How many tubes for a Coriolis flowmeter?

One is good, two is better, but why four?

05/12/2011

Dear Control Engineering: The recent story on large Coriolis flowmeters says the design uses four tubes. I’ve seen two-tube flowmeters, so is using more better? Will six or eight be next? It sounds like those fancy razor blades.

Understanding how Coriolis flowmeter technology works will help explain the concept, but it may not help with your shaving.

Recall if you will that Coriolis technology depends on sending your fluid through a vibrating tube. (Here’s a short tutorial as a refresher.) The mass of the flowing fluid changes the nature of the vibrations which provides data for the flow calculation. Single-tube Coriolis flowmeters have the problem that they are affected by ambient vibrations. The sensor has a hard time telling if it is seeing changes induced by the flow or it’s reading vibrations coming through the floor from that compressor down the aisle.

Adding a second tube helped designers reduce that effect by measuring the difference between the two tubes. This allows the device effectively to cancel ambient vibrations.

The move to four tubes is more complicated, so I put the question to Michael Nuber, who is E+H’s product manager for Coriolis flowmeters in Switzerland. He explains, “There are several advantages of the four tube design over conventional designs. First, it allows for better immunity towards external effects. The two-tube design is already a marked improvement, as one tube always moves in the opposite direction of the other, thus intrinsically stabilizing the measurement system. Each of the tubes is always impacted in the opposite way by external effects like pipeline vibrations.

“Having four tubes adds another dimension. Think of it this way: imagine the two tubes vibrating in one plane, for example along the x-axis. By adding two tubes for a total of four, and using what I call the ‘intelligent mechanical design,’ you also add another plane, the y-axis. That means that the whole measurement system is not only immune to external effects in one plane, but also in another plane that is angled at 90°. The x-y plane then allows for compensating virtually in any direction the external effect might come from.

“Second, having four tubes allows us better use of the circular area. In the same way that a high-performance car engine may have four valves instead of two for each cylinder, it allows us to use smaller measuring tubes. Those allow for reduced wall thicknesses, granting better density accuracy. In addition, the bending stiffness of the smaller tube is lower, either allowing for a higher sensitivity at the same overall length, or the same sensitivity while reducing the length of the sensor.”

Peter Welander, pwelander@cfemedia.com

The Top Plant program honors outstanding manufacturing facilities in North America. View the 2015 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
Doubling down on digital manufacturing; Data driving predictive maintenance; Electric motors and generators; Rewarding operational improvement
2017 Lubrication Guide; Software tools; Microgrids and energy strategies; Use robots effectively
Prescriptive maintenance; Hannover Messe 2017 recap; Reduce welding errors
The cloud, mobility, and remote operations; SCADA and contextual mobility; Custom UPS empowering a secure pipeline
Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
Mobility as the means to offshore innovation; Preventing another Deepwater Horizon; ROVs as subsea robots; SCADA and the radio spectrum
Research team developing Tesla coil designs; Implementing wireless process sensing
Commissioning electrical systems; Designing emergency and standby generator systems; Paralleling switchgear generator systems
Natural gas engines; New applications for fuel cells; Large engines become more efficient; Extending boiler life

Annual Salary Survey

Before the calendar turned, 2016 already had the makings of a pivotal year for manufacturing, and for the world.

There were the big events for the year, including the United States as Partner Country at Hannover Messe in April and the 2016 International Manufacturing Technology Show in Chicago in September. There's also the matter of the U.S. presidential elections in November, which promise to shape policy in manufacturing for years to come.

But the year started with global economic turmoil, as a slowdown in Chinese manufacturing triggered a worldwide stock hiccup that sent values plummeting. The continued plunge in world oil prices has resulted in a slowdown in exploration and, by extension, the manufacture of exploration equipment.

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
The maintenance journey has been a long, slow trek for most manufacturers and has gone from preventive maintenance to predictive maintenance.
Featured articles highlight technologies that enable the Industrial Internet of Things, IIoT-related products and strategies to get data more easily to the user.
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.
Maintenance Manager; California Oils Corp.
Associate, Electrical Engineering; Wood Harbinger
Control Systems Engineer; Robert Bosch Corp.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.