Flowmeters Pass the Muster

Measuring the flow of fluids is critical in many industrial plants. For some applications, measuring flow accurately can make the difference between making a profit or taking a loss.Application media = technologyFlow measurement is media dependent. According to a study of flowmeter makers and worldwide users recently conducted by Automation Research Corp.

04/01/1998


FLOWMETERS AT A GLANCE

 

  • Coriolis flowmeters

  • Fieldbus communications

  • Media dependence

  • Self-diagnostics

Measuring the flow of fluids is critical in many industrial plants. For some applications, measuring flow accurately can make the difference between making a profit or taking a loss.

Application media = technology

Flow measurement is media dependent. According to a study of flowmeter makers and worldwide users recently conducted by Automation Research Corp. (ARC, Dedham, Mass.), in industry, liquids account for 68% of flow measurement applications, followed by gases (22%) and steam (10%).

Liquids can be described by various values—viscosity, density, specific gravity, and friction of the liquid in contact with the pipe, temperature, and pressure. No single factor directly determines the performance of a flowmeter. Performance is also affected by a dimensionless unit, called the Reynolds Number. The Reynolds Number is defined as the ratio of the liquid's inertial forces to its drag forces.

ARC's study discloses that the specific application's requirements are the most important factor users consider to aid in the determination of the final flowmeter selection, followed by accuracy, reliability, and others (fig. 1).

ARC's study also shows 5% is the degree of accuracy most often required by flowmeter users (29.2% of respondents). In decreasing order of preference are 1%, 3%, and 2%. Accuracies over 3% and less than 0.5% each account for 10.4% of the responses.

Numerous types of measurement technologies have been developed to monitor flow. Figure 2 shows the 10 most popular types of flowmeters specified by users.

Omega Engineering's (Stamford, Conn.) web site ( www2.omega.com/techref/table1.html ) contains a flowmeter selection table in which several different flow measurement technologies are tabulated for factors including: recommended service, rangeability, pressure loss, typical accuracy, required upstream pipe diameters, the effect of viscosity, and relative cost.

Picking the right flowmeter

In a Technical Reference on flowmeter selection by Omega Engineering Inc. (found on its web site: www2.omega.com/techref/flowcontrol.html ), "Experts claim that over 75% of the flowmeters installed in industry are not performing satisfactorily. And improper selection accounts for 90% of these problems.

To aid proper selection, Omega offers these questions to ask when specifying a flowmeter:

  • Is the measurement for process control (where repeatability is a major concern), for accounting, or for custody transfer (where high accuracy is important)?

  • Is local or remote signal indication required?

  • If a remote output is required, is it to be a proportional signal, or a contact closure to start or stop another device?

  • Is the liquid viscous, clean, or a slurry?

  • Is the media electrically conductive?

  • What is the specific gravity or density?

  • What flow rates are involved in the application?

  • What are the processes' operating temperatures and pressures?

Accuracy, range, linearity, repeatability, and piping requirements must also be considered.

Are approvals needed?

ARC's study indicates that almost 80% of applications require some sort of certification (fig. 3). One of the newest required certifications is the CE Mark. The study shows that 15.4% of the respondents are already specifying the CE Mark as a requirement when they purchase a new flowmeter.

Larry Rice, vice president of Field Measurement and Control, The Foxboro Co. (Foxboro, Mass.), relates "End-users are demanding flowmeters that are easier to install and configure, easier to field verify for ISO 9000 and regulatory compliance, and easier to maintain over time."

Improving flowmeter usage/ownership

Dennis Ciccarelli, product manager, Bailey-Fischer & Porter Co. (Warminster, Pa.), says "The trend in flowmeter design today is for increased functionality, self-diagnostics, and ease of maintenance."

Increased functionality— to supply information on multiple process conditions. According to Warren Meyer, vice president, Marketing, Fisher-Rosemount Flow (Micro Motion Inc., Boulder, Colo.—), The Coriolis flowmeter, for example, in addition to volume flow, directly measures mass flow, density, temperature, and with a differential pressure input, can infer viscosity as well."

Self-diagnostics— customers want to be able to troubleshoot the equipment with ease, or have an alarm indicate the equipment has failed. Mr. Rice remarks, "The increasing communications flexibility and intelligence of today's flow transmitters simplifies initial configuration and long-term maintenance. Today's flowmeters can be configured in engineering units and other parameters using techniques ranging from local configuration via pushbuttons—to dedicated hand-held terminals, laptop PCs, or the control system itself."

Ease of maintenance— The emergence of digital communications has minimized the need to travel to the flowmeter, which is frequently installed in distant or hazardous locations. Built-in user prompts, Help dialogs, and plain-English diagnostics are minimizing the need for specialized product training. Digital communications eliminate the need to tediously "ring out" the correct field wiring, thus reducing the manpower required in a start-up.

Talking flowmeters? The jury's out

Is being able to "talk" to flowmeters increasingly important to users? ARC's study showed reasons to adopt a fieldbus include (in decreasing importance): save on wiring costs, interoperability, better diagnostics, easier to add new instruments, lower maintenance costs, remote diagnostics, remote calibration, and remote reranging.

