FM20

CAPTURE

CENTRIFUGAL PUMP DEMONSTRATION UNIT

FM20

ISSUE 2AUGUST 1996

LECTURERS' NOTES

Parameters File

All numerical constants involved with the Capture unit are included inthe file P ARAM. TXT .

The file can be altered with any text editor (eg. the MSDOS ~nvcommand), should the user wish to change any of the values.

Care should be taken not to damage or corrupt the file. Should thishappen, re-install the software from the floppy disks.

Assignment File

The questions given in the student assignment are all stored in the fileFM_ASGN.TXT.

The assignment file already has several questions included, but is designedto allow lecturers to enter their own questions, depending on theparticular course content.

As for the parameters file, any text editor can be used to edit the questions.The format should be similar to the questions already included. Answersshould be placed at the end of the question surrounded by the {} brackets.

Font Installation

software, the fontTo ensure correct operation of the CaptureIGreekMathSymbolsl should be installed in Windows.

This can be checked by double clicking on Control Panel in the Mainprogram group of the Program Manager. SELECT Fonts and check that'Greek/Math/Symbols' is included in the installed fonts list.

If it is not, click on Add... and select the font 'SYMBOLS' from the list offonts 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 screens available within thesoftware.

ARMFIELD LIMITED

OPERATING INSTRUCTIONS AND EXPERIMENTS

FM20 - CAPTURE CENTRIFUGAL PUMP DEMONSTRATION UNIT

PAGE NO.

1SAFETY

5RECEIPT OF EQUIPMENT

MINIMUM COMPUTER SYSTEM REQUIREMENTS 6

INSTALLING THE ARMFIELD INTERFACE CONSOLE IFD 7

INSTALLING THE SOFTWARE 8

DESCRIPI10N 10

PREPARING THE CENTRIFUGAL PUMPDEMONSTRA nON UNIT FOR USE 13

ROUTINE MAINTENANCE 15

INDEX TO EXPERIMENTS 16

GENERAL SAFETY RULES a

SAFETY IN THE USE OF EQUIPMENT SUPPLIED BY ARMFIELD

Before proceeding to install, commission or operate the equipmentdescribed in this instruction manual we wish to alert you to potentialhazards so that they may be avoided.

Although designed for safe operation, any laboratory equipment may

. INJURY THROUGH MISUSE

INJURy FROM ELECfRIC SHOCK (Particularly in presence ofwater)

.INJURy FROM ROTAnNG COMPONENTS.RISK OF INFEC110N THROUGH LACK OF CLEANLINESS.

Accidents can be avoided provided that equipment is regularly maintainedand staff and students are made aware of potential hazards. A list ofgeneral safety rules is included in this manual, to assist staff and studentsin this regard. The list is not intended to be fully comprehensive but forguidance only.

Please refer to the notes overleaf regarding the Control of SubstancesHazardous to Health Regulations.

1

involve processes or procedures which are potentially hazardous. Themajor potential hazards associated with this particular equipment arelisted below.

The COSHH Regulations

Regulationsto HealthThe Control(1988)

of Substances Hazardous

The COSHH regulations impose a duty on employers to protect employeesand others from substances used at work which may be hazardous tohealth. The regulations require you to make an assessment of alloperations which are liable to expose any person to hazardous solids,liquids, dusts, vapours, gases or micro-organisms. You are also required tointroduce suitable procedures for handling these substances and keepappropriate records.

Since the equipment supplied by Armfield Limited may involve the use ofsubstances which can be hazardous (for example, cleaning fluids used formaintenance or chemicals used for particular demonstrations) it isessential that the laboratory supervisor or some other person in authorityis responsible for implementing the COSffii regulations.

Part of the above regulations are to ensure that the relevant Health andSafety Data Sheets are available for all hazardous substances used in thelaboratory. Any person using a hazardous substance must be informed ofthe following:

Physical data about the substanceAny hazard from fire or explosionAny hazard to healthAppropriate First Aid treabnentAny hazard from reaction with other substancesHow to dean/ dispose of spillageAppropriate protective measuresAppropriate storage and handling

Although these regulations may not be applicable in your country I it isstrongly recommended that a similar approach is adopted for theprotection of the students operating the equipment. Local regulationsmust also be considered.

Water-Borne Infections

The equipment described in this instruction manual involves the use ofwater which under certain conditions can create a health hazard due toinfection by harmful micro-organisms.

For example, the microscopic bacterium called Legionella pneumophilawill feed on any scale, rust, algae or sludge in water and will breed rapidlyif the temperature of water is between 20 and 45°C. Any water containingthis bacterium which is sprayed or splashed creating air-borne droplets can

2

produce a form of pneumoniapotentially fatal.

called Legionnaires Disease which is

Legionella is not the only hannful micro-organism which can infect water,but it serves as a useful example of the need for cleanliness.

bemustUnder the COSHH regulations,observed:-

the following precautions

Any water contained within the product must not be allowed to stagnate,ie. the water must be changed regularly.

Any rust, sludge, scale or algae on which micro-organisms can feed mustbe removed regularly, i.e. the equipment must be cleaned regularly.

Where practicable the water should be maintained at a temperature below20°C or above 4S°C. If this is not practicable then the water should bedisinfected if it is safe and appropriate to do so. Note that other hazardsmay exist in the handling of biocides used to disinfect the water.

the riskA scheme should be prepared for preventing or controllingincorporating all of the actions listed above.

Further details on preventing infection are contained in the publication"The Control of Legionellosis including Legionnaires Disease" - Healthand Safety Series booklet HS (G) 70.

USE OF EARTH LEAKAGEELECTRICAL SAFETY DEVICE

CIRCUIT AS ANBREAKER

The equipment described in this Instruction Manual operates from amains voltage electrical supply. The equipment is designed andmanufactured in accordance with appropriate regulations relating to theuse of electricity. Similarly, it is assumed that regulations applying to theoperation of electrical equipment are observed by the end user.

However, to give increased operator protection, Armfield Ltd haveincorporated a Residual Current Device or RCD (alternatively called anEarth Leakage Circuit Breaker - ELCB) as an integral part of this equipment.If through misuse or accident the equipment becomes electricallydangerous, an RCD will switch off the electrical supply and reduce theseverity of any electric shock received by an operator to a level which,under normal circumstances, will not cause injury to that person.

