Showing posts with label ultrasonic. Show all posts
Showing posts with label ultrasonic. Show all posts

Tuesday, March 27, 2018

Understanding Flow Sensing Technologies

When selecting a flow sensor, flow meter, or flow switch, one of the first considerations is always the process media: air, gas, steam or liquid. Some flow sensing technologies measure gas, some are better at liquids, some are best for a single media, such as steam, and others are good in multiple media. The industry’s major flow sensing technologies now available include:
Thermal flow meters.
Depending on the process media and your application’s requirements, all of these technologies have their advantages/ disadvantages. By considering the process media to be measured, as well as your plant’s equipment and layout, environmental conditions, maintenance schedules, energy cost and ROI, you will be able to narrow the field to one or two best choices.

Coriolis (Mass): Coriolis flowmeters use the oscillating movement of two symmetric metal tubes that are made to vibrate from an internal driver coil.  When liquids or gases flow through the tubes, a phase shift occurs (like you see in the hose) and pickups measure the “twist” and then relate that value to the actual flow. In other words, the amount of twist is proportional to the mass flow rate of fluid passing through the tubes. The greater the twist, the larger the distance between, and the greater the flow.

Differential Pressure: The differential flow meter is the most common device for measuring fluid flow through pipes. Flow rates and pressure differential of fluids, such as gases vapors and liquids. The differential flow meter, whether Venturi tube, flow nozzle, or orifice plate style, is an in line instrument that is installed between two pipe flanges and measures the pressure drop across the flow restrictor and equates it to flow.

Electromagnetic: Magnetic flow meters, also called electromagnetic flow meters or "magmeters",operate on a very simple principal. An electrically conductive liquid moving through a magnetic field will generate a voltage that is related to the velocity of the liquid.

Positive Displacement: Provides a direct indication of actual volumetric flow rate. The fluid motion drives the mechanical assembly. As the fluid motion drives the positive displacement flowmeter assembly, its rotational, oscillating, or other regular movement is counted, often by electronic means using magnetic pickups on moving assembly. There are a number of different positive displacement flowmeter designs including oscillating piston, gear, nutating disk, rotary vane, and diaphragm.

Thermal (Mass): Measure flow by delivering heat into the flowing media and measuring the loss of heat between temperature measurement points. They are popular because they provide unrestricted flow, contain no moving parts, work well on large or small diameter pipes, provide accuracies over a wide range of flow rates, do not require temp/press compensation, and provide mass flow instead of volume.

Turbine: These types of flowmeters operate under the simple principle that the rotation of the turbine will be constant as the turbine is acted upon by a fluid passing through the flowmeter. The rotational velocity of the turbine is then interpreted as output, allowing for the operator to consistently monitor the flow rate of the process fluid. They are easy to maintain and reliable.

Ultrasonic: Measure, via sound waves, the velocity of liquid flowing through a pipe.  Doppler shift technology reflects ultrasonic beams off sonically reflective materials. The transit time method exploits the fact that the transmission speed of an ultrasonic signal depends on the flow velocity of the carrier medium. The use of ultrasonic flow technology is most used in the oil, nuclear, wastewater, pharmaceutical, food and beverage industries.
Variable Area
Variable Area

Variable Area: Measures flow rate by allowing the cross-sectional area the fluid travels through to vary, causing a measurable effect. Flow measurement is performed according to the float principle. Used to measure many different types of liquids and gases passing through closed piping.

Vortex Shedding
Vortex Shedding: Refers to the phenomenon wherein flowing gas or liquid forms vortices around a solid obstruction placed in the flow path, which can be measured to calculate volumetric or mass flow. Measure the volumetric flow rate of steam, gas, and low viscosity liquids.

Contact Flow-Tech for any industrial or commercial flow application by calling 410-666-3200 in Maryland, or 804-752-3450 in Virginia. Visit

Tuesday, February 28, 2017

Non-invasive, Ultrasonic Flowmeters Are Clear Winners in Wastewater Pumping Stations

non-invasive flowmeters on wastewater pumping stations
Non-invasive flowmeters installed on
wastewater pumping line.
Pumping stations are an integral part of each wastewater network. Flow measurement at such stations is critical as the quantities which are fed to the treatment plant have to be monitored.

