is known, as is the mains frequency. The pump size and speed can be determined from the performance chart (also called selection chart) (see 8.0 Fig. 26); then the other parameters of the pump selected, such as efficiency q, input power P and NPSH, can be established from the appropriate individual performance curve (see 8.0, Fig. 3). Unless there is a particular reason to the contrary, arrange the operating point near Qopt (b.e.p.). For pumps handling viscous liquids see sections 6 and 7.6.2

2.6 Calculating the Power Consumption

2.6.1 Pump Power Input (see example in 7.2.1)

The pump power input P of a centrifugal pump is the mechan- ical energy at the pump coupling or pump shaft absorbed from the drive. It is determined using the following equation:

with p in kgIdm3 g in m/s2 Q in 11s H inm q between 0 and 1

or another equation which is still used:

with p in kgIdm3 Q in m3/h H inm 367 conversion factor (constant)

The pump power input P in kW can also be directly read with sufficient accuracy off the characteristic curves (see 2.7) where the de-nsity p = 1000 kgIm3. The pump power input P must be cbnverted (see 7.2.1) for other densities p.

2.6.2 Calculating the Drive Rating (see example under 7.2.2)

Since it is possible that the system volume flow, and thus the operating point, will fluctuate, which could mean an increase in the pump power input P, it is standard practice to use the following safety margins when determining the motor size, unless the customer specifies otherwise:

up to 7.5 kW approx. 20% from 7.5 to 40 kW approx. 15%

from 40 kW approx. 10%.

If extreme volume flow fluctuations are expected, the motor size must be selected with reference to the maximum possible pump capacity on the characteristic curves, taking the follow- ing into consideration:

impeller diameter required, condition NPSHav L NPSH,,, (see 3.2),

0 permissible P/n values for the bearings. Handling 'liquids with a high proportion of solids, as well as handling pulp, means using special pumps and/or special impellers.

2.7 Pump Characteristic Curve In contrast to positive-displacement pumps (e.g. reciprocating pumps) at constant speed (n = const.) centrifugal pumps have a capacity Q which will increase if the head decreases. They are thus capable of self-regulation. The pump power input P, and therefore the efficiency q, plus the NPSHreq depend on the capacity. The behaviour and relationship of all thesevariables are shown by the curves (see Fig. 3) which thus illustrate the operating characteristics of a centrifugal pump. The characteristic curves apply to the density p and kinematic viscosity v of water, unless stated otherwise.

129001 l lm in Laufrad Impeller Roue Rodete 0 mm 130-169 Breite Width Largeur Anchura mm 9

Fig. 3 Centrifugal pump characteristic curves

The duty conditions determine which is the more favourable - a flat or a steep curve. With a steep curve the capacity changes less than with a flat curve under the same differen- tial head conditions AH (see Fig. 4). The steep curve thus possesses better control characteristics.

~ i g . 8 Paraiiei operation of two similar centrifugal pumps with the same shut-off head HO

Fig. 9 shows an alternative solution: two pumps with the same shut-off head Ho but different capacities Qi and Qll pumping at a given operating point B in one piping system. Ql of pump I and QII of pump II combine to produce the total capacity QI+II at the same head H.

/ Pump1 + 11 curve

B opersting point no Shut-off head

~ i g . 9 Parallel operation of 2 pumw withthe same shut-off head no

3 Suction Characteristics

3.1 NPSH Required (= NPSH,.,) (NPSH = Net Positive Suction Head)

Centrifugal pumps will only operate satisfactorily if there is no build-up of vapour (cavitation) within the pump. Therefore the pressure head at the NPSH datum point must exceed the vapour pressure head of the medium handled. The NPSH datum point is the impeller centre, i.e. the point of intersection between the pump shaft centreline and the plane at right angles to the pump shaft and passing through the outer points of the vane inlet edge.

The NPSH,., isthevalue required bythe pumpand isexpressed in meters on the pump characteristic curves. The value often includes a safety margin of 0.5 m.

3.2 NPSH Available (= NPSH,,) The datum point for the NPSH,, is the centre of the pump's suction nozzle. With standard, horizontal volute casing pumps the centreiines of the suction nozzle and impeller are on the same level (Figs. 10 and l l ) , i.e. the geodetic height is 0. However, if there is a difference of geodetic height (e.g. with vettical pumps), it has to be taken into account. NPSH,, is calculated as follows:

a) Suction lift operation; the pump is above the liquid level (Fig. 10) NPSH., is defined as:

However, with a cold liquid, e.g. water, and an open tank,

i.e. oh - 1 bar 1= 105 NIm2) . - p, = 0 bar p = 1000 kgIm3 g = 10 mls2 (incl. 2% error on 9.81 mIs2) v.212g - can be eliminated because of the negligible

velocity head in the tank,

The following simplified version is used in practice:

NPSH,, 10- H,, - Hsgeo.

~ i g . 10 NPSH~., for suction iin operation

b) Suction head operation; the pump is below the liquid level (Fig. 11) NPSH, is defined as:

NPSH -Pe+Pb-Po ve2 BV - + - H,s + Hz geo p.9 29

The following equation is used in practice, assuming the same conditions as in a):

NPSH,-10-H,,+H ,,,,.

~ i g 11 NPSH~V for ~uci ion head operation

In all cases the following is a prerequisite for cavitation-free operation: NPSH,, 2 NPSH,,

4. Pressure Losses p,, The pressure loss p, is the pressure differential arising as a result of wall friction and internal friction in piping runs, fittings, valves and fittings etc. The generally valid formula for the pressure loss of a flow in a straight length of pipe is:

where p, pipe friction loss, A pipe friction coefficient, U wetted periphery of section A through which the fluid

flows.

Straight lengths of circular cross-section piping are defined by the following equation:

h . L p.v2 p " - where

D 2

D bore of pipe.

The pipe friction coefficient h varies with the state of flow of the medium and the internal surface finish of the pipeline through which the medium is flowing. The state of flow is deter- mined by the REYNOLDS number (model laws):

V.D Re=- V

for non-circular sections L length of pipe, v. 4 A p density of the medium pumped, Re=- v . U v flow velocity across a section A characteristic of the pres- where

sure loss. v kinematic viscosity.

Table 1: Mean peak-to-valley heights k (absolute roughness)

1 ) Nonferrous metals, light alloys 9

Valves

m KSB - j can be ca.cLlate0 for smooth bore pipes (new rolied steel oioesl: .< . " , . . . , -

C in the region of laminar flow in the pipe (Re < 2320) the .$ 0.050 friction coefficient is: 5

64 o a=- . 0

Re g 0.020 .- in the region of turbulent flow in the pipe (Re > 2320) the 9 I

test results can be represented by an empirical equation '-, 0.010 by ECK: a h

0.005 g 2 4 6 8 2 4 6 8 2 4 6 8 2 4 6 6 2 4 6 8

\ I /

In the region of 2320 < Re < 108 the deviations are less than 1 %.

Fig. 12 shows, that h is solely dependent on the parameter D/k at relativelv hiah REYNOLDS numbers: k/D is the "relative roughness", obtained from the "absolute roughnessm kand the DiDe bore diameter D, where k is defined as the mean deDth bf the wall surface roughness (coarseness). According to MOODY the following applies:

Table 1 gives rough approximations of k,

4.1 Head Losses H, in Straight Pipes Fig. 13 gives the losses of head H, per 100 m of straight pipe run for practical usage. The head losses H, in this context are calculated according to ..2

v.D REYNOLDS number Re = - " ~ i g . 12: pipe fridion coenicient A in fundion of REYNOLDS number and of relative wall roughness Dlk

where i loss coefficient, v flow velocity, g gravitational constant.

