Valves / Flow

Flow technologies team up to offer users better measurements

Several distinct flow control technologies are coordinating efforts to give users more complete and accurate measurements in challenging phases and flow conditions

By Jim Montague, executive editor, Control

Similar to the onrushing and shape-shifting liquids and gases they manage, flow control technologies may appear static, even though economic forces are churning them and many innovations are precipitating below the surface. One of the most notable recent trends in flow is that, besides perfecting their individual technologies, several established flow methods are combining efforts more closely to take up the slack for each other, fill in gaps in each other's capabilities, and present more comprehensive and accurate information, even for phases and flows that were previously too difficult to measure.

"We're in the narrower gas flow and air/gas measurement segment, but the forces driving flowmeter technologies continue to escalate," says Randy Brown, marketing manager, Fluid Components International (FCI). "In our case, U.S. Environmental Protection Agency rules on pollution, CO2 and greenhouse gases keep the bar up, and require measurements that weren't done before, so we're improving accuracy and building in recording devices.

"Also, because regulations demand more pervasive sensing, we developed in-situ calibration verification, so users will know their flowmeter is within specification without having to pull it out and test it in a lab. As a result, FCI's ST100 multivariable flowmeters have VeriCal, which is the only wet, in-situ calibration verification for thermal dispersion flow measurement. It uses a retractable process connection, which pulls up from the sensor in the pipe into a ball valve area."

Multi-pronged fluid strategies

Similarly, mass balance is equally crucial for complex processes in reactors and distillation columns, but achieving it requires accurate and reliable flow measurement. Unfortunately, Carom in Onesti, Romania, reports the differential pressure (DP) flowmeters in its methyl tertiary butyl ether (MTBE) plant previously required frequent maintenance because process fluids sometimes polymerized inside the meter, clogging impulse lines and leading to bad measurements (Figure 1).

Consequently, Carom implemented Micro Motion Coriolis flowmeters from Emerson Process Management, which enabled the MTBE plant to achieve required mass balance, reduce product loss by 150 metric tons per month, increase overall plant efficiency by 2%, and save €700,000 per year. Also, because Micro Motion flowmeters have no moving parts, maintenance costs were reduced. Carom adds that the Coriolis flowmeters worked so well, it also installed them on its diesel truck-loading system, cutting its loading time by more than half and saving more than 300 labor hours and €90,000 per year.

In addition, Carom formerly used three orifice flowmeters on impulse lines to measure the flow of superheated steam from nine boilers to the plant's production units, but the lines had chronic leaks, and required about 300 hours of maintenance per year. They also lost up to two tonnes of steam per hour, which meant more fuel was needed to meet production demands. In this case, Carom picked Emerson's vortex flowmeters.

"Following the installation of Rosemount 8800D Vortex flowmeters with integral temperature sensors for each line, improvements were immediately evident," says Marian Stancu, chief energy engineer at Carom Onesti. "Maintenance requirements were reduced to almost nothing, and because steam loss was eliminated, boiler efficiency improved by 3%, saving more than €200,000 per year in fuel. This meant our initial investment was recovered in just 25 days of operation."

To further simplify its flow technologies and provide measurement verification in fiscal applications, Emerson is releasing on Oct. 12 its newly combined, two-in-one, redundant designs for Daniel Gas ultrasonic flowmeters. This new flow platform elevates Daniel's proven British Gas design by providing two ultrasonic meters and transmitters in a single body, and permitting two completely independent measurements with the installation of just one flowmeter. The 3415 (four-path plus one-path) and 3416 (four-path plus two-path) gas ultrasonic flowmeters combine a four-path fiscal meter with an added check meter, while the 3417 (four-path plus four-path) meter provides two fiscal meters for full redundancy and equal accuracy in one meter body. This two-in-one redundant design provides continuous online verification of custody transfer measurement integrity, device health and process conditions, and improves fiscal metering confidence, while ensuring regulatory compliance.

"The packaging of direct path measurement and reflective path technology combined in one ultrasonic flowmeter body, as is the case in the 3415 and 3416 meters, helps avoid common mode error," says Lonna Dickenson, Emerson's marketing manager for ultrasonic meters. "The primary fiscal flow measurement is performed by a four-path chordal meter, while the verification of this primary measurement is achieved by a single reflective path meter. The reflection technology sees even small amounts of liquid or contamination on the pipe wall that remain completely hidden in a direct path design. This is particularly important when metering rich, dirty or wet gas."

Dickenson adds that each measurement by 3415, 3416 or 3417 has its own independent signal processing unit. Should the fiscal meter ever fail, the check meter will provide a complete backup measurement, ensuring availability and uptime. In the past, natural gas operators needed a second flowmeter for monitoring the first one, while some didn’t even have a way to monitor the fiscal meter, and had to make field trips to get a maintenance log. Now, monitoring is inclusive and verification is simplified, detecting process upsets long before the measurement is impaired and reducing time and money spent on assets.

Ultrasonics optimize biogas

To push into new applications and remote locations, ultrasonic flowmeters are adding paths and combining previously separate support functions.

For instance, the municipal wastewater facility in Reading, Pa., is using Proline Prosonic Flow B 200 ultrasonic flowmeters and support software from Endress+Hauser to monitor gas flows, temperatures and methane fractions from its anaerobic digesters and biogas application, which must be carefully managed to produce methane, generate electricity, and reduce plant operating costs.

Reading's three 800,000-gallon digesters can handle up to 28.5 million gallons per day, but they need to maintain an optimum 95 °F for their anaerobic bacteria to efficiently generate a wet biogas flow of 3,500 standard cubic feet per hour with a 65-70% methane fraction. This gas is drawn off to fuel three 70-horsepower boilers, which provide the heat needed to keep the each digester's heat constant, even in subzero weather.

