pumps.pdf

FM20

CAPTURE CENTRIFUGAL PUMP DEMONSTRATION UNIT

FM20

ISSUE 2 AUGUST 1996

LECTURERS' NOTES ParametersFile All numerical constantsinvolved with the Capture unit are included in the file PARAM. TXT. The file can be altered with any text editor (eg. the MSDOS ~nv command), should the user wish to changeany of the values. Care should be taken not to damage or corrupt the file. Should this happen, re-install the software from the floppy disks. Assignment File The questions given in the student assignment are all stored in the file FM_ASGN.TXT. The assignmentfile already has severalquestionsincluded, but is designed to allow lecturers to enter their own questions, depending on the particular course content. As for the parametersfile, any text editor can be used to edit the questions. The format should be similar to the questions already included. Answers should be placed at the end of the question surrounded by the {} brackets. Font Installation To ensure correct operation of the Capture software, the IGreekMathSymbolsl should be installed in Windows.

font

This can be checked by double clicking on Control Panel in the Main program group of the Program Manager. SELECTFonts and check that 'Greek/Math/Symbols' is included in the installed fonts list. If it is not, click on Add... and selectthe font 'SYMBOLS' from the list of fonts in the windows\system directory, then click on OK. The font should now be shown in the installed fonts list.

The following manual is taken from the help screensavailable within the software.

ARMFIELD OPERATING FM20

- CAPTURE

LIMITED

INSTRUCTIONS CENTRIFUGAL

AND EXPERIMENTS

PUMP DEMONSTRATION

UNIT

PAGE NO.

SAFETY

1

RECEIPTOF EQUIPMENT

5

MINIMUM COMPUTER SYSTEMREQUIREMENTS

6

INSTALLING THE ARMFIELD INTERFACECONSOLEIFD

7

INSTALLING THE SOFTWARE

8

DESCRIPI10N

10

PREPARINGTHE CENTRIFUGAL PUMP DEMONSTRAnON UNIT FOR USE

13

ROUTINE MAINTENANCE

15

INDEX TO EXPERIMENTS

16

GENERAL SAFETYRULES

a

SAFETY IN THE USE OF EQUIPMENT SUPPLIED BY ARMFIELD

Before proceeding to install, commission or operate the equipment describedin this instruction manual we wish to alert you to potential hazardsso that they may be avoided. Although designed for safe operation, any laboratory equipment may involve processesor procedures which are potentially hazardous. The major potential hazards associatedwith this particular equipment are listed below.

. . . .

INJURY THROUGH MISUSE INJURy FROM ELECfRIC SHOCK (Particularly in presence of water) INJURy FROM ROTAnNG COMPONENTS RISK OF INFEC110N THROUGH LACK OF CLEANLINESS

Accidents can be avoided provided that equipment is regularly maintained and staff and students are made aware of potential hazards. A list of generalsafety rules is included in this manual, to assiststaff and students in this regard. The list is not intended to be fully comprehensive but for guidance only. Please refer to the notes overleaf regarding the Control of Substances Hazardous to Health Regulations.

1

The COSHH Regulations

The Control of Substances Hazardous to Health (1988)

Regulations

The COSHH regulations impose a duty on employers to protect employees and others from substancesused at work which may be hazardous to health. The regulations require you to make an assessment of all operations which are liable to expose any person to hazardous solids, liquids, dusts, vapours, gasesor micro-organisms.You are also required to introduce suitable procedures for handling these substancesand keep appropriate records. Since the equipment supplied by Armfield Limited may involve the use of substanceswhich can be hazardous (for example, cleaning fluids used for maintenance or chemicals used for particular demonstrations) it is essentialthat the laboratory supervisor or some other person in authority is responsiblefor implementing the COSffii regulations. Part of the above regulations are to ensure that the relevant Health and Safety Data Sheetsare available for all hazardous substancesused in the laboratory. Any person using a hazardous substancemust be informed of the following: Physicaldata about the substance Any hazard from fire or explosion Any hazard to health Appropriate First Aid treabnent Any hazard from reaction with other substances How to dean/ disposeof spillage Appropriate protective measures Appropriate storageand handling