The values in Fig. 13 apply to clean water at 20 OC and to fluids of equal kinematicviscosity, assuming the piping is completely filled, and consists of new cast iron pipes, with an internal bi- tumen coating (k = 0.1 mm). The head losses H, of Fig. 13 should be multiplied by:

0.8 for new rolied steel pipes, 1.7 for pipes with incrustations (the reduced pipe cross-

section due to the incrustations is the determining factor), 1.25 for old slightly rusty steel pipes.

Capacity Q ~ i g . 1 3 Head losses in straightpipes (cast iron pipe,newoondition)irom DN 15 to2000 mrn and for capacities Q from 0.5 to 50000 m3/h ifiowvelocityvin mls. nom, bore in mm, water at 209.

In the case of pipes with very heavy incrustations, the actual head loss can only be determined by experiments. Deviations from the nominal diameter have a profound effect on the head loss, e.g. an actual bore of 0.95 times the nominal bore (i.e. only a slight bore reduction) pushes up the head loss Hv to 1.3 times the "as new" loss. New rubber hoses and rubber- lined canvas hoses have H, values approximately equal to those indicated in Fig. 13. How to use Fig. 13 - an example: Assuming a rate of flow Q = 140 m3/h and a new cast iron pipe, inside diameter D = 150 mm, we obtain: head loss Hv = 3.25 m1100 m pipe length, flow velocity v = 2.2 m/s.

4.2 Head Losses H, in Plastic Pipes Head losses in plastic pipes H,,. The head losses of PVC and polythene "hard" and "soft" (drawn) plastic pipes are approxi- mately equal. For the practical calculation of H,,, the respective head losses for cast iron pipes HvG (Fig. 13) should be multi- plied by the correction coefficients p of Fig. 14, which are de- pendent on the flow velocity v. The head losses evaluated in this way apply to water at a temperature of 10 OC.

If the water temperature is other than 10 OC, these head losses must in addition be multiplied by a temperature factor cp (Fig. 15). Thus

H v ~ = H V ~ - p . c p where HvK head losses in plastic pipes, HVG head losses in cast iron pipes acc.

to Fig. 13, p correction coefficient acc, to Fig. 14,

temperature factor acc. to Fig. 15. 1 .o

2

Flow velocity v . Fig. 14: Correction coefficient p for conversion of head losses in a cast iron pipe at 20 OC water temperature to values in a plastic pipe at 10 OC water temperature; plotted in function of flow velocity v

Temperature t Fig. 15: Temperature factor q for calcuiatlon of head losses in plastic pipes at water temperatures between 0 and 60 'C

Increments of 20 to 30% should be added for sewage or un- treated water.

4.3 Head Losses H, for Viscous Liquids in Straight Pipes The head loss of a viscous fluid (subscript FI) can be ascer- tained for practical purposes with the aid of Fig. 16, after having obtained the head loss for cold water (20 OC, v = m2/s) (subscript W) from Fig. 13:

- IFI ' H~~ H v ~ i - --- .

hw

See viscosity for conversion of viscosity values.

Rg 16 Res~stance coefflclents A. for flow of VISCOUS flulds ~n stra~ght plpes

How to use figure 16 - an example: Given: capacity Q = 100 m3/h, new cast iron pipe, inside diameter D = 250 mm, kinematic viscosity v = 2 . 1 0-4 m2/s. Found in figure 13: Hvw = 0.14 m/100 m. It follows from figure 16 that: A,, = 0.08,hW = 0.021.

One quite common viscous fluid is cellulose (pulp pumping), the viscosity of which depends on the flow velocity, since the material in question is "non-NEWTONian"! Figures 17 a through 17 f offer reference values for the head losses Hv per 100 m length of straight steel pipe run plotted against capacity Q (H, = f(Q); nominal bore: 100,150,200,250,300 and 350 mm) for conveying unbleached sulfite cellulose at 15 OC, 26 OSR

Valves

II KSB - (grinding state, OSR - Schopper-Riegler degree of freeness) and with a pulp density (pulp pumping) of 1.5 to 7 010 bone dry. If the pump slurry concerned differs from that used for the pur- pose of plotting the curves of Fig. 17, then the values obtained from Fig. 17 should be multiplied by the following factors: K = 0.9 for bleached sulphite - sulphate cellulose, waste paper

pulp K = 1.0 for boiled (digested) wood pulp, K = 1.4 for white and brown raw wood pulp.

300

pl - 1 OOm 100

50 40 30

$ 2 0 0 - u $10 I

5 4 3 2

1 2 3 5 10 20 m3/h 50 100 Fig. 17a Rate of flow Q

Pulp density in 010 bone d r y l

- 10 20 30 50 100 200 m3/h 500 1000

Fig 17b Rate of flow Q

200 m

1 OOm 100

50 40 ; 30 $ 20 0 - U g 10 I

5 4 3

'1 0 20 30 50 100 200 m3/h 500 1000

Flg 1 7 ~ Rate of flow Q

'1 0 20 30 50 100 200 m3/h 500 1000 Flg. 17 d Rate of flow Q

l m N ' s b b j 1 1 1 / 1 ', pulp bensity 4 fin-e , ,, ~n 010 bone drv

20 30 50 100 200 m3/h 500 1000 2000 Fig. 17e Rate of flow Q

Fig. 17f Rate of flow Q

Figs. 17a-f: show a plot of the head losses Hv for conveying sulphite cellulose of various pulp densities at a temperature of 150 OC and a grinding grade of 26 "SR (pipe diameters DN 100 to DN 350) A-A = maximum velocity (2.44 or 3.05 mls) in the discharge pipe for economical operation.

Furthermore, the head loss obtained from Fig. 17, and if ne- cessary corrected by one of the factors listed above, should be corrected additionally if the pulp slurry concerned is at a temperature higher than 15 OC. In this case, 1 OIo of the head loss value which applies to 15 OC should be deducted for every 2 OC of temperature difference. In the case of plastic pipes, the HvK value is obtained by multiplying the Hv value for steel pipes by 0.9. The head loss value is reduced even further if fillers such as kaolin (China clay) are contained in the pulp slurry concerned. For an 18 010 kaolin content, the head loss value will decrease by 12 010, and for a 26.5 010 kaolin content, it will decrease by 16 010. 4.4 Head Losses H, in Valves and Fittings

For pressure losses in valves and fittings the following equa- tion applies:

where C loss coefficient, p density of pumped medium, v flow velocity across a section A which is characteristic

of the head loss. Tables 2 to 4 and Figs. 18 to 24 give details of the indivi- dual loss coefficients C and head losses Hv in valves and fitt- ings for operation with water.

Head loss Hv

Elbow radius RK Duct width an

Fig 20 influence of roundrng off of concave and convex s~de on the loss coeff~c elbows wlth quadratic cross sectlon

Fig. 18: Determination of head losses Hv in vaives and fittings; flow velocity v relating to the actual cross-sectional area through which the fluid flows I o3

5

Knee piece a 4 5 O 60° 90°

Surface Surface Surface

smooth rough smooth rough smooth rough

i 0.25 0.35 0.50 0.70 1.15 1.30

Combinations with 90° knee pieces

T pieces (subdivision of flow) 0.5

with sharp edges rounded with spherical with spherical straight bottom inward-rounded

1= 1.3 1 = 0.7 I neck 1 = 2.5 to 4.9

ient of

Relative opening angle (90 - 9)/9o

Degree of opening yla

1 = 0.9

Fig. 21: Loss coefficients of butterfly vaives, globe and gate vaives in function of ope- Fig. 19: Illustration of fittings with related loss coefficients ( ning angle or degree of Opening (Position numbers according to Table 2, design)

Table 2: Loss coefficients (of valves and fittings (referred to the velocity of flow in the adjoining cross-section DN - nominal diameter)

