Centrifugal Pumps Design and Application 2nd ed - Val S. Lobanoff, Robert R. Ross (Butterworth-Heinemann, 1992)

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2 Specific Speed and Modeling Laws Specific speed and suction specific speed are very useful parameters for engineers involved in centrifugal pump design and/or application. For the pump designer an intimate knowledge of the function of specific speed is the only road to successful pump design. For the application or product engineer specific speed provides a useful means of evaluating various pump lines. For the user specific speed is a tool for use in comparing various pumps and selecting the most efficient and economical pumping equipment for his plant applications. A theoretical knowledge of pump design and extensive experience in the application of pumps both indicate that the numerical values of specific speed are very critical. In fact, a detailed study of specific speed will lead to the necessary design parameters for all types of pumps. Definition of Pump Specific Speed and Suction Specific Speed Pump specific speed (N s ) as it is applied to centrifugal pumps is defined in U.S. units as: Specific speed is always calculated at the best efficiency point (BEP) with maximum impeller diameter and single stage only. As specific speea can be calculated in any consistent units, it is useful to convert the calculated number to some other system of units. See Table 2-1. The suction specific speed (N ss ) is calculated by the same formula as pump specific speed (N s ) 11
12 Centrifugal Pumps: Design and Application Table 2-1 Specific Speed Conversion Capacity UNITS Head/ Stage U.S. to Metric Multiply By .0472 .0194 ,15 1.1615 Metric to U.S. Multiply By 21.19 51.65 6.67 .8609 Ft 3 /Sec M 3 /Sec M 3 /Min M 3 /Hr Feet Meters Meters Meters but uses NPSHR values in feet in place of head (H) in feet. To calculate pump specific speed (N s ) use full capacity (GPM) for either singleor double-suction pumps. To calculate suction specific speed (N ss ) use one half of capacity (GPM) for double-suction pumps. It is well known that specific speed is a reference number that describes the hydraulic features of a pump, whether radial, semi-axial (Francis type), or propeller type. The term, although widely used, is usually considered (except by designers) only as a characteristic number without any associated concrete reference or picture. This is partly due to its definition as the speed (RPM) of a geometrically similar pump which will deliver one gallon per minute against one foot of head. To connect the term specific speed with a definite picture, and give it more concrete meaning such as GPM for rate of flow or RPM for rate of speed, two well known and important laws of centrifugal pump design must be borne in mind—the affinity law and the model law (the model law will be discussed later). The Affinity Law This is used to refigure the performance of a pump from one speed to another. This law states that for similar conditions of flow (i.e. substantially same efficiency) the capacity will vary directly with the ratio of speed and/or impeller diameter and the head with the square of this ratio at the point of best efficiency. Other points to the left or right of the best efficiency point will correspond similarly. The flow cut-off point is usually determined by the pump suction conditions. From this definition, the rules in Table 2-2 can be used to refigure pump performance with impeller diameter or speed change.
Page 2 and 3: CENTRIFIUGAL PUMPS Design & applica
Page 4 and 5: CENTRIFUGAL PUMPS Design & Applicat
Page 6 and 7: Contents Preface —..... —......
Page 8 and 9: ern Pumps, Mine Dewatering Pumps. W
Page 10 and 11: Stage Pumps. Single-Suction Single-
Page 12 and 13: Preface When Val and I decided to c
Page 14 and 15: CENTRIFUGAL PUMPS Design & applicat
Page 16 and 17: Part 1 Elements of Pump Design
Page 18 and 19: 1 Introduction System Analysis for
Page 20 and 21: Introduction 5 Figure 1-2. The syst
Page 22 and 23: Introduction 7 mate responsibility
Page 24 and 25: Introduction 9 Figure 1-6. Maximum
Page 28 and 29: Specific Speed and Modeling Laws 13
Page 38 and 39: Figyre 2-7, New pump from model pum
Page 44 and 45: Impeller Design 29 Figure 3-1. Requ
Page 46 and 47: Impeller Design 31 Figure 3-4. Capa
Page 48 and 49: Impeller Design 33 Step 8: Estimate
Page 50 and 51: Impeller Design 35 Figure 3-7. Volu
Page 52 and 53: impeller Design 37 (2) 5 , as final
Page 54 and 55: Impeller Design 39 The vane develop
Page 56 and 57: Impeller Design 41 Figure 3-12. Are
Page 58 and 59: impeller Design 43 Figure 3-16. Inf
Page 60 and 61: 4 General Pump Design It is not a d
Page 62 and 63: General Pump Design 4? Figure 4-1.