Although theseregulationsmay not be applicablein your countryI it is strongly recommended that a similar approach is adopted for the protection of the students operating the equipment. Local regulations must also be considered. Water-Borne Infections

The equipment describedin this instruction manual involves the use of water which under certain conditions can createa health hazard due to infection by harmful micro-organisms. For example, the microscopic bacterium called Legionella pneumophila will feed on any scale,rust, algae or sludge in water and will breed rapidly if the temperature of water is between 20 and 45°C.Any water containing this bacterium which is sprayed or splashedcreating air-borne droplets can

2

produce a form of pneumonia called Legionnaires Disease which is potentially fatal. Legionella is not the only hannful micro-organism which can infect water, but it servesas a useful example of the need for cleanliness. Under the COSHH regulations, the following precautions must be observed:Any water contained within the product must not be allowed to stagnate, ie. the water must be changedregularly. Any rust, sludge, scaleor algaeon which micro-organisms can feed must be removed regularly, i.e. the equipment must be cleanedregularly. Where practicablethe water should be maintained at a temperature below 20°C or above 4S°C.If this is not practicable then the water should be disinfected if it is safe and appropriate to do so. Note that other hazards may exist in the handling of biocides used to disinfect the water. A scheme should be prepared for preventing or controlling the risk incorporating all of the actions listed above. Further details on preventing infection are contained in the publication "The Control of Legionellosis including Legionnaires Disease" - Health and SafetySeriesbooklet HS (G) 70.

USE OF EARTH LEAKAGE ELECTRICAL SAFETY DEVICE

CIRCUIT

BREAKER

AS

AN

The equipment described in this Instruction Manual operates from a mains voltage electrical supply. The equipment is designed and manufactured in accordancewith appropriate regulations relating to the use of electricity. Similarly, it is assumedthat regulations applying to the operation of electrical equipment are observedby the end user. However, to give increased operator protection, Armfield Ltd have incorporated a Residual Current Device or RCD (alternatively called an Earth LeakageCircuit Breaker- ELCB)as an integral part of this equipment. If through misuse or accident the equipment becomes electrically dangerous, an RCD will switch off the electrical supply and reduce the severity of any electric shock received by an operator to a level which, under normal circumstances,will not causeinjury to that person. At least once each month, check that the RCD is operating correctly by pressing the TESTbutton. The circuit breaker MUST trip when the button is pressed.Failure to trip means that the operator is not protected and the equipment must be checkedand repaired by a competent electrician before it is used.

4

RECEIPT OF EQUIPMENT

.1.

SALESIN THE UNITED KINGDOM

The apparatus should be carefully unpacked and the components checked against the Advice Note. A copy of the Advice Note is supplied with this instruction manual for reference. Any omissions or breakagesshould be notified to Armfield Ltd wi thin three days of receipt.

2.

SALES OVERSEAS

The apparatus should be carefully unpacked and the components checked against the Advice Note. A copy of the Advice Note is supplied with this instruction manual for reference. Any omissions or breakages should be notified immediately to the Insurance Agent stated on the Insurance Certificate if the goods were insured by Armfield Ltd. Your own insurers should be notified immediately if insurance was arrangedby yourselves.

MINIMUM

COMPUTER

SYSTEM

REQUIREMENTS

Appropriate CAPTURE Demonstration Unit. CAP'IURE Interface Device (Cat. Ref.IFD) Disk containing software (~") entitled "FM20 Centrifugal Pump" IBM 386 Microcomputer (or 100%compatible) Windows 3.1 1.44MB3 1/2" floppy drive. Printer (if copiesof results are required). NOTE:

An SWAt Integrating Wattmeter may be used to measurethe electrical power supplied to the electric motor associatedwith this hydraulic machine. Since this Wattmeter takes readings of the current and voltage supplied to the electric motor, any noise on the electrical supply or earth connection will result in noisy readings from the Wattmeter. Excessivenoise on the electrical supply will therefore causethe Wattmeter readings displayed on the computer monitor to be unstable. A stable/noise free electrical supply is therefore required for optimum results.