Type of valvelfitting / ~esignsl Loss coefficient (for DN = 1 Remarks

') If the narrowest shut-off diameter d~ is smaller than the nominal diameter DN, the loss coefficient ( must be increased by pN/dE)', with x = 5 to 6 2) In the case of partial opening, i.e. low flow velocities, the loss coefficients increase 3) Designs: cf. page 15

valves

KSB -

11 12 13 14 15 16 17 18 19

Designs according to Table 2

The minimum and maximum values listed in Table 2 include figures taken from the most pertinent trade literature and apply to fully open valves and fittings under uniform conditions of flow. The losses attributable to flow disturbances in a length of pipe equalling ca. 12 X DN downstream of the valve or fitting are also included in those values (cf. VDINDE guideline 2173). Nonetheless, the actual values are subject to wide variance, depending on the conditions of inf owand outf ow, the model in question, ana tne design objcctives

Table 3: Loss coefficients for fittings

Elbows:

Cast elbows 90°, R = D + 100 mm, all nominal size i - 0.5 Pipe bends 90°, R = 2 to 4 X D Nominal size DN 50 100 200 300 500 i -0.26 0.23 0.21 0.19 0.18 If the deflection angle only 60° 45' 30" 15O, amounts to the above i values should be multiplied by 0.85 0.7 0.45 0.3

Knee pieces:

Deflection angle 90' 60" 45' 30' 15' i - 1.3 0.7 0.35 0.2 0.1 Combinations of elbows and pipe bends:

The i value of the single 90' elbow should not be doubled, but only be multiplied by the factors indicated to obtain the pressure loss of the combination elbows illustrated:

Expansion joints:

Bellows expansion joint withlwithout guide pipe i = 0.310.2 Smooth bore pipe harp bend i - 0.6 to 0.8 Creased pipe harp bend i -1.3to 1.6 Corrugated pipe harp bend [ - 3.2 to 4

lnlet pipe fittings:

Inlet edge t t f t sharp i = 0.5 3 for 6 = 75O 60" 45" chamfered i - 0.25 0.55 0.20 0.05 i- 0.6 0.7 0.8

Discharge pieces:

i = 1 downstream of an adequate length of straight pipe with an approximately uniform velocity distribution in the outlet cross-section.

1 - 2 in the case of very unequal velocity distribution, e.g. immediately downstream of an elbow, a valve etc.

Loss coefficients of flow meters:

Short venturi tube a = 30° Standard orifice plate

i is related to the velocity v at diameter D.

Diameter ratio dlD = 0.30 0.40 0.50 0.60 0.70 0.80 Aperture ratio m = (dlDP = 0.09 0.16 0.25 0.36 0.49 0.64

short venturi tube i = 21 6 2 0.7 0.3 0.2 Standard orifice ( - 300 85 30 12 4.5 2 plate

Water meters (volumetric meters) i - 10 In the case of domestic water meters, a max. pressure drop of 1 bar is wescribed for the rated load, and in practice the actual pressure loss is seldom below this figure.

Branch pieces: (Branch of equal bore)

The resistance coefficients i. for the diverted flow Q, or id respectively for the main flow Qd = Q - Q, relate to the velo- city of the total flow Q in the nozzle. On the basis of that definition, i, and/or id may take on negative values, in which case they are indicative of pres- sure loss. Not to be confused with reversible pressure changes according to BERNOULLI'S equation (cf. annota- tion to Table 4).

Table 4: Pressure change coefficients in transition piece for arrangements illustrated in Fig. 14 A coefficient E in accordance with the values in the table below applies to each of the illustrated shapes of transition pieces1 reducers. If the pressure rises across the transition piece in the direction of fiow (divergent section), E is positive, and if the pressure drops (reducer), E is negative. Coefficients:

Expansion 1 Reduction

Form I iI Ill IV

Form d/D = 0.5 0.6 0.7 0.8 0.9

i i - 0.56 0.41 0.26 0.13 0.04

1 a = 1 - 0.07 0.05 0.03 0.02 0.01 II for a = 15' i - 0.15 0.1 1 0.07 0.03 0.01

a = 20° 5 - 0.23 0.17 0.1 1 0.05 0.02 111 1 = 4.80 2.01 0.88 0.34 0.11 IV for 20° < a < 40' 5 - 0.21 0.10 0.05 0.02 0.01

Note: In the case of branch pieces as per Table 3 and transition pieces as per Table 4, differentiation is made between irrevers- ible pressure loss (=pressure reduction)

on the one hand and reversible pressure changes involving hictionless flow as per BERNOULLI'S equation (fluid dynamics)

on the other. in the case of accelerated fiow, e.g. through a pipe constriction, p2 - pl negative. Conversely, it is positive in pipe expansions. By contrast, the pressure losses ascertained by way of the loss coefficients 5 are always negative, if the overall pressure change is calculated as the arithmetic sum of p, and p2-p,.

in the case of water transport through valves and fittings, the loss coefficients is occasionally neglected in favour of the so-called b-value:

where Q volume flow in m3/h, p density of water in kglm3 (effective temperature vapour

pressure, Table I), p, pressure loss in bar.

The !+value [m3/h] represents the volume flow of cold water (p = 1000 kglm3) at p, = 1 bar through a valve or fitting; it therefore gives the relationship between the pressure loss p, in bar and the volume flow Q in m3/h.

Conversion: d4 (-16.-

where e d reference diameter (nominal diameter) of the valve or

fitting in cm.

5 Changing the Pump Performance

5.1 Changing the Speed The same centrifugal pump has different characteristic curves for different speeds; these curves are interconnected by the similarity law. If the values for Q1, H1 and P1 are known at speed nl, then the new values for n2 will be as follows:

A change in the speed also causes the operating point to shift (see 2.9). Fig. 22 plots three QH curves for the speeds nl, n2 and n3, each curve is intersected by the system curve HA at points B1, B2 and B3 respectively. The operating point will move along the system characteristic HA from B1 to B3 when the speed is changed as indicated.

A

system curve HA

z 2 I

B Operating paint n Speed

0,aa 30'

capaciv Q

~ i g . 22 Enen of change in speed

5.2 Trimming the Impellers

Permanently reducing the output of a centrifugal pump oper- ating at constant speed (see Fig. 23) entails reducing the impeller diameter D. The characteristic curve booklets contain the pump curves of selected impeller diameters in mm.

When trimming radial flow impellers (see 8.4) (trimming is not a geometrically similar reduction of an impeller since the outlet width normally remains constant), the relationship between Q, H and impeller diameter D is:

KSB - The actual diameter can be determined as follows (see Fig. 23): Run a line in the QH graph (linear graduation) passing from the point of origin (take into consideration with curves with a suppressed point of origin) through the new operating point B2 and intersecting at B1 the full diameter curve Dl. The Q and H values 1 and 2 can then be plotted and used in the equation to obtain the approximate diameter DP.

Capacity Q

Fig. 23 Influence of impeller diameter

6 Handling Viscous Liquids

This conversion process can be used

to convert from Bw to operating point BZ using Fig. 25a (see 7.6.1)

0 and to select the appropriate pump size from the given operating point Bz via the operating point Bw using Fig. 25b (see 7.6.2).

The conversion is valid for single-stage volute casing pumps with radial flow impellers (see 8.4),

0 specific speeds nq of 6 to 45 1 Imin (see 7.6.1 and 9.1 2), kinematic viscosities v, of 1 to 4000 . 10-6 m21s (kinematic viscosities below 22 . 10-6 m2Is are normally disregarded).

As the viscosity v of the medium handled increases (at con- stant speed) the capacity Q, head H and efficiency q fall; at the same time the pump power input P rises. The best efficiency point shifts to smaller flow rates. The operating point Bw drops to BZ (see Fig. 24).