Conventionally, magnetic inductive flowmeters are used for such measurement tasks. However, due the medium, which is heavily charged with solid matter, these instruments are subject to wear, leading to incorrect readings and subsequent failure.

Non-invasive ultrasonic flow meters prove to be the better measuring solution. Since these meters measure from outside the pipe wall, there is no wear and tear on the meter making them virtually maintenance-free. Furthermore, there is no need to open the pipe for installation, which would result in at least a partial interruption of operation. There isn't a need for multiple workers or heavy equipment for installation. The entire measuring system, consisting of ultrasonic transducers and a measuring transmitter, is easily carried to the measuring location and installed by a single person. There is no disconnection of pipes or flanged joints, unlike when installing a magmeter. Finally, there is no need for block valves to hold back flow during installation, repair, or replacement.

  • Reliable and accurate non-invasive wastewater flow measurement without any wear and tear or measurement drift
  • Extremely easy to set up a measuring point without any impairment of the plant’s normal operation
  • ATEX-certified transducers with protection degree IP68 for use in hazardous areas as well as in flooded chambers
For more information on non-invasive ultrasonic flow measurement, contact Flow-Tech in Maryland at 410-666-3200, in Virginia at 804-752-3450, or online at

Thursday, October 13, 2016

Accurate Measurement of Low Flow In Compressed Air Systems

Plant operators are well aware of the cost associated with continuous delivery of compressed air, a useful medium utilized as an energy source. Large or multiple compressors consume considerable amounts of electric power maintaining system pressure and flow requirements. With extensive piping and countless fittings, there are many potential points of leakage. Scheduling of various production operations can vary the demand for compressed air significantly. Getting control of your compressed air system and reducing operating cost is a noble goal. One of the primary tools needed to manage energy costs will be accurate and reliable flow measurement equipment. Here are some characteristics of flow measurement instrumentation that should prove advantageous:
Portable ultrasonic flow meter with clamp on transducer
Portable Ultrasonic Flow Measurement Instrument

  • Non-invasive measurement from the outer pipe wall that does not add potential leak sources or pressure drop.
  • Availability in fixed or portable configuration.
  • Highly accurate, with paired temperature compensated traceable calibrated transducers
  • Installed without disturbance to piping.
  • Bidirectional measurement
  • Rugged instrument design suitable for any kind of industrial environment
Ultrasonic flow measurement technology can provide all of these characteristics, providing information that enables the operator to make fact based decisions about system design, management, and maintenance. Learn more about how ultrasonic flow meters specifically configured for compressed air system application can help you start reducing your operating cost and developing a higher level of control over your compressed air system. Share your process challenges with a product specialist and work together to build the best solution.

Friday, July 22, 2016

The Transit-Time Difference Method to Measure Flow

Transit-time flowmeter
Transit-time flowmeter
(courtesy of FLEXIM)
The transit-time difference method for measuring flow exploits the fact that the transmission speed of an ultrasonic signal depends on the flow velocity of the carrier medium.

Similar to a swimmer swimming against the current, an ultrasonic signal moves slower against the flow direction of the medium than when in the flow direction.

For the measurement, two ultrasonic pulses are sent through the medium, on in the flow direction, and a second on against it. The transducers are alternatively working as an emitter and receiver.

The transit-time of the ultrasonic signal propagating in the flow direction is shorter than the transit-time of the signal propagating against the flow direction.

A transit-time difference, Δt, can thus be measured and allows the determination of the average flow velocity based on the propagation path of the ultrasonic signals.

An additional profile correction is performed by the proprietary FLEXIM algorithms, to obtain an exceptional accuracy on the average flow velocity on the cross-section of the pipe - which is proportional to the volume flow.

Since ultrasounds propagate in solids, the transducers can be mounted onto the pipe. The measurement is therefore non-intrusive, and thus no cutting or welding of pipes is required for the installation of the transducers.