At least once each month, check that the RCD is operating correctly bypressing the TEST button. The circuit breaker MUST trip when the buttonis pressed. Failure to trip means that the operator is not protected and theequipment must be checked and repaired by a competent electrician beforeit is used.

4

RECEIPT OF EQUIPMENT

SALES IN THE UNITED KINGDOM.1.

The apparatus should be carefully unpacked and the components checkedagainst the Advice Note. A copy of the Advice Note is supplied with thisinstruction manual for reference.

Any omissions or breakages should be notified to Armfield Ltd wi thinthree days of receipt.

SALES OVERSEAS2.

The apparatus should be carefully unpacked and the components checkedagainst the Advice Note. A copy of the Advice Note is supplied with thisinstruction manual for reference.

Any omissions or breakages should be notified immediately to theInsurance Agent stated on the Insurance Certificate if the goods wereinsured by Armfield Ltd.

Your own insurers should be notified immediately if insurance wasarranged by 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

1.44MB 3 1/2" floppy drive.

Printer (if copies of results are required).

An SWAt Integrating Wattmeter may be used to measure theelectrical power supplied to the electric motor associated withthis hydraulic machine. Since this Wattmeter takes readingsof the current and voltage supplied to the electric motor, anynoise on the electrical supply or earth connection will resultin noisy readings from the Wattmeter. Excessive noise on theelectrical supply will therefore cause the Wattmeter readingsdisplayed on the computer monitor to be unstable. Astable/noise free electrical supply is therefore required foroptimum results.

NOTE:

6

INSTAlliNG THE ARMFIELD INTERFACE CONSOLE IFD

The ARMFIELD POD is the interface between the sensors and the softwarein the PC It plugs into a parallel port on the PC, and any printer thatwould occupy this port may be plugged into the output printer port on thePOD.

A program (sortport.exe) is supplied as part of the software, and will runduring the installation process. The program will identify the parallelport(s) , and, in the case of computers with more than one such port, it willoffer the user the choice of locations for the POD.

The sortport.exe program may be run after the initial installation of thesoftware should the user wish to change the port being used.

7

INSTAlliNG THE SOFTWARE

Each item in the Armfield CAPTURE range of equipment is supplied witha program which runs under Microsoft Windows 3.1.

The application disk contains a set-up program which will install thesoftware onto your hard disk. The default condition will install thesoftware into a Windows Group named ARMFIELD. Should you wish tochange this, 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, andthen 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 bedecompressed.

. . .Installing the software for the first time:

thesoftware,To ensure correct operation of the Capture'GreekMathSymbols' should be installed in Windows.

font

This can be checked by double clicking on Control Panel in the Mainprogram 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 select the font 'SYMBOLS' from the list offonts in the windows \ system directory, then click on OK.

The font should now be shown in the installed fonts list.

8

1]

7

7~ ~It

00~ 26 59 7

FM 20 CENTRIFUGAL PUMP DEMONSTRATION UNIT

DESCRIPTION

All numerical references in brackets relate to the diagram on page 9.

The equipment comprises of a centrifugal water pump (6) driven by anelectric motor (19) which is mounted on a support plinth (2) together witha clear acrylic reservoir (11) and associated pipework for continuouscirculation. Clean water is used as the operating fluid and a drain valve(10) at the base of the reservoir allows the water to be drained after use.

Appropriate sensors are incorporated on the unit to facilitate analysis ofthe pump performance when connected to the par~el port of a suitablemicrocomputer via an Armfield 'POD' interface (IFD).. In addition to thetappings required by the pressure sensors, additional tappings (5, 15 and 18)are included in the pipework to allow appropriate calibration instrumentsto be connected.

The flow of water through the centrifugal pump is regulated by a flowcontrol valve (16) installed in the discharge pipework of the pump.Adjustment of this valve allows the head/flow produced by the pump tobe varied. A valve (9) in the inlet pipework of the pump allows the effectof suction losses to be investigated.

A spare impeller (8) is installed on the plinth to allow visual inspection ofthe impeller which is installed inside the volute of the water pump.

the performance of theThe following sensors are used to monitorcentrifugal water pump:-

.Differential pressure sensor SPWI connected to Channell on IFD:

This comprises of a pressure sensitive piezoresistive device withappropriate signal conditioning all contained in a protective case(13) and is used to measure pressure developed across the orificeplate (14) installed in the discharge pipework of the pump. .Thevolume flow rate of water through the pump can be calculatedusing this measurement.

The sensor is connected to the appropriate tappings in the pipeworkusing flexible tubing. Additional tappings (15) are provided for theconnection of appropriate instrumentation (not supplied) tofacilitate calibration of the differential pressure sensor.

Qifferential pressure sensor SPW3 connected to Channel 2 on IFD:

This comprises of a pressure sensitive piezoresistive device withappropriate signal conditioning all contained in a protective case (4)and is used to measure the difference in pressure between the inlet

r-t.

10

and outlet of the centrifugal pump. The head developed by thepump can be calculated from this measurement.

The sensor is connected to the appropriate tappings in the pipeworkusing flexible tubing. Additional tappings (5 and 18) are provided forthe connection of appropriate instrumentation (not supplied) tofacilitate calibration of the differential pressure sensor.

Rotational speed sensor 5501 connected to Channel 3 on IFD:

This comprises of a reflective infra-red opto switch (1) on a remotelead with appropriate signal conditioning in a protective case (3) andis used to measure the rotational speed of the motor/pump

impeller.

The opto switch is mounted on a support bracket adjacent to the endof the motor shaft which incorporates a reflective strip to facilitatemeasurement of the rotational speed. An appropriate non-contacting optical tachometer (not supplied) may be used to calibratethe 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 aprotective case (7) and is used to measure the temperature of thewater entering the centrifugal pump.

The sensor is inserted through the wall of the pipe using awaterproof gland. The sensor may be removed from the gland forthe purpose of calibration using appropriate equipment (notsupplied).

