Liquid Flow Measurement

Liquid Flow Measurement

There are multiple methods used to measure the flow of a liquid.

Positive Displacement

Positive displacement (PD) flow meters measure the volumetric flow rate of a moving fluid by dividing the media into fixed, metered volumes (finite increments or volumes of the fluid). These devices consist of a chamber(s) that obstructs the media flow and a rotating or reciprocating mechanism that allows the passage of fixed-volume amounts. The number of parcels that pass through the chamber determines the media volume. The rate of revolution or reciprocation determines the flow rate.

Nutating Disc

Liquid enters a precision-machined measuring chamber containing a disc which nutates (wobbles). The measuring chamber contains an exact known quantity of fluid. Fluid pressure causes the disc to nutate and the control roller causes the nutating disc to make a complete cycle. The measuring chamber is filled and emptied each cycle. The nutations of the disc are transmitted by a gear train to a totalizer or pulse transmitter.Nutating Disc Cross Section_NA2

Close machined tolerances between the disc and chamber ensure minimum leakage for accurate and repeatable measurement of each volume cycle.

  • Eliminates upstream and downstream straight run piping requirements
  • Power not required for mechanical version
  • Tolerant of foreign particles
  • Mechanical totalizers and pulse transmitter

Various size options available of the mechanical Nutating Disc model or electronic, SmartPD Nutating Disc model.

Oscillating Piston

Liquid enters a precision-machined measuring chamber containing a piston which oscillates (rotates). The measuring chamber contains an exact known quantity of fluid. Fluid pressure causes the piston to oscillate at its center hub. The measuring chamber is filled and emptied each cycle. The oscillations of the piston are transmitted through the meter wall by a follower magnet to a totalizer or pulse transmitter.

Oscillating Piston Internal

Close machined tolerances between the piston and the chamber ensure minimum leakage for highly accurate and repeatable measurement of each volume cycle.

  • Eliminates upstream and downstream straight run piping requirements
  • Power not required for mechanical version
  • Standard 316 SS/ETFE allows user flexibility with different fluids
  • Mechanical totalizers & pulse transmitters

Various size options available of the mechanical Oscillating Piston model or electronic SmartPD Oscillating Piston model.

 Inferential

Measures flow by inferring the flow through a pipe from some physical property of the flow stream, such as, differential pressure; orifice plates; flow nozzles; venturi tubes or variable area rotameters. A differential pressure drop device creates a pressure drop an obstruction in the flow.

Target Meter

Flow is measured in terms of dynamic force acting on a target (solid disk) in the flow stream. Four strain gages connected in a bridge circuit configuration mounted outside the fForceMeter_NA_Cutaway_GPHlow stream translate force into an electrical output. This output is proportional to flow rate squared.

  • No frictional moving parts to wear out
  • Fast response time
  • Can be used with liquids, gases, steam, and cryogenics

 ForceMeter™ Target Meter

Velocity

Measures flow by measuring the velocity and multiplying it by the flow area.

Turbine

Liquid enters the precision metering insert containing the turbine rotor. The liquid pressure drives the turbine rotor rate of rotation proportional to the volumetric flow rate. The rotor’s rotation is magnetically coupled to a hermetically sealed indicator or indicator/transmitter.Turbine Meters 2

  • Only one moving part (Rotor)
  • Very compact size, lightweight
  • Flexible, unique design
  • Sealed register prevents condensation or fogging

Hot and Cold water MTX & WPX Turbine Models

 Magnetic FlowMagmeter Cross Section 2

A conductive fluid flowing through a magnetic field generates a voltage proportional to its velocity. Electrodes sense the voltage for transmission to the converter. A simple calculation using the cross-sectional area of the flowmeter provides the volumetric flow. The strategic placement of additional electrodes provides a measurement of background noise, enabling noise reduction for higher accuracy.

  • Multiple electrode design eliminates the need for grounding rings
  • Noise reduction maintains accuracy throughout flow range
  • No moving parts
  • Straight flow tube eliminates the need for strainers and minimizes pressure loss

Model 6600 Magmeter magnetic flow meter

 Open Channel

Measures flow by measuring the height of the fluid as it passes over an obstruction in an open channel. Open channels may include flumes, a specially shaped open channel flow section with an area or slope that is different from that of the channel and weirs, a dam built across an area that the liquid flows over. Each type and structure will have an associated equation for determining the flow rate.

Ultrasonic

The most commonly used technique of measuring the rate of flow in an open channel is that of hydraulic structures. Flow in an open channel is measured by inserting a hydraulic structure into the channel, which changes the level of the liquid in or near the structure.

By selecting the shape and dimensions of the hydraulic structure, the rate of flow through or over the restriction will be related to the liquid level in a known manner. Therefore, the flow rate through an open channel can be derived from a single measurement of the liquid level.

Hydraulic structures used in measuring flow in open channels are known as primary measuring devices and are divided into two categories: flumes and weirs.Open Channel

  • Uniform and reliable flow measurement data.
  • Aids in meeting water quality regulatory requirements.
  • Easy to install.
  • Requires minimal maintenance.
  • Non-contact system so is not affected by grease, suspended solids, silt, corrosive chemicals or liquid temperature fluctuations.

Model 5600 Ultrasonic System