10 Questions You Should to Know about Water Meter Test Bench Systems

As the installation of flowmeters increases on farms and on irrigation schemes, the need and demand for verification and re-calibration services are also increasing. Inaccurate meters refute the purpose of water metering, and a grower can incur a steep fine from the local Water User Association if he withdraws more than his allocation as a result of an inaccurate meter.

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Regulation 131 of of the Department of Water and Sanitation requires that the accuracy of a water measuring device be &#;verified at least once every five years or for such period as required by the manufacturer, whichever is the shortest period, by a person or an institution accredited to verify the accuracy of the device and furnish proof of such verification and the accuracy of the water measuring device to the authority within thirty days after the verification&#;.

Many growers and scheme managers are unsure of verification and re-calibration. Questions that are typically raised include:

• What is the difference between calibration, verification, and re-calibration?
• What are the methods available? And which will give the most accurate results?
• How often do I have to verify and re-calibrate my water meters?
• Who can assist me with it?
  • Will the verification and re-calibration happen on-site or in a laboratory?
  • How long will it take?
  • What will it cost?

What are calibration, verification, and re-calibration?

After flowmeters are manufactured, they need to be calibrated before they can be sold. Most flowmeter manufacturers have their own flowmeter calibration facilities to do this initial calibration.

All instrumentation, whether a flowmeter or another type of instrumentation, loses its accuracy over time due to wear and tear and other factors. To correct this loss in accuracy, instrumentation needs to be regularly tested or verified, and re-calibrated if necessary. The two most common methods of verifying a flowmeter are:

• Using a master meter
• Volumetric calibration.

Using a master meter, which is simply another flowmeter, to verify and re-calibrate your flowmeter is a valid method, but only if the master meter itself has been recently calibrated, or verified and re-calibrated, through a process that can be traced back to some national or international standard.

The South African National Accreditation System (SANAS) is mandated through the Accreditation for Conformity Assessment, Calibration and Good Laboratory Practice Act (Act 19 of ) to accredit calibration laboratories. In the United States, the national standards laboratory is the National Institute of Standards and Technology (NIST), with locations in Gaithersburg, Maryland, and Boulder, Colorado. In Europe, the main national standards laboratory is the Netherlands Metrology Institute (NMI), also referred to as the Van Swinden Laboratory.

Important: You, the grower or scheme manager, must make sure that you know where and how the master meter that you are using has been calibrated and how long ago. 

Volumetric calibration is an alternative method to calibrate a flowmeter. Volumetric calibration means that you push a known volume through your meter, test the meter readings against the known volume, and make the necessary adjustments. Volumetric calibration is the most accurate method, but it is time-consuming and difficult to do on-site. It is usually done in a laboratory.

What are the most suitable master meters?

Clamp-on ultrasonic water meters are considered in the industry as the most suitable and accurate master meters.

There are two types: the &#;Doppler&#; type and the &#;transit time&#; type. Isobel van der Stoep recommends the &#;transit time&#; type for irrigation water. The Doppler type works best with very dirty water, with suspended solids, and is more suitable for the municipal environment.

The price of these meters varies between R30 000 and R200 000 or more. Suppliers include Flotec, Flometrix, Switches International and Flexim (Peter Jones Electronic Equipment are the agents for Flexim in South Africa).

Isobel van der Stoep recommends that you buy the best master meter that you can afford.

She stresses that clamp-on ultrasonic master meters will only be successful if it is used correctly:

• The pipe onto which the ultrasonic meter is clamped should be straight, without any valves or fittings that can cause disturbances, and with a constant diameter for a length of at least 10 times the pipe diameter upstream of the meter and at least 5 times the pipe diameter downstream of the meter.
• The pipe should not vibrate, because the vibration will interfere with the accuracy of the meter.
• The pipe should be preferably PVC or HDPE (high-density polyethylene) and not steel because steel pipes tend to rust, especially older ones. If there is rust, the ultrasonic meter will struggle to take a reading, because the air that gets trapped behind the rust layer in the pipe interrupts the ultrasonic signal.

She recommends that growers and scheme managers create permanent verification &#;&#;stations&#;&#;, for example, by opening a suitable section of the pipe close to a pump station and covering it with a lid.

How often do I have to verify my water meters?

When you buy a water meter, the manufacturer will recommend how often the meter must be verified, and re-calibrated if necessary.

