Latest developments in flowmeters

Written by: Paul Fanning | Published:

Flowmeters measure the amount of liquid, gas or vapour that passes through them. However, there all attempts to generalise about this technology end. There are many types of flowmeter, each with its own specific applications and installation constraints.

Some flowmeters measure flow as the amount of fluid passing through the flowmeter during a time period (such as 100 litres per minute). Others measure the total amount of fluid that has passed through the flowmeter (such as 100 litres).

Flowmeters consist of a primary device, transducer and transmitter. The transducer senses the fluid that passes through the primary device. The transmitter produces a usable flow signal from the raw transducer signal. These components are often combined, so the actual flowmeter may be one or more physical devices.

However, innovation is a constant in this market. One example of this is Siemens' Sitrans FC410, Siemens presents the lightest and most compact Coriolis flowmeter currently available, featuring a measuring accuracy of 0.1%.

Coriolis meters make direct mass flow measurements based upon the Coriolis effect: the deflection of moving objects when they are viewed in a rotating reference frame. Coriolis flow meters artificially introduce a Coriolis acceleration into the flowing stream. As the fluid is "deflected", the forces generated cause an extremely slight distortion or 'twisting action' of the measuring tube that is directly proportional to the mass flow rate.

This distortion is picked up by special sensors and converted to an output signal.

With dimensions of 265mm x 280mm x 90mm and a weight of 4.6kg in the smallest version (DN 15), the meter is ideal for machine and plant construction or for frame-mounted equipment. The combination of compact design, high accuracy, IP67 degree of protection and a wide variety of functions orients Sitrans FC410 toward use in almost any facility, even where space is very limited.

The combination of compact design, high accuracy, IP67 degree of protection and a wide variety of functions orients Sitrans FC410 toward use in almost any facility, even where space is very limited.

With the new Mini Flow Link (MFL) concept, Siemens has succeeded in accommodating transmitter functionalities in the sensor. The digitally based MFL permits a much more compact design without additional assembly work. Sitrans FC410 is therefore flexible enough for installation in confined spaces without any compromise in measuring accuracy or reliability. The digital MFL features a very fast signal update of 10 milliseconds and provides not only flow rate data but also the mass, volume, density, and temperature of the medium.

The innovative CompactCurve design of the sensor developed by Siemens ensures a high level of reliability due to its stable zero point, low-pressure loss, and high immunity to process noise and plant vibrations. Sitrans FC410 is therefore especially suitable for use in challenging applications where accuracy and reliability in measurements of density and mass are required. The flowmeter also works at pressure levels of up to 100 bar and temperatures of -50 to +200° Celsius without any loss of measuring accuracy. Sitrans FC410 is certified for use in the pharmaceutical as well as food and beverage industries according to the most important standards, such as 3A, EHEDG and FDA.

Turbine or paddlewheel flow meters are mechanical meters that have a freely rotating turbine set in the path of a fluid stream. The flowing liquid or gas causes the turbine to spin upon its axis. The rate of spin will be proportional to the velocity of the flow.

Insertion flowmeters measure the point velocity of the liquid in a pipe. Due to the relatively small disturbance the insertion turbine metering head introduces to a pipe, pressure losses for this type of flowmeter are very low thereby producing energy savings by reducing pumping costs.

Typical applications for insertion turbine flowmeters include water distribution mains, fire hydrant monitoring, boiler feed measurement, irrigation systems, district heating and HVAC systems.

Titan's innovative, robust insertion turbine combines proven technology with modern materials and innovative design. The PVDF turbine rotates freely on a 316 stainless steel shaft and has special aerofoil shaped blades to extend the dynamic range of the meter. The specially contoured housing further improves the meter linearity particularly at lower fluid velocities. Installation from the side of the flow line is made via a 1.5" BSP or NPT fitting, and versions are available for 'hot-tap' insertion into pressurised lines.

Each insertion turbine meter contains two sensors, one self-powered (for battery operated equipment) and the other an open collector transistor.

Ultrasonic flowmeters, on the other hand, use sound waves to measure the velocity of a fluid from which the volumetric flow rate can be calculated. Unlike most flowmeters, ultrasonic meters do not include any moving parts and thus are more reliable, accurate and provide maintenance-free operation. Since ultrasonic signals can also penetrate solid materials, the transducers can be mounted onto the outside of the pipe offering completely non-invasive measurement eliminating chemical compatibility issues, pressure restrictions, and pressure loss.

The Atrato from Titan Enterprise is true inline non-invasive flow meter without the contorted flow path and disadvantages of alternative ultrasonic designs. It can handle flows from laminar to turbulent and is therefore largely immune from viscosity. It also offers excellent turndown, linearity and repeatability. Atrato flowmeters use patented 'time-of-flight' ultrasonic technology that enables them to operate over very wide flow ranges (250:1) with excellent accuracy (better than ±1.5%) over the whole span.

Constructed from Victrex PEEK polymer - the low cost, high accuracy Atrato ultrasonic flow meter from Titan Enterprises offers accurate and cost effective flow measurement is increasingly important to industries requiring a high degree of cleanliness including pharmaceuticals, industrial engineering and food and beverages.

The Atrato flow meter leverages Titan's patented ultrasonic flow meter technology enabling the direct-through meter to handle flows from laminar to turbulent. The device deploys the 'time of flight' measurement system where a signal is passed along the pipe with the flow and back up the pipe against the flow, the difference in these signals produces the flow rate.

In developing the ATRATO, Titan Enterprises selected a high performance polymer that would enable the thread forms which attach the flow meter to the flow pipes to be moulded. This was not possible to achieve using traditional metal thread forms. The polymer also needed to be chemically resistant and have the capability to operate at high temperature up to 110ºC (230ºF). Due to its intended use in beverage dispensing applications the material needed to be FDA compliant. Additionally, low moisture absorption was a prerequisite for medical and pharmaceutical applications.

The Atrato's unique clean bore construction makes it ideal for these applications. The smooth finish achieved in the bore of the Victrex PEEK polymer-based components aids the flow of liquids. In addition, the polymer's high resistance to cleaning fluids and solvents enhances the cleaning process.

Gas flow can also be measured in this way and Morgan Advanced Materials offers a range of ultrasonic sensors developed for gas flow measurement. This technology utilises two or three transducers for smart metering of natural gas or air-coupled level sensing of liquids and solids. Capable of operating in temperatures between -20°C and 70°C in air, and -10°C and 40°C in natural gas, the transducers deliver an assured solution for assessing gas flow measurement.

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