# Liquid Velocity Measurement Meters

###### Accurate Liquid Velocity Measurement Meters : Proteus Industries Inc.

Liquid velocity flow meters are used when it becomes necessary to calculate the volumetric flow rate of a stream. A velocity flow meter calculates flow by computing the speed in one or several points in the flow and assimilating the flow speed over the total flow area.

Velocity flow meters are commonly used in industries because they provide a nonstop measurement of fluid velocity; a trait commonly associated with flow rate. This type of flow meter is one of the most sensitive to processing conditions.

Liquid velocity measurement meters function under the theory that there is a constant velocity profile. As a result, they are erroneous in the laminar regime. Inaccuracy occurs due to the large difference between fluid velocity at the center of the pipe and near the wall. As a result, velocity flow meters are very sensitive to Reynolds numbers and piping geometry.

Examples of liquid velocity measurement meters include turbine, paddlewheel, electromagnetic and vortex shedding flow meters. The following is a brief discussion of each type:

These two types of flow meters are the most versatile. When a fluid flows across a turbine meter, the vanned rotor begins to rotate. A similar action occurs with the paddlewheel type except that its blades are perpendicular to the flow direction. In both types of flow meters, the angular velocity of the rotor is proportionate to the fluid’s velocity.

#### Examples of Use

Paddlewheel and turbine meters are used in similar applications. A petroleum pipeline may use an insertion turbine flow meter to detect leaks. A petroleum plant may also use turbine meters to load light hydrocarbon products into rail cars and road tankers. Apart from metering water, fuel and chemicals, both types of flow meters are used in metering cryogenic gases and oil drilling processes.

#### Electromagnetic

Often called mag meters, these are used to measure conductive fluids. Electromagnetic flow meters operate on Faraday’s Law. When the conductor moves to the right angle of the magnetic field, a voltage difference is provoked in the conductor. This difference is proportional to the velocity of the conductor.

There are two types of electromagnetic flow meters: insertion style and wafer style. Both rely on different methodologies for creating a magnetic field through which conductive fluids flow.

#### Examples of Use

Electromagnetic flow meters are used in several industries including pharmaceutical, food, beverage, cosmetic and chemical industries. Mag meters may be used to measure the flow of cream and milk. Specially designed mag meters are used to measure flow in an open channel. Mag meters may be inserted into a stream or manhole to monitor the flow rate.

#### Vortex Shedding

This type of liquid velocity flow meter relies on turbulence to measure flow rate. When the fluid flows across a non-streamlined object, it creates turbulences on the sides of the object. These are called vortices or eddies. As these vortices move downstream, they shed or separate from the object and grow in size. The vortices shed from each side of the non-streamlined object and swirl off in opposing directions. The size of the vortices and rate of shredding is proportionate to the flow rate of the liquid. This phenomenon is similar to what makes a flag flap in windy conditions.

#### Examples of Use

Vortex flow meters are often used to handle contaminated materials. They are frequently used to monitor liquid, gas and steam flows in turbulent conditions. Petrochemical and chemical industries frequently rely on vortex meters.