Capacity Q

Fig. 24 Change in operating point when handling viscous liquids (Z) end water (W)

a , I 1 1 ' 1 10 I* m 1o'"a 1)D m __am lOeO em

ThestandardoperatingpointforwaterBwwithQw,Hwand " ' " " " " " " ' " " ' " ' " " ' ' ' ' """""" ' " rn3 1

qw (W = water) is converted to the viscous liquid operating Capacity Qz,~etr, Q W , O ~ ~ in -' h ' s -

point BZ with Qz, HZ and qz (Z = viscous liquid) using the conversion factors lor viscous liquids f ~ ' fu and fq (see Figs.

Fig 25a Determining the conversion f a h r s f ~ w . f * w and f q w for handiing viscous 25a and 25b). liqu~ds (enlarged version see 9 lo), if the operathg point for handling water IS glven

&)pumps Valves

II KSB - 7 Typical Selection Examples

7.1 Selecting the Pump Size (see 2.5)

The following variables are known: Q = 25 11s (= 90 mVh) H = 8 0 m Frequency 50 Hz

Medium 60% sulphuric acid (index s) Density ps = 1.5 kgldm3 Temperature ts = 20 OC Kinematic viscosity vs = 3.8 . 10-6 m2Is (can be

disregarded, see 6) (ps and vs taken from standard reference tables)

The pump selected for this particular liquid is a CPK series standardized chemical pump. Technical data and characteristic curves for the CPK are given in the characteristic curve booklet and selection booklet (Figs. 26 and 27 are extracts).

Selecting the size of the pump: Using the CPWHPK characteristic curve booklet for 50 Hz the selection charts give the following pump selections for the specified operating data:

CPK 65-250 at n = 2900 Ilmin and CPK 150-250 at n = 1450 I Imin.

The CPK 65-250 is selected for reasons of economy.

Fig. 25b Determlnlng the conversion factors f~ z and f~ z for handling VISCOUS llqulds (enlarged verslon see 9 111, if the operating poltit for handl~ng VISCOUS l ~ q u ~ d s IS glven

200 300 400 500 1000 2000

200 300 400 500 1000 200

100

80 H rn

50

40

30

20

-_ A / - 40 ----- - 10 1

45 1 QIIS 2 , 3 4 5 10 20 25 30 LO 50 100 140 2 4 5 Qrn31h 10 20 30 40 50 100 200 300 400 500

2121 L 0 5 2 / 8

Fig. 26 CPKIHPK, selection chart n = 2900 l lm in

Valves

KSB - 7.2 Calculating the Power Consumption

7.2.1 Pump Input Power (see 2.6.1) Using the known variables and pump selection from 7.1 the power input is calculated as follows:

7.2.2 Calculating the Drive Rating (see 2.6.2)

Taking the pump power input P (see 7.2.1)

a 10% safety margin is added to the 43.3 kwatthe operating point.

with p, in @/dm3 g in mlsz Q in 11s H in m P in kW

or an alternative frequently used in practice:

So the drive rating must be at least 47.6 kW: the selection is a standard 55 kW motor, 2pole, iP 54lIP 44, type B 3. Pln value must be checked (see selection booklet, section Technical Data).

If the operating Point tem~orarilv chanaes to hioher flow rate. the moror ratlng musr bc lncreascd accord~ng,;, 11 necessary JP lo the maxlmLm poss~ble Pumo Dower consumollon . . .

A recheck of the Pln value then becomes important as a criterion for the bearing bracket.

with p, in kgldma Q in m31h H in m P in kW

The pump power input Pcan also be established with sufficient accuracy from Fig. 27. P is interpolated as - 29 kW for water, the value for sulphuric acid is:

p - 2 9 . k = 29 . - 1.5 = 43.5 kW, Pwater 1

'1 Eniciency q from Fig. 27) interpolated

7.3 Calculating the NPSH,, (see 3.2) To achieve cavitation-free operation of the pump the limit of maximum possible suction lift H, ,,,, ,., or the minimum required suction head H, ,,, ,in must be adhered to.

7.3.1 Suction Lifl from OpenlClosed Tank Here the pump is above the liquid level (see Fig. 10). Selected pump is a CPK 65-250. technical data see 7.1 Calculation of H, ,,, .,, is based on following system and pump data:

P = 1500 kgIm3 Pb = 1 bar=1~105N/m2 Po = 0.0038 bar = 0.0038.1 05 Nlm2

(from reference table) (60% sulphuric acid at 20 OC)

H,, = 1.5 m (estimated from Fig. 13 for 10 m suction pipe DN 100, incl. fittings and valves)

Ve can be disregarded because negligible NPSH,,,= 3.3 m (interpolated from Fig. 27 incl. 0.5 m safety

margin)

Open tank 1 Closed tank

Given: p, = 0 bar 1 Given: p, + p, = 1.5 bar = 1.5 . 105 Nlm2

- Pe+Pb-PD - H,, - NPSH,,, (acc. to 3.2 with NPSH,,, = NPSH,) Hs ueo, ",ax - P.'S

With H ,,,o,,,, = 1.97 m, NPSH,= NPSH,,, = 3.3 m; With H .,.o,,., = 5.37 m, NPSH, = NPSH,, = 3.3 m; therefore NPSH, 2 NPSH,,, requirement is satisfied. therefore NPSH, 2 NPSH,, requirements is satisfied

7.3.2 Positive Suction Operation from OpenIClosed Tank Here the pump is below the liquid level (see Fig. 11). Selected pump is a CPK 65-250, technical data see 7.1 to 7.3.1.

Open tank I Closed tank

Given: p. = 0 bar ~iven:p,+p,=1.5bar=1.5.10~N/m2

= 1.5 + 3.3 - 6.77 i =3.3+ 1.5-10.17 = -1.97 m. = -5.37 m.

Negative heads -Hz,,, are suction lift heads +H.,., of the same value. The minus sign in the result tells us that the centrifugal pump, with an open or closed tank, could draw roughly the absolute amounts as in example 7.3.1 where the requirement NPSH,, 2 NPSH,., is just about satisfied. This requirement would be more than satisfied in example 7.3.2 with a positive static suction head (as shown in the diagram).

7.3.3 Positive Suction Operation from Closed Tank at Vapour Pressure

(internal tank pressure = Vapour pressure of liquid, 1.e. pe + pb = PD) The pump is below the liquid level (see Fig. 11). Theselected pump is a CPK 65-250, see 7.1 for technical data. See 7.3.1 for system and pump data required to calculate Hzgeo, min but with pe + ~b = PD.

Hz,,,, ,in = NPSHreq + H,, - Pe+Pb-Po P s ' ~

From4.8mupwards(H ,,,,,,,,) thecondition NPSH,,ZNPSH,., is fulfilled.

Actual (now):

Q, = 25.56 11s HI = 73.2 m D, =240 mm Desired:

QZ = 25 11s Hz =70 m i.e.

Turning the impeller down from 240 mm (D,) to 237 mm (Dz) restores the original duty given in 7.4. It is, however, standard practice not to make such minor changes (less than 5 mm) to the impeller diameter.

7.4 Changing the Speed (see 5.1)

The CPK 65-250 selected in 7.1 but with the following per- formance data (present duty: index 1, new duty: index 2)

Qq = 25 11s (= 90 mslh) HI = 70 m at n, = 2900 l lmin and D, = 240 mm (impeller diameter) is driven by a 55 kW three-phase motor with a nominal speed (n2) of 2965 llmin. The higher speed shifts the operating point, without considering the system characteristic HA, as follows to:

if this increase is not acceptable, the original duty can be restored by e.g. reducing the impeller diameter (see 7.5).

7.5 Trimming the Impeller (see 5.2) The unacceptably high pump output (see 7.4) caused by the higher motor speed is rectified as follows by trimming the impeller (present duty: index 1, new duty: index 2).

