Gauging flow rate is critical in any fluid or gas handling system. A water treatment plant that requires regular cleaning of filtration devices needs pumped water to flow through the filters. A flow meter is a critical and necessary device to determine the amount of water that passes through the filters. Various applications use flow meters to measure accurately and sometimes control flow rates.
When measuring the amount of water flowing through the filters to clean it, the time used in the process is multiplied by the GPM(Gallons per minute) value. In a CIP(Clean in place) process, the same principle applies when the number of chemicals, including caustic and acids. Equipment should always be kept safe during the cleaning process; that is where flow meters come in.
When gauging the flow rate of gas, it is fluid. The physical changes are used in the formula. When calculating flow rate in liquids, indirect flow measurement units are used by flow meters. Advanced flow meters can measure physical parameter changes such as pressure and temperature. Other flow meters, like the rotameter, have a readout that uses the analog system to measure the flow rate. Other flow meters have digital display systems that send electrical signals to a remote location.
In this post, I will look at different flow meter types to help you know how they work, how to install them, and their applications. We are also discussing the cost of these flow measurement units and their working principles. To gain more excellent knowledge, continue reading.
Types of flow measurement units and devices
Since fluids and gas substances come in different characteristics, conditions, and properties, you must pair the tight flow meter with a suitable liquid or gas. To select the proper flow meter, you must understand flow measurement concepts such as voltage connection, physics, and current. Below are some of the flow meter types you need to know about.
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Ultrasonic flowmeters
Judging by its name, an ultrasonic flow meter uses ultrasound to gauge flow rate. It is used to calculate velocity when measuring flow rate. The value of the estimated fluid velocity is then used by the ultrasonic flow meter to calculate the liquid’s volumetric flow. When using this flow meter, the rate of the fluid is measured using two methods:
One of these methods uses the Doppler effect. At specific frequencies, ultrasonic waves are incidents where the flow is measured through an emitter. A receiver on the opposite end of the tube measures frequency waves. The velocity of the fluid is what determines the received frequency.
The other method involves measuring the amount of time difference that sound uses to travel downstream and upstream of the liquid. The velocity of the fluid is calculated using both values.
Ultrasonic flow meters have various benefits, one being that they can be installed without adjusting the pipeline or tubing. What makes this possible is that this flow meter is usually clamped around the pipe or tube. To get accurate flow rate results, parameters such as the tube diameter, material, and thickness go into the flow meter. The only setback of these flow meters is that viscosity and temperature variations can affect their accuracy. Suspended particles in the liquid may also affect flow measurement.
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Thermal flow meter and flow measurement units
A heated probe is immersed in the flowing liquid when using a thermal flow meter. The probe’s heat is lost in the liquid, and maintaining the heat at certain levels requires an electric current. To know the amount of heat that is getting lost, the flow meter measures the electric current. The increase in liquid flow increases heat loss. As a result, there will also be an increase in the electric current drawn to maintain the heat. Measuring the current growth helps to calculate the flow rate. Thermal flow meters are often used to measure the flow rate in gas substances, not fluids.
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Magnetic flowmeters
Magnetic flow meters can only work on conductive liquids such as water. These are fluids that conduct electricity. When measuring flow rate, fluid passes through a conduit, exposing it to a magnetic fluid. The flow meter induces a voltage and creates an effect that works the same way as Faraday’s law. The produced voltage is measured by electrodes found in the walls of the flow meter. Flow rate increases with induced voltage. The flow meter measures the flow rate based on the induced voltage and the pipe or tube size.
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Differential pressure flowmeters
Another type of flow meter is the differential pressure flow rate gauge. In this type of flow meter, the pressure change is caused by the constriction in the conduit. Pressure is measured before and after the compression when a liquid goes through the line. The flow rate is calculated by getting the pressure difference. The square root of the pressure difference is directly proportional to the flow rate. When the flow rate drops, differential flow meters calculate the flow rate. The flow rate drop can be significant or minor based on the flow meter type. One benefit of DP flow meters is that they can measure gas substances and fluids.
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Coriolis mass flowmeters
Coriolis mass flow meters come in various types. What makes these flow meters different from others is how they measure flow rate. Unlike other flow meter types, mass flow meters such as Coriolis measure the flow rate in mass per unit of time and volume. When calculating the flow rate, the liquid goes through vibrating tubes. How the pipes move depends on the flowing liquid inside the tube. Sensors are built to monitor motion and any changes in the flow density or mass flow. Coriolis flow meters are used in applications such as the oil industry. Among the many benefits of mass flow meters is high accuracy levels. Their downside, however, is their high price and the lack of ability to measure matter in a gaseous state.
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Rotameter and flow measurements units
Rotameters are used to give readings of liquid flow rate in volume. Their design is straightforward, consisting of a simple float and tubing. The tube is either made from glass, plastic, or stainless steel. The tube should always remain vertical to get accurate flow measurement units. This allows the fluid to flow upwards. Although it’s called float, this component should not float in the column of the liquid. Vertical graduations give the flow rate readings in a rotameter.
Their benefits include low buying and maintenance costs. Rotameters can measure both liquids and gasses without the need for an expert. Rotameters are used for commercial and residential purposes. The float will go up the tube when the flow rate increases and down when the flow rate reduces. One of the setbacks of rotameters is that they are only for local display purposes because they can’t send any electrical signal. Their measuring principle is relatively easy to understand and does need an expert. Since fluid passes through it, you must adjust the tubing or the pipeline during installation.
Conclusion
Accurate readings of the flow rate passing through a pipeline can only be achieved using proper flow meters. Flow measurement units simplify the process of flow rate reading. Rotameters are the cheapest type of flow meter due to their simplicity when gauging flow rates. Mass flow meters such as Coriolis flow meters are among the most expensive flow meters. Knowing your flow system requirements is essential before choosing or buying a flow rate gauge.
