While most people associate the beginning of Coriolis flowmeters with Jim Smith and Micro Motion, there were several patents filed in the 1950s and 1960s that laid the foundation for Smith’s pioneering work. A patent filed in 1958 on behalf of American Radiator & Standard Sanitary Corp. appears to be the earliest patent that mentions the “Coriolis force.” The flowmeter is described as
“The present invention relates to instruments for measuring the mass rate of flow of fluids and to an improved flowmeter of the type in which mass flow rate is made responsive to Coriolis force … In instruments of the class described, the fluid to be measured is subjected to tangential acceleration in a whirling tube, or impeller, the torque exerted on the tube in reaction to the Coriolis force of the accelerated fluid being measured as an indication of the mass flow rate.”
In May 1960, Yao Tzu Li patented an invention called “Mass Flowmeter” that involves rotating the flow:
“The present invention operates by causing the fluid to be rotated as it flows radially outward from an axis. This produces a Coriolis acceleration in the fluid, and therefore a Coriolis force is applied by the fluid to the member through which the fluid flows. This force is measured, and the mass rate flow of the fluid is obtained.”
Interestingly, Yao Tzu Li cites Ernest F. Fisher, who filed a patent in 1917.
In August 1972, Smith patented a “Balanced Mass-Moment Balance Beam with Electrically Conductive Pivots.” The patent was filed in June 1975. Beginning in August 1978, Smith began patenting a series of devices that became the basis for the flowmeters produced by Micro Motion, which he founded in his garage in 1977. His August 1978 patent was filed in 1975. These patents explicitly evoke the Coriolis force. Smith’s patents substituted a vibrating and oscillating tube for a rotating tube, which worked better than the earlier ones and is still used today in many different forms.
Micro Motion debuted its first Coriolis flowmeter in 1977—an “A” meter for laboratory use. It was followed by the “B” meter in 1978. In 1981, Micro Motion introduced the first single-bent tube Coriolis meter, the “C “meter. Then in 1983, the company added the first dual-bent tube Coriolis meter, the “D” meter, which has a 2-inch diameter. In 1984, Emerson acquired Micro Motion.
Heinrichs Messtechnik GmbH says on its website that it is the first European company to offer Coriolis flowmeters. Heinrich’s introduced its first Coriolis meter in 1986, which was the same year that Rheonik debuted its Omega-shaped Coriolis meter. However, that was a year after Endress + Hauser released its first Coriolis meter in 1985. This meter was a dual-tube, straight-tube meter, which evolved into the Proline Promass F. Krohne Group followed up with a single-tube, straight-tube meter in 1994, following an earlier design from Schlumberger, now SLB, that was withdrawn from the market. One of the moving forces behind Krohne’s meter was Dr. Yousif Hussain, who holds several patents on Coriolis meters.
In 1984, Rheonik’s founder, Karl Küppers, began developing what was to become the company’s technology base and patent portfolio. The design that began the success of the firm was the patented Omega-shaped Coriolis flowmeter. Rheonik was founded in 1986, the same year it introduced its Coriolis meter. Continued growth caused the firm to move operations in 1993 to the current facility in Odelzhausen, Germany. In February 2008, GE Sensing and Inspection Technologies acquired Rheonik, but in 2015, Rheonik purchased the assets and business back from the GE unit.
Micro Motion introduced its Elite series of Coriolis meters in 1992. This line was designed for flow and density measurements of liquids, gases, and multiphase flow. Micro Motion still carries its Elite series meters. In 1995, the company brought out its F-Series line, which has a robust design, and is compact and drainable.
During this same period, in 1993, the company Rota in Germany introduced the Rotamass, developed in Wehr, Germany. This dual-tube flowmeter featured a heavy wall that was designed to minimize the effects of vibration or pipeline stress and to provide increased reliability and output stability. In 1995, Rota became a subsidiary of Yokogawa Europe.
Straight-tube, radial-mode gas flowmeter
Direct Measurement Corporation (DMC) was founded in 1991 by seven ex-employees of Micro Motion. The company’s focus was on Coriolis flowmeters for the oil and gas industry. In 1996, DMC was acquired by FMC Technologies, now TechnipFMC. DMC’s main product was the straight-tube, radial-mode Coriolis meter for measuring gas flow.
By 2000, FMC had three different Coriolis meters: S-Mass, Apollo A400, and the radial-mode flowmeter. Both the S-Mass and the Apollo A400 were Smith Meter brands and designed for liquid applications. The S-Mass meter derived its name from the S-shaped design of its flow tube. Available models included the S25, S50, S100, S200, and S300. The S-Mass was designed for a variety of applications including custody transfer, blending, leak detection, batch control, online density measurement and petroleum production.
The Apollo A400 was designed for use in petroleum applications. It measured mass flow at rates up to 20,000 lbs/min. The A400 was available with the HART communication protocol. Applications include loading rack terminals or bulk deliveries, transportation of crude oil and refined products, and LACT systems.
FMC had two models of the radial-mode flowmeter for measuring gas flow: the R200 and R400. The R200 was a 2-inch meter. The R400 was a larger meter with greater throughput capabilities. While FMC was still selling the meter in 2003, it was discontinued a few years later.
Since the challenges of measuring gas flow with a straight-tube meter are significant, it is worth considering the benefits of a straight-tube meter that measures gas flow. One of the benefits of a straight-tube meter is that liquid doesn’t build up at the curves. But gas does not collect at the curves. Also, bent-tube meters cause pressure drop. But gas causes minimal pressure drop, even in bent-tube meters. The benefits of using a straight-tube meter to measure gas flow are limited, although they may be better suited to hygienic and sanitary applications than bent-tube meters.
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Why the dual-tube Coriolis flowmeter was invented
Based on research into the patents underlying the flowmeters introduced in the early 2000s, there are patents by Don Cage assigned to Micro Motion, Direct Measurement Corporation, and FMC Technologies in the period from 1995 to 2004. He is the inventor of the radial straight-tube Coriolis meter from Direct Measurement Corporation, which was purchased by FMC Technologies. He continued to be active in Coriolis design for other companies after this period. Cage has truly been influential in the design and development of many Coriolis flowmeters over the past 30 years.
One of the most interesting quotes from one of Cage’s 1995 patents explains the invention of the dual-tube meter. The patent is called “Coriolis Mass Rate Flow Meter.”
“It is well known that a vibrating flow conduit carrying mass flow causes Coriolis forces which deflect the flow conduit away from its normal vibration path proportionally related to mass flow rate…
This effect was first made commercially successful by Micro Motion Inc. of Boulder Colo. Early designs employed a single vibrating U-shaped flow conduit which was cantilever mounted from a base. With nothing to counterbalance the vibration of the flow conduit, the design was sensitive to mounting conditions and so was redesigned to employ another mounted vibrating arrangement which functioned as a counterbalance for the flow conduit. Problems occurred, however, since changes in the specific gravity of the process-fluid were not matched by changes on the counterbalance, an unbalanced condition could result causing errors. Significant improvement was later made by replacing the counter-balance arrangement with another U-shaped flow conduit identical to the first and splitting the flow into parallel paths, flowing through both conduits simultaneously. This parallel path, Coriolis mass flow rate meter solves this balance problem and has thus become the premier method of mass flow measurement in industry today.”
Today, more than 40 companies manufacture Coriolis flowmeters. While there was intense development of this technology from 1977 to 2010, the development didn’t stop there. The story of the last 15 years is even more complex and fascinating than the story going from 1975 to 2010.