7.6 Handling Viscous Liquids (see 6) Schedule on page 44.

7.6.1 Caiculation the Operating Point The product is a mineral oil with a kinematic viscosity vz of 500.10-6 m21s and density p, = 0.897 kgldms.

We know the characteristic curve and operating dataof a pump handling water, where:

Qw = 34 11s (= 122.4 m31h) Hw=18m n = 1450 l lmin

To obtain the new data for mineral oil, the pump data at the b.e.p. must also be calculated and the following additional information must be known:

Efficiency Speed 1450 l lmin Kinematic viscosity Density 1 Pz / 0.897 kgIdm3

Gravitational constant / g 19.81 / mls2

'1 horn individual characteristic curve (see Fig. 21)

4 points on the new characteristic curve can be established using the calculation chart below:

n w from graph in 9.12

fo,w from Fig. 25a fH,W Or sect. 9.10,

0.49

if HZ > Hw, use HZ = Hw

Theaevaiues mean 4 points on Q H ~ a n d OTZ line plus 3 points on the QPz line are establirhed. Plotled aver Q (see Fig. 28)

Caiculation in graphic form

valves KSB -

7.6.2 Establishing the Pump Size The product is mineral oil, we are looking for the size of the pump capable of meeting the following operating data:

Kinematic viscosity I vz 1 500 - 10-6 1 m21s Density 1 PZ 0.897 / kgIdm3

Capacity I Q Z , B ~ ~ , / 31 Il ls

Head ] Hz,setr / 20 rn

Use the following calculation table to convert to operating data with water and thereby find the appropriate pump size.

0 1 - - 1 20 Pumps 0 10 2 0 Q 11s 30 LO A series of national standards have been introduced in

Germany since the early sixties governing the manufacture, design, procurement and use of centrifugal pumps. These standards are drawn up by both operators and manu- facturers and are now established in virtually all sectors of industry using and producing pumps (see Fig. 29, page 23).

a This is particularly true of DIN 24256 "End suction centrifugal

5 pumps (PN 16) (chemical pumps)" which even in its first edition was virtually identical to the international standard IS0 2858 "End-suction centrifugal pumps (rating 16 bar)

0 10 2 0 11s 30 LO - Designation, nominal duty point and dimensions". These two standards occupy a central position because they

Capacity Q form the basis for a range of standards already in existence and under preparation covering centrifugal pumps, access-

Fig 28 Characteristic curve3 for both water NY) and viscous liquids (2) (see 76.1) ories, guidelines and specifications.

22

n selected

n,,~ 3) from graph in 9.12 fQ2 from Fig. 25b or

~H ,Z section 9.1 1, page 42

C)r.setr Qw,~eir =

0.2

Hz.8eti Hw,setr = f

a m

A The definitive operating data when handling water are thus:

QW,Betr = QW = 38.8 11s (= 139.7 mVh) Hw,B~,~ = Hw = 23.3 m

Based on these data a suitable pump is selected from the sales documents selection chart. Using the curve thus estab- lished, follow section 7.6.1 to establish 4 points on the new

Hw characteristic curve.

15 - These 4 points can now be used to establish the curve to be

H,Z ih Om-2 Qwlpt Q

3, where Qz,~~t , = Qopt H z , B ~ ~ ~ = Hopt Calculation in graphic form

1450

27 0.8 0.86

38.8

23.3

1 % I

l lmin l lmin -

-

H78.a

11s

m Q z s n Qwsnr

9 expected for handling mineral oil, see Fig. 28.

a I

10

5

- 80

- - 70

'Iw - 60 0 C

- 50 a , - 0

- LO 5 8 General

3 0 8.1 National and International Standards for Centrifugal

Scope of ~ppl icat lon Dimensional Standards - Pumps A C C ~ S S D ~ ~ ~ S Guidelines and Specifications and ReSpOnsibilities

24253 ~ s s ~ o i a t t ~ n Centrifueal of German P U ~ P S wi!h Engioeering armoured

Pump Iemoured Comminee

single- siege wlth axis1 inlet; duties. principal

DiN 24251 DIN 24252

Drainage Centrifugal

Standslds with Institute heads

Commiffee 1000 m duties,

Engineer-

Pump8

DIN 45635 DIN 24293 DIN 24295

ments in technical pumpsets machinew documen- for liquids.

terms, require- measure- scope of ments ments. suppiy, enveloping exeoutlan Surface method,

Pumps

dispatch, speoiii- cstione

DIN IS0 DIN 24420

Centr~fugal spares pump*; liSts technical reguire-

pp

. [ European Standards

,,,,,, Coordinating

e sation Cornminee

w'

Technical

lions tor centri- fugal pumps - Class I1

% 3 e 8

I l l I I I I .12 EC and 6 E R A member countries

N W Fig. 29 Chart of German and international standards for centrifugal pumps, accersories, guidelines and specifications (as o i ~ebruary 1990)

Inter- national OWBni- zat>on far stan- derdizatior

TCi15, Pumps

The high degreeof similarity between DIN24 256and IS0 2858 means that a series of national standards and draft standards such as: DIN 24259 "Pump baseplates",

DIN 24960 "Mechanical seals; shaft seal chamber, principal dimensions, designationsand material . codes",

VDMA 24297 "Centrifugal pumps; technical requirements, specifications"

need minor or no changes in content even afterthe publication of the corresponding IS0 standard.

8.2 Shaft Deflection Shaft deflection is principally caused by radial forces resulting from the hydraulic thrust in the impeller plane generated by the interaction between the impeller and pump casing (or diffuser). The magnitude and direction of the thrust changes with the rate of flow and affects the shaft and bearings. The pump maker can favourably influence these hydraulic radial forces by selecting the right casing (see Figs. 30 and 31). This guarantees conformity with the specified maximum per- missible shaft deflection (e.g. API 61 0 or ISO) and also means cost-effective sizing of shafts, especially seals and bearings.

0.5

, 0.4 - a, .. " .. - 5 0.3 0 - 2 + 0.2 m - 2 5

0.1 q = 1 . 0 I I I I

3

o W n 0 10 20 30 40 min-' 60

Spezilic speed nq

~ i g . 31 ~agnitude of the radial thrust coefficient K for volute rasing pumps as a funnion ol the spec~iic speed nq and the pump flow level q=Q/Qopt

8.3 improving the NPSH Requirement

It is possible in special cases to reduce the NPSH require- ment of a pump to approx. 50-60% of the original level by fitting an inducer in front of the impeller, for example when a plant is extended and the available NPSH is inadequate or where economic factors prevent the available NPSH being increased (by raising the suction tank) or a lower speed larger-sized pump (with lower NPSH requirement) being fitted.

The radial thrust FR can be calculated with the help of the equation FR=K.p.g.H.D2.b2

with F, Radial thrust K Radial thrust coefficient acc. to Fia. 31 p Density of the medium pumped g Gravitattonal constant H Head D2 Impeller outside diameter b2 Impeller outlet width

~ i g . 32 Centrifugal pump flted with induce!

Circular casing

volute caring

6 --___--- VOlULe CBS!"~

Double volute

I casing

Combined single volute circular oouble volufe casing voiute casing Circular casing casing

~ i g , 30 ~ a d i a l thrust in centrifugal pumpswiih various caring types

It must be noted that the reduction in the NPSH requirement applies only to a particular section of the flow range and not the complete range of the pump concerned (see Fig. 33).

Capacity Q a = NPSHreq - without inducer b = NPSHreq - wNh inducer A

C = NPSHreq - with inducer B

A and B are different types of inducers

~ i g 33 NPSH requirement ~ i t h and ~ i i n o u t inducer plotted against the capacity

8.4 Impeller Types 8.4.2 Non-clogging Impellers

8.4.1 Vaned lmoellers Large-clearance impellers are used on pumps handling con- taminated liquids containing solids, the single-vane impeller

pumps handling 'lean products have standard has an unrestricted passageway from inlet to outlet (so-called impellers fitted with vanes. Such impellers go from the radial free passage) "), flow type through the mixed flow type for higher flow rates up to the axial flow impeller for high flow rates and low heads.

