kSIST FprEN 16480:2021

Pumps - Rotodynamic pumps - Minimum required efficiency of water pumps and determination of Minimum Efficiency Index (MEI)

This European Standard specifies performance requirements (methods and procedures for testing and calculating) for determining the Minimum Efficiency Index (MEI) of rotodynamic glanded water pumps for pumping clean water, including where integrated in other products.
The pump types and sizes covered by this standard are described in the Annex A. These pumps are designed and produced as duty pumps for pressures up to 16 bar for end suction pumps and up to 25 bar for multistage pumps, temperatures between -10 °C and +120 °C and 4" or 6" size for submersible multistage pumps at operating temperatures within a range of 0 °C and 90 °C.
In addition, this standard specifies how the value of the Minimum Efficiency Index (MEI) of a pump size indicated by the manufacturer can be checked by market surveillance.
Even if it is left free to the manufacturer of a pump size how to prove the rated value of the Minimum Efficiency Index (MEI), nevertheless this standard specifies a method to prove that this rated value meets the requirements within the confidence intervals with a sufficiently high probability.

Pumpen - Kreiselpumpen - Geforderte Mindesteffizienz für Wasserpumpen sowie Bestimmung des Minimum Effizienz Indexes (MEI)

Pompes - Pompes rotodynamiques - Rendement minimal requis des pompes à eau et détermination de l'Indice de rendement minimal (MEI)

Le présent document spécifie les exigences de performance (méthodes et modes opératoires d’essais et de calculs) pour la détermination de l’indice de rendement minimal (MEI) des pompes à eau rotodynamiques dotées d’un dispositif d’étanchéité employées pour pomper de l’eau propre, y compris les pompes intégrées dans d’autres produits.
Les types et les gammes de pompe visés par le présent document sont décrits dans l’Annexe A. Ces pompes sont conçues et fabriquées comme des pompes de service pour des pressions inférieures ou égales à 16 bar pour les pompes à aspiration en bout et inférieures ou égales à 25 bar pour les pompes multi-étagées, pour toutes les pompes conçues pour des températures de fluides comprises entre -10 °C et +120 °C. Sont également couvertes les pompes multi-étagées de 10,16 cm (4") et 15,24 cm (6") pour les pompes submersibles multi-étagées à des températures de fluides comprises entre 0 °C et 90 °C.

Črpalke - Centrifugalne črpalke - Minimalna zahtevana učinkovitost vodnih črpalk in določevanje indeksa minimalne učinkovitosti (MEI)

General Information

• Status: Not Published
• Public Enquiry End Date: 07-Mar-2018
• ICS: 23.080 - Pumps
• Technical Committee: I13 - Imaginarni 13
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 20-Oct-2021
• Due Date: 25-Dec-2021
• Directive: 2009/125/EC - Directive 2005/32/EC of the European Parliament and of the Council of 6 July 2005 establishing a framework for the setting of ecodesign requirements for energy-using products and amending Council Directive 92/42/EEC and Directives 96/57/EC and 2000/55/EC of the European Parliament and of the Council
• Directive: 547/2012 - Commission Regulation (EU) No 547/2012 of 25 June 2012 implementing Directive 2009/125/EC of the European Parliament and of the Council with regard to ecodesign requirements for water pumps
• Mandate: M/498 - Mandate to CEN, CENELEC and ETSI in the field of pumps
• Ref Project: EN 16480:2021 - Pumps - Rotodynamic pumps - Minimum required efficiency of water pumps and determination of Minimum Efficiency Index (MEI)

RELATIONS

• Revised: SIST EN 16480:2016 - Pumps - Minimum required efficiency of rotodynamic water pumps
• Effective Date: 08-Feb-2017
• Replaces: SIST EN 16480:2016 - Pumps - Minimum required efficiency of rotodynamic water pumps
• Effective Date: 20-Oct-2021

Standards Content (sample)