6

INSTAlliNG

THE ARMFIELD

INTERFACE

CONSOLE IFD

The ARMFIELD POD is the interfacebetween the sensorsand the software in the PC It plugs into a parallel port on the PC, and any printer that would occupy this port may be plugged into the output printer port on the POD. A program (sortport.exe)is supplied as part of the software, and will run during the installation process.The program will identify the parallel port(s) , and, in the caseof computerswith more than one such port, it will offer the user the choice of locations for the POD. The sortport.exeprogram may be run after the initial installation of the software should the user wish to changethe port being used.

7

INSTAlliNG

THE SOFTWARE

Each item in the Armfield CAPTURErange of equipment is supplied with a program which runs under Microsoft Windows 3.1. The application disk contains a set-up program which will install the software onto your hard disk. The default condition will install the software into a Windows Group named ARMFIELD. Should you wish to changethis, you will have the opportunity during the set-up. To install the software, place the applications disk into the floppy drive A:. Choose 'File' from the menu bar in the Windows Program Manager, and then choose'Run' from the drop-down menu. Type A:SETUP

in the command box, and then choose'OK'. The installation procedure may take a little while, as the files have to be decompressed.

.

. .

Installing the software for the first time:

To ensure correct operation of the Capture software, the font 'GreekMathSymbols' should be installed in Windows. This can be checked by double clicking on Control Panel in the Main program group of the Program Manager. Select Fonts and check that 'GreekMathSymbols' is included in the installed fonts list. If it is not, click on Add... and selectthe font 'SYMBOLS' from the list of fonts in the windows \ systemdirectory, then click on OK. The font should now be shown in the installed fonts list.

8

1] 7

It 9

~

7

6

7~ 5

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0

2

FM 20 CENTRIFUGAL PUMP DEMONSTRATION UNIT

0

DESCRIPTION All numerical referencesin bracketsrelate to the diagram on page 9. The equipment comprises of a centrifugal water pump (6) driven by an electric motor (19) which is mounted on a support plinth (2) together with a clear acrylic reservoir (11) and associated pipework for continuous circulation. Clean water is used as the operating fluid and a drain valve (10) at the baseof the reservoir allows the water to be drained after use. Appropriate sensorsare incorporated on the unit to facilitate analysis of the pump performance when connected to the par~el port of a suitable microcomputer via an Armfield 'POD' interface (IFD)..In addition to the tappings required by the pressuresensors,additional tappings (5, 15 and 18) are included in the pipework to allow appropriate calibration instruments to be connected. The flow of water through the centrifugal pump is regulated by a flow control valve (16) installed in the discharge pipework of the pump. Adjustment of this valve allows the head/flow produced by the pump to be varied. A valve (9) in the inlet pipework of the pump allows the effect of suction lossesto be investigated. A spare impeller (8) is installed on the plinth to allow visual inspection of the impeller which is installed inside the volute of the water pump. The following sensors are used to monitor the performance of the centrifugal water pump:Differential pressure sensor SPWI connected to Channell

on IFD:.

This comprises of a pressure sensitive piezoresistive device with appropriate signal conditioning all contained in a protective case (13) and is used to measure pressure developed across the orifice plate (14) installed in the discharge pipework of the pump. .The volume flow rate of water through the pump can be calculated using this measurement. The sensoris connectedto the appropriate tappings in the pipework using flexible tubing. Additional tappings (15)are provided for the connection of appropriate instrumentation (not supplied) to facilitate calibration of the differential pressuresensor. Qifferential pressure sensor SPW3 connected to Channel 2 on IFD:

This comprises of a pressure sensitive piezoresistive device with appropriate signal conditioning all contained in a protective case(4) and is used to measure the difference in pressurebetween the inlet r-

t.

10

and outlet of the centrifugal pump. The head developed by the pump can be calculated from this measurement. The sensoris connectedto the appropriate tappings in the pipework using flexible tubing. Additional tappings (5 and 18) are provided for the connection of appropriate instrumentation (not supplied) to facilitate calibration of the differential pressuresensor. Rotational speed sensor 5501 connected to Channel 3 on IFD:

This comprises of a reflective infra-red opto switch (1) on a remote lead with appropriate signal conditioning in a protective case(3) and is used to measure the rotational speed of the motor/pump impeller. The opto switch is mounted on a support bracket adjacentto the end of the motor shaft which incorporates a reflective strip to facilitate measurement of the rotational speed. An appropriate noncontacting optical tachometer(not supplied) may be used to calibrate the rotational speed sensor. A tem~erature sensor STSl connected to Channel 4 on IFD:.

