Article | June 15, .
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Water utilities rely on accurate and dependable flow measurement for critical process controls. Regulatory agencies also require flow monitoring and reporting, with specific accuracy limits.

Flow metering technology is continually improving, and a variety of meter types and styles are available. Each flow meter application is unique, and flow meter selection should not be based on “low bid.” While cost is always important, other factors carry more weight when it comes to selecting a flow meter.

Here are six important considerations for choosing the best flow meter.

1. Understand the Process

Before specifying a meter, it’s important to clearly understand the entire process and where the meter fits in that process. Involve plant operators during design to discuss issues of maintenance, calibration, and access. Does flow need to be totaled? Does information need to be transmitted to a supervisory control and data acquisition (SCADA) system or be available on the Web? Knowing who will be using the meter and specifically how it will be used is the starting point.

2. Media Being Measured

The media being measured is one of the most important considerations when choosing a flow meter. Conductivity, temperature, pressure, and viscosity can affect certain types of flow meters. How clean or dirty the water is may also impact the type and style of meter.

So, the next step in choosing a flow meter is to thoroughly understand the characteristics of the flow to be measured. In an existing facility, data on the matrix should be readily available for review. Standard engineering criteria can be used for new facilities if needed.

For example, propeller meters are often used in drinking water systems, especially for measuring well water withdrawal. These velocity meters can measure fluids containing a certain amount of sand, dirt, iron, and other contaminants. However, these meters would not be recommended for raw wastewater containing stringy materials and wipes, which would foul or damage the meter.

On the other hand, electromagnetic “mag” meters are very accurate when measuring conductive materials like water and wastewater. They have no moving parts to corrode or break. Different styles of mag meters are available for specific fluid measurements, including drinking water, wastewater, and sludges.

3. Accuracy, Range, And Certification Requirements

How accurate must the flow measurement be? This depends on the meter’s purpose. Flow measured to control chemical feed may need greater accuracy than that used for general tracking of water treated. Flow measurement for billing purposes, such as a water supply authority selling water to a utility, must be extremely accurate.

Regulatory conditions may also apply. Most water and wastewater systems have permit limits for maximum flows and must measure and report daily flow totals. Be sure to check all existing permits for flow measurement accuracy requirements.

Measurement range and turndown rates must be considered as well. Engineers often size equipment and pipe for a 20-year growth period, which can lead to problems when current flows are much less than design rates.

Some utilities may require meters to have NSF-61, NSF-372 approvals or ISO certification. Manufacturers may also accredit their calibration laboratories through the National Voluntary Laboratory Accreditation Program (NVLAP). NVLAP provides NIST accreditation to testing and calibration laboratories using management and technical requirements of the international standard ISO/IEC :.

4. Meter Location and Installation

Proper location and installation of flow meters are critical for providing accurate measurement. Even the most sophisticated meter will read erroneously if installed improperly. Improper installation occurs most often when trying to “force” a flow meter into an existing plant or network or make it fit in a tight site.

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Most flow meters require a specific amount of straight run pipe to prevent flow disturbances. Pipe bends, valves, tees, and reducers can create significant flow measurement errors—up to 50 percent for certain meters. In a new system, straight runs can usually be designed appropriately. However, sufficient straight runs may be difficult to obtain in existing systems or constrained sites. Flow conditioners may help reduce inaccuracies. Also, some meters can measure more accurately than others under these conditions. Pipe size, material, and direction are part of the meter selection equation. For instance, downward flow should be avoided when measuring liquid. As noted previously, systems are sometimes overdesigned to accommodate future growth. In most cases, the pipe must be full for accurate measurement.

5. Reporting/Data Recording          

What information needs to be monitored and recorded, and how? Some applications require continuous recording of the flow, plus total flow readings. Do operators need event notification, such as high flow or zero flow alarms? Data must often be sent to a SCADA system. In some cases, flow meters are located remotely and need battery-powered devices.

During design, determine what type of output is needed. While 4 to 20 milliamp is most common, some facilities may need MODBUS cards or other instrumentation.

6. Consult With A Technical Partner

Flow meter manufacturers’ representatives have a great depth of expertise. They know the right questions to ask and can recommend the best solutions for each unique installation. Use them as a trusted technical partner.

Your technical partner can help to make cost-effective decisions as well. Manufacturers can help by outlining lifecycle costs, including installation, maintenance, and calibration in addition to purchase price.

Most of all, your technical partner can help you choose the right meter up front rather than trying to make the wrong meter work after it’s installed.

4 Steps to Select the Correct Natural Gas Flow Meter

Accurate gas flow measurement begins when selecting the correct gas flow meter for an application. Here are four steps to help choose a natural gas flow meter, along with a flow meter comparison and a flowmeter selection guide.

Need help selecting a flow meter?

1. Understand the Application.

Before selecting your flowmeter technology, understand the application. In a recent post, we provided tips to consider when choosing a gas flow meter technology. To paraphrase, better understand the application by determining:

1. What is the purpose? Why do you need the meter? Is it for custody transfer, submetering, monitoring, or industrial process gas? Do you need mass flow or volumetric flow? What is your budget?
2. What is the gas type? Single gas or a mixture? What is the operating flow range, accuracy requirement, process temperature, and pressure? Is the gas dry and clean? Alternatively, wet, corrosive, or dirty?
3. Where is the meter intended to be installed? What are the environmental conditions? Will there be extreme temperatures? Is there good straight run? Are there regulations to consider? Noise or vibration concerns?
4. What do you need from the meter? Do you need a totalizer or a local display? What are your calibration expectations? Do you need to be able to upgrade the meter to advanced electronics? What are your maintenance requirements?

Gathering this information will help you make an intelligent selection to measure your natural gas.

2. Review our Natural Gas Flow Meter Selection Guide.

After understanding the application, review our cheat sheet to help guide which technology to consider. Click on the image to view this guide. Additionally, keep in mind that there are four different natural gas flow meter types:

• mass flow
• volumetric flow
• velocity meters
• inferential flowmeters

3. Flow Meter Comparison and Selecting the Correct Technology

After reviewing the selection guide, you likely have honed in on one or two meter types. Compare these technologies to understand each flowmeter type’s operation principle, advantages, and disadvantages. Here are convenient links to the different meter types to guide your review.

• Coriolis and thermal mass flow meters measure mass flow and are new gas technology. The Coriolis is used in the fiscal measurement of natural gas, while thermal mass flow meters measure industrial process gas flow.
• Rotary and diaphragm gas meters are positive displacement or PD meters and are a traditional gas technology used for utility billing applications or custody transfer of natural gas.
• Turbine meters are a conventional technology and velocity-type device that measures natural gas for custody transfer applications.
• Ultrasonic flowmeters are considered a new gas technology; they measure natural gas for custody transfer applications and are velocity-type meters.
• Vortex gas flow meters, another velocity-style meter, measure natural gas primarily in industrial applications as they are a late-comer to custody transfer approval.
• Differential pressure flow meters (or DP meters) are inferential meters and include the orifice plate, Pitot tube, Venturi meter, and V-Cone meters. They are traditional technology and are approved for custody transfer.
• The Rotameter is a conventional gas technology used as an industrial flow meter to measure the volumetric flow rate of fluids in a closed tube.

4. Still unclear? Have questions? Call 303 697-.

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Our dedicated staff is happy to walk you through the selection process and may have recommendations on some natural gas meters for your application.

Want more information on oem flow meter? Feel free to contact us.

Bonus Video – Selection of Flow Meters

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