For example, FloCheck recommends that their ElectroFlo meters be verified every 2-3 years because of the normal wear and tear of the pump impeller and the motor. If the water has a high sand content, it will be necessary to verify and re-calibrate every 1-2 years.

Volumetric water meters must also be re-calibrated when:

• You replace the pump, or if you make any changes to the impeller
• You replace or re-wire the electric motor of the pump
• You change to a variable speed drive (VSD).

Who can help me to verify and re-calibrate my water meters?

We could find three companies in South Africa that offer verification (and re-calibration) services:

Flowmetrix:

Flowmetrix has a test facility at their factory in Durban where they can perform a volumetric calibration on flowmeters for a pipe diameter of up to 800mm.

They also have an on-site flow verification service where they use a clamp-on ultrasonic flowmeter as a master meter to test and re-calibrate the existing meter. After verification, a certificate is issued. The re-calibration service will depend on the type of meter and whether Flowmetrix can get electronic access to the meter.

Please contact Theo Dormehl at (031) 274 or Rollan Pillay at (031) 274 for details and cost.

FloCheck

FloCheck has an on-site service where they use a clamp-on ultrasonic flowmeter as a master meter to test and re-calibrate the existing ElectroFlo meter.

The company uses volumetric calibration to re-calibrate their ultrasonic master meters. Francois du Plessis outlines some of the challenges:

We re-calibrate our master meters every 2-3 years, or whenever we feel it is necessary. Recent re-calibrations for flow tempos less than 10 m³/hour took about three days. You have to test the meter for different pipe diameters and different flow strengths, and for each of these, you must push a known volume of water (we use a 2.5 m³ tank) through the meter.

Please contact Francois du Plessis at 083 626 for details and cost.

N&Z Instrumentation

N&Z Instrumentation has an on-site verification service. They also use clamp-on ultrasonic flowmeters. See http://www.nz-online.co.za/water-metering-mangement/check-or-verify-flow-meters-using-flow-loggers-and-clamp-on-flow-meters.htm for a description of their service. After verification, a certificate is issued. The re-calibration service will depend on the type of meter and whether N&Z can get electronic access to the meter.

If you buy their Fuji ultrasonic meters as test meters, they will give you training on how to verify water meters free of charge.

If you want to learn more, please visit our website tnma.

N&Z has offices in Johannesburg, Cape Town, and Durban.

Please contact Andries Schreuder at 082 361 for details and cost.

GWK, Hopetown

GWK has an on-site verification service. They also use clamp-on ultrasonic flowmeters. After verification, a certificate is issued. The re-calibration service will depend on the type of meter and whether GWK can get electronic access to the meter.

Please contact Gert Engelbrecht at 082 923 for details and cost.

Useful readings

https://www.tuv-sud.co.uk/uploads/images//calibration-of-flow-meters.pdf

https://ifsolutions.com/how-do-you-calibrate-a-flow-meter/

Choosing a water meter is not as straightforward as it might seem. Different applications may require different types of water meters. So it&#;s important to understand the factors that influence water meter selection, so you can choose the right one for your application, whether residential, commercial, or industrial. In this article, we explore nine important factors in water meter selection.

Factors to Consider When Selecting a Water Meter

Water meter selection has no room for error. Choosing the incorrect meter can complicate matters, leading to inaccurate readings, poor flow rates, unnecessary wastage, and faster meter deterioration. You can improve your proficiency in picking the ideal water meter for various applications by considering the nine factors below.

1. Meter Size

Size is among the first points to consider when choosing a water meter. The meter size determines the minimum and maximum flow rate from the supply source to your residential, commercial, or industrial application. It impacts water pressure and can influence readings and the service life of the meter.

Standard meters come in different sizes, including 5/8&#;, 3/4&#;, 1&#;, 1.5&#;, and 2&#;. Choosing the incorrect meter size can lead to inaccurate readings because of increased or decreased water pressure. The ideal meter size should ensure that the maximum flow rate does not exceed constant flow within nominal operating conditions. Check the flow rate in your distribution system to determine the appropriate meter size for your application.

2. Water Source and Cleanliness

When selecting a water meter, you&#;ll need to consider your water supply source. Does your water come from a river, a well, a pipe, or somewhere else? Where your water comes from will influence its quality, and therefore the type of meter you&#;ll need.

