Beyond Flow

AT A GLANCE

Window to the process

Higher accuracy

Low maintenance

Self-diagnostics

Communications capabilities

Non-intrusive technologies

New technology flowmeters really aren’t very new. Many of these devices—defined by most as encompassing Coriolis, ultrasonic, electomagnetic, vortex, and occasionally multivariable and thermal types—have been around for years. They are new, however, in that they are distinguishable from even older, traditional mechanical flow technologies (such as positive displacement, Venturi, and orifice plate) that have been the staple of industrial, municipal, and institutional operations. And they are noteworthy because of the developments they are undergoing, activities that are taking flowmeters beyond the instrument and making them, in many respects, windows to the process.

New technology flowmeters offer a variety of benefits for the devices themselves and the processes they monitor. They are characterized by higher accuracy, higher repeatability, and lower maintenance costs. Such flowmeters have few or no moving parts to wear; measure more kinds of fluids more easily and reliably; and, for the most part, are non-intrusive for lower pressure drop and greater security. Many are smart, equipped with microprocessor-based intelligence. They perform self-diagnostics and accommodate one or more of the common communications protocols to give users real-time feedback and historical data acquisition.

Moving to a higher level

Most growth in the flowmeter market today is in the new technology area. ‘There’s no question that the market is moving toward new technology flowmeters,’ says Jesse Yoder, president of Flow Research Inc., a market research company focused on instrumentation, flowmeters, and pressure and temperature transmitters. ‘But it takes time because of the large installed base of traditional meters.’

James ‘Jed’ Matson, senior product specialist, ultrasonic flowmeter line, GE Infrastructure Sensing, suggests that new and improved technology flowmeters go beyond instrumentation to solving problems: ‘The flowmeter is not just a flowmeter anymore. And for the aggressive or smart user, this works out well. The trick is to know what to do with all the information these devices can now obtain, to maximize their diagnostic capabilities, to know how to turn them into something that is useful for the process.’

One extension has been the recent application of new technology meters—in particular ultrasonic devices—to gas measurement. Clamp-on technology for gas measurement had once been considered impossible, says Matson, because the density of gas was considered insufficient for ultrasound to function properly. However, ‘we entered the market in 2001 with a meter that accomplished this with the transit time method. Using advanced transducer technology gave us a higher order of magnitude of ultrasonic sound energy so that we could make that gas traverse and obtain measurements with accuracies of

Newer clamp-on gas flow technology overcomes the pressure requirement in the Panametrics DigitalFlow CTF878, which brings clamp-on ultrasonic gas flow metering capability to atmospheric pressure applications at velocities up to 150 ft/s (46m/s). It uses a correlation tag method to measure the flow of natural gas, compressed air, inert gas, or any other gases. The meter has no wetted or moving parts, requires no maintenance, and causes no pressure drop.

Ultrasonic, Coriolis…

Together with ultrasonic devices, Coriolis meters form perhaps the fastest growing segment of the new technology flowmeter market. They feature high accuracy and low maintenance and can provide many years of service without recalibration. Their ability to supply mass flow and density measurements (as opposed to volumetric flow measurements) gives users insight into fluid composition, not just fluid quantity, an important feature in chemical industry applications.

Sonartrac clamp-on flowmeters from Cidra (inset) use two synergistic measurements. One tracks volumetric flow rate, the other uses speed at which sound propagates through the fluid to provide compositional information. Sonar-based array processing techniques “listen” to and interpret pressure fields generated by turbulent pipe flows. Accuracies of

Micro Motion’s Coriolis meters measure density, mass flow rate, and temperature to provide insight into the process beyond the flow. Says Marc Buttler, product line business manager, Micro Motion, Emerson Process Management, ‘Customers have come to expect more and more from their flowmeters and have found new ways to apply the advantages of the data richness that is available. Flowmeter technology has evolved to where you can learn more about the process than just a flow rate.’

Self-diagnostic abilities form the cornerstone of Coriolis meters, according to Buttler, and are applicable to meter health and process health. ‘Customers need to be able to identify when a meter has a problem. Just as importantly, they need to be able to rely on the flowmeter to tell them when the process is having problems that are not related to the meter. A flowmeter that can alert someone to a problem in the process is very useful.’

In a similar vein, Krohne’s Optimass Coriolis flowmeters measure up to four process variables in one device and boast high levels of diagnostics to check performance. Optimass features modular construction, with a sensor-specific front end and an electronics back end. Says Jonathan Fiedler, product specialist for the NAFTA region at Krohne, ‘The concept of breaking apart the converter from the sensor specific role and the general I/O output role lets a flowmeter communicate digitally from as far a distance as we want. It also has additional benefits when this concept is carried over an entire product line—one base converter with sensor specific modules. This simplifies development, manufacturing, and use. When we have new protocols, instead of adding them to 20 new product lines, we do it once across the board. This holds down costs with no sacrifice in quality.’

…and more

Beyond ultrasonic and Coriolis technologies are other technologies that also provide the benefits of high accuracy, low maintenance, and self-diagnostics. Krohne’s Optiflux magmeter, for example, provides measurements of volume flow as well as a concentration measurement (conductivity) and temperature. Optiflux self checks 100% of its hardware and software, performing traditional resistance and continuity checks that determine magnetic flow tube health, as well as monitor field current for maintained accuracy, and electrode resistance to detect coating. It also performs calibration linearity checks to verify that the meter is within accuracy specifications. It detects partially full pipes, distorted flow profiles, change in fluid composition due to aeration, high solids content or non-homogeneous liquid mixes, and alerts users to possible problems. These actions let users identify a meter that’s beginning to have a problem and indicate probable cause, reducing downtime.

