In brief
A flow meter measures how much liquid, gas or steam flows through a pipe per unit of time, either as volume or as mass.
Contents
What is Flow meter?
Flow meters measure volume or mass flows in process plants, water supply, cooling circuits or dosing lines. Measurements are taken for process control, consumption metering or monitoring pumps and filters. Depending on the measuring principle, they are suited to particular media, temperatures and pressures. Many devices consist of a sensor in the pipe and a transmitter that is either mounted compactly on top or installed separately.
Electromagnetic flow meters measure conductive liquids without any obstructions in the pipe. Coriolis meters measure mass flow and density directly. Ultrasonic meters work with transit time differences, some even clamped onto the outside of the pipe. Vortex meters are suitable for gases and steam, while variable area flow meters often display the flow purely mechanically. Key parameters are nominal size, measuring range, accuracy, pressure rating, process connection, liner and electrode materials, output signal and degree of protection.
Typical problems are deposits, entrained air, abrasion of the liner and unfavourable inlet runs. For measurements relevant to billing or quality, regular calibration is also required. Straight, undisturbed inlet and outlet runs upstream and downstream of the device significantly improve the measuring accuracy of many methods.
In practice: maintenance and procurement
For a replacement, the measuring principle, nominal size, pressure rating, flange or connection standard, medium, temperature, measuring range, materials, output signal and power supply are needed. For a remote version, state whether the sensor, the transmitter or both are required.
Synonyms and abbreviations: flowmeter · flow sensor · magnetic flow meter (magmeter) · flow measuring device · flow transmitter
Frequently asked questions
What types of flow meter are there?
Common types are electromagnetic meters for conductive liquids, Coriolis meters for mass flow and density, ultrasonic flow meters, vortex meters for gases and steam, thermal mass flow meters for gases, and mechanical devices such as variable area, oval gear or turbine meters. The choice depends on the medium, the accuracy and the process conditions.
What is the difference between volume flow and mass flow?
Volume flow states how much space the medium occupies per unit of time, for example in litres per minute. Mass flow states the weight per unit of time, for example in kilograms per hour. For gases and temperature-dependent liquids, mass flow is more meaningful, because volume changes with pressure and temperature.
What information is needed to replace a flow meter?
Needed are the measuring principle, nominal size, pressure rating, connection standard, medium with temperature and conductivity, measuring range, liner and electrode materials, output signal, supply voltage and degree of protection. The nameplate usually contains an order code that encodes these features and makes identification easier.
Does a flow meter need to be calibrated?
Whether and how often calibration is carried out depends on the application. For measurements used for billing, dosing or product quality, quality management or statutory requirements set the inspection intervals. Replacement devices are generally supplied factory-calibrated; a calibration certificate should be requested when ordering if it is needed.