In addition to the above sensors. which are all ~ermanentl~ attached t,Q, theFM20 unit. an IntegIating Wattmeter (SWA1) ma~ be connected toChannelS on IFD:

The Wattmeter is connected between the mains lead (20) from thepump and a suitable power supply to facilitate measurement of theelectrical power supplied to the motor. The Integrating Wattmetermay be calibrated using a suitable twin trace oscilloscope (not

supplied).

When using the FM20 program in conjunction with a suitablemicrocomputer, measurements from the above sensors are displayed andused to compute appropriate calculated variables. These allow thefollowing performance curves to be displayed on the monitor or copied toa printer:

L

Volume Flow Rate1. Rotational Speed versus

Volume Flow Rate2. Motor Input Power versus

Volume Flow Rate3. Pump Total Head versus

Volume Flow Rate4. Pump Power Output versus

Volurne Flow Rate5. Overall Efficiency versus

12

UNITPREPARING THE CENTRIFUGAL PUMP DEMONSTRATIONFOR USE

All numerical references in brackets relate to the diagram on page 9

Before using the unit for the first time attach the two sections of deliverypipework (12) between the discharge of the centrifugal..pump (6) and thereservoir (11). Ensure that all unions are tight before filling with water.Connect the flexible tubing from sensor SPWI (13) to the tappings on theorifice plate (14) with LOW PI connected to the top tapping the ffiGH P2connected to the bottom tapping.

Place the Centrifugal Pump Demonstration Unit in a suitable locationadjacent to a compatible microcomputer.

Place the Interface IFD alongside the microcomputer. Place the IntegratingWattmeter SWAI (if available) alongside the IFD as convenient.

Ensure that all tappings in the pipework of the Pump Unit are connectedto appropriate sensors or blanked.

Open the inlet valve (9) and close the outlet control valve (16).

Ensure that the drain valve (10) at the base of the reservoir is fully closedthen fill the reservoir with clean, cold water.

The pressure sensors on the unit require priming with water before initialoperation (and whenever the tank has been emptied and refilled). Ahypodermic syringe and micro-bore tubing are supplied for this purpose.

To prime the tubes with water remove the flexible tubing from the PVCpipe by removing the pipe clip and gently pulling the tube from thestainless steel tapping. Fill the syringe with water and gently insert themicro-bore tubing into the sensor's flexible tubing until it is a fewmillimetres away from the sensor. Hold the flexible tubing vertically.

Slowly inject water into the tube until it is completely filled, then removethe syringe and micro-bore tubing, and replace the fleXIble tubing on to thestainless steel tapping.

There are two stainless steel tappings at each tapping point. One isconnected to the sensor, whilst the other is used to connect a manometerfor calibration. It should be noted that there is a difference between the twopoints. The sensor tapping is fitted with a nylon restrictor to dampenpressure fluctuations. The calibration tapping has no restrictor. Ensure thesensor is connected to the correct tapping point.

Connect the mains lead (20) from the motor of the centrifugal pump to theIntegrating Wattmeter SWAI. Connect the Wattmeter to the POWEROUTPUT of IFD.

Connect the mains supply lead from an appropriate electrical supply to theMAINS INPUT socket on IFD ensuring that the voltage of the electricalsupply is compatible with the console (indicated on the rear of theconsole).

Switch on the mains supply. Switch on the IFD. Check that the pumpoperates. Open the outlet flow control valve fully and allow water tocirculate until all air bubbles are expelled. Switch off IFD.

Connect each of the sensor conditioning boxes to the appropriate SENSORSOCKETS on the front of IFD, using the numbered connecting leads, asfollows:-

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 SW Al

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

NOTE: The apparatus is classified as Education and TrainingEquipment under the Electromagnetic Compatibility(Amendment) Regulations 1994. Use of the apparatus outsidethe classroom, laboratory or similar such place invalidatesconformity with the protection requirements of theElectromagnetic Compatibility Directive (89 /336/EEq andcould lead to prosecution.

14

ROUTINE MAINTENANCE

To preserve the life and efficient operation of the equipment it isimportant that the equipment is properly maintained. Regularservicing/maintenance of the equipment is the responsibility of the enduser and must be performed by qualified personnel who understand theoperation of the equipment.

the following notes should beIn addition to regular maintenanceobserved:-

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

1.

Water should be drained from the equipment when it is not in use.2.

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

3.

The reservoir should be periodically cleaned to remove debris anddeposits on the walls. DO NOT use abrasives or solvents.

4.

FM20

INDEX TO EXPERIMENTS

Page NoExperiment

Warning!

iiIntroduction - Instructional Objectives.

IIIIntroduction - Energy Transfer in a Pump.

Practical Exercise No 1 - Using Engineering Units

PE2-1Practical Exercise No 2 - Pump Inherent Characteristics

PE3-1Practical Exercise No 3 - Pump Constant Speed Characteristics

PE4-1Practical Exercise No 4 - Introduction to Scaling

PEs-IPractical Exercise No 5 - Pump Suction

Practical Exercise No 6 - System Characteristic - duty point

.

Warning!

Each of the practical exercises described in the Labsheets help file requiresthe equipment to be set up and in working condition according to theinstructions given in the menu-bar 'Install'. If you have not done this, orare 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 pumpsettings can be seen numerically on screen. For example, adjusting theposition of the rotary dial by hand on the SW Al Integrating Watt meterwill cause the pump speed to change, as well as the flow rate and headdeveloped by the pump. Similarly, adjusting the valves on the pump inletand outlet pipes by hand will also cause changes in pump flow and head.Check that the changes in these pump settings give trends in the measuredvariables, as displayed in the boxes on screen, which you would intuitivelyexpect. If no change in pump speed or measured power or flow or headoccurs whatever changes you make to the power input or to the valvepositions, then clearly something is wrongly set up and you need toestablish what the problem is by working through the 'Install' proceduresagain.

Introduction - Instructional Objectives.

The objects of the practical work exercises described in the 'Labsheet' helpscreens, are to understand the operating characteristics of a centrifugalpump.

In this type of pump (Fig 1), the fluid is drawn into the centre of a rotatingimpeller and is thrown outwards by centrifugal action. As a result of thehigh speed of rotation, the liquid acquires a high kinetic energy. Thepressure difference between the suction and delivery sides arises from theconversion of this kinetic energy into pressure energy.