The plant can usually maintain a closed-loop to optimize digester bacteria, but chief electrical engineer John Gerberich reports this goal used to be elusive due an outdated pressure transducer monitoring biogas flow via its SCADA telemetry network, manual temperature monitoring, and time-wasting analysis of gas samples to determine methane fractions. This lack of real-time data led to operational latency and high costs, such as the methane fraction dropping below 20% and temperature falling to 80 °F.

"When these conditions occur, a digester can sour, causing the bacteria to produce higher levels of other gases that can accelerate  corrosion of all our plumbing’s metal parts—piping, controls, regulators, and so on," says Gerberich. "What’s more, if the methane fraction falls too much, we have to tap external natural gas to fuel the boilers, and that can cost us up to $16,000 a month. I really wanted a way to measure temperature and methane fraction in real time, so we could dispense with lab testing, which took us so much time."

Gerberich implemented B 200 ultrasonic flowmeters after learning they were designed for applications like real-time monitoring of wet, dirty biogas with variable composition, and low flow and pressure. This gave the operators real-time measures of biogas flow, temperature and methane fraction, which enabled them to adjust the sludge they feed the digesters more precisely without waiting for test results.

He estimates the labor savings in sampling and lab testing time at approximately $20,000 per year, and that tear-down maintenance on the boilers has been cut in half due to less corrosion and wear and tear, saving another $15,000 per year. "The biggest savings, however, come from minimizing, if not eliminating, the need for external natural gas to fuel the boilers," adds Gerberich. "Before, the plant would have to supplement its methane fuel in cold winter months at a cost averaging $37,500 a year. With total annual savings of $72,500 a year, B 200 paid for itself several times over in its first year."

Beyond incremental improvements, Jerry Stevens, senior product manager for the flow group at Endress+Hauser, sees three main trends affecting all the flow measurement methods. "The focus is on how flow and other technologies can conform to relevant safety requirements, improve their reliability and functional safety, remove hazardous detection faults, and design safety instrumented systems (SISs) that still reduce maintenance and calibration frequency," says Stevens. "The second trend is quality of measurements that can be expected from flowmeters in adverse conditions, and then designing to improve device quality and efficiency. Users need flow measurements and meters that up to the quality of their overall engineering efforts, but they also need devices that are more predictive, and allow them to react to events with predefined remedies.

"Finally, device availability is the third trend. Users want platform-agnostic components, so they can pick and choose what's best for their applications, and not be forced into drastic upgrades. They also want equipment that can interface with any field devices via remote, Ethernet and wireless protocols, as well as HMIs with local and embedded-memory displays that allow auto-configuration and hot swapping."

All along the pipeline

Farther out in the field, Honeywell Process Solutions (HPS) reports its ultrasonic flowmeters, flow computers and temperature and pressure transmitters will help improve operations on China's long-distance Guangxi liquefied natural gas (LNG) high-pressure pipeline, which is a strategic project of Sinopec Ltd. and the Guangxi Zhuang autonomous region (Figure 2). The pipeline is scheduled for completion later this year, and will have a capacity of 8 billion cubic meters of LNG per year and a total length of more than 1,300 miles from Maoming to Beihai in the Guangxi region. The pipeline will be part of a network that transports natural gas and LNG to China from as far away as Kazakhstan.

"Pipelines have challenges that are very different from processing plants because you have to manage an operation that is hundreds or sometimes thousands of miles long," says Aldous Wong, vice president at HPS for greater China. "Measurements such as flow and pressure must be accurate and immediately accessible to keep the pipeline operating efficiently."

Integrated gas technologies from HPS that will help maintain optimum performance on the long-distance Guangxi LNG include: ultrasonic flowmeters to measure natural gas for custody transfer applications; flow computers to perform parallel calculations of compressibility according to established methods, including GERG 88 S, AGA 8 and AGA NX 19; and SmartLine temperature and pressure transmitters.

Coriolis redoubles efforts

Though Coriolis flowmeters aren't the exotic novelties they were years ago, they're still finding new frontiers and applications to conquer.

To improve the accuracy of its new, automatic mixing line for manufacturing shampoo products, Unilever's plant in Gebze, Turkey, recently adopted six Micro Motion Elite and F-Series Coriolis flowmeters from Emerson Process Management to measure mass flows of its silicone feedstock, which improved product quality and reduced production time by 10-15% (Figure 3).

Though blending accuracy is crucial to final product quality, Unilever discovered that the line's original Coriolis flowmeters couldn't measure feedstock flow because of entrained gas in the silicone, and found that an early fix using weigh scales and load cells took too long and wasted raw material and energy.

Several other flowmeters were tested, but they couldn't work in the mixer's operating vacuum of -700 mbarg that helps remove the bubbles. Next, Unilever tested the Elite Coriolis flowmeters, which have low-frequency flow sensors that increase flow accuracy in the presence of two-phase flow, as well as multivariable digital (MVD) technology that improves accuracy and stability of Coriolis signals from the flow sensors. This enhanced signal processing, sensor stability and design ensures accurate measurements even under entrained gas conditions.

"Our tests found that the Micro Motion Elite Coriolis flowmeters were the only meters that can successfully measure silicone feedstock flow with high density bubbles," says Atilla Bozkaya, Unilever's project control and system design engineer. "The meters maintained measurement accuracy despite operating in the -700 mbarg vacuum needed in this application."

Unilever saved 17% on operating costs by eliminating the scales and load cells, and added 12 more Elite and F-Series Coriolis flowmeters when the Gebze plant added two more mixers.