New Device Provides Low-Flow Direct Measurement and Control

The first Coriolis meter specifically designed for low-flow use promises direct measurement of mass flow and density in critical processes.

Contents
Major Production
Targeting Thermal Mass
Coriolis Effect
The Shrinking Meter
New Markets

Brooks Instrument (Hatfield, PA), a division of Emerson Electric Co., has launched a new Coriolis meter/controller to provide direct measurement in low-flow applications. Most competing instruments use less accurate inferred measurement. Brooks says Quantim is the first Coriolis device developed specifically for low-flow (<1000 g/hr) liquids, gases, and slurries.

Quantim combines a precision mass multivariable flow meter, valve, and controller. It achieves accuracies of 0.5%, and also provides direct measurement of product density and temperature. At roughly $7500, Brooks believes it will prove cost-competitive with many precision systems used in the chemical, pharmaceutical, semiconductor, and biotechnology industries.

Major Production(Back to Top)
Although the company has been showing Quantim since the Chem Show last November, it chose Philadelphia's Franklin Institute museum for the official rollout. Ceremonies included a video in the OmniMax Theater hosted by an actor playing Ben Franklin, followed by cocktails, music (a harpist), an elegant dinner, and questions from the press.

Such big rollouts have not been typical of Brooks. Numerous company representatives, however, say that Quantim is a revolutionary product that will change the company. One Brooks marketing executive estimates the market for low-flow meters at $450 million worldwide.

Brooks, which specializes in low-flow meters, believes Quantim will make a major impact on the industry because of its four key benefits:

• Precision. Quantim achieves fluid accuracy of 0.5% regardless of fluid measured. Because it measures flow directly, it requires no calibration.
  
• Flexibility. The to measure mass flow directly enables Quantim to achieve precise results despite variations in temperature, viscosity, pressure, or flow.
  
• Reliability. Quantim uses a straight-through flow path that reduces measurement errors caused by clogging. This reduced downtime for maintenance.
  
• Versatility. Quantim provides a single device to handle mass flow, density, and temperature. Its versatility enables users to reduce spare flow controller inventories.

Targeting Thermal Mass(Back to Top)
Brooks is positioning Quantim to compete against thermal mass flow meters, which Brooks also manufactures. "Thermal mass flow is about 30 years old and is the state of the art now, especially in the semiconductor industry," says Brooks business development VP Tim Scott.

Thermal mass works by heating a process fluid as it enters a tube and measuring the change in temperature as it exits. It infers the amount of mass from the difference in temperature. Thermal mass devices typically have accuracies of about 1% of full scale, compared to 0.5% for Coriolis meters.

Inherent accuracy is only one of the problems surrounding thermal mass meters, says Scott. "You have to know what you're measuring," he explains. "You have to know the material's density and temperature, its pressure, and possibly its viscosity. All fluid properties impact flow measurement. You have to play 20 questions with the customer to find out what they're trying to do in order to provide the right flowmeter.

"Sometimes, that information is proprietary," he continues. "Other times, temperature or viscosity changes during the process, and this impacts the measurement. Some fluids can't handle the rise in temperature, while other materials are too corrosive."

(For a more detailed critique of thermal mass devices, click here.)

"That leaves conventional metering pumps, but they are mechanical devices with seals and bearings that will wear," Scott concludes. Mechanical meters are only 2-5% accurate. That's not good enough for such critical applications as feeding growth media into a bacteria colony or metering reactants for chemical vapor deposition (CVD) of integrated circuits.

Coriolis Effect(Back to Top)
Quantim promises a paradigm shift—direct measurement of mass flow and product density. It does this by taking advantage of the Coriolis effect. The phenomenon gets its name from Gustave Coriolis, a French mathematician who, in 1835, showed that the earth's rotation imparts a sideways motion to moving objects.

Anyone who has ever shaped a garden hose into a "U" and spun it while water runs through it has felt the Coriolis effect. The end of the hose, where the water exits, exhibits a slight pull sideways. Measuring the difference in that sideways pull between the water entering and exiting the loop provides a direct measurement of mass running through the hose.

Coriolis meters have been used in custody transfer and other high-volume applications for years. In fact, Brooks' sister company, Micro Motion Inc. (Boulder, CO), is a major supplier of conventional Coriolis meters.

The meters, which are shaped like a large "U," vibrate at a given frequency. The Coriolis effect causes the fluid coursing through the "U" to twist the vibrating structure. Measuring the deflection as the exit twists yields the amount of mass moving through the tube. Changes in density are determined by measuring any alteration in the frequency of the Coriolis tube.

The Shrinking Meter(Back to Top)
Shinking large-volume mass Coriolis meters down to micro size was not a trivial task. Brooks says the idea came about when top Emerson management challenged the company to find new ways to grow its business. Brooks managers hit upon the idea of applying Micro Motion's Coriolis technology to its own low-flow, high-precision business.

Scott and other Brooks professionals avoid specifics when speaking about Quantim. They imply that Quantim's Coriolis unit may not have a typical "U" configuration. They suggest that vibrating the Coriolis tube reliably proved difficult. Measurements of vibration changes are apparently taken with an optical device.

The first Quantim meter/controller is rated at a nominal flow rate of 1000 g/hr and a maximum flow rate of 2000 g/hr. "Some existing Coriolis meters get down to tens of grams/hr, but they are not optimized for it," says Scott. "Our unit is only 3 in. x 5 in. x 1.5 in. The smallest competing unit is three to four times that size. As a result, the volume of the meter takes up significant amount of material."

Scott says the meter will work well at flows as low as 20 g/hr. Its stainless steel construction makes it compatible with a broad range of chemistries. In the future, the company plans to expand the product line to include exotic materials that stand up better to corrosive chemicals.

Brooks is also looking at micromachining, a technology that uses semiconductor production techniques to create ultrafine features, to produce meters cable of measuring gas flows down to 0.1 g/hr.

New Markets(Back to Top)
Scott sees several key markets for the new meter/controller. These include:

• Semiconductors. Most semiconductor manufacturers would benefit from direct mass measurement because they work with relatively small, precisely metered amounts of processing gases, high-k and low-k dielectrics, and chemical vapor deposition (CVD) precursors at a time. Scott says Brooks is already talking with Applied Materials, Novellus, Tokyo Electron about Quantim use in copper interconnect deposition and Applied Materials for TEOS.
  
• Chemicals. Quantim provides precise metering from research through scaleup to benchtop, pilot, and even production manufacturing. Brooks is talking to Xytel, Zeton, and Deposition Sciences about potential chemical uses.
  
• Pharmaceutical/Biotechnology. Pharmaceutical applications are similar to chemical uses. Biotech companies are especially interested in automating culture maintenance and growth. Camile Products (lab/pilot systems), ABEC (bioreators), and GEA-Niro (pill coating) have all expressed interest in Quantim.

"We see this as specialized, high-value product," says Scott. "This is the way Coriolis meters started in the first place, only today are they coming down in price."

Scott emphasizes that Quantim is cost-effective in many applications. A specialized weigh scale and exotic pumping system might cost $10,000-15,000, he says. A single thermal meter, without controller or valve, can go for $1,500-2,000. Syringe pumps used in biotech often cost $5,000-10,000 or more. "Quantim is a meter, controller, and valve for $7500," he says.

For more information: Tim Scott, VP, Business Development, Brooks Instrument Div. Emerson Electric Co., 407 W. Vine St., Hatfield, PA 19440. Tel: 215-362-3713. Fax: 215-362-3745.

By Alan S. Brown

Source: Chemical Online, sister website to Medical Design Online.