This comprises of a temperature sensitive semiconductor device (17) on a remote lead with appropriate signal conditioning in a protective case(7) and is used to measure the temperature of the water entering the centrifugal pump. The sensor is inserted through the wall of the pipe using a waterproof gland. The sensor may be removed from the gland for the purpose of calibration using appropriate equipment (not supplied). In addition to the above sensors. which are all ~ermanentl~ attached t,Q,the FM20 unit. an IntegIating Wattmeter (SWA1) ma~ be connected to ChannelS on IFD:

The Wattmeter is connectedbetween the mains lead (20) from the pump and a suitable power supply to facilitate measurement of the electrical power supplied to the motor. The Integrating Wattmeter may be calibrated using a suitable twin trace oscilloscope (not supplied). When using the FM20 program in conjunction with a suitable microcomputer, measurements from the above sensorsare displayed and used to compute appropriate calculated variables. These allow the following performancecurves to be displayed on the monitor or copied to a printer:

L

1. Rotational Speed

versus

2. Motor Input Power 3. Pump Total Head 4. Pump Power Output 5. Overall Efficiency

versus versus

Volume Flow Rate Volume Flow Rate Volume Flow Rate

versus Volume Flow Rate versus

Volurne Flow Rate

12

PREPARING FOR USE

THE CENTRIFUGAL

PUMP DEMONSTRATION

UNIT

All numerical referencesin bracketsrelate to the diagram on page 9 Before using the unit for the first time attach the two sectionsof delivery pipework (12)between the dischargeof the centrifugal..pump (6) and the reservoir (11). Ensure that all unions are tight before filling with water. Connect the flexible tubing from sensor SPWI (13) to the tappings on the orifice plate (14) with LOW PI connectedto the top tapping the ffiGH P2 connectedto the bottom tapping. Place the Centrifugal Pump Demonstration Unit in a suitable location adjacent to a compatible microcomputer. Placethe InterfaceIFD alongside the microcomputer. Placethe Integrating Wattmeter SWAI (if available) alongside the IFD as convenient. Ensure that all tappings in the pipework of the Pump Unit are connected to appropriate sensorsor blanked. Open the inlet valve (9) and close the outlet control valve (16).

Ensure that the drain valve (10)at the baseof the reservoir is fully closed then fill the reservoir with clean, cold water. The pressuresensorson the unit require priming with water before initial operation (and whenever the tank has been emptied and refilled). A hypodermic syringe and micro-bore tubing are supplied for this purpose. To prime the tubes with water remove the flexible tubing from the PVC pipe by removing the pipe clip and gently pulling the tube from the stainless steel tapping. Fill the syringe with water and gently insert the micro-bore tubing into the sensor's flexible tubing until it is a few millimetres away from the sensor. Hold the flexible tubing vertically.

Slowly inject water into the tube until it is completely filled, then remove the syringe and micro-bore tubing, and replacethe fleXIbletubing on to the stainlesssteel tapping. There are two stainless steel tappings at each tapping point. One is connectedto the sensor,whilst the other is used to connect a manometer for calibration. It should be noted that there is a difference betweenthe two points. The sensor tapping is fitted with a nylon restrictor to dampen pressure fluctuations. The calibration tapping has no restrictor. Ensure the sensoris connectedto the correct tapping point.