Page 64 and 65: General Pump Design 49 designed and
Page 66 and 67: Volute Design 51 Figure 5-1. Volute
Page 68 and 69: Volute Design 53 Figure 5-2. Radial
Page 70 and 71: Volute Design 55
Page 72 and 73: Volute Design 57 Figure 5-4. Effici
Page 74 and 75: Volute Design 59 Figure 5-5. Typica
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Volute Design 61 Figure 5-8. Univer
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Volute Design S3 Manufacturing Cons
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6 Design of Multi-Stage Casing Mult
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Design of Multi-Stage Casing 67 How
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Design of Multi-Stage Casing 69 Fig
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Design of Multi-Stage Casing 73 sec
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7 Double-Suction Pumps and Side-Suc
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Double-Suction Pumps 79 two. Experi
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Double-Suction Pumps 81 Figure 7-3.
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Double-Suction Pumps 83 LOCATION AR
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8 NPSH The expressions NPSHR and NP
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NPSH 87 Predicting NPSHR The other
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NPSH 89 Figure 8-4. Pressure loss b
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NPSH 91 SUCTION VELOCITY TRIANGLES
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NPSH 93 Figure 8-8. Performance cur
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NPSH 95 Figure 8-10. Leakage across
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NPSH 97 Figure 8-13. Plate inserts
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NPSH 99 Figure 8-17. Influence of p
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NPSH 101 Figure 8-19. Estimating K
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NPSH 103 Step 3: Determine KI* From
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Figure 8«22. Calculating NPSHA for
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NPSH 107 Figure 8-24. NPSHR cavitat
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NPSH 109 Notation KI Friction and a
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Part 2 Application
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9 by Erik B. Fiske BW/JP Internatio
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Vertical Pumps 115 Figure 9-2. Well
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Vertical Pumps 117 Figure 9-4. Subm
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Vertical Pumps 119 Figure 9-6. Inst
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Vertical Pumps 121 Figure 9-8. Barr
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Vertical Pumps 123 • Loading pump
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Vertical Pumps 125 Wet Pit Pumps Th
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Vertical Pumps 127 • Fresh water
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Vertical Pumps 129 Condensate and H
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Vertical Pumps 131 mally insulate w
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Vertical Pumps 133 Figure 9-15. Imp
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Vertical Pumps 135 checked for corr
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Vertical Pumps 137 crating paramete
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10 Pipeline Pipe line, Waterflood,
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Pipeline, Waterflood and CO 2 Pumps
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Pipeline, Waterfiood and CO 2 Pumps
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Figure 10-11. Performance change wi
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Figure 10-13. Seven-stage pump dest
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Pipeline, Waterflood and COa Pumps
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11 By Edward Gravelle Sundstrand Fl
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High Speed Pumps 175 History and De
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High Speed Pumps 177 Figure 11-2. (
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High Speed Pumps 179 some portion o
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High Speed Pumps 181 This is to say
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High Speed Pumps 183 This expressio
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High Speed Pumps 185 Figure 11-3. P
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High Speed Pumps 187 As an aside, p
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High Speed Pumps 189 Figure 11-5. I
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High Speed Pumps 191 Figure 11-7. I
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High Speed Pumps 193 Figure 11-9. R
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High Speed Pumps 195 Figure 11-10.
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High Speed Pumps 19? Figure 11-11.
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High Speed Pumps 199
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High Speed Pumps 201 Figure 11-13.
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High Speed Pumps 203 nal bearings a
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High Speed Pumps 205 Barske, U, M.,
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Double-Case Pumps 207 jected to ext
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Double-Case Pumps 209 Figure 12-3.
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Double-Case Pumps 213 ally by split
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Double-Case Pumps 215 The throttle
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Figure 12-11. pump for 4,000 psi In
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Double-Case Pumps 219 so that the t
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Doubte-Case Pumps 223 Volute Casing
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Double-Case Pumps 225 5. Survey of
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Slurry Pumps 227 An approximate com
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Slurry Pumps 229 Figure 13-2. Nomog
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Slurry Pumps 231 Table 13-2 Alloys
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Slurry Pumps 233 Figure 13-3. Class
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Figure 13-4, (A) (B) (C)
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Slurry Pumps 237 There is little to
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Figyre 13-7, (courtesy Pumps, Inc.)
