centrifugal pump - Mechanical Engineering in Process Equipments

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CENTRIFUGAL PUMP SELECTION AND APPLICATION INTO THE SYSTEM

Foreword This article is a note or manual for mechanical engineer where work as rotating engineer or where concern to apply centrifugal pump into the system. Article contain how to select pump, performance analysis, power estimation, NPSH estimation and also to create or complete calculation sheet, datasheet and specification sheet as a part of detail engineering and purchasing activity. The following sequence of rotating engineer activity that usually do in engineering, procurement and construction for pumps. Receive, review and to complete Pump Calculation Sheet from Process Engineer Preliminary selection of appropriate pump. Plan to apply to system. Discuss and send back to Process engineer Receive, review and to complete Pump Data Sheet from Process Engineer Produce Specification Sheet based on Data Sheet Information where related National Standards may be applied. Produce General or Individual Specification for selected pump where related National Standards may be applied. Produce Technical Inquiry or Technical Requisition Collect appropriate Vendors. Send those documents in systematic bundle to Purchaser : Technical Inquiry, General or Individual Specification for Pump, Specification Sheet of Pump and other related Specification such as motor driver or turbine specification and the turbine specification sheet, Painting Specification. Purchaser will send the bundle to Vendors to inquire proposals. Technical evaluation Vendor’s proposal. Ask winner vendor for detail information about complete pump will be supplied. Base on this, create loading data for Civil Engineer and also send information related to pump nozzles to Piping Engineer include nozzle size & rating, position and allowable force and moment. Approval vendor’s documents before fabricating the pump. Witness during pump test as specified in the specification. Quality Control when pumps are received. Item to be checked are : manufacturer name, model no., serial no, painting color and completeness of supply that should be same with proposed and approved documents. Other detail items such as damages parts, main dimension of pump, shaft easy to rotate by hand, correct driver, correct coupling. Install the pumps. Electrical and instrument cables connection. Pre-commissioning. Making pre-commissioning procedure and supervise precommissioning. Commissioning. Prepare commissioning procedure and supervise commissioning

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CONTENT PAGE I.

GENERAL 1.1. Purpose of This Manual ................................................................. 1.2. Types of Centrifugal Pump ........................................................... 1.3. Components of Centrifugal Pump .............................................. 1.4. Operating Range of Centrifugal Pump ...................................... 1.4.1. Mechanically ................................................................. 1.4.2. Hydraulically ................................................................... 1.5. Nomenclature of This Manual …………………………………… ...

3 3 3 4 4 4 6

II. LIQUID AND THE PUMP PERFORMANCE 2.1. Mathematical Relations……………………………………………… 2.2. Centrifugal Pump Performance ................................................... 2.3. Best Efficiency Point ...................................................................... 2.4. Affinity Law ………. ........................................................................ 2.5. Specific speed ……………….. ...................................................... 2.6. Special Liquid ………………………………………………………….. 2.6.1. Viscous Liquid ................................................................. 2.6.2. Hydrocarbon Liquid .......................................................

6 7 7 8 9 9 9 10

III. CENTRIFUGAL PUMP IN THE APPLICATION 3.1. Pump and The System ................................................................. 10 3.1.1. Single Pump in The System ........................................... 10 3.1.2. Centrifugal Pump in Parallel Duty ................................ 11 3.2. Minimum Required Flow ............................................................... 11 3.3. Piping Around The Centrifugal Pump .......................................... 12 IV. DRIVER 4.1. Motor Driver .................................................................................... 15 4.2. Turbine Driver .................................................................................. 15 V. COUPLING .....................................................................................................

15

VI. PUMP SUPPORT ............................................................................................. 16 VII. VERTICAL PUMP ............................................................................................ 16 VIII. PACKING OR MECHANICAL SEAL .............................................................