SLOVENSKI STANDARD
oSIST prEN 16480:2018
01-marec-2018
ýUSDONH&HQWULIXJDOQHþUSDONH0LQLPDOQD]DKWHYDQDXþLQNRYLWRVWYRGQLKþUSDON
LQPHWRGH]DNYDOLILNDFLMRLQYHULILNDFLMR
Pumps - Rotodynamic Pumps - Minimum required efficiency of water pumps and
methods of qualification and verification
Pumpen - Kreiselpumpen - Geforderte Mindesteffizienz für Wasserpumpen sowie
Methoden zur Qualifizierung und Verifizierung
Pompes - Pompes rotodynamiques - Rendement minimum requis des pompes à eau et
méthodes de qualification et de vérification
Ta slovenski standard je istoveten z: prEN 16480
ICS:
23.080 ýUSDONH Pumps
oSIST prEN 16480:2018 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN 16480:2018
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oSIST prEN 16480:2018
DRAFT
EUROPEAN STANDARD
prEN 16480
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2017
ICS 23.080 Will supersede EN 16480:2016
English Version
Pumps - Rotodynamic Pumps - Minimum required
efficiency of water pumps and methods of qualification
and verification

Pompes - Pompes rotodynamiques - Rendement Pumpen - Kreiselpumpen - Geforderte Mindesteffizienz

minimum requis des pompes à eau et méthodes de für Wasserpumpen sowie Methoden zur Qualifizierung

qualification et de vérification und Verifizierung

This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee

CEN/TC 197.

If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations

which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other

language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC

Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and United Kingdom.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are

aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without

notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 16480:2017 E

worldwide for CEN national Members.
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Contents Page

European foreword ....................................................................................................................................................... 4

Introduction .................................................................................................................................................................... 5

1 Scope .................................................................................................................................................................... 7

2 Normative references .................................................................................................................................... 7

3 Terms, definitions, symbols and abbreviations ................................................................................... 7

3.1 Terms and definitions ................................................................................................................................... 7

3.2 Symbols and abbreviations ...................................................................................................................... 11

4 Minimum Required Efficiencies and Minimum Efficiency Index ................................................ 14

4.1 The concept of “house of efficiency” ...................................................................................................... 14

4.2 Mathematical representation of minimum required efficiency ................................................. 15

4.3 Minimum efficiency at part load and overload ................................................................................. 16

4.4 Minimum Efficiency Index ........................................................................................................................ 17

5 Determination of the Efficiency of a Test Pump ................................................................................ 20

5.1 General ............................................................................................................................................................. 20

5.2 Test Procedures ............................................................................................................................................ 20

5.3 Test conditions .............................................................................................................................................. 21

5.4 Measuring uncertainties ............................................................................................................................ 22

5.5 Evaluation of test data ................................................................................................................................ 25

6 Proving the Minimum Efficiency Index of a pump size ................................................................... 29

6.1 General remarks ........................................................................................................................................... 29

6.2 Determination of the Minimum Efficiency Index of a pump size ................................................ 30

7 Verification of the Minimum Efficiency Index for a pump size .................................................... 31

7.1 General remarks ........................................................................................................................................... 31

7.2 Procedure and decision ............................................................................................................................. 31

Annex A (normative) Pump types in scope ...................................................................................................... 35

Annex B (informative) General remarks on the efficiency of rotodynamic pumps .......................... 37

Annex C (informative) Mean Values of a Size Relevant for its Minimum Efficiency Index ............. 39

Annex D (informative) Methods recommended for manufacturers to determine the mean

values of hydraulic quantities of a size relevant for MEI ............................................................... 44

D.1 General remarks ........................................................................................................................................... 44

D.2 Determination of the mean efficiency of a pump size from a test on one single test

pump ................................................................................................................................................................. 44

D.3 Determination of the mean efficiency of a pump size from a sample of M test pumps....... 46

Annex E (informative) Numerical example...................................................................................................... 49

Annex F (informative) Application of mathematical statistics on tests ................................................ 54

