Coriolis Flow Meters

Machines for mixing and delivering two-part (or more) chemicals for paint and adhesive coatings in industrial manufacturing plants must be accurate and reliable if the quality of the final product is to be maintained. High performance pumps are used to combine various chemicals in a predetermined mix ratio that are then delivered directly to the production line. Any unintended or unnoticed change in the proportioning of these chemicals being mixed can have a large impact and be very expensive in terms of rejected or off-spec product that often cannot be reworked.

Manufacturing plants have limited space, resulting in the installation of gear meters with small footprints which quickly lose accuracy due to wear and tear.

Painting machine equipped with Coriolis flow meter — Painting machine equipped with compact Rheonik Coriolis flow meter system.

While metering pumps are generally very reliable—and their throughput is well correlated to their speed of operation—it is common practice to fit a flow meter in line with them to provide flow rate feedback. This is done to confirm that the desired amount of material is delivered, as over time pumps will wear and their delivery versus speed will change slightly. The flow meter also provides an independent indication should there be an issue, such as blockage or leakage, in the flow line.

In any manufacturing facility, factory floor real estate must be maximized in terms of the final product(s) output potential. To meet this goal, machinery is designed to be compact, and paint and adhesive preparation machines are no exception. Often purchased in skid form from specialist suppliers, a great deal of piping and components are crammed into a small space and when it comes to flow meters, those that are small, handle high viscosity liquids and do not require long upstream/downstream straight runs are greatly preferred. Gear meters have been the meter of choice for many of these machines in part because of their ability to handle high pressures, but also because they meet these requirements while having reasonable accuracy. The downside of using gear meters is that they are mechanical devices and as such, are affected by the same issues as metering pumps. Blockage, leakage and mechanical wear will, over time, cause measurement drift.

Gear meters give good performance when new, but they must be maintained if they are to continue to provide that same performance over long periods.

Unfortunately, maintenance is typically reactive rather than proactive and only happens after a problem has occurred. When problems occur with a gear meter, the most likely cause is debris or foreign particles in the process line. Foreign particles become enmeshed in meters’ tight tolerance gears, causing wear and increasing resistance to flow.

Large pieces of debris can cause the meter to seize and stop working altogether. Foreign material can be introduced into a meter in a variety of ways: a quality issue from the fluid supplier, an upstream component—such as another pump—failing, or as a result of an unrelated repair task in upstream piping. Whatever the source of the foreign material, whenever such a problem occurs, the meter must be disassembled, and its internals inspected for damage.

Should “chips and dings” or score marks in the gearing be observed, then the rotors must be replaced to ensure integrity and accuracy. Also important is to ensure that the measuring chamber walls have not been damaged as this may further contribute to operation issues. In almost all instances, damage to the measuring chamber will require replacement of the flow meter. While the meter is being repaired, the production line is down.

Even when gear meters are not exposed to foreign material, over time, bearings can fail and rotors potentially crack. Unless the failure is catastrophic, the only indicator of a problem would be a change in tone or an increase in noise level when the meter is operating.

Compact Coriolis meters are a superior modern alternative to gear meters in applications where space is at a premium.

Like gear meters, Coriolis meters require no upstream/downstream straight pipe run, but have the distinct advantage of having no moving mechanical parts and being immune to the effects of foreign material passing through them. Furthermore, the availability of advanced diagnostic information from Coriolis meters allows maintenance to be proactive. Diagnostic messages can alert users to deteriorating performance in the process before failure actually occurs.

But the adoption of Coriolis meters by fluid handling and mixing equipment manufacturers has been limited, in part, by their pressure handling capabilities and perceptions that they are high cost.

Newer Coriolis models, like the Rheonik L series sensors feature high pressure (up to 20,000psi) and high temperature (up to 350°C) variants, greatly increasing the applicability of the technology in industrial applications. Machine and skid builders can use these high-performance, low-maintenance units with their multi-functional performance to enhance value to their customers. For corrosive material measurement applications, Rheonik Coriolis meters can be configured with a wide variety of exotic wetted materials more cost effectively than gear meters, and Coriolis meters have the distinct advantage of being able to measure both viscous and non-viscous materials to the same accuracy.

With the availability of smaller, more compact Coriolis flow meter bodies and small remote electronic units suitable for DIN rail mounting, the advantages of using Coriolis meters as an embedded component in paint and adhesive mixing equipment can be easily realized. Coriolis meters provide increased value to produced goods through increased quality and consistency while saving cost through higher machinery uptime and lower maintenance requirements while their incredibly small footprint allows for even more compact process skids, maximizing the use of available factory floor space.