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Flgyr« 13-8, with (courtesy Goulds
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Slurry Pumps 243 ing the pump speed
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Slurry Pumps 245 Where there exists
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Hydraulic Power Recovery Turbines 2
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Figure 14-14. Internally adjustable
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14-22, Flow of hydraulic recovery a
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15 by Frederic W. Buse Ingersolf-Ra
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Chemical Pumps Metallic and Nonmeta
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Driver Chemical Pumps Metallic and
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Part3 Mechanical Design
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16 Shaft Design and Axial Thrust Sh
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Shaft Design and Axial Thrust 335 S
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Shaft Design and Axial Thrust 337 W
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Shaft Design and Axial Thrust 339 T
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Shaft Design and Axial Thrust 341 b
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Shaft Design and Axial Thrust 343 K
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Double-Suction Single-Stage Pumps S
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Shaft Design and Axial Thrust 347 F
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D (with subscript) P D P s T T (wit
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Mechanical Seals 355 Figure 17-1. M
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Mechanical Seats 357 Figure 17-2B.
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Mechanical Seals 359 Figure 17-2D.
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Mechanical Seals 361 Figure 17-4. H
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Mechanical Seals 363 Pressure-Veloc
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Mechanical Seals 365 The temperatur
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Mechanical Seals 367 Figure 17-7. B
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Mechanical Seals 369 Figure 17-9. P
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Mechanical Seals 371 where C 3 = 53
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Mechanical Seals 373 Classification
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Mechanical Seals 375 Double seals m
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Mechanical Seals 377 less than 100,
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Mechanical Seals 379 Figure 17-19.
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Mechanical Seals 381 Table 17-4 Tem
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Mechanical Seats 385 steam, is to p
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Mechanical Seats 38? rather than a
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Mechanical Seals 389 Mechanical Sea
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Mechanical Seals 391 seal to work i
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Mechanical Seals 395 The measured l
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Mechanical Seals 39? Figure 17-34.
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Mechanical Seals 401 This design is
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Mechanical Seals 403 alignment, par
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Mechanical Seats 419 Figure 17-58.
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Vibration and Noise in Pumps 421 Re
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Vibration and Noise in Pumps 423 me
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Vibration and Noise in Pumps 425 in
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Vibration and Noise in Pumps 427 pr
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Vibration and Noise in Pumps 429 ot
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Vibration and Noise in Pumps 431 Fi
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Vibration and Noise in Pumps 433 fi
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Vibration and Noise in Pumps 435 pr
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Vibration and Noise in Pumps 437 up
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Vibration and Noise in Pumps 441 na
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Vibration and Noise in Pumps 443 A
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Vibration and Noise in Pumps 453 Re
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Vibration and Noise in Pumps 457 Ac
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Vibration and Noise in Pumps 461 As
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Vibration and Noise in Pumps 463 ci
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Vibration and Noise in Pumps 467 sp
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Vibration and Noise in Pumps 469 Be
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Vibration and Noise in Pumps 475 Vi
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Vibration and Noise in Pumps 489 pe
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Vibration and Noise in Pumps 491 th
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Vibration and Noise in Pumps 4S3 fo
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Part 4 Extending Pump Life
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19 by Malcolm G. Murray, Jr. Murray
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Alignment 499 Figure 19-2. Pump dam
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Alignment 501 The best designs fail
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Table 19-1 Vertical Alignment Movem
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Table 19-2 Continued Horizontal Ali
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Alignment 507 bearing motors becaus
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Alignment 509 meet results. It shou
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Alignment 511 Determination of Tole
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Table 19-3 Continued Primary Alignm
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Alignment 515 Figure 19-3 A & B. Tw
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Table 19*4 Continued Methods of Cal
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Alignment 510 parallelism/perpendic
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Alignment 521 Table 19-5 continued
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Alignment 523 3. Essinger, J. N., B
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Rolling Element Bearings and Lubric
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Roiling Element Bearings and Lubric
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Roiling Element Bearings and Lubric
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Failure Analysis Mechanical Seal Re
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Table 21-2 Causes of Seal Failures
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Mechanical Seal Reliability 561 ^mi
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Mechanical Seal Reliability 563 Sea
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Mechanical Seal Reliability 565 run
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Reliability Mechanical Seal Reliabi
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Index A thermal growth, 519-522 ver
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Critical speed analysis. See also V
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Index 573 inlet angle, 37 classific
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Index 575 Shaft design, 333-343 ind
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double, 52-54 velocity ratio, 50-51
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Centrifugal Pumps Design and Application 2nd ed - Val S. Lobanoff, Robert R. Ross (Butterworth-Heinemann, 1992)

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