Connect the mains lead (20) from the motor of the centrifugal pump to the Integrating Wattmeter SWAI. Connect the Wattmeter to the POWER OUTPUT of IFD. Connectthe mains supply lead from an appropriate electrical supply to the MAINS INPUT socket on IFD ensuring that the voltage of the electrical supply is compatible with the console (indicated on the rear of the console). Switch on the mains supply. Switch on the IFD. Check that the pump operates. Open the outlet flow control valve fully and allow water to circulate until all air bubbles are expelled.Switch off IFD. Connecteachof the sensorconditioning boxes to the appropriate SENSOR SOCKETSon the front of IFD, using the numbered connecting leads, as follows:Channell to sensor 5PWl (13) Channel 2 to sensor 5PW3 (4) Channel 3 to sensor 5501 (3) Channel 4 to sensor ST51 (7) Channel 5 to the Integrating Wattmeter SWAl

The equipment is ready for use with the Armfield Windows software. NOTE:

The apparatus is classified as Education and Training Equipment under the Electromagnetic Compatibility (Amendment) Regulations 1994.Use of the apparatusoutside the classroom, laboratory or similar such place invalidates conformity with the protection requirements of the Electromagnetic Compatibility Directive (89/336/EEq and could lead to prosecution.

14

ROUTINE

MAINTENANCE

To preserve the life and efficient operation of the equipment it is important that the equipment is properly maintained. Regular servicing/maintenance of the equipment is the responsibility of the end user and must be performed by qualified personnel who understand the operation of the equipment. In addition to regular maintenance the following notes should be observed:-

1.

The equipment should be disconnected from the electrical supply when not in use.

2.

Water should be drained from the equipment when it is not in use.

3.

The exterior of the equipment should be periodically cleaned.00 NOT use abrasivesor solvents.

4.

The reservoir should be periodically cleaned to remove debris and deposits on the walls. DO NOT use abrasivesor solvents.

FM20 INDEX TO EXPERIMENTS

Experiment

PageNo

Warning! Introduction - Instructional Objectives.

Introduction - Energy Transfer in a Pump.

PracticalExerciseNo 2 - Pump Inherent Characteristics PracticalExerciseNo 3 -Pump ConstantSpeedCharacteristics PracticalExerciseNo 4 -Introduction to Scaling

ii III

PracticalExerciseNo 1 Using EngineeringUnits

PracticalExerciseNo 5 - Pump Suction PracticalExerciseNo 6 - SystemCharacteristic- duty point

PE2-1 PE3-1 PE4-1 PEs-I

.

Warning! Eachof the practical exercisesdescribedin the Labsheetshelp file requires the equipment to be set up and in working condition according to the instructions given in the menu-bar 'Install'. If you have not done this, or are not sure whether the unit is correctly set up, go back to the 'Install' pull-down screens,and follow the instructions given there to completion. The final test of readiness is made under the selection button 'Diagrm' when the effect on the measured variables of changing the various pump settings can be seen numerically on screen. For example, adjusting the position of the rotary dial by hand on the SWAl Integrating Watt meter will cause the pump speed to change, as well as the flow rate and head developed by the pump. Similarly, adjusting the valves on the pump inlet and outlet pipes by hand will also causechangesin pump flow and head. Check that the changesin thesepump settings give trends in the measured variables,as displayed in the boxes on screen,which you would intuitively expect.If no change in pump speed or measured power or flow or head occurs whatever changesyou make to the power input or to the valve positions, then clearly something is wrongly set up and you need to establishwhat the problem is by working through the 'Install' procedures again.

~

Introduction

- Instructional

Objectives.

The objectsof the practical work exercisesdescribedin the 'Labsheet' help screens,are to understand the operating characteristicsof a centrifugal pump. In this type of pump (Fig 1),the fluid is drawn into the centreof a rotating impeller and is thrown outwards by centrifugal action. As a result of the high speedof rotation, the liquid acquiresa high kinetic energy. The pressuredifference between the suction and delivery sides arises from the conversion of this kinetic energy into pressureenergy.

~

EfficiaM:yE

N-lOOO

~

N-lSOO

N'".2000

rev/mia

1500 ~p 1000 :ttt1"

Fig.

