Water Meter Management PRODUCTION DMA AND DOMESTIC METERS

Water Meter Management PRODUCTION, DMA AND DOMESTIC METERS

Contents Introduction Generalities Production meters Bulk water meters Domestic water meters 2

1. Introduction WATER METERING

Introduction Water meters are devises that are installed in a water pipe to measure the flow that goes through that pipe Knowing the quantity of water that is produced and distrubuted to different places and customers helps a water company to keep its account and make financial as well as technical analysis Water meters can measure flow based on different methods. For exmple mechanic or electro-magnetic It is important that water meters are sized, installed and maintained correctly, so that they will work well INTRODUCTION 4

Introduction In this workshop we will look at: • • • Selecting the right type of flow meter Sizing the flow meter Installing the flow meter We will consider: Production Meters DMA and bulk water meters INTRODUCTION Domestic revenue meters 5

2. Generalities VELOCITY PROFILES, GENERAL METER INSTALLATION

Velocity Profiles All flow meters are only accurate if the water has a uniform Velocity Profile around the pipe’s centre axis: • Upstream fittings have a bad effect on the profile, some fittings have a worse effect than others (e. g. butterfly valve) • The fittings cause ‘swirl’ in the water which causes the meter to either under (-) or over (+) read the flow • Some types of meter are less effected by turbulent flow than others (electromagnetic meters are better than mechanical) • Turbulent flow can be avoided by keeping a straight pipe before and after the meter (no bends or fittings). All manufacturers state a minimum upstream and downstream straight pipe lengths from the meter Average velocity at 1/8 diameter GENERALITIES 7

Distorting Velocity Profiles Turbulence caused by bend or obstruction Swirl caused by two bends in different planes GENERALITIES 8

General Advice on Meter Installation • • Comply with manufacturers recommended minimum upstream and downstream straight pipe lengths from the meter Install the meter in the correct direction of flow Avoid fitting insertion and ultrasonic clamp-on meters on the top of the pipe where trapped air can distort the reading Ensure the pipe is always full of water 9

Meter Accuracy Curve GENERALITIES 10

Water meter maintenance Water meters can get clogged, break or wear due to dirty water. They can also age with time. For optimal benefit and use of water meters it is important to regularly inspect all types of water meters, clean and calibrate them GENERALITIES 11

3. Production Meters INSERTION, ELECTOR-MAGNETIC AND CLAMP-ON METERS AND THEIR INSTALLATION

Production Meters – Common Types Production meters are large flow meters that are usually located: • • On the outlet of water treatment works On trunk / carrier mains / large diameter pipes Generally there are three types: 1. Insertion 2. Electro-magnetic 3. Ultra-sonic 1 2 PRODUCTION METERS 3 13

Production Meters – Insertion meter Specification Value Flow range 0 to 10 m/s Accuracy ± 2% Pipe Size Up to 8, 000 mm • • Easy to install and use For permanent or temporary installation Economical way of measuring flow - especially in large diameter pipes Useful for surveying and network analysis, flow profiling or bulk meter calibration application Can be inserted and moved under pressure Can be used with any pulse/4 -20 m. A data logger Easily damaged PRODUCTION METERS 14

Insertion Meter – Installation Centre Line Velocity Factored Must be First Calculated Mean Axial velocity at 1/8 Diameter PRODUCTION METERS 15

Insertion Meter – Installation Type of Upstream Disturbance Minimum Upstream Straight Length for Mean Straight Length for Pipe Axial Velocity Method Centre Line Method 90 o elbow or bend 50 25 Multiple co-planar bends 50 25 Multiple non co-planar bends 80 50 Fully opened butterfly valve 45 25 Fully open gate valve 30 15 PRODUCTION METERS 16

Production Meters – Electro-magnetic Specification Value Flow range ? m/s Accuracy ± 1% Pipe Size up to 2, 600 mm • • Example manufacturers are ABB, Elster, Siemens and Badger Meter Usually AC powered Full bore meter with no moving parts – not easily damaged Can be buried PRODUCTION METERS 17