~ EfficiaM:yEN-lOOO N-lSOO

~N'".2000 rev/mia

1500 ~p

1000

HaclH:ttt1"

~

~

ACentrifuaalPmnpFig.Disc8geQ

F II- 2 ()pa8iDc CI8KtaiIIicI of . C=rifup1 ~

The operating characteristics of a pump are often conveniently shown byplotting head H, power P, and an efficiency E against discharge flow Q fora series of constant speeds N, as shown in Fig 2. It is important to note thatthe efficiency reaches a maximum and then falls, whilst the head at firstfalls slowly with Q but eventually falls off rapidly. The optimumconditions for operation occur when the required 'duty point' of head andflow coincides with a point of maximum efficiency.

This Armfield 'Capture' unit, ref FM20, is designed to allow students todetermine the operating characteristics of a centrifugal pump rapidly andmeaningfully, using 'on-line' data acquisition and analysis. Test resultsmay be displayed in tabular and graphical forms, and it is a simple matterto repeat or add to the data to cover areas of the pump performance ofparticular interest

At the conclusion of the work, students are asked a series of questions 0 nan interactive basis, to ensure that a true understanding of pumpcharacteristics has been gained.

[-i i

Introduction - Energy Transfer in a Pump.

Fluid machines are usually characterised in two distinct classes:rotodynamic or positive displacement. In the former of these, relativemotion is required between the rotating element of the machine (the'rotor') and the fluid stream, whereas in the latter case the machinecomponents mechanically displace a set volume of fluid. In a rotodynamicmachine, therefore, the changes in fluid velocity and pressure betweeninlet and outlet are of considerably greater significance in determiningperformance than for a positive displacement machine, where essentiallymachine speed is the key operating parameter.

The centrifugal pump, of which the Armfield FM20 unit is a small-scaleexample, is a radial flow rotodynamic machine, wherein fluid enters therotor or impeller at one radius and leaves at a larger radius. In so doing,changes in kinetic, potential and pressure energy occur, and anyunderstanding of pump behaviour and performance assessment requiresmeasurement or calculation of these quantities.

The general relationship between the various forms of energy, based onthe 1st Law of Thermodynamics applied to a unit mass of fluid flowingthrough a 'control volume' (such as the pump itself) is expressed as:-

(1)voLdp + F-WI = d(V2/2) + g.dz +

where:-

is the mechanical shaft work performed on the fluid

d(v2/2) is the change in kinetic energy of the fluid

is the change in potential energy of the fluid

is the change in pressure energy, where 'vol' is the volumeper unit mass of the fluid. For an incompressible fluid ofconstant density Rho , this term is equal to jdp/Rho or (P2-PI where P2 refers to the pump discharge outlet andpI to thepump inlet.

F is the frictional energy loss as heat to the surroundings or inheating 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 represents the actual work performed in changing the energystages of a unit mass of the fluid. This may alternatively be presented asthe total dynamic head H of the pump, by converting the units from workper unit mass to head expressed as a length :-

(3)

It can be assumed for the purposes of the following practical experimentsthat 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 ofquantity to those of the variables necessary to calculate pump performance.

Theoretical Background:-

The basic tenns used to define, and therefore measure, pump performanceinclude

i)ii)iii) power input and efficiencies.

Each of these is considered in turn.

i) Discharge Qv

The discharge, or flow rate or capacity, of a pwnp is the volume of fluidpwnped ~er unit time. In 51 units, this is expressed in cubic metres persecond m Is, or, for convenience with small flows, in cubic decimetres persecond dm3/s.

The Armfield FM20 unit employs an orifice plate in the pump dischargepipeline to measure QYI according to the conventional relationshipbetween the measured pressure drop dpo across the orifice and the flowrate :-

(4)

Where Cd is the orifice discharge coefficient.

(This applies when the orifice diameter d is no more than 50% of the pipediameter.)

The appropriate constants needed to use this equation for deducingdischarge Qv from dpo are given in the "Params" section of the menu-bar.Similarly, the calibration of the orifice necessary to confirm these values ofparameters is described in the "Calibrt" section of the menu-bar.

ii) Head H

The term 'head' refers to the elevation of a free surface of water above orbelow a reference datum. Terms specifically applied to the analysis of

L

discharge,head.

FM20

pumps and pumping systems are illustrated graphically in Fig 3, and arebriefly defined below.

T - - II VI T-~~ff~~ Lioe

--H ---

Hydraulic Gradient

I. Pwnp Inlet

2. Pwnp <Altlet

H Total Head (m)

v Flow velocity (m/~)2

P Pressure (N/m )- -2- - --.!!- --

~ IRho.1 r

PI

&g

1- ~ r=- h:::~Da1um LineF1ow- - +-~ -:I" ' / z-O --+- - ' '

\ 1-1- :.-- - 3>--

2"-vPump

Fig 3 Definitions of Head across a pump.

Manometric suction head ~1 is the suction gauge reading (metres)measured at the suction nozzle of the pump referenced to theimpeller centre line datum.

1)

Manometric discharge head Hm2 is the discharge gauge reading(metres) measured at the discharge nozzle of the pwnp referencedto the impeller centreline.

2)

Velocity head relates to the kinetic energy of the fluid when flowingat a velocity v, ie. v2 /2g

3)

therefore, the suction velocity head is v~ /2gand the discharge velocity head is v~ /2g.

4) Total dynamic head (H) is the head against which the pump mustwork when fluid is being pumped. For the pump shown in Fig 3, His given by:

(5)

Equation (3) relates precisely to Equation (5) for a control volumeenclosing the pump outlet and inlet, as ~ and ~1 are themeasured pressures equal to

Z2 + (P2/RhO) and ~ + (PI/RhO) respectively.