Bitumen is one of the heaviest and most viscous products produced in refineries. It is created from “vacuum bottoms,” the asphalt-like residue extracted from the bottom of vacuum distillation columns.

Bitumen is a long chain hydrocarbon molecule and appears to be solid at ambient temperatures. However, bitumen is really a highly viscous liquid and does “flow,” though only very slowly. Heating bitumen causes it to soften and eventually become a runny liquid at high temperature. This property of bitumen, near solid at ambient temperature, but liquid at higher temperature, together with its adhesive and waterproofing qualities, is the reason why bitumen is so useful in construction. Most bituminous coated materials are workable when mixed and applied hot, but on cooling become solid. While bitumen is best known for its extensive use as a binding agent in road asphalt, it is also used in the roofing and carpet industries, as well as for making sheets of corrugated papier-mâché water repellant. Many of its uses require unique hardness properties, so there are many different grades of bitumen produced. Different grades are made at refineries by blowing oxygen through bitumen to make it harder when cold.

The measurement of bitumen flow is notoriously difficult because of high process temperatures and viscosity conditions. Conventional meters are challenged with this measurement and failure is a common problem. Rheonik ET and HT Coriolis mass flow meters are ideally suited for the task:

High temperature ratings to 350°C/662°F
No moving parts to wear
Built-in trace heating jacket options
High intrinsic accuracy and measurement stability, even at larger sizes

Steam purging for cleaning purposes will not damage meter internals, nor will over-temperature conditions. Wildly changing fluid properties caused by small variances in temperature are automatically compensated for. The use of Rheonik Coriolis mass flow meters significantly increases measurement reliability while dramatically reducing the maintenance costs often associated with other meter technologies, such as differential pressure devices and mechanical meters. Product quality and consistency are consequently improved, leading to less waste and rework, and greater plant productivity.

Rheonik meters can be used throughout bitumen process operations for a wide variety of applications:

General process metering
Batching
Blending
Coating
Packaging
Truck and railcar loading.

All Rheonik meters are suitable for hazardous area installation and operation and are simple to implement and use.

In offshore oil and gas fields, deep water developments are producing high-pressure, high-temperature (HPHT) wells with standard operating conditions that are pushing 20,000 psi (1,378 bar) and 360°F (182°C). In addition, subsea systems are creating exceptionally long pipe runs from wells to gathering points. Some well heads can be as much as 60 miles (100 km) from the platform. High-pressure operation is essential to overcome friction losses within the pipelines.

HPHT wells require the continuous injection of chemicals to avoid production interruptions, but these chemicals are extremely costly.

HPHT wells, like their lower pressure counterparts, are highly susceptible to a wide variety of conditions that can affect production rates and equipment reliability. Such wells require the continuous injection of chemicals to prevent conditions such as hydrate formation, asphaltene/wax buildup, line corrosion, and scaling. Left unchecked, failures will occur, and these can be expensive in terms of both repair/resolution and lost production.

Chemical injection systems (skids) are commonly installed in production facilities in the oil and gas industry. They are used to deliver a customized cocktail of chemicals to prevent and mitigate a wide range of downhole problems that can negatively affect production flow from wells. Production chemicals are expensive and can account for up to 30% of the day-to-day running cost of a production platform. Metering is a vital component of chemical injection systems as it is important to monitor and deliver the right dosage at the lowest possible cost.

Metering for offshore chemical injection systems has traditionally been provided by mechanical gear meters because of high-pressure rating requirements. However, the tight mechanical tolerances within gear meters cause seizure when particulates are present in the flowing chemical stream, making them a highly maintenance-intensive item. Furthermore, internal wear over time creates measurement inaccuracy, even more so with low-viscosity materials, as they will easily pass through the meter where it is worn and not be properly registered.

Given the high cost of chemical usage, there are great advantages to be found with chemical injection system metering solutions that are low maintenance and have no moving parts to wear.

Rheonik meters are ideal for chemical injection applications and are trusted in high-pressure installations around the world.