On a different note is a sonar-based technology recently introduced by Cidra for liquid and gas flow measurement, in single and multiphase flows. Sonar trac system’s ‘clamp-on’ configuration can be installed on existing process lines, eliminating process disruptions.

Dan Gysling, chief technology officer, Cidra Corp., elaborates, explaining, ‘A Sonar trac system provides a volumetric flow measurement and also a sound speed measurement. In many applications, it provides a very accurate measurement of the gas volume fraction. In some situations, an aerated fluid may cause trouble with calibration and measurement. It can be hard to identify. This meter accurately tracks the amount of gas volume fraction in your lines and provides a good picture of what’s going on inside a pipe.’

Extending the reach

New technology flowmeters also extend their reach with a variety of support functions ranging from communications to wireless capabilities. Eric Wible, engineering director, Fluid Components International (FCI), observes how PCs and plug-and-play electronics have advanced new technology instrumentation. ‘Customers are not looking for analog output that gives them one process variable anymore. They want digital bus that gives them multiple process variables that they can plug into their computer with user-friendly installation.’

An example is FCI’s Model ST98, a plug-and-play device equipped with the Profibus protocol. It features self-diagnostics built into the device that alerts the user to a problem and requires signal acknowledgement to reset.

‘More and more instrumentation is being used to fine tune a process,’ adds Sam Kresch, FCI’s OEM manager. ‘When an event occurs, a customer needs to verify what’s happened. He can link the devices to a preventive maintenance system. Or, a wireless PDA can communicate with a flowmeter and obtain data. We see wireless applications on the rise. They save labor and allow remote monitoring.’ FCI’s ST50 and ST75 flowmeters have wireless IR ports. With a standard PDA, a user can do anything that he can do with a hardwired connection.

Outside the devices, themselves, is instrumentation that supports the parameters used in flow calculations. ‘We have a number of tools that measure pressure,’ points out Jim Shields, product marketing manager, process calibration tools, Fluke Corp. ‘We’re helping people who use new technology flowmeters obtain more precise data and confirm that data. Custody transfer is one example. A 1% difference in measurements is not acceptable. That amount could mean millions of dollars a day in lost revenue. The calibration and accuracy of these devices are critical.’

Not an easy job

A diverse range of new and improving technologies is unequivocally influencing the industrial flowmeter market. Although no dominant technology has emerged, Coriolis and ultrasonic devices show strong evidence of the fastest market growth. Innovative concepts are being introduced, and intelligence in the form of self-diagnostics and communications are characterizing these devices.

Some expertise is required to choose the right flowmeter to make a measurement. Says Cidra’s Gysling, ‘You need to know how you’re using a device, how you’re applying it. Flowmeters have been around for a hundred years. You’d think it would be simple to pick one. But it’s not.’

Gysling believes the future will bring more non-intrusive technologies. Krohne’s Fiedler sees devices becoming smarter and universally applicable, easy to specify, install, and maintain, all at an affordable price. Says GE Infrastructure Sensing’s Matson, ‘Mass flow is a potentially growing part of the market. Most people have settled for obtaining volumetric flow, but would really like to have mass flow. Applying Coriolis meters to gas measurement is being sought, as is applying ultrasonic clamp-on technology. These concepts are very new, but they are where new technology flowmeters are trying to go.’

Flow Research’s Yoder suggests inertia’s a greater problem: ‘Cost plays a role, but the greatest barrier to the proliferation of these devices is that people tend to stay with what they know unless there are strong reasons to change.’

Online Extra

Coriolis flowmeters improve transfer efficiency

Replacing PD (positive displacement) flowmeters with new technology Coriolis units increased flow measurement accuracy, eliminated maintenance downtime, and improved efficiency for a Scottish tanker and cask filling operation.

The Diageo plc storage and cask filling facility in Stirlingshire, Scotland, handles grain and malt spirits delivered by tanker from outlying distilleries to the site where they are matured, and later blended to create high-quality Scotch whiskeys. The off-loading operations require flow measurement to record and control deliveries. At the site, some spirits are reduced, others are stored for transfer later, and still others are loaded back into the tankers for delivery elsewhere. The facility needed to control flow rates and batch totals for production and inventory control. In addition, all transfers required customs and excise-approved measurement systems to ensure payment of correct duties.

CMF300 3-in. Coriolis flowmeters from Micro Motion used at this transfer operation require no maintenance and calibration and improve measurement accuracy and efficiency. (Illustration courtesy of MicroMotion, Emerson Process Management)

The site sought to increase transfer and fill flow rates from 70 cu m/hr to 90 cu m/hr to reduce tanker loading/offloading times. Existing 3-in. PD meters had moving parts, experienced wear, and required regular recalibration and repair. To obtain the improved flow rates using existing piping, the facility replaced its PD meters with Micro Motion CMF300 3-in. meters. The instruments experienced no significant pressure drop, and could be blown through with air following each operation to remove traces of previous product and avoid contamination.

To obtain customs and excise approval, the site had to demonstrate the meters would consistently measure flows accurately. Tests showed an accuracy of 0.1% or better with an accuracy of 0.05% achieved most of the time. Customs and excise requirements are based on volume flow measurement. The mass flow meters provide this output by measuring liquid density, then computing flow volume.

Sixteen flow meters are now installed at the facility’s main control center. Additional units are used for reduction processes. Conventional process control used a sampling system to monitor alcohol percentage. Density and temperature outputs from the new flowmeters provide on-line alcohol measurement and, subsequently, the potential for greater control and efficiency.

More than 52 million liters of spirits were measured by the new flowmeters in the first year with no change in meter calibration. No maintenance has been required. The facility is now considering installing flowmeters with 4-in. lines to attain lower fluid velocities and pressure drops to reduce the possibility of problems from static electricity build-up, according to Micro Motion, Emerson Process Management.

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