The Armfield FM20 instrumentation is such that (Hm2 - HmJ is actuallymeasured as a differential pressure dpp (pascals), but converted in

PEl-2

FM20

subsequent calculations to dpp/Rho.g metres (see 'Formulae Used' in thisHelp File).

iii) Power Input and Efficiencies

The power P consumed by the fluid in producing the total dynamic head Hat a discharge Qy is given by Equation (6):

(6)[Nm/s = Watts]P = Rho.g.Qy.H

However, the fluid friction 'losses' in the pump itself, represented as FinEquation (1), require a hydraulic efficiency En to be defined as:-

'Useful' fluid power absorbed (P u) x 1000/0E =h Power supplied by the impeller (Ph)

Further, the mechanical losses in the bearings etc. require a mechanicalefficiency Em to be defined as

The Armfield FM20 Centrifugal Pump Unit does not include the directmeasurement of mechanical power Pm for cost reasons, but insteadmeasures electrical power P Sf to the pump motor. A further efficiency istherefore required, expressing the electro-mechanical losses in the motorE:-

E = Power supplied to the impeller (P m)xl000/oe Power supplied to the motor (P gr)

The overall efficiency Egr is thus:-

It will be seen that

Egr = ~.~.Ee

PEl-3

FM20

EQuipment Set-U~:-

As described in the 'install' help section, with the pump running at amaximwn speed setting (100% setting on SWA1). The 'Diagrm' screenbutton from the menu bar should be selected, in order that the measuredvariables are displayed on-line in the appropriate boxes of the pumpschematic diagram.

Procedure:-

Open inlet valve VI fully. Close discharge valve V 2 then start the pump(pump motor started under minimum load). Open discharge valve V 2fully, and allow the water to circulate until all air bubbles have dispersed.Select 'Diagmt' and note the value of the volume flow indicated at thebottom of the screen. Gradually close discharge valve V 2 until the volumeflow is approximately half of the maximum reading.

When the indicated readings of the 5 measured variables are reasonablyconstant, select the 'Take Sample' button from the menu-bar. It is onlynecessary to take one set of results for this exercise. Now select the Tables'button from the menu-bar, and you will see the results of your test samplelaid out as one row of a Tab.1e under one of two headings:- 'MeasuredVariables' and 'Calculated Variables'. Write down on a piece of paper thevalues of the measured variables your sample took, as follows:-

Differential pressure across orifice dpoDifferential pressure across pump dppMotor rotation speed NMotor Input Power P

fWater Temperature w

[kPa]:-[kPa]:-(Hz] :-(W] :-[DegC] :-

From your own classroom notes, or using the appropriate theory andequations in the 'Theory' section of the Help menu, you can calculate thevarious pump performance variables for yourself and compare yourcalculated figures with those computed in this software and displayed as'Calculated from Measurements' in the row of tabulated results from yoursample. In your own calculation, you will have to use the values of thevarious physical constants listed in the menu choice button 'Params'.

PE14

FM20

PEl-5

FM20

Objective:-

To obtain a head-flow curve for a centrifugal pump operating at inherent

speed.

Theoretical Background:-

The best way to describe the operating characteristics of a Centrifugal Pumpis through the use of characteristic curves. (Fig 4). This figure shows theinterrelation of discharge pressure or head H , capacity ~ , and efficiencyEgr , and power input P gr , for a given pump at inherent speed (motor speedchanges with load). The H - Qy curve shows the relation between totalhead and capacity. The pressure increase created by a centrifugal pump iscommonly expressed in terms of the head of the fluid following. Thisdischarge head H is independent of the density of the fluid.

In Fig 4, the head increases continuously as the capacity is decreased; thistype of curve is referred to as a rising characteristic curve. A stable head-capacity characteristic curve is one in which only one capacity can beobtained at anyone head. Pump selection should be made such that stableoperating characteristics are available.

Fig 4. Characteristic curves for a single FM20 centrifugal pump.

The P gr - Qy curve of Fig 4 shows the relation between power input andpump capacity. The Egr - Qy curve relates pump efficiency to capacity. For a

PE2-1

FM20

pump having the characteristics of Fig 4, maximum efficiency would occurat a volume flow rate of 0.7 dm3 / sec, and a total head of 6.75 metres.

Equipment Set-Up:-

Exactly the same as that for Practical Exercise No 1. Valve Vt should befully open, and remain so for this exercise.

Procedure:-

i) Select maximum pump speed N 1 by adjusting the power controllerto 1000/0.

ii) Open inlet valve V 1 fully. Close discharge valve V 2 then start thepump (pump motor started under minimum load). Open dischargevalve V 2 fully and allow the water to circulate until all air bubbleshave dispersed. Select 'Diagrm' and note the value of the volumeflow indicated at the bottom of the screen. Decide on suitableincrements in flow to give adequate sample points (typically 15points between zero and maximum flow).

iii) Close Valve V 2 to correspond to the condition of no flow ie. Qy = O.

When the measured readings as indicated in the boxes on theschematic diagram are sufficiently steady, select 'Take Sample'. Thisrepresents the first point on the characteristic curve. 00 NOT leavethe pump in this condition of a closed outlet valve V 2 as the waterwill heat up and so change in viscosity as to invalidate the results!Go on to the next point (iv) as soon as possible:-

iv) Open valve V 2 slightly, to give the first increment in volume flowat the bottom of the screen. When readings are steady enoughi select'Take Sample'.

v) Repeat step (iv) above for a gradually increasing set of valve V 2openings, ie. increasing values of flow Qy. The final sample pointwill correspond to valve V 2 being fully open.

vi) The recorded set of head-flow data may now be examined andassessed in the various selectable options of 'Graphs', 'Tables' ordownloaded into a spreadsheet. (see 'Software' help screens ifnecessary).

PE2-2

FM20

SpeedPump ConstantPractical ExerciseCharacteristics

No 3 -

Objective:-

To obtain the head-flow curves for a centrifugal pump at a range of pumpspeeds, and to relate these parameters to pump efficiency.

Theoretical Background:-

Pump Operating Characteristics

Pump manufacturers provide information on the performance of theirpumps in the form of characteristic curves, such as those shown in Fig 5for a typical, variable speed centrifugal pump.

Eft:.:icll:y %

'i

5

b.l 0.2DiIcb.F Q (cu.m/~)

8.30

Fig 5 Typical characteristic curves for a 375mm dia impeller pump(courtesy of Smith &; Loveless, quoted in 'EnvironmentalEngineering' by HS Peavy, DR Rowe &; G Tchobanoglous, McGraw-Hill 1985)

The curves allow engineers to see the maximum efficiency of a particulardesign of pump for a range of operating speeds, and hence helps with theselection of pumps for a required pressure-flow. Other charts may showthe influence of change in impeller diameter, or altering the blade angle.