Single-vane impeller*) closed

Radial flow impeller')

Mixed flow impeller') closed

Two-passage impeller') closed

Three-passage impeller*) closed

Mixed flow impeller open

8.4.3 Special Impellers For contaminated and gaseous liquids.

Mixed flow impeller? closed, double entry

Axial flow impeller

') Front view with coverpiate removed *') Single-vane impellers are also avaiieble with slightly reduced passage for greater

eniciency Free flow impeller

8.4.4 Star Wheels Mainly used in self-priming pumps handling clean media

Star wheel for side channel pump

8.4.5 Peripheral Impellers Used for clean media, low flow rates and high heads.

Peripheral impeller

8.5 Pump Types (typical examples) Figs. 34 to 39 show the various main design features:

Fig. 34 Slngle~entr~. single-stage, overhung, e.g, standardized chemicai pump

Fig. 36 Multistage, rudion and discharge side bearings, e.g. ring section high pressure centrifugal pump

Fig 37 ciose-coupled, e.g. in-line pump

Fig 38 Vertical shan-driven sump pump, e.g submersible chemical pump

,:i \ ,

Fig. 35 Doubie-entry, suction and discharge side bearings, e.g, pipeline p u m ~

iY-- i,,?,,,

~ i g 39 submersible close-coupled pump. e.g. sewage pump

8.6 Pump Installation Arrangements The factors which determine how a pump is installed are:

the position of the shaft, i.e. horizontal or vertical, the arrangement of the drive,

the position of the feet, i.e. underneath or shaft centreline, the weight distribution of the pump and drive (see Figs. 40 and 41).

horizontal

horizontal I horizontal

centreline coaxial with coupling common or gearbox baseplate

underneath with parallel axis above pump, compact, belt drive simple speed variation

underneath with parallel axis above pump compact, wlth belt drive and outboard simole meed variation bearing or jackshaft I

underneath close-coupled, forming a I I fully submersible water tight unit with pump

Fig. 40 Examples of horizontal installation

Alternative installation 1 Shaft

vertical

Feet Drive Remarks

I I - above ground on drive stool wet installation

a) surface level discharge pipe

soleplate a) above ground on dr~ve stool dry installation beneath b) above ground on drive stool discharge through cardan shaft nozzle C) below surface on drive stool

a) automatic submersible close-coupled wet installation engagement unit a) permanent with claw b) portable

b) on support stand

8.7 Pump Sump Configuration Pump sumps are designed to receive liquids and be inter- mittently drained. The sump size depends on the capacity Q and permissible start-up frequency Z of the pump set, i.e. the electric motor. The start-up frequencies of dry motors are as follows:

Start-up frequency Z Motor rating up to 7.5 kW max 15lh Motor rating up to 30 kW ma%. 12lh Motor rating above 30 kW max 10/h

8.8 Suction Pipe Layout The suction pipe should be as short as possible and run with a aentie siooe UD to the oumo. The suction oioe and inlet oioe mist be sufficiently wide apart to prevent'air entrainment'in the suction pipe. Furthermore the mouth of the inlet pipe must always lie below the liquid level (see Fig. 43).

Suction pipe - Start-up frequency is calculated using:

where Z no. of starts per hour Q, inlet flow in 11s .

Q, capacity at switch-on pressure in l/s Q, capacity at switch-off pressure in l/s VN useful volume of pump sump including possible

flowback volume in I

The maximum start-up frequency occurs when Qm = 2 x Q,, i.e. when the capacity Qm is twice the incoming flow Q,.. The max star-up frequency is therefore:

With dirty liquids, solids must be prevented from being de- posited and collecting in dead zones and on the floor. 45O walls, or better still 6W wails, help prevent this (see Fig. 42).

Fig. 42 Inclined rump vallsm prevent solids tmm being depogltea and colls*lng

' pos. deflector

Flg. 43 Aping emanpernevi to prevent sir emminmM

The medium handled must cover the suction pipe inlet to a suitable depth, otherwise rotation of the iiquid could cause air-entraining vortices (hollow vortices) to form; starting with a funnel-shaped depression at the iiquid su~face, a tube- shaped air cavity forms instantaneously, extending from the surface to the suction pipe. By ensuring that the medium handled always has a suitable level (see Figs. 44 and 45) or by taking measures to prevent vortices (see Figs. 46 to 48) this can be prevented, which is the more important, the higher the Row rate is.

Fm. 44 Arrangement ot pi- h me sunion hnk (rump1 to wevent vwticea

The minimum iiquid cover Smi. in m must be the velocity head plus a 0.1 rn safety margin for non-uniform velocity distribution. The maximum flow velocity v, in the suction pipe or inlet pipe should not exceed 3 m/s; we recommend 1 to 2 m/s.

with v. flow velocity in m/s Sm. minimum liquid cover in m.

I I00

I I I 1 I I l l I I 1 2 1 5 6 $ 8 9 1000 2 1 5 A ! 43:h

Capacity Q - F i g 45 Liguid OOYBI S 88 a lundion of the prplng bore ON and camcity Q

Fig. 45 shows the interdependence between liquid cover S, piping bore DN and capacity Q. The values obtained give sufficient protection against vortices. The graph can be used for the suction plpe layout illustrated.

h k rPiDe suction

I

Fm. 47 Use of swirl-oreverding bani-

Figs. 46 and 47 show typical arrangements used to prevent air-entraining inlet vortices where the minimum liquid cover is either not available or cannot be ensured.

Fig. 48 shows a special arrangement which is frequently used - a round tank with a tangential inlet DiDe which causes the contents to rotate.

10 pump

Fig. 48 Use of baMes in me tankm ensure disblmance-bee n m m pump

8.9 Shaft Couplings Shaft couplings used with centrifugal pumps can be divided into rigid and flexible types. Rigid couplings are mainly used to connect shafts In perfect alignment. The smallest degree of misalignment will cause considerablestress on thecoupling and on the shafts. The following types are used:

Sleeve couplings, Muff couplings, Serrated couplings, Split couplings (DIN 11 5), Face plate couplings (DIN 758, DIN 759), Flange couplings (DIN 760).

Fm. SO TYPical couplings Flexible couplings to DIN 740 are elastic, slip-free connecting elements between drive and driven machine which accom- modate axial, radial and angular misalignment (Fig. 49) and damp shock loads. The flexibility is usually achieved by the deformation of damping and rubber-elastic spring elements whose life is governed to a large extent by the degree of misalignment. Fig. 50 shows the most common types of flexible couplings. Fig. 51 shows a spacer couolina between a oumD and drive: . . itsfunction is to permit removal ;I the pump rotating assembl; without disturbing the pump casing or drive (back-pull out design).