F.1 Purposes of applying statistics in the frame of qualification and verification ...................... 54

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F.2 Confidence interval ...................................................................................................................................... 55

F.3 Law of error propagation ........................................................................................................................... 57

Annex G (informative) Measurement uncertainties ..................................................................................... 63

G.1 General remarks ........................................................................................................................................... 63

G.2 Determination of the overall measurement uncertainty of efficiency ...................................... 65

Annex H (informative) Explanations concerning the methodology of the verification

procedure and the probability of the results ..................................................................................... 67

Annex I (informative) Reporting of Test Results ............................................................................................ 70

I.1 Test Report Requirements ........................................................................................................................ 70

I.2 Pump test sheet ............................................................................................................................................. 70

Annex ZA (informative) Relationship between this European Standard and the Essential

Requirements of EU Directive 2009/125/EC, establishing a framework for the
setting of ecodesign requirements of energy related products and implemented by

the European Commission Regulation (EU) No. 547/2012 ........................................................... 73

Bibliography ................................................................................................................................................................. 74

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European foreword

This document (prEN 16480:2017) has been prepared by Technical Committee CEN/TC 197 “Pump”,

the secretariat of which is held by AFNOR.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 16480:2016.

This document has been prepared under a mandate given to CEN by the European Commission and the

European Free Trade Association, and supports essential requirements of EU Directive(s).

For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this

document.
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Introduction
Purpose and content of the standard

The water pumps within the scope of this European Standard are typically produced and sold by pump

manufacturers as series of large to very large numbers. The performance characteristics of pumps of

one size produced by a manufacturer show some scatter caused by manufacturing tolerances, but are

described by mean values and curves which represent that size.

The total consumption of electric energy by water pumps installed in applications within the scope of

this European Standard depends on the total number of installed pumps of each size and on its mean

efficiency. The quality of a size in respect to its mean efficiency is quantitatively described by the

Minimum Efficiency Index (MEI) which is defined and used in this standard. To achieve a certain value

of the Minimum Efficiency Index (MEI), a corresponding minimum value of the mean efficiency of a size

is required.

This European Standard defines – for each pump type and size within the scope of the standard - the

minimum required value of efficiency depending on the value of the Minimum Efficiency Index (MEI).

Also, this standard prescribes how the value of the Minimum Efficiency Index (MEI) of a pump size

indicated by the manufacturer can be verified by an independent institution (e.g. in the frame of market

surveillance). For the manufacturer of the pump size it is generally left free how to prove the indicated

value of the Minimum Efficiency Index (MEI) of a size. Nevertheless, this standard describes also a

method to prove by the manufacturer that the mean values of efficiency meet the requirements for

indicating a certain value of the Minimum Efficiency Index (MEI).

Normally, the qualification of a pump size for a certain MEI value done by the manufacturer will be

based on tests and evaluations made on a sample of pumps of this size. Tests and evaluations carried

out for the purpose of qualifying the corresponding size should fulfil certain requirements:

— From the tests on the sample pumps, it becomes possible to predict for the corresponding size the

confidence intervals within which the true mean values of efficiencies which are relevant for the

qualification are enclosed with a sufficiently high probability. Only in that way, the qualification of

the size in respect to a required and/or indicated value of Minimum Efficiency Index (MEI) will

make sure that the aspired effect of energy saving will be reached.

— If a pump size has been qualified according to the criteria described in this European Standard,

every test on one or more test pump(s) of the same size (with a full impeller diameter) which is

carried out in the frame of a verification procedure should result with a very high probability in a

confirmation of the qualification.

Caused by technical alignment procedures of the single pump components e.g. bearings or shaft seals

the performance of the pump is gained after a certain running-in time.
Ways to prove and to verify the Minimum Efficiency Index (MEI) of a pump size

This European Standard describes different ways how manufacturers can achieve the qualification of a

pump size for a certain value of the Minimum Efficiency Index (MEI) and how this qualification can be

verified by an independent institution.