Equipment Set-Up:-

Exactly as Practical Exercise No 2, with pump suction valve V 1 fully openthroughout the exercise.

PE3-1

FM20

Procedure:-

Choose a relatively low pump speed ego 10Hz, and repeat theprocedure of Exercise No 2 above. Remember to take the series ofsample points in ascending steps of increased flow, and also tocorrect the power controller setting to ensure the pump speed is thesame for all head-flow readings.

i)

ii) Now increase the pump speed to a new, somewhat higher settingego 15Hz or even 20Hz, and repeat the taking of samples forgradually increasing values of flow rate, as in i) immediately above.

iii) Your recorded tables and corresponding graphs of head-flow atdifferent but fixed pump speeds should look like those in Fig 2 ofthe 'Introduction' section. It is instructive to superimpose theefficiency curves on to the graph, to indicate those combinations ofhead, flow and speed where efficiency is at a maximum.

1PF3-2

FM20

Practical Exercise No 4 - Introduction to Scaling

Objective:-

To predict the head-flow characteristic at one pump speed frommeasured at another speed.

Theoretical Background:-

It is not practicable to test the performance of every size of pump in amanufacturer's range at all speeds at which it may be designed to run.

Hence a mathematical solution is r~uired whereby assumptions can bemade as to the operating characteristics of a pump running at one speed,impeller size, etc from experimental results taken at another.

The multiplicity of such curves, which result from dimensional plotting,can be reduced to a single curve if appropriate dimensionless groups areused. It turns out that, provided that the effects of fluid viscosity on pumpperformance are small and that cavitation (see later) is not occurring, thecharacteristic of a given type and shape of pump is represented by:

function of JgLN.D3

gHN2I)T

=

where Nand D

= pump speed (rpm or Hz)= impeller diameter (m)

For a single curve of the type suggested by Equation (9) to represent morethan one operating condition of the particular type of pump, the criterionof 'dynamic similarity' must be fulfilled. That is, all fluid velocities atcorresponding points within the machine are in the same direction andproportional to impeller speed. When this is the case, as for a particularpump operated at different speeds, a simple graph of data is formed, asdepicted in Fig 6:

PE4-1

FM20

Flow coefficient Q/(ND)

'if0+ +Key: X<;o o<>~ x

x 2500 rpm + '<>

0 3500<> 4500+ 5000

~+\,9;.~

~ ~

,

Fig 6 Dimensionless head-discharge characteristic of a particular

centrifugal pump operated at different speeds. (ack. to IIFluidMechanics, Thermodynamics of Turbomachinery" , SL Dixon,Pergamon 1966.)

Use of these so-called 'affinity laws' allows performance of geometricallysimilar pumps of different sizes or speeds to be predicted accuratelyenough for practical purposes. Exact accuracy would require that effects ofsurface roughness of the pump, the viscosity of the fluid, etc. to be takeninto account.

The methods used for forming these dimensionless groups will not beentered into here, but the groups themselves are known by the followingnames:

P / pN3Ds = PQ/ND3=cj)gH/N2D2 = 'II

the power coefficientthe flow coefficientthe head coefficient

These laws are most often used to calculate changes in flow rate, head andpower of a pump when the size, rotational speed or fluid density ischanged. The following formulae are derived from the aboveconsiderations, and allow calculation of head H, power P and efficiency Eat one speed N] to be deduced from those measured at another speed N2:

Q)

Q2Nt--

-N2

N2-1.

N22

HIH2

=(10)

PE4-2

I I I0.02 0.04 0.06

°50-~ .

~4.0.bb-.~3.0-(.)e82.0-(.)

-0 /:+- x~ 10 I"\L det . . . ,i"/:+- <)::c . - ~rve enoraDon m y- . .

perfonnance at high speeds(effect due to cavitation)

I

FM20

N31N3 2

Pt ---P2

More generally, the relationship between two geometrically similarmachines with characteristic diameters Dt and D2 operating at rotationalspeeds Nt and N2 is shown in Fig 7. For any two points at which values of

~gH )N2- D2 and

are the same (these are termed 'corresponding points'), it follows that:-

2 2

~Nt

O2-OJ

andH2=H1

3N2 (~ )Q2 = Qt°N-; Dt (11)

:I:~(UQ)

:I:

~ NO~ ~ ;2.~

yv

FQt

Q~(W;° )3

ON/ .1 1

01 -~ ~Volume F~ Q q;

geometricallyFig 7 Relationship of performance characteristicssimilar machines operating at different speeds.

for

PE4-3

FM20

Equipment Set-Up:.

Exactly as Practical Exercise No 2, with pump suction valve V 1 fully openthroughout the exercise.

Procedure:-

i) As discussed, there is no need to perform further test runs to gainall pump performance characteristics, as in Experiment 3, as theresults so far obtained can be used as they are to test the 'scalinglaws'.

From the Equation (10) in the Theory section, the Head H and FlowQy at one speed N 1 are, for dynamically similar pumps (here ofcourse the same pump), related to those at another speed N2 by:

ii)

H1/H2 = N~ /N~Ql/Q2 =N1fNz and

iii) Therefore take anyone pair of readings of H and ~ at a chosenspeed N 1 and predict the values of H and Qy at another speed forwhich you happen to have the measured values of H and Qy as well.A comparison between predicted and measured values will beinstructive. It is of course possible to predict the entire characteristiccurve of H - Qy at one speed from the measured results at another.

PE4-4

FM20

Practical Exercise No 5 - Pump Suction

Objective:-

To investigate the effect on pump performance of different suctionconditions at the pump inlet.

Theoretical Background:-

CA VITAllON AND SUcnON HEAD

In both the design and operation of a rotodynamic machine, carefulattention has to be paid to the fluid conditions on the suction side. Inparticular, it is important to check the minimum pressure that can arise atany point to ensure that 'cavitation' does not take place.

i) Cavitation.