~ ACentrifuaalPmnp

HaclH

Disc8geQ FII- 2 ()pa8iDc CI8KtaiIIicI of . C=rifup1 ~

The operating characteristicsof a pump are often conveniently shown by plotting head H, power P, and an efficiency E against dischargeflow Q for a seriesof constantspeedsN, as shown in Fig 2. It is important to note that the efficiency reachesa maximum and then falls, whilst the head at first falls slowly with Q but eventually falls off rapidly. The optimum conditions for operation occur when the required 'duty point' of head and flow coincideswith a point of maximum efficiency. This Armfield 'Capture' unit, ref FM20, is designed to allow students to determine the operating characteristicsof a centrifugal pump rapidly and meaningfully, using 'on-line' data acquisition and analysis. Test results may be displayed in tabular and graphical forms, and it is a simple matter to repeat or add to the data to cover areas of the pump performance of particular interest At the conclusion of the work, students are asked a series of questions 0 n an interactive basis, to ensure that a true understanding of pump characteristicshas been gained.

ii

-[

Introduction - Energy Transfer in a Pump. Fluid machines are usually characterised in two distinct classes: rotodynamic or positive displacement. In the former of these, relative motion is required between the rotating element of the machine (the 'rotor') and the fluid stream, whereas in the latter case the machine componentsmechanically displace a set volume of fluid. In a rotodynamic machine, therefore, the changesin fluid velocity and pressure between inlet and outlet are of considerably greater significance in determining performance than for a positive displacement machine, where essentially machine speedis the key operating parameter. The centrifugal pump, of which the Armfield FM20 unit is a small-scale example, is a radial flow rotodynamic machine, wherein fluid enters the rotor or impeller at one radius and leaves at a larger radius. In so doing, changes in kinetic, potential and pressure energy occur, and any understanding of pump behaviour and performance assessmentrequires measurementor calculation of these quantities. The general relationship between the various forms of energy, basedon the 1st Law of Thermodynamics applied to a unit mass of fluid flowing through a 'control volume' (such as the pump itself) is expressedas:-WI = d(V2/2) + g.dz + voLdp + F

(1)

where:is the mechanicalshaft work performed on the fluid d(v2/2)

is the changein kinetic energy of the fluid is the changein potential energy of the fluid is the change in pressure energy, where 'vol' is the volume per unit mass of the fluid. For an incompressible fluid of constant density Rho , this term is equal to jdp/Rho or (P2PI where P2refers to the pump dischargeoutlet andpI to the pump inlet.

F

is the frictional energy loss as heat to the surroundings or in heating the fluid itself as it travels from inlet to outlet.

(2) where subscript 2 refers to the pump outlet and subscript 1 to the inlet. The term Wa representsthe actual work performed in changing the energy stagesof a unit mass of the fluid. This may alternatively be presented as the total dynamic head H of the pump, by converting the units from work per unit massto head expressedas a length :(3) It can be assumed for the purposes of the following practical experiments that the fluid is incompressible (ie. Rho is constant).

iv

FM20

Practical Exercise No 1

- Using Engineering Units

Qbjective:-

To ensure users fully understand the conversion of measured units of quantity to those of the variables necessaryto calculatepump performance. Theoretical Background:-

The basic tenns used to define, and therefore measure,pump performance include i) ii) iii)

discharge, head. power input and efficiencies.

Eachof theseis consideredin turn. i) Discharge Qv

The discharge,or flow rate or capacity,of a pwnp is the volume of fluid pwnped ~er unit time. In 51 units, this is expressedin cubic metres per secondm Is, or, for conveniencewith small flows, in cubic decimetres per seconddm3/s. The Armfield FM20 unit employs an orifice plate in the pump discharge

pipeline to measure QYI

according to the conventional relationship

between the measured pressure drop dpo across the orifice and the flow rate :(4) Where Cd is the orifice discharge coefficient.

(This applies when the orifice diameter d is no more than 50% of the pipe diameter.) The appropriate constants needed to use this equation for deducing

dischargeQv from dpoare given in the "Params"sectionof the menu-bar. Similarly, the calibration of the orifice necessaryto confirm thesevalues of parametersis describedin the "Calibrt" section of the menu-bar. ii) HeadH The term 'head' refers to the elevation of a free surface of water above or below a reference datum. Terms specifically applied to the analysis of

L

FM20 pumps and pumping systemsare illustrated graphically in Fig 3, and are briefly defined below.

T - -~~ff~~ I

I. Pwnp Inlet 2. Pwnp