16

APPENDIX A. NPSH REQUIRED ........................................................................... APPENDIX B. CENTRIFUGAL PUMP EFFICIENCY ............................................... APPENDIX C. SOME FLUID PROPERTIES ............................................................ APPENDIX D. SUCTION NOZZLE INFORMATION ............................................... APPENDIX E. EXAMPLES ..................................................................................... APPENDIX F. CREATING PUMP CALCULATION SHEET...................................... APPENDIX G. UNIT CONVERSION ………………………………………………….

18 19 20 21 22 24 26

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I. GENERAL 1.1. Purpose of This Manual. This manual guides the reader for selection and application of centrifugal pump into the system. This manual does not guide to design centrifugal pumps or the related components. 1.2. Type and Construction Feature of Centrifugal Pump. Type and construction features of centrifugal pump : 1. Position - Vertical - Horizontal - Submerged 2. Casing, Mechanically - Horizontal Split - Radial Split - Barrel Casing - Rings 3. Casing, Hydraulically : Volute , Diffuser 4. Number of Impellers in One Casing : Single Stage, Multi Stage 5. Impeller Type - Radial (closed or open impeller) - Francis - Mixed Flow - Axial Usually the name of centrifugal pump is for radial & francis impeller. Mixed flow and axial are named same as impeller types. 6. Impeller mounting : Over hung, Between bearing 7. Other type and features : - Suction type : Single suction or Double suction - Type of support : Centerline support, foot mounted or bracket - Services type such as cryogenic service, slurry pump. 1.3. Components of Centrifugal Pump. Main components of centrifugal pump : - Baseplate - Casing - Coupling - Impeller - Shaft - Wear rings - Shaft sleeve - Stuffing box or sealing chamber, Packing/Mechanical seal and Auxiliary Piping & the Instruments

4 - Bearing and Lube system and the instruments - Barrel or column pipe for vertical pump.

Fig.1. Cross sectional drawing of typical overhung single impeller centrifugal pump Driver

Coupling

Pump

Base plate

Fig. 2. Typical Complete Pump Arrangement Drawing 1.4. Operating Range Of Centrifugal Pump. 1.4.1. Mechanically . Casing Pressure : Up to about 300 kg/cm2 Speed : Up to about 4500 rpm for pump without increasing gear and up to 15000 rpm for high speed pump with increasing gear. Power : Up to about 2 MW.

5 1.4.2. Hydraulically. Capacity : Up to about 20000 m3/h for axial impeller pump, 10000 m3/h for mixed flow impeller vertical pump, up to about 4000 m3/hr for double suction radial, up to 10000 m3/hr for francis impeller pump and up to about 2000 m3/h for single suction radial type impeller pump. Total head : Up to about 200 m for single stage and up to about 2000 m for multistage centrifugal pump. The following chart shows the operating range of centrifugal pumps.

Fig. 3. Operating range of Centrifugal pumps.

Suction Equipment

Discharge Equipment

P2

P1

PD

PS

H

H2

H1

P2

DP2

DP1

OR

Pump Fig. 4. Simplified System Flow Diagram Around Centrifugal Pump

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1.5. Nomenclature In This Manual. All equations in this manual use the following nomenclature. : Suction Equipment Pressure (kg/cm2 A) : Suction liquid head (m) + (plus or positive) when liquid level is higher than the pump shaft - (minus or negative) when liquid level is lower than pump shaft DP1 : Pressure loss in the suction line (kg/cm2) PS : Pump suction pressure (kg/cm2A) H : Pump total head (m) PD : Pump discharge pressure (kg/cm2A) DP2 : Pressure loss in the discharge line (kg/cm2) DIP : Differential pressure = PD – PS (kg/cm2) H2 : Discharge liquid head (m) V : Liquid average velocity at suction flange (m/s) PV : Vapor pressure of liquid at pumping temperature (kg/cm2A) SG : Specific gravity of liquid at pumping temperature VIS : Viscosity at pumping temperature (cP, Centipoise) NPSHA : Net positive suction head available (m) given by system NPSHR : Net positive suction head required (m) given by pump characteristic LHP : Liquid horse power (kW) BHP : Brake horse power (kW) Q : Pump capacity (including minimum required flow, m3/h) E : Pump efficiency (%) D : Impeller diameter (m) N : Speed (RPM, rotary per minute) Nsq : Specific speed based on quantity or capacity (RPM) Nsp : Specific speed based on power (RPM) P1 H1

Note : See appendixes for NPSHR, liquid properties (SG, VP, VIS), Pump Efficiency and Unit conversion.