Electro-Magnetic – Installation PRODUCTION METERS 18

Production Meters – Ultrasonic clamp-on Specification Value Flow range ? m/s Accuracy ± 1% Pipe Size Up to to 7, 600 mm • • • Example manufacturers are Panametrics, Micronics and Siemens Battery or AC powered, not suitable for permanent installation Full bore meter with no moving parts – not easily damaged Very useful for checking the accuracy of other meters Easy target for theft Essential that pipe material and lining is known PRODUCTION METERS 19

Production Meters – Summary Issue Insertion Meter Electro-Magnetic Meter Clamp-On Ultrasonic Meter Cost Cheapest for larger pipes Medium Expensive Irregular Velocity Profile Significant effect on accuracy – long sections of straight pipe required Small effect on accuracy Medium effect on accuracy (though still significant) Security Must be installed in locked chamber Can be buried Must be installed in locked chamber Accuracy Better than ± 2% Better than ± 1% Ease of Installation Very easy – can be done without pipe shut-off Requires pipe shut -off Very easy – can be done without pipe shut-off Pipe Size Up to 8, 000 mm Up to 2, 600 mm Up to 7, 600 mm Reliability High, but easily damaged High Power AC AC AC Flow Ratio 1 : 100 1 : 1500 1 : 400 PRODUCTION METERS 20

4. Bulk Water Meters ELECTRO-MAGNETIC AND MECHANICAL METERS AND THEIR INSTALLATION

Bulk Water Meters DMA and bulk water meters are usually located: • • On the in- and outlet pipes of District Meter Areas (DMAs) On supply pipes to large commercial customers Generally there are two types of bulk water meters: 1. Electro-magnetic 2. Mechanical 1 BULK WATER METERS 2 22

DMA Meters – Electro-Magnetic Specification Value Accuracy ± 1% Meter Sizes 15 to 600 mm • • E. g. ABB Aqua. Master S EM Battery or AC powered Meter also contains a data logger Flow data automatically sent by SMS message to PMAC database Usual to send 1 SMS/day – equal to 48 x 15 minute readings Ability to use greater resolution for step-testing etc Also (as an option) records and transmits pressure Automatically transmits alarm signals on failure BULK WATER METERS 23

Electro-Magnetic Meter – Installation • • Can be buried Great care must be taken in bonding the meter to the pipes Recommend the transmitter kiosk is ventilated and cooled by solar powered / battery fan Refer to manufacturer’s Installation Manual BULK WATER METERS 24

Electro-Magnetic Meter – Installation BULK WATER METERS 25

Electro-Magnetic Meter – Installation BULK WATER METERS 26

Electro-Magnetic Meter – Installation BULK WATER METERS 27

DMA Meters – Mechanical Specification Value Accuracy ± 2% Meter Sizes 40 to 500 mm • • Traditionally used as DMA meters – now being replaced by EM meters No power required Beware of pressure drop caused by meter Can be damaged by poor quality water Strainer requires regular cleaning Now also becoming available with SMS capability Available as a combination meter to capture both low and high flows BULK WATER METERS 28

DMA Meters – Mechanical Many types on the market, including: • • • Velocity meters (e. g. single and multi-jet) Volumetric meters (e. g. piston and rotary) Woltmann meters Single jet meter Volumetric meter BULK WATER METERS Woltmann meter 29

Mechanical Meters – Installation • • • Installed in a chamber Usually on a bypass arrangement to easily allow maintenance and replacement Minimum 10 D and 5 D upstream and downstream straight length pipe BULK WATER METERS 30

Production and DMA Meter Sizing • • • The correct meter size is critical for accurate flow measurement As a general rule, install the next size down from the pipe diameter Refer to manufacturer's sizing tables and software BULK WATER METERS 31

Meter Size Example What is the correct meter size for a DMA inlet flow of: • Minimum flow = 50 m 3/hour • Nominal flow = 200 m 3/hour • Maximum flow = 300 m 3/hour Meter Size 50 m 3/hour 200 m 3/hour 300 m 3/hour Minimum 40 mm 80 mm 100 mm Maximum 200 mm 450 mm Pressure Drop Across the Flow Meter Size 50 m 3/hour 200 m 3/hour 300 m 3/hour 100 mm 0. 5 metres 7. 6 metres 17 metres 150 mm 0. 1 metres 1. 5 metres 3. 4 metres 200 mm 0. 02 metres 0. 4 metres 0. 85 metres BULK WATER METERS 32

