D3 Meter Types

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Integrated customer meter management - Module 1/2: Background 1

The views expressed in this paper/presentation are the views of the author and

do not necessarily reflect the views or policies of the Asian Development Bank(ADB), or its Board of Governors, or the governments they represent. ADB does

not guarantee the accuracy of the data included in this paper and accepts noresponsibility for any consequence of their use. Terminology used may not

necessarily be consistent with ADB official terms.



Integrated customer metermanagement

Module 1:Background information

Meter types and metrological classes




Accuracy

Defines how close a measurement is to anaccepted value

InaccurateAccurate




Precision

Indicate how close together or howrepeatable the results are

Low precision

Low accuracy




Precision

Precision vs. AccuracyHigh precision but low accuracy High precision and high accuracy


http://slidepdf.com/reader/full/d3-meter-types 6/48Integrated customer meter management - Module 1/2: Background 6

Accuracy curve of a water meter

Gives an indication of the accuracy of themeter at different consumption flow rates

-10

-5

0

5

10 100 1000 10000Flow rate (l/h)

E r r o r ( % )




Interpretation

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-5

0

5

10 100 1000 10000

Flow rate (l/h)

E r r o r ( % )

30 l/h

-3.5%

For a flow of 30 l/hthe error is -3.5%

It means:For every 100 lconsumed at 30 l/hthe meter registers 96.5 l




Interpretation

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-5

0

5

10 100 1000 10000

Flow rate (l/h)

E r r o r ( % )

500 l/h

+1%

For a flow of 500 l/hthe error is +1%

It means:For every 100 lconsumed at 500 l/hthe meter registers 101 l





Measuring range

Set of values for which the instrument meetssome specified accuracy requirements

An instrument should always be selected in

such way that it works within its measuringrange (sizing of meters)



Measuring range

Measuring range of a domestic water meter

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0

5

10 100 1000 10000

Flow rate (l/h)

E r r o r ( % )

Maximumerror = 2%

Maximum error = 5%



Measuring range

Measuring range of a domestic water meter

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5

10 100 1000 10000

Flow rate (l/h)

E r r o r ( % )

Effective range: 30 l/h – 3000 l/h




Measuring range

Typical house use flow rates

10 100 1000 10000

0

+5

-5

-10

-15

-20

E r r o r %

Flow rate (l/h)

+

H HHH




Weighted accuracy of a meter

How much water used by a customer is not registerdue to meters inaccuracies?

Consider the following aspects:

The measuring error of a meter is not constant with flow

Water consumption is done at different flow rates

Water used at a flow rate lower than the starting flow rate isnot measured at all

Therefore we need to know both: The way water is used by customers

The accuracy curve of the meter




Weighted accuracy of a meter

Conclusions: The same meter installed at different customers

may have a different weighted error (percentageof water not registered)

o A water meter installed in a leaking facility may havea weighted accuracy of -25%

o The same meter installed in a house with no leaks mayhave a weighted accuracy of -5%

We can never say that a meter has a givenweighted accuracy since this parameter dependson both, the meter itself and the customers

characteristics




International StandardsISO 4064:1993




Introduction

Only applies to mechanical meters To be conform to ISO 4064:1993 a meter

model needs to be successfully tested for:

Accuracy Water tightness

Pressure Loss

Fatigue test

Ideally, these tests should be carried out in

an accredited laboratory




Metrological quality

The flow capacity of a meter is defined by its nominal

or permanent flow The measuring range is defined by three flow rates:

Qmin

Qt Qmax

The metrological quality of a water meter is definedby its class. (A, B, C, D)

The maximum error is the same for all Classes 5% in the lower range

2% in the upper range





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10 100 1000 10000

Flow rate (l/h)

E r r o r ( %

)

Qmin

Typical ISO 4064:1993 Domestic water meters

Qmin :

For flow rates

higher than theminimum flow theerror should beless than the

permitted5%

5%




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10 100 1000 10000

Flow rate (l/h)

E r r o r ( %

)


Qt


Qt :

For flow rateshigher than the

transitional flowthe error shouldbe less than the

permitted 2%

2%




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0

5

10 100 1000 10000

Flow rate (l/h)

E r r o r ( %

)


Qmax

Typical ISO 4064:1993 Domestic water metersQmax :

The highest flowrate at which themeter is requiredto operate for a

short time with anerror less than

2%

The pressure drop atQ

maxshould be lessthan 1 bar

2%




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-5

0

5

10 100 1000 10000

Flow rate (l/h)

E r r o r ( %

)


Qp

Typical ISO 4064:1993 Domestic water metersQp:

The meter shouldwork in a satisfactory

manner for normal

operating conditions(continuous orintermittent flow)

Qp: is half Qmax

• expressed in m3 /h• used to select the

water meter

2%




Metrological classes

10 100 1000 10000

0

+5

-5

-10

-15

-20

E r r o r %

Flow rate (l/h)

ABC


D




Conclusions

The maximum permissible error for allClasses is the same

Class D is better than Class A because it has

a wider measuring range When water consumption is near the nominal

flow rate a higher metrological Class is not

needed:

Class A meters can achieve the same weightedaccuracy of Class D meters!