II. LIQUID AND THE PUMP PERFORMANCE 2.1. Mathematical Relations 1. Suction Pressure, Where

PS = P1 − DP1 + 0.1( H 1.SG ) − (500.SG.

V2 ) 98066.5

V =

0.5481(Q) D2

if D in inch, Q in m3/hr

V =

353.63 (Q) D2

If inside diameter D in mm (millimeter), Q in m3/hr

When velocity (V) low or neglected, PS become

PS = P1 − DP1 + 0.1( H 1.SG ) 2. Discharge Pressure,

PD = P 2 + DP 2 + 0.1( H 2.SG )

7 3. Differential Pressure, 4. Pump Total Head,

DIP = PD − PS

H = ( H 2 − H 1) + 10(

5. NPSHA,

=

10.DP SG

=

10( PS − PV ) SG

P 2 − P1 DP 2 + DP1 ) + 10( ) SG SG

NPSHA should be greater than NPSHR 6. Liquid Horse Power (LHP),

LHP = 0.00272 x DH x Q x SG

7. Brake Horse Power (BHP),

BHP =

100( LHP) E

2.2. Centrifugal Pump Performance. Usually, centrifugal performance is shown in Head vs Capacity curve. The performance curve shows the relation between capacity and total head for available impeller diameter in one model number and included also the NPSH Required, BHP and Efficiency.

Fig. 5. Typical Centrifugal Pump Performance Curve For One Casing or Model. Usually, performance curve presents impeller diameter range that possible to be installed in one casing or model, efficiency and NPSHR. In the proposal, manufacturer or vendor will extract in specific impeller diameter together with pump specification sheets that been designed in accordance with purchaser specification. See fig. 6.

8 2.3. Best Efficiency Point. In case of selection or evaluation, the capacity of the best efficiency point shall be at between normal capacity and the rated capacity . Best efficiency point is important when the pump is operated on continues duty (See Fig. 5 and Fig. 6 ).

Operating point

Head

Rated point BHP

Efficiency

BEP

Head Efficiency

BHP

Capacity Fig. 6. Typical Single curve 2.4. Affinity Law. Based on following velocity diagram, Q = A x Cr

where A = Outlet impeller gap area and Cr is radial velocity

Cr = K1 . D . N

where K1, K2 , K3 …… are constants

Then, if A is designed in constant value : Q = K2 . D . N If SG of liquid constant or based on water, H = K3 . Cr2 = K4 . D2 . N2 If D constant, Q become = K5. N, H = K6 . N2 and LHP = K7 . N3 Cr When a centrifugal pump operates at different speed, relation between speed and other variables become : H2 Q2

= H1 x ( N2 / N 1 )2 = Q1 x ( N2 / N1 )

LHP2 = LHP1 x ( N2 / N1 )3

9 And when centrifugal pump and axial pump operates at different total head and capacity but at the same speed and impossible to modify the system, impeller diameter shall be resized and the performance will depend on diameter, see fig. 3. H2

= H1 x ( D2 / D1 )2

Q2

= Q1 x ( D2 / D1 )

LHP2

= LHP1 x ( D2 / D1 )3

D2, N2, H2, Q2 and LHP2 are new condition. D1, N1, H1, Q1 and LHP1 are previous condition. Please note that those equations are only for impeller that possible to be applied in one casing and at speed range that permitted by manufacturer. 2.5. Specific Speed The speed where geometrically similar shape impellers (even different size) deliver liquid 1 liter / second (3.6 m3/hr) against 1 meter head is defined as “Specific speed based on unit quantity”, Nsq. And when absorb 1 metric HP for 1 meter head defined as “Specific speed based on power”, Nsp.