For the manufacturer it is generally left free to choose and apply appropriate methods to prove that the

mean efficiency values of a size are at least equal to or higher than particular threshold values of

efficiency. These particular threshold values of efficiency are related to the value of the Minimum

Efficiency Index (MEI) to be indicated for the size. The way to determine these values of efficiency is

described in this standard. If the way chosen by the manufacturer to prove the MEI value of a size

deviates from the way mentioned in the next paragraph, the manufacturer has to document all tests,

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evaluations and/or calculations which are carried out and the methods which are applied to prove the

justification of the indicated MEI value.

If the manufacturer decides to determine the mean performance values of the size by one of the

methods described in Annex D of this standard, he has to carry out tests according to the requirements

given in Annex C of this standard and evaluations as described in Annex C of this standard and to prove

– as described in Clause 7 of this standard – that the criteria for the achievement of a certain value of

the Minimum Efficiency Index (MEI) of the size are fulfilled. The test conditions, the results of test

evaluation and the fulfilment of the criteria are documented and stored. The time period to keep

documentation available for the authorities to prove conformity is fixed by the legal text.

The independent institution carries out tests on pumps of the size in question according to the

requirements given in 5.2 to 5.4 of this standard as well as evaluations as described in 5.5 of this

standard and applies the methodology and procedure described in Clause 4 of this standard.

For an independent institution, two ways are possible and specified by this standard to verify the value

of Minimum Efficiency Index (MEI) indicated by the manufacturer:

1) If the documentation of the qualification is presented by the manufacturer to the independent

institution on request, the procedure of verification executed by the independent institution is

based on the documentation of tests and evaluations done and documented by the manufacturer. In

this case, the documentation will be checked by the independent institution in respect to being in

accordance with requirements and criteria given in this standard.

2) If no documentation is presented by the manufacturer on request or if the documentation

presented by the manufacturer on request is not accepted as proof of the indicated value of MEI,

the independent institution carries out tests on pumps of the size in question according to the

requirements given in Annex C of this standard as well as evaluations as described in 5.5 of this

standard and applies the methodology and procedure described in Clause 4 of this standard.

Relevance of clauses of this standard for manufacturers or independent institutions

Clause 4 describes nominal values of minimum required efficiency for a certain value of the Minimum

Efficiency Index (MEI) and is generally relevant when applying this standard.

Section 5 specifies test procedures, test conditions and evaluations and has to be applied

— by a manufacturer in the case that he decides to determine mean values of a size by tests on sample

pumps of this size (e.g. by methods described in Annex D),

— by an independent institution in the case that the Minimum Efficiency Index (MEI) of a pump size

should be verified by the procedure described in Clause 7.

Clause 6 describes the procedure to be applied by a manufacturer in order to determine particular

threshold values of efficiency for a certain value of the Minimum Efficiency Index (MEI) of a size and to

prove the justification of this MEI value by the fulfilment of criteria for the mean efficiency values.

Clause 7 describes the methodology and procedure to be applied by an independent institution in the

case that the Minimum Efficiency Index (MEI) of a size indicated by the manufacturer should be verified

by third party tests on pumps of this size.

Annex C is concerned with mean values of a pump size which are relevant for manufacturers to prove

that a pump size achieves a certain value of the Minimum Efficiency Index (MEI).
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1 Scope

This document specifies performance requirements (methods and procedures for testing and

calculating) for determining the Minimum Efficiency Index (MEI) of rotodynamic glanded water pumps

for pumping clean water, including where integrated in other products.

The pump types and sizes covered by this standard are described in the Annex A. These pumps are

designed and produced as duty pumps for pressures up to 16 bar for end suction pumps and up to 25

bar for multistage pumps, temperatures between −10 °C and +120°C and 4” or 6” size for submersible

multistage pumps at operating temperatures within a range of 0 °C and 90 °C.

In addition this standard specifies how the value of the Minimum Efficiency Index (MEI) of a pump size

indicated by the manufacturer can be checked by market surveillance.