International StandardsISO 4064:2005




Introduction

For mechanical and non-mechanical meters To be conform to ISO 4064:2005 a meter

model should meet:

Metrological requirements Technical requirements

Materials and construction requirements

There are special requirements for electronicmeters




Definitions

Minimum flow rate Q1

Lowest flow rate at which the water meter is required to operatewith an error lower than 5%

Transitional flow rate Q2

For flow rates higher than the transitional flow the error should belower than 2%

Permanent flow rate Q3

Highest flow at which a water meter is required to operate in asatisfactory manner within the 2%

Overload flow rate Q4

Highest flow rate at which a water meter is required to operate fora short period of time within the 2% without deterioration




Metrological requirements

Meters are selected according to thepermanent flow rate Q3

Its value should be selected from the

following table (expressed in m3/h)

1.0 1.6 2.5 4.0 6.3

10 16 25 40 63100 160 250 400 630

1000 1600 2500 4000 6300




The measuring range is defined by the ratio R: Q3/ Q1

R should be selected from the following table

The higher the value the better the metrological

Class Transitional flow rate: Q2 = 1.6 x Q1

Overload flow rate: Q4 = 1.25 x Q3

Metrological requirements

10 12.5 16 20 25 31.5 40 50 63 80

100 125 160 200 250 315 400 500 630 800




Comparing ISO 4064 domestic meters

1993 vs 2005

Q1 Q2 Q3 Q4

Minimum Transitional Permanent Maximum

Class B

30 l/h 120 l/h 1500 l/h 3000 l/h

31.3 l/h 50 l/h 2500 l/h 3125 l/h

R80

5% 2%




Comparing ISO 4064 domestic meters

1993 vs 2005

Q1 Q2 Q3 Q4

Minimum Transitional Permanent Maximum

Class C

15 l/h 22.5 l/h 1500 l/h 3000 l/h

12.5 l/h 20 l/h 2500 l/h 3125 l/h

R200

5% 2%




Mechanical water metertechnologies




Velocity meters

Use flow velocity to move a sensor (paddle wheel,

turbine) The velocity of the sensor is proportional to the

impact velocity of water Often, their metrological performance is affected by

flow profile distortions Examples of velocity meters:

Single jet

Multiple jet Woltmann meters Compound meters




Positive displacement meters

Volumes are totalized by accounting the number oftimes a chamber is filled and emptied

The volume of the measuring chamber is fixed

Their metrology is not affected by flow profiledistortions

Water quality may blocked the meter

Example of positive displacement meters: Oscillating piston

Nutating disc




Single jet meters




Single jet meters

Low cost and small size

Suitable for water with only moderate quality andhard water

ISO 4064:1993 Class B and C models

Diameters from 10 mm to 125 mm Designed to work in a fully horizontal position

The single jet causes that the forces on the turbine

are not symmetrically distributed The shaft/bearings of the turbine and the turbine

itself have to compensate for this asymmetrical

forces




Multiple jet meters




Multiple jet meters

Not affected by upstream flow distortions

ISO 4064:1993 Class B and C models Diameters from 15 mm to 50 mm Designed to work in a fully horizontal position

The forces on the turbine are symmetricallydistributed. Suitable for hard working conditions Suitable for water with only moderate quality and

hard water

Often a slightly over-registration occurs after a fewyears of use

More material needed to manufacture the housing(higher cost)




Woltmann meters

Horizontal Woltmann Vertical Woltmann




Horizontal Woltmann meters

Adjusting device

Flow straightener

Diffuser




Horizontal Woltmann meters

Affected by upstream flow

distortions

Installation in any position

It is recommended to install a

strainer upstream the meter (at least5-10 diameter away)

ISO 4064:1993 Class B models

Diameters from 50 mm to 800 mm The measuring chamber is

exchangeable without affectingthe metrology




Vertical Woltmann meters

Higher low flow sensitivity than horizontalWoltmann meters

Barely affected by upstream flow distortions

Installation only in horizontal position It is recommended to install a strainer

upstream the meter (at least 5-10 diameteraway)

ISO 4064:1993 Class B models

Diameters from 50 mm to 300 mm




Compound meters




Compound meters

Not according to ISO 4064:1993

Very wide measuring range

Metrology affected by flow

disturbances upstream Often, separate totalizers for the

main and the secondary meters

Maintenance of the changeovervalve required

Not suitable for water with doubtful

quality




Tangential meters




Tangential meters

ISO 4064:1993 Class A

models Metrology is extremely

affected by flow disturbances

upstream Need for long lengths of

straight pipe upstream

Ideal for poor water quality Suspended solids can pass

trough the meter

Low pressure drop




Oscillating piston meters

ISO 4064:1993 Class C and D models

Very low starting flow rate (down to1l/h)

Not suitable for water with only

moderate quality and hard water Not affected by upstream flow

distortions


The most common diameters rangefrom 13 mm to 40 mm

Some models are noisy at high flow

rates



Nutating disc meters

Usually not produced

under ISO 4064:1993specifications

Low starting flow rate

Not suitable for water withonly moderate quality andhard water

Not affected by upstreamflow distortions


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D3 Meter Types