Nsq =

0.527 N .Q 1 / 2 ) H 3/ 4

Nsp =

1.341N .BHP1 / 2 ) H 3/ 4

where Q in m3/hr

where BHP in kW

Specific speed is helpful for selection a centrifugal pump. The following table presents specific speed for various type of pump. Type of impeller

Specific speed, Nsq

- Radial impeller - Mixed flow - Fast runner mixed flow - Axial pump

10.5 – 60 38 – 85 85 – 165 165-500

2.6. Special Liquids in The Centrifugal Pump. 2.6.1. Viscous Liquid. When a centrifugal pump is tested with water and to be applied for high viscosity liquid ( higher than 5 centipoise ) at the same speed, the performance of pump will decrease. The following equations are the decreasing factors due to viscous liquid. Defined capacity factor : Qf Qf = 0.71162 x (Q/60)-0.22767 x (H)-0.13292 x ( VIS/SG)0.497 If Qf <= 0.6 , Pump performance no need any correction If Qf > 0.6 , Pump efficiency shall be corrected by correction factor Ce If Qf > 0.9 , Pump head shall be corrected by correction factor Ch If Qf > 3 , Pump capacity shall be corrected by correction factor Cq

10 Ce = 0.01 x (102.27 - 7.291 x Qf ) Ch = 0.01 x (101.65 - 1.829 x Qf ) Cq = 0.01 x ( 109.64 - 3.214 x Qf ) Written in water test performance : QWATER

= QVIS / Cq

DHWATER = DHVIS / Ch E WATER = E VIS / Ce Qvis, DHvis, E vis: Conditions shall be performed by pump to service the viscous liquid . Qwater, DHwater, Ewater : Conditions shall be performed by water tested pump to provide the correct performance on viscous liquid. 2.6.2. Hydrocarbon Liquids. When the centrifugal pump to be applied for hydrocarbon liquid, NPSHR of water tested pump shall be corrected. NPSHR water tested = NPSHR hydrocarbon / Chyd Where Chyd = 0.01 x { 60 + 551.2 x (1- SG ) x ( 14.223 x PV) -0.4757 } For ammonia liquid, typical user require NPSHR < (NPSHA - 1 meter)

III. CENTRIFUGAL PUMP IN THE APPLICATION. 3.1. Pump and The System. The system is defined as overall piping and equipment where liquid is flowing from defined suction equipment to defined discharge equipment. See Fig. 4. 3.1.1. Single Pump in System.

Fig. 7. Centrifugal Pump in Operation.

11 Operating point is condition where characteristic curve of system cross with the pump curve. In plant operation, there are several operating condition : Normal operation (100 %), cut rate (below 100%), uprate (more than 100%). Rated point for pump is condition where pump operates continuously at upper the normal condition and mechanically (include driver), is still permitted. Those conditions are listed in API standards. Fig. 7 shows static head and head loss. Static head is static liquid head plus differential pressure head between discharge equipment and suction equipment (P2-P1 in head). Head loss is total differential pressure drop head (DP1+DP2 in head), see Fig. 4. Simple conversion from pressure to head H = 10 x (Differential pressure) / SG or 10 time diff. pressure divided by SG. Please note that unit shall be as Nomenclature above. To create or plot system characteristic, pressure drop along of system shall be calculated for each flow on Excel sheet or using software. See Piping Manual for this purpose. 3.1.2. Centrifugal Pump in The Parallel Duty. When centrifugal pumps operate in parallel, equal pump is recommended. The following figure shows performance curve of two equal pump in parallel duty in the same system. For high head loss system, capacity in new operating point will not equal to 2 time.

Fig. 8. Two Equal Pump in Parallel Operation But for system where head loss is low comparing with differential pressure between discharge and suction equipment, capacity will nearly to 2 time of previous operating point. 3.2. Minimum Required Flow . Centrifugal pump is not permitted to operate at no flow (shut off). There are two reason why centrifugal pump require minimum flow. 1. Flow Stability : Some pump have performance curve with uncontinous negative slope from zero flow until the stable region. If centrifugal pump shall operate at no flow to the system for

12 relatively long time, pump shall have minimum flow line or bypass line.