Even if it is left free to the manufacturer of a pump size, how to prove the rated value of the Minimum

Efficiency Index (MEI), nevertheless this standard specifies a method to prove that this rated value

meets the requirements within the confidence intervals with a sufficiently high probability.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

EN ISO 9906, Rotodynamic pumps - Hydraulic performance acceptance tests - Grades 1, 2 and 3 (ISO

9906)
ISO 31, General principles concerning quantities, units and symbols
3 Terms, definitions, symbols and abbreviations
3.1 Terms and definitions

For the purposes of this document, the terms and definitions given in EN ISO 9906 and the following

apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
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3.1.1 List of quantities with definitions
3.1.1.1
reynolds number

dimension less number that gives a measure of the ratio of inertial forces to viscous forces and

consequently quantifies the relative importance of these two types of forces for given flow conditions.

In this standard, it is defined by the relation:
Du⋅
imp
Re=
where u is the peripheral velocity at the outer impeller diameter D
imp
3.1.1.2
(volume) rate of flow

external rate of flow of the pump, i.e. the rate of flow discharged into the pipe from the outlet branch of

the pump
NOTE 1 to entry: Losses or abstractions inherent to the pump, i.e.:
— discharge necessary for hydraulic balancing of axial thrust;
— cooling of bearings of the pump itself;
— water seal to the packing;

NOTE 2 to entry: Leakage from the fittings, internal leakage, etc., is not to be reckoned in the rate of flow. On the

contrary, all derived flows for other purposes, such as cooling of the motor bearings; cooling of a gear box

(bearings, oil cooler), etc. are to be reckoned in the rate of flow.

NOTE 3 to entry: Whether and how these flows shall be taken into account depends on the location of their

derivation and of the section of flow-measurement respectively.
3.1.1.3
driver power input
power absorbed by the pump driver
3.1.1.4
pump efficiency
Hydraulicoutput
hyd
Pumppowerinput
3.1.1.5
driver efficiency
Pumppowerinput
Driver powerinput

3.1.1 gives specific definitions of terms - in deviation of EN ISO 9906 - used in this European Standard, together

with any associated symbols which have been allocated and is based on ISO 31.
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3.1.1.6
overall efficiency
hyd Pumppoweroutput
tot Driver powerinput
3.1.1.7
specific speed

dimensional number characterising the impeller type (radial, semi-axial, axial) of rotodynamic pumps

BEP
nn⋅
0.75
BEP

Note 1 to entry: For multistage pumps, H is the head per stage which results from dividing the total pump

BEP
head at the point of best efficiency by the number of stages i

Note 1 to entry: The specific speed of an individual pump or the mean specific speed of a pump size is a

(dimensional) value which characterizes the impeller shape (radial, semi-axial, axial) of the pump or the size. The

numerical value of the specific speed is defined by an equation given in 3.2.7 by using special units for the

quantities contained in this equation. As described in Clause 4, the specific speed is one of the parameters which

the nominal values of minimum required efficiency depend on.
3.1.1.8
minimum efficiency index (MEI)

value which determines the minimum required efficiency for the qualification criteria and, thereby, is a

measure of the quality of a pump size in respect to efficiency

Note 1 to entry: dimensionless scale unit for hydraulic pump efficiency at BEP, PL and OL

Note 2 to entry: The MEI is the result of a statistical analysis of the performances of a large number of commercial

pump sizes, and corresponds to the various “quartiles” of the statistical distribution.