Rheonik Coriolis mass flow meters offer the right balance between capital investment (CAPEX) and operating costs (OPEX). Key features of Rheonik flow meters include:

The only flow meters with pressure ratings up to 20,000 psi (1,378 bar)
Low flow capabilities down to 0.0004 lbs/min (2 g/min) with exceptional accuracy
Corrosion-resistant wetted material options (316L, SuperDuplex, Hastelloy)
Wide variety of process connections (including autoclave MP and hubs)
Resilient to pump pulsations
Low maintenance due to having no moving parts
Useable in hazardous areas
Supplied with build-in detailed diagnostic capabilities
Cost effective and space efficient

Rheonik meters can currently be found in such subsea applications as:

Production Chemical Injection

Using Rheonik Coriolis flow meters in high pressure production chemical injection systems helps guarantee flow assurance requirements are met in pipeline and process equipment, optimizing processes in production operations. Chemical injection systems deliver flow assurance chemicals into production wells to prevent wax, asphaltene and scale buildup, and to improve flow of oil from the well. In addition to flow assurance, production injection systems also deliver chemicals used to protect and prolong the lifetime of pipelines and associated equipment by reducing and removing undesirable substances that can create failure modes.

Rheonik flow meters are fitted to accurately measure the dosage rates of chemicals such as corrosion inhibitors, biocides, demulsifiers, drag reducing agents, and foam inhibitors.

Produced Water Treatment Chemical Injection

When extracted from the ground, crude oil and natural gas are accompanied by water. The water/oil and water/gas ratio seen from wells gradually increases over the life of the well. The implementation of modern secondary and tertiary recovery processes has also increased water content in recovered fluids.

Chemical injection systems provide a convenient solution for adding chemicals like biocides, antifoam agents, deoilers, demulsifiers, nitrate inhibitors, and (sodium) hypochlorites to treat produced water prior to reinjection into a reservoir. Rheonik flow meters are used in those systems to accurately monitor chemical addition rates on the high-pressure side of the injection pumps, saving wear and tear on what can be expensive and critical components in the system.

Hydrate Control

Gas hydrates are crystalline structures that can form during natural gas extraction. Hydrates attach to the internal surfaces of pipelines and inline equipment, reducing (and eventually blocking) the effective cross-sectional area in flow lines and gas handling equipment. Typical chemicals used to control hydrate formation are methanol, MEG and LDHI / KHI. High-pressure Rheonik meters are available to measure hydrate inhibitors from drip feed rates to full flow rates in 2” lines.

Contact South Fork Instruments today to learn how Rheonik’s high-pressure Coriolis flow meters can drastically reduce your HPHT well operating costs.

Most types of flow meters, especially mechanical types that rely on rotating gears, tend to lose accuracy over time. However, Coriolis flow meters deliver extremely accurate measurements for years or even decades of continuous usage, as they don’t rely on mechanical parts. But even this technology can in some cases produce noisy measurements due to vibration. This presents concerns, as vibration is common within the industrial and commercial environments where Coriolis flow meters are found.

Below is a brief overview of contexts where accurate operation of a mass flow meter can be impacted by vibration, and how to remedy the issue.

Problems arise when the frequency of process vibrations match the resonant frequency of the Coriolis flow meter—a rare issue, as their resonant frequency changes continuously.

Most objects have a resonant frequency, also known as a natural frequency, which is determined by an object’s mass, size, shape, and other variables. When an object is exposed to a vibration at or close to its resonant frequency, it will store that physical energy and then release it against in the form of a vibration at its resonant frequency. This phenomenon is seen in the well-known ‘singing wine glass’ party trick. It often happens by accident, such as when a passing car causes a table to vibrate.

While any meter or other piece of hardware has a resonant frequency, this poses a special problem for Coriolis flow meters. These devices rely on vibration to measure mass flow, by measuring the amount of deflection in two vibrating tubes as the measured liquid or gas flows through them. If an outside vibration were to match the natural frequency of the meter, it would vibrate in turn, affecting the accuracy of the mass flow measurement.

Most flow meters take steps to account for outside interference. Rheonik and some other manufacturers incorporate a mass bar (or “mass block”) and torsion rod into their measuring mechanisms. The mass bar is used to increase the mass of the two tubes, while the torsion bars impart constant momentum on the tubes, back and forth. Increased mass and movement mean the tubes have greater inertia, and are less affected by outside vibration. (Consider how a daily peeking out of your lawn may tremble when a motorcycle drives by, while the tree next to it doesn’t show any visible movement.)

But increasing the inertia of a flow meter’s mechanism isn’t the only means of resistance it has.

The resonant frequency of a Coriolis flow meter is a product of its size and the scale of the mass flow being measured, and thus is always changing.

Larger meters designed to measure larger mass flows utilize lower frequencies, while small meters that measure very small mass flows utilize higher frequencies. Typical operational frequencies for long-path, bent-tube Coriolis flow meters, such as those made by Rheonik, utilize frequencies ranging from 300 Hz in the smallest meters to 80 Hz in the largest.