Fig. 9. Continuous and Uncontinuous Negative Slope Performance Curve. 2. Thermal : Heat is generated by the friction between impeller and liquid in the casing. And also packing or mechanical seal are generates heat. When casing is not enough surface to transfer the heat to surrounding, casing and related component temperature will gradually increase and may cause pump component damages. If pump shall be operated at shut off condition for long time for any reason, bypass line with cooler is required. But this condition is rarely used. The exact values of minimum required flow is informed by the Pump vendor in the datasheet. But for roughly estimation (usually to determine the piping size for minimum flow), the required minimum flow is about 30 % of the normal capacity. When necessary, restriction orifice is required to provide more precise minimum required flow. For hydrocarbon liquid, the flash point of the liquid is recommended to be taken account. Purchaser (user) shall prepare the bypass line for this minimum required flow. 3.3. Piping Around Centrifugal Pump. In general, piping around pump is shown as the following figure as minimum requirement.

Fig. 10. Piping System Around Centrifugal Pump. Two insulation valve at suction and discharge to insulate pump while repair or overhaul. Non return valve prevent pump from back flow. Back flow liquid entering to pump will rotate impeller

13 and driver in reverse direction with un-controlled speed that may course pump or driver damage. Drain valve need to drain liquid in pump casing when pump will be repaired. Vent valve necessary for venting air or vapor during priming. Strainer contain screen inside to prevent pump from solid matter that may course damage to mechanical seal or wearing rings. Priming is necessary before starting pump. The following figure shows which valve to be closed and open.

Fig. 11. Piping System While Priming After priming has completely done, pump can be started. Opening discharge valve is gradually to prevent sudden flow or hammering at discharge line if pump is quite big. Additional piping may required for bypass line and optional line. Bypass line or minimum required flow to prevent pump operate below minimum required flow. Optional line necessary for : - Preheat the piping or equipment in the down stream, when liquid is very hot - Cooling down the piping or equipment in the down stream, when the liquid is very cold - Equalizing line to protect non return valve and valve from high different pressure. - Initial opening when discharge line is sensitive for hammering Optional line is opened when the pump is completely running and may be used for temporary opened if all item above has been completely done before discharge valve start to cracking open.

Fig. 12. Optional Piping and Bypass Line Suction pipe shall be planned to provide enough NPSHA and no vapor or air pocket. The following figures show the recommended suction piping.

14 Good. When the suction liquid head is positive or NPSHA higher than estimated NPSHR

Generally not accepted.

Accepted when completed with foot valve and NPSHA is higher than estimated NPSHR

Fig. 13. Suction piping for Centrifugal Pump.

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IV. DRIVER 1. MOTOR DRIVER When API-610 is specified, power rating on motor nameplate shall be higher or equal to (>=) BHP time multiplier : Nameplate power 19 < kW 22 - 56 kW >= 75 kW

Multiplier 1.25 1.15 1.10

Example : Pump rated BHP = 18.3 kW. Motor nameplate power shall be >= 1.25 x 18.3 kW = 22.875 kW. But now, multiplier become 1.15, because 22.875 at between 22 and 56 kW. Recalculate : Pump rated BHP x multiplier = 18.3 x 1.15 = 21.045 kW. Selected motor HP = 22 is accepted, because 22 kW > 21.045 kW. Example : Pump rated BHP = 25 kW. Motor nameplate HP shall be >= 1.15 x 25 = 28.75 kW. Multiplier is 1.15 because 28.75 kW at between 22 to 56 kW. For autostart operation, motor HP shall be > max. pump BHP. User shall specify autostart operation in the data sheet and also check the quotation. 2. TURBINE DRIVER When API-610 pump is specified, power rating of steam turbine driver shall be > 1.1 x Pump rated BHP.