If the pressure at any point is Jess than the vapour pressure of the liquid atthe temperature at that point, vaporisation will occur. This is most likelyto arise in the suction side and , if so, the pump may not be capable ofdeveloping the suction head necessary to ensure the correct operatingpoint is achieved. Moreover, the vaporised liquid appears as bubbleswithin the liquid, and these subsequently collapse with such force thatmechanical damage may be sustained. This condition, known ascavitation, is accompanied by a marked increase in noise and vibration inaddition to the loss of head.

Suction headii)

For any pump, manufacturers specify the minimum value of the 'netpositive suction head' (NPSH) which must exist at the suction inlet pointof the pump. NPSH is the amount by which the pressure at this pointmust exceed the vapour pressure of the liquid. For any installation thismust be calculated, taking into account the absolute pressure of the liquid,the level of the pump, and the velocity and friction heads in the suctionline. The NPSH must allow for the fall in pressure occasioned by thefurther acceleration of the liquid as it flows onto the impeller and forlosses in the pump itself. If the required value of NPSH is not reached,partial vaporisation may occur, with the result that both suction anddelivery heads may be reduced. The loss of suction head is more importantbecause it may cause the pump to be starved of liquid.

PEs-I

FM20

Equipment Set-Up:-

As for the previous Exercises, but choose a pump speed N and outlet valvesetting V 2 (and thus flow rate) corresponding to one of the data points ofExercise No 3. This makes comparison easier. Probably a pair of mid rangevalues of N and Qy are the most suitable.

Procedure:-

This procedure is as Exercise 2 but changes the inlet valve, and leaves thedischarge valve fully open.

Initially, start with the inlet valve V fully open. Take Sample,which should produce a head and efficiency result correspondingprecisely to that from Exercise 3.

i)

Now dose the inlet valve V 1 somewhat, and Take Sample.ii)

Close the inlet valve a further amount, restore the pump speed andTake Sample. Continue this restriction of the inlet, taking datasamples at the same constant speed, until the pump no longerdraws any water from the feed tank. Then stop the pump operationimmediately to prevent damage.

iii)

iv) The resulting tabulation and graphs of pump head and efficiencyunder the gradually worsening conditions at the inlet can then becompared with those for the same speed and flow with anunrestricted inlet.

PF5-2

FM20

- dutyCharacteristicPracticalpoint

Exercise No 6 - System

Objective:-

To obtain a Head - Flow curve for the piping system through which thefluid has to be pumped.

Theoretical Background:-

Analysis Of Pump Systems

System analysis for a pumping installation is conducted to select the mostsuitable pumping units and to define their operating points. Systemanalysis involves calculating head-capacity curves for the pumping system(valves, pipes, fittings etc.) and the use of these curves with those ofavailable pumps. The s~tern curves are a graphic representation of allpossible duty points in so far that the total dynamic head (static lift pluskinetic energy losses) is plotted against discharge flows from zero to theexpected maximum, and a typical set are shown in Fig 8.

ISI 20'510 101

Discharge Qv

Fig 8 Typical head-discharge curves for a pumping installation (pipes,valves etc).

As noted previously, pump characteristic curves illustrate the relationshipbetween head, discharge, efficiency and power over a wide range ofpossible operating conditions, but they do not indicate at which point onthe curves the pump will operate. The operating point (or duty point) isfound by plotting the pump head-discharge curve with system head-discharge curve, as in Fig 9. The intersection of the two curves representsthe head and discharge that the pump will produce if operated in the

PE6-1

FM20

given piping system. It will be seen that the optimum operating conditionis achieved if this operating point coincides with the maximum point inthe efficiency-discharge curve of the pump.

40""1PumpbeedoCap8citycurve

~~

= I

) '-

~.

5 10 15

Discharge Q

Fig 9 Definition sketch for determination of pump operating point.

r90'--SO

Equipment Set- Up:-

It is necessary to use the pump outlet pressure tapping to measure thehead against which the fluid must be pumped relative to atmosphericpressure. The connection between the pump inlet pressure tapping andthe low pressure port on differential pressure sensor SPW3 must thereforebe temporarily broken. To do this, remove the small bore tubing from thepressure tapping adjacent to the inlet of the pump then temporarily blankthe tapping using a short length of flexible tubing with clamp to preventleakage through the tapping. The free end of the flexible tube which is stillattached to the low pressure side of sensor SPW3 should be left open toatmosphere with the end positioned approximately at the same height asthe centreline of the pump (height datum for measurements).

The pump motor may now be switched on and water circulated as in theprevious Exercise set-ups. Inlet valve VI should be fully open.

Procedure:-

i) Select a position for the outlet valve V 2 such that it is partly closedand forming a significant resistance to flow ego 2/3rds shut. Thissetting will be maintained throughout this Exercise (unless youhave to repeat the results at a different setting to achieve a betterrange, for example).

ii) Flow control of the pump will be made by altering the speed settingon the power controller rather than by altering the outlet valve asin the previous Exercises.

FM20

Iii) Select maximum speed as the starting point (5WA1 set to 1000/0).When the readings of pump outlet pressure and orifice pressuredrop are constant, Take Sample. (The pump outlet pressure, nowmeasured relative to atmospheric pressure, represents the 'systempressure', as conditions in the vessel to which the water is returnedremain constant.)

iv) Decrease the speed slightly by adjusting SW AI, ie. decrease the flowrate Qv, and Take Sample for the new conditions of system pressure.Continuation of this measurement at gradually decreased flow willprovide the data in Tables or Graphs as the 'system' head-flowcurve, as described in Theory section 6.

Note: It will not be possible to reduce the speed continuously down tozero.