For example, MEI = 0,40 corresponds to the efficiency performance level that 40 % of the pumps on the market do

not meet [7].
3.1.2 General definitions
3.1.2.1
qualification

procedure where the manufacturer of the pump size proves, by appropriate methods, the fulfilment of

the efficiency criteria defined in this standard

Note 1 to entry: Generally, the qualification criteria refer to the mean values of the size which are valid for the full

impeller diameter and which will be determined by tests and evaluations on pumps of the respective size. These

mean efficiency values and their confidence intervals are compared to nominal values of minimum required

efficiency. Also these values depend on parameters (see Clause 4) the values of which partly result from the tests

and are determined with some uncertainty or tolerance. Therefore, so-called particular threshold values of

efficiency are determined and used in the frame of the qualification procedure for comparison with the mean

values.
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3.1.2.2
verification

procedure where an independent institution checks the result of the qualification procedure, in the

frame of market surveillance

Note 1 to entry In this case, the tests and the evaluation of the test data are carried out according to Clause 5 of

this European Standard. The approval decision is taken according to the procedure described in Clause 7 of this

European Standard.
3.1.2.3
independent institution/market surveillance

organisation mandated by the market surveillance for verification of MEI values indicated by

manufacturers

Note 1 to entry these organisations are generally called independent institutions whatever the special type of the

institution (non-governmental organization (NGO), neutral institute, market surveillance authorities or similar)

may be.

Note 2 to entry neutral institutions or similar organisations can also be mandated by a manufacturer for the

qualification procedure, in this case they are not considered as independent institution when applying this

standard.
3.1.2.4
minimum required efficiency η
min,requ

value of efficiency that have to be reached in order to fulfil a particular MEI value

Note 1 to entry: the value of minimum required efficiency depends on certain properties of the pump size (pump

type, nominal speed of rotation, flow rate at best efficiency point and specific speed) and on the Minimum

Efficiency Index (MEI). For one size, different minimum required efficiencies are relevant at best efficiency point,

at specified part load and overload operating points, respectively.
3.1.2.5
particular threshold values of efficiency (η )
threshhold

values calculated from the minimum required efficiency by subtracting a total tolerance

3.1.2.6
pump size

range of pumps characterized by certain dimensions (e.g. nominal diameter of discharge flange and

nominal impeller diameter for end-suction and multistage pumps, number of stages for multistage

pumps, nominal outer casing diameter in the case of submersible multistage pumps) and given in his

catalogues by the manufacturer

Note 1 to entry: In a Q-H-chart each pump size covers a certain range of Q- and H-values. Within this range each

duty point can be served by a pump of the corresponding pump size by adapting its Q-H-curve by impeller

trimming, i.e. by cutting down the outer impeller diameter to an appropriate value. The upper limit of the Q-H-

range covered by one pump size is determined by the full diameter of the impeller corresponding to this size.

3.1.2.7
full impeller diameter of a pump size

impeller with the maximum diameter for which performance characteristics are given for a pump size

in the catalogues of a water pump manufacturer
3.1.2.8
best efficiency point, BEP

operating point where the greatest value of pumps efficiency is obtained, at nominal speed of rotation

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3.1.2.9
part Load PL

particular operating point in the range of operating points with lower flow than best efficiency point, at

nominal speed of rotation
3.1.2.10
overload OL

particular operating point in the range of operating points with higher flow than best efficiency point, at

nominal speed of rotation
3.2 Symbols and abbreviations

Table 1 gives an alphabetical list of symbols used and Table 2 gives a list of subscripts. As far as

possible, the quantities, definitions and symbols used in this standard comply with those used in

EN ISO 9906. Quantities, definitions and symbols used in EN ISO 9906, but not needed in this standard

are not contained 3.2 and Tables 1 and 2 while these tables contain some quantities, definitions and

symbols which are not used in EN ISO 9906.
In this document all equations are given in coherent SI-units.
Table 1 — Alphabetical list of basic letters used as symbols
Symbol Quantity Unit
A Area m
C Constant pure number
D Diameter m
e Measurement uncertainty, pure number
relative value
f Frequency s , Hz
g Acceleration due to gravity m/s
H Pump total head m
k number of instrument pure number
readings or sample pumps
m Mass kg
M number of pumps of a pure number
sample
−1 −1
n Speed of rotation s , min
N Number of instrument pure number
readings
n Specific speed min
p Pressure Pa
p Proba
...