V. COUPLING When pumping temperature is taken account or driver produces heat such as steam turbine, flexible coupling is better than rigid coupling. Flexible coupling will eliminate the thermal expansion of pump or driver during operation. Rubber bush type coupling is also flexible coupling and lower cost, but does not for high temperature services. Typical membrane coupling Typical rubber bush coupling

16 Flexible coupling may be gear, membrane coupling or rubber bush coupling. Flexible coupling is more tolerates with misalignments. Coupling spacer is usual for flexible coupling to make more tolerable on the angular misalignment.

VI. PUMP SUPPORT When horizontal pump will be operated at high temperature, centerline support is most suitable. Foot type support is suitable when pumping temperature is close to ambient temperature and driver is fan cooled motor or when the motor driver is integrated on the small pump.

VII. VERTICAL PUMP When caned vertical pump is installed in the concrete or metal lined concrete well and operating temperature is high, vent hole is necessary. When operating temperature is very low ( below 0 oC), insulation is necessary to prevent the concrete cracked or iceing. Remove any water in the well and purge well with dry gas (N2 or dry air) to remove water vapor before priming.

VIII. PACKING or MECHANICAL SEAL To prevent leakage from pump through the shaft , there are seals with packing or mechanical seal. Packing seal is less cost but more power loss due to large of contact surface between packing and shaft or shaft sleeve and suitable for limited speed. Mechanical seal is less power loss and suitable for higher speed and no wear on shaft sleeve. When the pumping liquid is toxic and flammable, there are bellow mechanical seal type. Flush piping is necessary for mechanical seal or packing seal. Flushing liquid shall be clean. Purpose of flushing liquid is for cooling the contact seal parts that always produce heat and remove dirty matter that cause a damages on those parts. Pumping liquid is usual for flushing liquid when the liquid is clean. Cooler and strainer are necessary when pumping temperature is very high.

Clean external flushing is applied when : - Pumping liquid is dirty. - External flushing liquid is permitted to mix with the pumping liquid. - External flushing liquid pressure is higher than the stuffing box pressure. Vent on the seal gland of mechanical seal is necessary to bleed air or vapor before starting the pump. Quenching is necessary when : - Pumping temperature is very low that may cause built ice between shaft and seal gland. - Pumping liquid is toxic or flammable. Quenching liquid shall dilute the pumping liquid. - Pumping liquid is easy to crystallize at below pumping temperature. Lip seal is required when necessary for sealing the quenching liquid. Quenching liquid and small

17 amount of pumping liquid flow through the pipe and drained to sewer. But sometime, quenching liquid and small amount pumping liquid flows through bushing or labyrinth to drain. Option about flushing, quenching, vent and drain and auxiliary piping are presented in API standard.

Typical mechanical seal. Single Seal (One pair of seal)

Typical mechanical seal. Double Seal (Two pair of seals)

Seal material Silicon carbide vs carbon and Tungsten carbide vs carbon are widely use in moderate temperature services. But for some liquid such as ammonia, facing seal material shall be selected carefully. Selection of mechanical seal type, material and auxiliary piping shall be based on pump specification sheet and other specification specially liquid properties to be handled, pressure, temperature and speed.

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APPENDIX A. NPSHR (Net Positive Suction Head Required)

Fig. A.1. NPSHR for Single Suction Centrifugal Pump All data presented in Fig. A.1 were collected from several manufacturers. Upper blue line is the highest NPSHR at 2975 RPM and lower yellow dot line is highest NPSHR at 1480 RPM. For speed below 1480 RPM, highest NPSHR can be calculated = Highest NPSHR at 1480 x (Speed in RPM / 1480). This chart is helpful for designing suction system of centrifugal pump.

Fig. A.2. NPSHR for Double Suction Centrifugal Pump Highest NPSHR at speed below 1480 RPM = NPSHR at 1480 x (Speed in RPM / 1480).

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APPENDIX B. CENTRIFUGAL PUMP EFFICIENCY

Fig. B.1. Efficiency of Single Impeller Centrifugal Pump Efficiency curves presented in Fig. B.1. is generalized curve from data that are taken from several manufacturers without diameter and speed as variables. This chart is helpful in basic and detail engineering where overall project need information about power consumption of pump in their power balance plan or needed by other discipline where they plan for supporting equipments, materials or in cost estimation.