PE6-3

GENERAL SAFETY RULES

1 Follow Relevant Instructions

a

b

Before attempting to install, commission or operate equipment, allrelevant suppliers/manufacturers instructions and local regulationsshould be understood and implemented.It is irresponsible and dangerous to misuse equipment or ignoreinstructions, regulations or warnings.Do not exceed specified maximum operating conditions (eg.temperature, pressure, speed etc. '

(

2 Installation

a

b

d

e

f

Use lifting tackle where possible to install heavy equipment. Wheremanual lifting is necessary beware of strained backs and crushedtoes. Get help from an assistant if necessary. Wear safety shoeswhere appropriate.Extreme care should be exercised to avoid damage to the equipmentduring handling and unpacking. When using slings to liftequipment, ensure that the slings are attached to structuralframework and do not foul adjacent pipework, glassware etc. Whenusing fork lift trucks, position the forks beneath structuralframework ensuring that the forks do not foul adjacent pipework,glassware etc. Damage may go unseen during commissioningcreating a potential hazard to subsequent operators.Where special foundations are required follow the instructionsprovided and do not improvise. Locate heavy equipment at lowlevel.Equipment involving inflammable or corrosive liquids should besited in a containment area or bund with a capacity 500/0 greater thanthe maximum equipment contents.Ensure that all services are compatible with the equipment and thatindependent isolators are always provided and labelled. Use reliableconnections in all instances, do not improvise.Ensure that all equipment is reliably earthed and connected to anelectrical supply at the correct voltage. The electrical supply mustincorporate a Residual Current Device (RCD) (alternatively calledan Earth Leakage Circuit Breaker - ELCB) to protect the. operatorfrom severe electric shock in the event of misuse or accident.Potential hazards should always be the first consideration whendeciding on a suitable location for equipment. Leave sufficient spacebetween equipment and between walls and equipment.

g

.L

A voiding fires or explosion7

a

b

c

d

e

f

Ensure that the laboratory is provided with adequate fireextinguishers appropriate to the potential hazards.Where inflammable liquids are used, smoking must be forbidden.Notices should be displayed to enforce this.Beware since fine powders or dust can spontaneously ignite undercertain conditions. Empty vessels having contained inflammableliquids can contain vapour and explode if ignited.Bulk quantities of inflammable liquids should be stored outside thelaboratory in accordance with local regulations.Storage tanks on equipment should not be overfilled. All spillagesshould be immediately cleaned up, carefully disposing of anycontaminated cloths etc. Beware of slippery floors.When liquids giving off inflammable vapours are handled in thelaboratory, the area should be ventilated by an ex-proof extractionsystem. Vents on the equipment should be connected to theextraction system.Students should not be allowed to prepare mixtures for analysis orother purpose without competent supervision.

g

Handling poisons, corrosive or toxic materials8

a

b

c

d

Certain liquids essential to the operation of equipment, for examplemercury, are poisonous or can give off poisonous vapours. Wearappropriate protective clothing when handling such substances.Clean up any spillage immediately and ventilate areas thoroughlyusing extraction equipment. Beware of slippery floors.Do not allow food to be brought into or consumed in the laboratory.Never use chemical beakers as drinking vessels.Where poisonous vapours are involved, smoking must beforbidden. Notices should be displayed to enforce this.Poisons and very toxic materials must be kept in a locked cupboardor store and checked regularly. Use of such substances should besupervised.When diluting concentrated acids and alkalis, the acid or alkalishould be added slowly to water while stirring. The reverse shouldnever be attempted.

e

9 A voiding cuts and bums

a

b

Take care when handling sharp edged components. Do not exertundue force on glass or fragile items.Hot surfaces cannot in most cases be totally shielded and canproduce severe burns even when not "visibly hot'. Use commonsense and think which parts of the equipment are likely to be hot.

3 Commissioning

Ensure that equipment is commissioned and checked by acompetent member of staff before permitting students to operate it.

a

Operation4

a

b

d

Ensure that students are fully aware of the potential hazards whenoperating equipment.Students should be supervised by a competent member of staff at alltimes when in the laboratory. No one should operate equipmentalone. Do not leave equipment running unattended.Do not allow students to derive their own experimental proceduresunless they are competent to do so.Serious injury can result from touching apparently stationaryequipment when using a stroboscope to 'freeze' rotary motion.

5 Maintenance

a

b

Badly maintained equipment is a potential hazard. Ensure that acompetent member of staff is responsible for organisingmaintenance and repairs on a planned basis.Do not permit faulty equipment to be operated. Ensure that repairsare carried out competently and checked before students arepermitted to operate the equipment.

Using Electricity6

a

b

c

d

At least once each month, check that ELCB's (RCCB's) are operatingcorrectly by pressing the TEST button. The circuit breaker must tripwhen the button is pressed (failure to trip means that the operator isnot protected and a repair must be effected by a competentelectrician before the equipment or electrical supply is used).Electricity is the commonest cause of accidents in the laboratory.Ensure that all members of staff and students respect it.Ensure that the electrical supply has been disconnected from theequipment before attempting repairs or adjustments.Water and electricity are not compatible and can cause seriousinjury if they come into contact. Never operate portable electricappliances adjacent to equipment involving water unless someform of constraint or barrier is incorporated to prevent accidentalcontact.Always disconnect equipment from the electrical supply when notin use.

e

b

Eye protection10

a

b

Goggles must be worn whenever there is a risk to the eyes. Risk mayarise from powders, liquid splashes, vapours or splinters. Beware ofdebris from fast moving air streams. Alkaline solutions areparticularly dangerous to the eyes.Never look directly at a strong source of light such as a laser orXenon arc lamp. Ensure that equipment using such a source ispositioned so that passers-by cannot accidentally view the source orreflected ray.Facilities for eye irrigation should always be available.c

Ear protection11

Ear protectors must be worn when operating noisy equipment.a

Clothing12

a

b

Suitable clothing should be worn in the laboratory. Loose garmentscan cause serious injury if caught in rotating machinery. Ties, ringson fingers etc. should be removed in these situations.Additional protective clothing should be available for all membersof staff and students as appropriate.

13 Guards and safety devices

a

b

c

d

Guards and safety devices are installed on equipment to protect theoperator. The equipment must not be operated with such devicesremoved.Safety valves, cut-outs or other safety devices will have been set toprotect the equipment. Interference with these devices may create apotential hazard.It is not possible to guard the operator against all contingencies. Usecommon sense at all times when in the laboratory.Before starting a rotating machine, make sure staff are aware how tostop it in an emergency.Ensure that speed control devices are always set at zero beforestarting equipment.

e

First aid14

a

b

If an accident does occur in the laboratory it is essential that first aidequipment is available and that the supervisor knows how to use it.A notice giving details of a proficient first-aider should beprominently displayed.A 'short list' of the antidotes for the chemicals used in a particularlaboratory should be prominently displayed.

c

d