For example, mechanical water meters are not ideal for applications where the water is not of good quality, as poor-quality water can quickly wear out the propeller and other moving parts inside the meter. This type of water meter is better suited to measuring less contaminated water. In addition, the water source will affect the range of flow rates and pressures and consequently the selection of the right water meter for the application.

3. Measurement Accuracy

The essence of installing a water meter is to ensure accurate readings. Knowing how much water flows into your building or unit can help minimize consumption and encourage conservation. Considering this, the ideal water meter should be as precise as possible, constantly delivering the same readings under similar conditions.

Inaccurate readings might result in quality issues and high energy costs. For a water meter to be accurate, the environmental conditions must meet the manufacturer&#;s requirements. These requirements include the flow range, temperature, vibration, installation, and flow profile.

4. Water Demand & Flow Rate

Normally observed over the course of a week, the water demand for a building can vary according to its use, the number of occupants, the time of day and the season. While some applications experience very little fluctuation in water consumption, others can experience significant variations. It&#;s therefore important to choose a water meter capable of operating under the flow conditions dictated by the building or application, whether they be variable or more or less stable.

To do this, you&#;ll need to know the operating flow rates of the chosen water meter, which include minimum, transitional, permanent and overload flow rates. The ideal water meter must be able to handle the different flow rates of your application, as choosing the wrong meter, once again, can lead to inaccurate measurements and premature meter wear.

5. Pressure Loss

Pressure loss is an important element to consider when selecting a water meter, as choosing the wrong meter for your application will impact your system&#;s performance. To choose the right meter, start by determining the acceptable pressure loss for your building or application.

The acceptable pressure drop across the meter should be 10% of the initial pressure in the pipe. For example, if the pound per square inch (PSI) in the piping system is 80 PSI, the acceptable pressure drop should be 8 PSI. If the pressure is too low, the meter may fail and give inaccurate readings.

Once this acceptable pressure loss has been identified, select a water meter that falls within this pressure range, or provide provisions to compensate for proper system operation, such as a booster pump.

6. Location

In Canada, water meters are mostly installed indoors to protect them from the harsh conditions of our northern climate. However, some regions with milder climates, such as southern British Columbia, may allow installation in underground chambers. Wherever the meter is installed, it&#;s essential to choose the right technology to enable it to operate under optimum conditions.

The piping system is another factor influencing location. The meter may be placed next to the pumping station, before a control valve or before an elbow. The direction of piping also affects whether the meter is installed vertically or horizontally. The right location for the meter determines its overall performance and guarantees more accurate readings.

7. Installation Requirements

In addition to the location and other factors mentioned above, it&#;s also important to check the conditions under which the water meter is installed. These conditions can vary from one water meter to another and include information such as orientation, accessibility, length of pipes, the addition of a strainer, installation of a certain type of valve and more. It&#;s therefore important to take these factors into account when selecting your meter to ensure optimal operation and optimize its service life. Many manufacturers and suppliers supply guides with their water meters to facilitate installation.

8. Budget & Cost

Price comparison is a vital part of water meter selection. After all, water meters come with different price tags based on their features and specifications. The most dependable and accurate meters are pricier thanks to their high-reliability ratings. They are less likely to fail and provide accurate readings all the time.

The buying price is not the only factor to consider. Buyers should consider other costs, including installation, maintenance, calibration, adjustment, longevity, and data collection. Talking to an expert can help you decide the appropriate meter for your application based on your budget.

9. Durability & Maintenance Requirements

The lifespan of a water meter depends on several factors, such as make, installation, technology, operating mechanism, workload, and maintenance. On average, a solid water meter should last at least 12 years before requiring a replacement. The ideal water meter should be durable and easy to maintain. Moreover, replacement parts should be readily available for easy repairs. Ensure the meter site is easily accessible and clear of any hazardous materials for proper maintenance.

Conclusion

Selecting the right water meter for an application is based on several factors. These include considerations related to the building, its use, location, available space and meter size, and more economic factors such as budget, measurement accuracy and maintenance. Defining the conditions of your application from the outset will enable you to choose the right water meter quickly from among the many options available. And while choosing the right water meter help conserve water and reduce energy costs, it can potentially help detect leaks.

If you&#;re considering the purchase of a mechanical water meter and need assistance, our experts are ready to answer all your questions. Please view our selection of mechanical water meters and contact us for more information.

If you are looking for more details, kindly visit Water Meter Test Bench Systems.