Fig 49 Misalignment Fig. 51 Pump with spacer cou~ling

9 Technical Data 9.1 Vapour Pressure p, and Density p of Water

9.3 Density p of Various Liquids at Atmospheric Pressure

a!7:rs KSB -

9.4 Extract of Important Legal Units for Centrifugal Pumps

Kinematic viscosity Dynamic viscosity

Specific speed

v

rl

n4

m2/s

Pas

1

Pascai- second (= N s/m2)

St (stokes), "E, ... P (Poise), ...

mZ/s

Pas

1

1 St = 10-1 m2/s 1 cSt = 1 mmYs 1 P=O.1 Pas

n,=333.n. & (g.Hom)q

in Si-units (m and s)

9.5 Conversion of British and U.S. Units

Length 1 mil 1 point 1 line I inch (in) 1 hand 1 link Ili) . . 1 span 1 foot 1 yard

(ft) (yd)

I fathom (fath) 1 rod (rd) 1 chain fch) 1 furlong (fur)

British 25.4 Km 0.3528 mm 0.635 mm 25.4 mm 10.16 cm 20.1168 cm 22.86 cm 0.3048 m 0.9144 m 1.8288 m 5.0292 m 20.1 168 m 201.168 m

U.S. 25.4 ~m 0.3528 mm 0.635 mm 25.4 mm 10.16 cm 20.1168 cm 22.86 ' cm 0.3048 m 0.9144 m 1.8288 m 5.0292 m 20.1168 m 201.168 m

1 mile (mi) (statute mile) = 1760 yd

1 nautical mile Area 1 circular mil

1 circular inch 1 square inch (sq in) 1 square link (sq li) 1 square foot (sq ft) 1 square yard (sq yd) 1 square rod (sq rd) 1 squarechain (sq ch) I rood I acre 1 square mile (sq mi)

Volume 1 cubic inch (cu in) 1 board foot (fbm) 1 cubic foot (cu ft) 1 cubic yard (cu yd) 1 register ton (FIT) = 100 cu ft 1 British shipping ton = 42 cu ft 1 US shipping ton = 40 cu ft

Basic unit gallon 1 minim (min) for fluids I fluid scruple

1 fluid drachm (fl.dr.) 1 fluid dram (fl.dr.) 1 fluid ounce (fi.02.) I gill (gi) 1 pint (iiq PO I quart (iiq qt) 1 pottle 1 gallon (gal) 1 peck 1 bushel 1 US oil-barrel (for crude oil) 1 quarter 1 chaldron

Basic unit bushel 1 dry pint (dry pt) for dry goods 1 dry quart (dry qt)

1 peck (pk) 1 bushel (bu) 1 dry barrel (bbl)

Mass and Weight 1 grain (gr) Avoirdupois system I dram (dr avdp) (trade and commerce 1 ounce (oz avdp) weights) 1 pound (Ib)

I stone 1 quarter 1 cental 1 short hundredweight (sh cwt) 1 hundredweight (Cd) 1 long hundredweight (1 cwt) 1 short ton (sh tn) 1 ton 1 long ton (1 tn)

Troy system 1 pennyweight (d-4 (for precious metals) 1 troy ounce (02 tr)

1 troy pound (Ib t)

1.6093 km 1.8532 km

506.709 pm2 5.067 cm2 6.4516 cm2

404.687 cm2 929.03 cm2 0.8361 m2 25.2929 mz 404.686 mz 1011.7124 mz 4046.86 mz

2.59 kmz 16.387 cmr 2.3597 dm3 28.3268 dm3 0.7646 ma 2.8327 ms 1.1897 rn3 -

59.1939 mm3 1.1839 cm3 3.5516 cma - 28.4131 cm3 142.065 cmr 0.5683 dm3 1.1365 dm3 2.2730 dm3 4.5460 dm3 9.0922 dm3 36.3687 dm3 - 0.291 ms 1.3093 ma - - - 36.3687 dm3 - 64.7989 mg 1.7716 g 28.3495 g 0.4536 kg 6.3503 kg 12.7006 kg 45.3592 kg - 50.8024 kg - -

1016.0470 kg -

1.5552 g 31.1035 g -

1.6093 km 1.8532 km

506.709 pm2 5.067 cmz 6.4516 cm2

404.687 cmz 929.03 cm2 0.8361 m2

25.2929 m2 404.686 m2

1011.7124 m2 4046.86 m2

2.59 km2 16.387 cm3 2.3597 dm3 28.3268 dm3 0.7646 m3 2.8327 ma

. - 1.1331 m3

61.6119 mma - - 3.6967 cma 29.5737 cma 118.2948 cm3 0.4732 dm3 0.9464 dm3 - 3.7854 dm3 - - 0.159 mS - - 0.5506 dm3 1.1012 dm3 8.8098 dm3 35.2393 dm3 0.1 156 m3 64.7989 mg 1.7718 g 28.3495 g 0.4536 kg - - - 45.3592 kg - 50.8024 kg 907.1849 kg

- 1016.0470 kg

1.5552 g 32.1035 g 0.3732 kg

35

&)PmPs valves

K S B -

Density 1 ounce (av) per cubic foot (oz/cu ft) 1 pound per cubic foot (lb/cu fi) 1 ounce (av) per cubic inch (ozlcu in) 1 pound per cubic inch (Iblcu in) 1 short ton per cubic yard (shtnlcu yd) 1 long ton per cubic yard (Itnlcu yd) 1 pound per gallon (Iblgal)

Velocity 1 foot per second (fils) 1 foot per minute (Wmin) 1 vard oer second fvdls) . . 5 Capacity 1 gallon per second (rate of volume flow) 1 gallon per minute (gpm)

1 cubic foot per second (cusec)

0.01 524 4.5460 0.07577

28.3268 1 cubic yard per second 1 0.7646

1 long ton per hour (Itnlh) Force 1 ounce (force) (02) (weight force) 1 pound (force) (Ib)

1 short ton (force) (shtn) 1 long ton (force) OW

Pressure pound (force) (~b ~f f t " " ) ) square foot

pound (force) Ib (force) square inch ( sq in ),(Psi:

short ton (force) (sh t;:~)) square inch

1 inch H20 (in H20) 1 foot H20 (ft H20) I inch ~g (in Hg)

Mechanical pound (force) stress square inch

British

0.0010 kgldma 0.0160 kgIdm3 1.7300 kgldms

27.6799 kgldma - - 0.09978 kgldms

0.3048 mls 0.00508 mls 0.9144 m/s

Mass flow 1 ounce per second ( O w 1 ounce oer minute lozlmin) 1 pound 'per second (lbls) '

1 pound per minute (Iblmin) 1 short ton per hour (shtnlh) 1 ton per hour

mls 11s 11s 11s msls

g/s g/s kgls kgls

U.S. 0.0010 kgIdm3 0.01 60 kgldms 1.7300 kgldms

27.6799 kgldms 1 .I 865 kgldma 1.3289 kgldma 0.1 198 kgldms

0.3048 mls 0.00508 mls 0.9144 mls

28.3495 0.4725 0.4536 0.00756 - 0.2822

68.9476 mbar

137.8951 bar

2.4909 mbar 29.8907 mbar 33.8663 mbar

N 0.006895 - mm2

0.01524 mls 3.7854 11s

0.7646 m31s

28.3495 gls 0.4725 gls 0.4536 kgls 0.00756 kgls 0.2520 kgls - 0.2822 kgls 0.2780 N 4.4483 N

68.9476 mbar

137.8951 bar

2.4909 mbar 29.8907 mbar 33.8663 mbar

N 0.006895 i;;;;;i

short ton (force) sh tn (force) N N

Work, energy, 1 foot-pound iff lb) 1 1.3558 J 1 1.3558 J quantity of heat, 1 ~ o r s e power hour ~ H P h) MJ 1 : , MJ internal (intrinsic) 1 Brit. Thermal Unit (BTU) I : , . . energy and enthalpy

5 T=7jtR+273.15; t=- tR 5 4 AT=At=-Att, 5 4 Where:

T thermodynamic temperature in K t Celsius temperature in OC tF Fahrenheit temperature in OF t. Rbaumur temoeratur in TI

Power 1 foot-pound (av) (heat flow) per second

1 Horse power(Hp) 1 British Thermal Unit

per second Dynamic pound (mass) Viscosity foot x second (Ib (ttmy))

pound (force) x second lb (force) s square foot ( sq fi )

Conversion of the specilic sped (type number) K customarily used in English-speaking conlries into n.acc. to IS0 2548:

1.3558 W

Temperature Conversion of temperature points: Conversion of temperature differences:

0.7457 kW

1.0558 kW

1.4882 Pas

47.8803 Pas

1.3558 W

0.7457 kW

1.0558 kW

1.4882 Pas

47.8803 Pas

pu

mp

s V

alves

= KSB -

9.6 Grap

h fo

r Calcu

lating

Flo

w V

elocity v

as

a Fu

nctio

n o

f Cap

acity Q an

d I.D

. of P

ipe D

- 0

pm

m r

(D

(D

-, 0

N

pm

mr

(D

(D

0

0

N

<

E

A hl!oolan ~

ol

j

a valves pump

=KSB-

9.7 Grap

h fo

r Calcu

lating

Velo

city Head

v2/2g as a F

un

ction

of C

apacity Q

and

I.D. o

f Pip

e D

6zfcn paall A

lloolaA

%m

mr

o

m

P

o

-~

~m

-

o

m

* n

pu

mp

V

alves

= KSB -

9.8 Grap

h fo

r Calcu

lating

Velo

city Head

Differen

tial A v2/2g a

s a F

un

ction

of C

apacity Q

and

Pip

e I.D. D

ifferential D

,/D,

~Z

/ZA

v le!w

ala

u!p

peau 4

loola

A

0

$m

ar

w

. f

0

" F

N

_ - ? z 0

m

m m

t-

t-

WI

D

9.9 Grap

h fo

r Calcu

lating

Head

Loss H, as a F

un

ction

of I.D

. of Pip

e D, Flow

Velocity v an

d C

apacity Q

0 Valves pumps

9.10 Graph for Calculating Conversion Factors fQ,w, fH,W and fqSw for Viscous Liquids

Available: data for operation with water Required: data for operation with viscous liquid

Calculation example: see page 21 Calculation chart: see page 44

0 Valves pumps

= KSB 9.11 Graph for Calculating Conversion Factors and fH,z for Viscous Liquids

Available: data for operation with viscous liquid Required: data for operation with water

Calculation chart: see page 44

Valves

II KSB - 9.12 Graph for Calculating Specific Speed n,

500 600 700800 1000 1500 2000 2500 3000 4000 1/m1n 6000 8000 10000 15000 20000 25000

I I 1 Speed n 960 1450 2900

All equations give numerically equal results.

Equations

nq = n . dc&n (Hopt 1 ) 3/rl.

n, = 333 - n . l,"Gz (g . Hopt) 3,4

nq = 5.55 . n - KG (g . Hod 3/4

With multistage pumps use the stage head. With double-entry impeller pumps use only half the capacity.

Example: Q0,, = 66 m3/h = 18.3 I/s; n = 1450 1 /min; Hop, = 17.5 m. Established: n, = 23 I /min

Units Qopt

mVs

mVs

m3/s

Hopt

m

m

m

n

l/min

l / s

I/min

n,

l/min

1

1

g = 9.81

m/s2 DIN 24 260

m/s2

/ Type series Quotation No

Rated speed Item No.

Schedule for Calculating the Operating Point and Pump Size for Handling Viscous Liquids.

Procedure

Operating Point To determine the new operating data it is also necessary to

Available data: calculate the data at b.e.p.

n. ,A! from araoh in 1 Illmin

I/s m -

Capacity Head

Speed

If Hz > Hw, use HZ = Hw

u... section 9.12 1

These values mean 4 points on QHz and Q ~ z line DIUS 3 points on the QPz line are established. Plotted over a.

Kinematic viscosity

Density Gravttational constant

fa,w tom section f,. ,.. 9.10

Calculation in graphic form

Qw,m ') HWW')

)1w,opt '1

Qw Hw n

-

I -

Pump Size Available data:

11s Capacity rn Head llmin Efficiency

Vz

Pz 9 9.81

capacity I Qz. ~~t~ 1 111s

Procedure

m2/s '1 from ind8vldual characterlstlc curve

kgIdm3 m/s2

Head I Hz,setr I 1 vz m2/s

m

Density 1 Pz / kgldma

n selected n,,~ 3) from section 9.1 2 faZ from section 9.1 1

Calculation in graphic form

I l/min

I l lmin -

-& %,6eic -

f ~ . ~

-b Hw,B~~- - fu.2

\/s

m

3, where Qz,~etr = Qopt approx. Hz.setr Hopt

Divisions

Gate and Globevalves Division Globe valves with soft or metallic seat, gate valves, ball valves, swing check valves, non-return valves and actuated valves for building services! industrial applications, chemical and proc:ss engineering as well as for conventional and nuclear power stations. Sector: Building Services Location and factory: Frankenthal

Sector: lnduskial Enginnering, conventional and Nuclear Power Stations ~.

Location and factory: Pegnitz

Butterfly valves Division : Butterfly valves with soft and metallic seat, swing check valves and actuators for building services, industrial applications, chemical and process engineering as well as for conventional and nuclear power stations. Location: Bagnolet Factory: LaRoche Chalais Building Setvices Division ~car 'n iano industrial warcr pLmps. Submersiulenloror p ~ m p s for the hanollng of sewage, elf Lent an0 fecccs h~ng planls. pumps for water supply, complete pump sets for pressure boosting and fire-fighting, pumps for irrigation and sprinkling, garden pumps. Systems for pump speed control. Location: Courbevoie Factories: Frankenthal, Neuvy, Pegnitz Engineered p i i p s division^ Centrifugal pumps for conventional and nuclear power plants: boiler feed and circulating pumps, condensate pumps, main coolant pumps, reactor feed pumps, cooling water pumps, pumps for seawater desalination plants, pumps for onshore and offshore applications as well as for refineries and the petrochemical industry. Location: Frankenthal Factories: Frankenthal, ~ n n e c y ~ '~

New Technologies Development and manufacture of new pump types, valves, systems and electronic controls as well as engineering services in the fields of hydrodynamics, materials technology, measurement techniques, open and closed loop control, plastics technology, cold-drawing methods for chrome nickel steel, machine dyfamics, product and packing design, patent rights. Location: Frankenthal Factories: Frankenthal, Chateauroux

Environmental Engineering Division Pumps for the treatment of municipal effluents (purification and transport), industrial effluents, surface drainage (shore protection, locks, lifting plants), aquaculture, agriculture (storage and transport of liquid manure), drainage in deep mining, delivery of cooling water and clean water. Planning, optimization, rehabilitation, supply, installation and commis- sioning of pumping stations for clean water and effluents. Components and systems for sewage treatment. Services to the planners and operators of the plants. Location: Frankenthal Factories: Pegnitz, Bremen, Lille

Industrial and Process Pumps Division Standardized Dumos and multi-staae DumDs for heat transfer - . . and industrial' water. Process pumps for the chemical and petrochemical industries, for refineries, high-temperature heating systems and cryogenics. Pumps for flue gas desul- phurization plants and for air and gas purifiers. Nan-clogging centrifugal pumps for paper, cellulose, sugar and foodstuffs industries and for the handling of solids. Location: Pegnitz Factories: Pegnitz, Ch?iteauroux, Deville, Frankenthal Water Pumps Division Multi-stage submersible motor pumps for municipal and industrial water s u ~ ~ l v . irriaation. buildina services. offshore . . .. - and mining applications as well as all special app~idations. Borehole shaft-driven Dumps for irriaation, water suo~lv . fire- . . .. fighting, and industrial'ap6ications.- Single-stage bearing pedestal mounted pumps for irrigation duties. Vertical propeller pumps for irrigation, water supply and agricultural drainage duties. Horizontal and vertical multi-stage pumps for irrigation and water supply systems. Location: Courbevoie Factories: Homburg (Saar), Chateauroux, Annecy

h J KSB Aktiengesellschaft Telephone: (06233) 86-0 Postfach 17 25 Fax: (0 62 33) 8633 95 D-6710 Frankenthal Teletex: 62333 = ksbft