Will flowmeter users adopt some sort of fieldbus? Forty-five percent of respondents to ARC's study have no current plans for fieldbus implementation. An additional 31% said they're waiting until some sort of fieldbus is proven. Reasons cited for not adopting a fieldbus are: products not available, too expensive, no cost benefit, and don't know its benefits.

Is 'mass' replacing 'volume?'

When asked, Bailey-Fischer & Porter's Dennis Ciccarelli replied, "Industries such as chemical, food and beverage, and pulp and paper are looking for instruments that provide a true mass flow measurement [instead of volume-only measurement]." He attributes the reason for this trend to the fact, "[The control of] the mass of a chemical used in a key process reaction will result in a better product and yield [than from the control of the volume of that chemical]."

Mass flow measurement is an emerging technology. While the number of mass flowmeters currently installed is relatively low (ARC's study showed only 3.9% of the reported installations tallied measured mass flow), the ARC study reports, "Over 70% of users responding said they would consider buying a mass flowmeter." Other reasons cited by respondents to the study for increased interest in mass flowmeters were governmental regulations and the need for increased accuracy.

Future plans?

Forty-six percent of the respondents to ARC's study cited new construction as a driving factor behind new flowmeter purchases over the next several years. Other significant factors related include replacement of existing equipment (26%) and revamps and upgrades (25%). A few users cited regulations as a driving factor (3%).

For information about various marketing studies on flowmeters, contact Automation Research Corp. Three Allied Dr., Dedham, MA 02026, tel: 617/461-9100, fax: 617/461-9011, e-mail: info@arcweb. com , or visit ARC's web site at: www. arc.com .

For information about specific marketing information referenced in this article, contact Jesse Yoder at ARC, tel: 617/461-9100, ext. 128 or e-mail: jyoder@arcweb. com .

Compressed air mass flowmeter

San Marcos, Calif.— The FlexMASSter ST95B-CA compressed air mass flowmeter provides a true mass flow output and eliminates the need for additional components, such as pressure and temperature transducers. Ranges are from 6 to 600 sfps in air or nitrogen. By inputting the pipe ID, the unit will provide selectable mass flow units such as scfm, lbs/hr, and NCMH.

Fluid Components Intl.

Single-tube Coriolis flowmeter

Greenwood, Ind.— The Promass I single-tube, full-bore, Coriolis mass flowmeter requires no additional installation or mounting hardware. Because of its high operating frequency, the Promass I is said to be immune to plant vibrations.

The single full-bore flow path is claimed to provide increased cleaning safety, reduced risk for clogging, easy inspection, and no shear stress on the fluid.

Endress + Hauser

2-wire electromagnetic flowmeter

Warminster, Mass.— COPA-XT electromagnetic flowmeter is designed to meter liquids, slurries, and sludges when the conductivity exceeds 50

Bailey-Fischer & Porter Co.

Intelligent flow simulator

Foxboro, Mass.— The hand—held Intelligent Magnetic Flow Simulator (IMTSIM) is resistant to dust, rain, and chemicals and is powered entirely from the IMT25 intelligent magnetic flow transmitter. Enhancements include preprogrammed help messages that are viewed by the touch of a button, providing step-by-step instructions on programming the IMT25. Internal diagnostic functions now have informative messages that provide the user with more detailed information about any diagnostic condition, as well as trouble shooting techniques.

The Foxboro Co.

Interchangeable electronics

Irvine, Calif.— Type 8030 electronic, inline continuous flow sensor features a built-in paddlewheel and quarter-turn "bayonet"-style mounting platform for use with the company's Type 8035 flow transmitter or batch controller. Modules can be changed or upgraded as needed. The inline fittings for both the 8030 and 8035 are available in plastic, brass, and stainless steel in sizes from

Bukert Contromatic

Multijet turbine flowmeter

Roselle, N.J.— The Multi-Jet Turbine Flowmeters are available in 1/2 to 12-in. pipe sizes and are designed for cold water up to 122 °F or with fiberglass components for hot water up to 250 °F. Turbine rotation is transferred with magnets from the totally sealed flow chamber to the counter. The counter has a "trickle dial" to indicate rotation of the turbine at an extremely low flow rate.

Istec Corp.

Differential-pressure flow measurement

Boxborough, Mass.— The Model 209 pressure transducer measures pressures as low as 0-2 psi and retains its accuracy in spite of mechanical shock, vibration, thermal shock, RFI, corrosive media, and other extremes encountered in industrial environments.

Setra Systems Inc.

Mass flow measurement

Eden Prairie, Minn.— Rosemount Inc. and Dieterich Standard combined the Rosemount Model 3095 MV mass flow transmitter and Dieterich Standard's Annubar to create the Mass Pro-Bar. Mass Pro-Bar provides measurement of four process variables in one device: differential pressure, static pressure, temperature, and mass flow. Accuracy is rated within 1.3% for fluids over an 8:1 flow turndown.

Fisher-Rosemount

Media independence

Chaska, Minn.— The Accu-tek flowmeter product line has been designed for precise meteringle NPT ports are standard.

Fluoroware Inc.





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