Flowmeters are devices designed to measure the rate of flow of a fluid moving past a certain point within a specific system, such as water moving through a pipe. They are commonly used by water utilities, but also have uses in industrial and manufacturing capacities. The precise purpose often dictates which design is ideal. Take a look at some of the different types of water meters below.
Flowmeters and Water Utilities
Water utilities are one of the major users of flowmeters, using the technology every day to ensure that their customers are billed properly based on their actual usage. These flowmeters, commonly referred to as water meters, are placed at points along the water utility infrastructure where the lines branch out to provide services to residential and business customers.
Water meters can also be used at other points in the utility system. For example, flowmeters can be used in the larger part of the infrastructure to ensure that the rate of flow is as expected. This helps identify issues in the utility owned lines such as leaks or breaks. They can also be used to monitor the rate of flow from a well or other water source.
Flowmeters and Other Industries
Essentially, any industrial or manufacturing process that could make use of water may also need a flowmeter. For example, water is a common method for cooling certain production processes. To ensure cooling is managed properly, the flow of water may need to be monitored.
Certain ecological organizations may also be interested in tracking the flow of water across a particular point. This could include monitoring the flow of fluid between bodies of water. Additionally, hydroelectric power plants will also have a specific interest in observing flow rates as it relates to the creation of power within the system.
Types of Water Meters
When it comes to monitoring the flow of water within any system, one of a few approaches is normally taken. The first method uses displacement, while the second most common option focuses on velocity. Other methods that can be used include electromagnetic and ultrasonic. Within each flowmeter category, there can be multiple designs that can complete the task successfully.
Displacement Water Meters
A displacement water meter is the variant most commonly used in residential applications as well as certain small commercial operations. Displacement water meters, also referred to as Positive Displacement meters, can be divided into two subcategories: oscillating piston and nutating disk meters. Regardless of the subcategory, each displacement water meter measures the rate of flow based on the movement of a specific element within the meters construction. The amount of movement recorded correlates to the amount of water that has flowed through that portion of the system.
Velocity Water Meters
Velocity water meters are also known as internal capacity meters. These meters are designed to determine the volume of water that has flowed through the meter based on the speed of the flow. Within the velocity flowmeters category are the following subcategories:
Multi-jet meters are used when a high level of accuracy is required in a small space. These meters use multiple ports that surround an internal chamber. Each port creates a jet of water that hits an impeller. Ultimately, the rotation of the impeller determines the amount of water that has passed through the meter.
Turbine meters can be less accurate than displacement or multi-jet meters, but provide a benefit in that they do not significantly impede the flow of water within a pipe. For higher flowrates, this means less pressure is lost based on the need to negotiate the meter. Often, the turbine meter is ideal for large commercial operations, as well as fire protection. They are also used as master meters within larger water distribution systems.
Compound meters are designed to meet situations with highly variable needs, such as fluctuations in high flowrates and low rates of flow, but where accuracy is required in all circumstances. Often, these meters feature traits of other meters that can be switched between based on need. During times of high flow, a turbine portion can be in use then, when flow decreases, water can be diverted to a multi-jet or positive displacement portion for improved accuracy.
Electromagnetic meters, also known as mag meters, are a variant of velocity-type water meters. These measure velocity using electromagnetic properties, instead of the flow through mechanical measurement mechanisms. Operations of mag meters are based on Faraday’s law of induction.
Since electromagnetic meters do not rely on mechanical components to measure flow, they have the added benefit of being able to operate in either direction. Additionally, they can be ideal for situations where unfiltered water flow needs to be measured, as there is a limited risk of buildup harming the water meter. However, the presence of magnetic material can impact accuracy.
Ultrasonic meters use ultrasonic transducers to send sound waves through the water to determine velocity. This is done by compensating for the known resistance associated with the meter’s construction, as well as the impact of any piping. One advantage of this design is that, when installed externally, the meter does not have to impact the rate of flow through the pipe. Additionally, these clamp-on designs are often easier to maintain, since they are external devices.
There are two main versions of ultrasonic meters in use. The first uses the Doppler Effect to determine velocity, while others focus on transit time between two stationary points. Either approach tends to be highly accurate, and they can provide for substantial flow measurement ranges.
While most water companies rely on postpaid systems when billing customers. However, prepaid versions are available. These work similar to gas pumps or water dispensing machines where, based on the amount that has been paid, a specific amount of water is provided. To ensure accuracy, the flowrate is monitored by a flowmeter. Once the required amount has passed through the meter, the system stops dispensing water until more funds are added.
The ability to operate as prepaid or postpaid can be applied to almost any flowmeter, allowing a business to choose a method that works best for them based on their unique situation.
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What is the difference in accuracy between different types of water meters