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APPENDIX C. PROPERTIES OF SOME LIQUID Following table presents properties of some liquids.

21

APPENDIX D. SUCTION NOZZLE SIZE Following table presents typical nozzle sizes. Nozzle size is necessary when dynamic pressure or velocity of liquid is important in determing NPSH. Diameters are presented in inches as per ANSI standard. These dimensions shall be converted to meter before equations in section 2.1 are used. Velocity can be determined with equation V = Q / (3600.A) in m/s, where Q is capacity in m3 /hr and A is suction nozzle area = 3.14 x 0.25 x ID2 in m2 where ID in meter.

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APPENDIX E. EXAMPLES A quantity of process liquid shall be delivered by centrifugal pump from vertical vessel to process vessel through discharge system shown in following figure. Net volume flow to be delivered is 200 m3 / h. Pump is possible to shut off at any time and by pass valve is always open in normal operation. Liquid properties are, vapor pressure = 0.43 kg/cm2 A, viscosity = 0.09 cP and Spec. Gr. = 0.87 at pumping temperature. Liquid is not hydrocarbon. Driver is 50 Hz electric motor. Other given data, P1=1 kg/cm2 A, P2= 8 kg/cm2 A, suction system pressure drop DP1=0.2 kg/cm2, DP2 include HE = 0.5 kg/cm2, discharge liquid head at minimum level H2=40 m. Items to be estimated : - Select pump type - Estimate the NPSHR, - Minimum level of liquid at suction equipment H1 - Expected NPSHA after deciding the minimum level of the suction equipment H1. - Total head required. - Capacity required in normal operation. - Estimate BHP

Calculation without H1. 1. 2. 3. 4.

Suction pressure PS = P1 – DP1 = 1 – 0.2 = 0.8 kg/cm2 A Discharge pressure PD = P2 + DP2 + 0.1 (H2)(SG) = 8 + 0.5 + 0.1 (15)(0.87) = 9.805 kg/cm2 A Total head H = 10 (PD – PS)/SG = 103.506 m Estimate minimum required flow 15 %. Capacity include minimum flow Q = 1.15 x 200 = 230 m3/h. From Fig.3 in chapter 1.4 , the point of Q =230 m3/h and H=103.5 m is in single stage, single suction centrifugal pump range. Select this pump type. 5. At 2975 RPM (50 Hz motor without reduction gear), the highest NPSHR from Appendix A = 7 m 6. NPSHA = 10(PS-PV)/SG = 10(0.8-0.43)/0.87 = 4.25 m Calculate H1. 1. Minimum liquid level required H1 = NPSHR – NPSHAwithout H1 = 7 - 4.25 = 2.75 m

23 Calculation with considering of H1. 1. 2. 3. 4. 5. 6.

PS = P1 – DP1 + 0.1 (H1)(SG) = 0.8 + 0.1(2.75)(0.87) = 1.039 kg/cm2 A H = 10 (PD-PS)/SG = 100.76 m NPSHA = H1 + 10 (PS-PV)/SG = 9.75 m LHP = 0.00272 (Q)(H) = 0.00272 (230)(100.76) = 63 kW From Appendix B, average eff. = 66% and highest eff. = 67.5%. Lower eff. E = 66-(67.5-66)= 64.5 % BHP at lower efficiency = 100 (LHP)/E = 100 (63) / 64.5 = 97.7 kW

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APPENDIX F. CREATING PUMP CALCULATION SHEET Following is typical calculation sheet for Centrifugal Pump. In the first sheet shows formula and the next sheet is example using this sheet.

25

26

APPENDIX G. UNIT CONVERSION

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centrifugal pump - Mechanical Engineering in Process Equipments

1 CENTRIFUGAL PUMP SELECTION AND APPLICATION INTO THE SYSTEM Foreword This article is a note or manual for mechanical engineer where work as rotatin...

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