Bulk Water Meters – Summary Issue Aqua. Master Electro. Magnetic Meter Mechanical Meter Cost Expensive Cheap Irregular Velocity Profile Small effect on accuracy Large effect on accuracy Orientation No effect Must be horizontal Security Can be buried Must be installed in chamber Accuracy Better than ± 1% Better than ± 2% Ease of Installation Requires pipe shut-off, bypass, strainer and chamber Pipe Size Up to 600 mm Up to 500 mm Reliability High Damaged by poor quality water Power AC or battery No power required Flow Ratio 1 : 1000 1 : 400 BULK WATER METERS 33

3. Domestic Water meter

Domestic Meters – Common Types Domestic meters are usually located as revenue meters on the supply to: • Houses and apartments • Small commercial premises Generally, there are two types of domestic meters: 1. Mechanical 2. Ultrasonic 1 DOMESTIC WATER METER 2 35

Domestic Meters – Installation 10 X pipe diameter in length DOMESTIC WATER METER 36

Domestic Meters – Installation The meters are designed only for use with clean water, a strainer is recommended upstream of the meter. The strainer should be installed at least 10 x diameter of straight pipe before the meter, to avoid turbulent flow. DOMESTIC WATER METER 37

Domestic Meters – Accuracy Water meters come in different varieties: Class A (cheapest, least accurate), B, C and D (most expensive, most accurate ), each with their own price and accuracy. Meter Class Q nominal Q min Class B 1. 5 m 3/hour 30 litres/hour Class C 1. 5 m 3/hour 15 litres/hour Class D 1. 5 m 3/hour 11. 25 litres/hour Class B is very commonly used for domestic water users. However, Class B water meters are not advised for consumption below 0, 02 m 3/h for they will have a deviation in accuracy over 5%. Class B water meters over DN 40 consumption below 0, 3 m 3/h will not be accurately measured. DOMESTIC WATER METER 38

Domestic Meters – Sizing Accuracy curve of a meter compared to an accuracy range • Water meters should be sized between transitional flow Qt (the point at which the meter is accurate) and nominal flow Qn (everyday flow) • A water meter receiving the maximum flow for more then 1 -2 minutes will be damaged At low flows, the meter is not accurate. Minimum flow is the flow required to operate and record on the meter Never use maximum flow as a basis for sizing the meter • • DOMESTIC WATER METER 39

Domestic Meters – Specifications DOMESTIC WATER METER 40

Domestic Meters – Testing DOMESTIC WATER METER 41

4. Meter Management for NRW Reduction

Water meters and NRW The state and use (or non-use) of water meters plays a large role in NRW. Mainly through: • Illegal consumption o Meter by-passes and tampering • Meter inaccuracies o Volume under-recorded by revenue meter due to its condition or wrong sizing or installation NRW REDUCTION 43

Meter tampering is customers illegally altering the revenue meter so that it under-reads. Common methods are: 1. Inserting a pin or needle to stop the totaliser moving 2. Blocking the meter inlet or chamber 3. Placing a powerful magnet to break the magnetic coupling of impellors and gears 4. Reversing the meter 5. Temporary removal of the meter 6. Hitting the meter hard – some meters now come with an impact warning system 7. Cutting or damaging the impellor To complete the water balance, we have to identify the reduced consumption of these tampered meters NRW REDUCTION 44

Examples of meter tampering NRW REDUCTION 45

Revenue Meter Errors Almost all meter errors result in them under-reading: the meters will read less than the actual water volume being consumed. Consequently, a proportion of the consumed water is not billed to the customer – loss in revenue Meter errors can be caused by: • • • Incorrect sizing Their class Their condition: o o o • • Age Water quality Maintenance regime Incorrect installation Meter tampering NRW REDUCTION 46

Meter installation NRW REDUCTION 47

Meter sampling surveys can be organised to find out issues with water meters caused by: • Meter size • Meter age • Meter maintenance • Meter installation Meter errors can be caused by: • • • Find out the ages of the customer water meters. Organise regular sessions to test (old) water meters, either with portable meters or by doing a bucket test. Bucket test Random survey Age survey NRW REDUCTION 48