What is a Flow Meter?

A flow meter is a calibrated instrument or device that measures how much media (gas, liquid, or steam) is moving through or has moved through something, generally a piping system that is part of a process. Flow meters normally measure the media volume or mass referencing some unit of time, such as gallons per minute (gpm), pounds per hour (lb/h), or cubic feet per minute (CFM). Flow meters are used in limitless industrial, commercial, residential, and medical applications.

Flow meters are everywhere, quietly doing their jobs and helping to make many products and services that we use daily. For example, the bottle of water that you may have had today was more than likely filled by a batching system that included a flow meter as an integral part of the process. A flow meter may have been part of the filtration and treatment process as well. The fabric in the clothes you are wearing was more than likely made in part by liquids that were controlled by flow meters. The nice ripe banana that you bought yesterday from the grocery store is probably only ripe because a flow meter helped controlled the climate it was shipped and stored in as it made its way to your grocery cart. The gas that you paid for this week when you fueled up? Hopefully, a well working flow meter delivered the amount to your tank that you paid for. Flow meters are an integral part of how many products today.

Flow meters measure an almost limitless amount of media types. From a general perspective, they measure fluids (gas or liquids) and steam. The most common gas that is measured by flow meters is air. Some other examples of common gases include oxygen, nitrogen, argon, fluorine, helium and more. The most common liquid example is water. Other common liquids include chemicals, fuels, acids, oils, coatings, pastes, resins, waxes, and more.

Industrial flow meters are made specifically to monitor, measure, or control industrial processes or systems. There are countless industrial applications that require flow meters as part of their operations. Common applications for industrial flow meters include:

• Water and Wastewater Industries
• Gas, Oil, Petroleum, Petrochemical, Rubber, and Biogas Industries
• Chemical Industry (Additive Injection, Additive Storage, and Feed Lines)
• Automotive Industry
• Agriculture, Irrigation, Food Production, Breweries, and Winemaking
• Power Generation, Co-Generation, Nuclear Power, Solar, and Geo-thermal Power
• Hydraulics
• Laboratories, Testing Institutes, and Test Benches
• Marine Applications and Shipbuilding
• Transportation and Mining
• Paper and Pulp Production
• Pumps and Pipelines
• Utilities and Municipalities

The field of flow instrumentation offers a wide variety of flow meter technologies which generally operate by measuring mass or volume. Each flow meter technology type delivers certain advantages depending on the media and application requirements. When choosing a flow meter without a technical background, it is usually advisable to consult a professional, like our expert engineers here at KOBOLD, who will ask you the key questions about your process variables to help you narrow down your choices and fit your budget.

• Variable Area Flow Meters
• Also known as Rotameters
• Magnetic Flow Meters
  • Also known as Magnetic Inductive Flow Meters, Magmeters, or Electromagnetic Flow Meters
• Paddle Type Flow Meters
  • Also known as Flap Type Flow Meters
• Positive Displacement Flow Meters
  • PD types include: oval gear, helical gear, screw gear, rotary piston, and gear meters
• Differential Pressure Flow Meters
• Ultrasonic Flow Meters
  • Available as clamp on models, as well as inline models
• Vortex Flow Meters
  • Available as multi-variable models
• Coriolis Flow Meters
  • A type of mass flow meter
• Thermal Flow Meters
  • A type of mass flow meter
• Paddle Wheel Flow Meters
  • Also known as impeller flow meters
  • Includes Pelton wheel flow meters
• Turbine Flow Meters
• Oscillation Flow Meters

Inline flow meters are flow meters that already have a flow body integrated into their build. That means that the entire flow meter, as a unit, is installed into the pipeline itself, via a threaded or flanged connection on either end of the flow meter. Many flow meter technologies require the presence of a flow body for the flow meter to operate correctly. Inline flow meters have historically been the majority of flow meter installations. One disadvantage of inline flow meters is that when they require maintenance or replacement, the entire process must be shut down so that the instrument can be removed. KOBOLD carries a wide variety of inline flow meters in various technology types. View our flow meter offering, which includes a wide variety of inline flow meters.

Unlike inline flow meters, insertion flow meters do not have a built-in flow body. These types of flow meters, when fitted with an extraction device, offer the distinct advantage of not requiring the full shut down of the process when they need maintenance or replacement. These meters can sometimes also be integrated into an existing process without as much work and down-time. Insertion flow meters are typically available in magnetic, paddle wheel and thermal mass technologies. Some insertion flow meters are also available with an extraction device to help in the easy removal of the flow meter, such as our PIT Insertion Type Magnetic Flow Meter.

Clamp-on flow meters are typically ultrasonic flow meters, which utilize transit-time technology. Portable clamp-on flow meters are models that are easily removed from the installation and can be quickly used in other areas of the application or other application areas because they are temporarily installed on the outside of the pipe and are not integrated into the piping system itself. They typically feature a transducer that is held to the pipe area with a quick release system and calculation/display electronics. Stationary clamp-on flow meters typically have a more permanent manner of adhering the transducers to the outside of the pipe.

These types of flow meters require a pipe that has ultrasonic conductive properties, like steel or plastic. Because these ultrasonic clamp-on flow meters utilize technology that does not require it to be installed within the process line, they can be easily added on to an existing process with no disruption to the process. Common application areas for this type of flow meter include power plants, water and wastewater processes, facility management, chemical and petrochemical industries, and the food and beverage industries. Clamp-on flow meters are also a great choice for larger line sizes as they typically cost less than an inline flow meter in the same diameter. View our DUC clamp-on ultrasonic flow meter for more details about this technology.

A flow rate flow meter gives a visual indication of the current flow rate passing through the flow meter. This can be done visually via a mechanical assembly or it can be displayed electronically/digitally. The flow rates are typically scaled in a variety of common units of measure per unit of time. A few examples would be gallons per minute (GPM) and pounds per hour (lbs/hr).

A flow switch flow meter lets the user know whether media is flowing in their system. Most flow switch flow meters are “blind”, meaning they have no accompanying rate display. Flow switches are a common option used in conjunction with Flow Rate Flow Meters. An example of common Flow Switch Flow Meter technologies would be Paddle Type and Variable Area Type.

Many times, end-users want to know the status of their system remotely and not at the actual flow meter installation point. To do this, many flow meters are equipped with electronics that can transmit a signal relative to the scaled associated flow rate. Common types of output signals are 4-20mA and 0-10VDC. Not only do flow meters collect the flow data differently depending on the technology type, but the way that the data is communicated by the flow meter to the process and/or end user varies as well.