Short-path bent-tube and straight-tube meters made by other manufacturers typically use much higher frequencies, as they must generate greater sideways velocity to produce tube deflections of a magnitude great enough to measure. With higher frequency of operation, they also take more measurements per second—needed to ‘massage’ the measurement electronically due to greater inherent mechanical instability, which is why Rheonik opted for a long-path, bent-tube design. The documentation for your Coriolis flow meter will indicate the frequency used for generating measurements.

The mass of your Coriolis flow meter, plus the operating frequency used to generate tube deflection and derive measurement, plus the mass, temperature, and density of the fluid being measured all contribute to the resonant frequency of a Coriolis flow meter in a given moment. This means that the resonant frequency of a Coriolis flow meter constantly changes while in operation.

A key symptom of vibrational interference is that process outputs will change unexpectedly, or the meter itself will go into a fault state.

Thankfully, vibrational interference is rare nowadays, but it does still happen. When an external vibration causes a Coriolis flow meter to generate inaccurate measurements, the result is typically obvious changes in the output being generated. For instance, if you utilize a Coriolis flow meter to regulate the addition of hardener into a resin mix, discovering that the resin isn’t setting as expected can mean that the flow meter is registering inaccurate measurements, and thus over- or under-dosing.

However, rather than causing a meter to work inaccurately, vibrational interference will often simply cause a Coriolis flow meter to enter a fault state. This is because mass flow meters require a control feedback loop in order to establish and maintain the resonant frequency of the tubes at the heart of the meter. They constantly measure the frequency and amplitude of the tubes’ vibrations in order to know how much additional power is needed to maintain consistent oscillations in the range necessary to produce accurate measurements. Should the fluid passing through the tubes suddenly increase or decrease in density, the meter must compensate so that the oscillation of the tubes doesn’t correspondingly decrease or increase in frequency.

When vibrational interference occurs, it is rare that the effect will be so subtle as to generate a seemingly normal measurement. More often than not the result is that signals from the mechanism will be so outside the norm that the meter’s electronics can’t understand what’s going on, and will instead throw up a fault.

This is a good thing. Your meter will not be merrily generating inaccurate measurements until you discover the issue via your process output. It’s the equivalent of your car’s ‘check engine’ light coming on and calling your attention to the issue.

One of the most common causes of vibrational interference of a Coriolis flow meter is placing two flow meters in proximity to one another.

If two of the same model of Coriolis flow meter are installed in close proximity to one another, and they are measuring the same process fluid, then interference will likely arise. This is because two identical meters will have the same resonant frequency. The consequence is that they will each generate external vibrations that match the frequency of the other meter, superimposing in each mechanism and causing instability and interference. This phenomenon is known as “crosstalk.” Given the general rarity of interference, and the existence of the above phenomenon, our first suspicion whenever interference occurs is that two or more Coriolis flow meters are being operated in close proximity.

Usually, the only solution is to redesign the installation so that the two meters are not placed close to one another. But Rheonik is one of the few manufacturers that allows the measuring mechanisms in meters of the same model to be tuned to different frequencies, so that they can coexist near one another.

If the source of interference cannot be narrowed down to a nearby flow meter or other obvious source, selecting a more robust meter may be necessary.

Sometimes, an environment is so literally and figuratively noisy that isolating the source of interference is extremely difficult. Vibrations can be conducted through the air from nearby sources (hence the “crosstalk” between proximate meters), or across hundreds of feet through mechanical systems, pipes, floors, etc.

Some manufacturers advise getting a better sense of what’s going on by examining the raw, unfiltered signal produced by the meter. But it’s rare that scrutinizing this data yields a meaningful diagnosis of the issue. This is especially the case in most applications, since personnel are often not equipped to make such diagnoses, nor do they desire to do so.

More delicate Coriolis flow meter simply cannot be expected to deliver accurate measurements in those rare environments that generate problematic vibrations. This is why we work exclusively with Rheonik meters, which rely on mechanical solutions to mitigate outside interference, rather than the high degree of electronic signal filtering that many other measurement solutions rely on.

But what many end users find even more useful is that Rheonik meters feature internal diagnostic capabilities. They can indicate the degree of reliability of the measurements being generated, and show if operating conditions are out of range. For example, their meters have an option to change the backlight of the display to indicate the “Assurance Factor” of the measurement:

White for normal operation
Amber when measurements may be compromised by the presence of noise or changing conditions
Blue when a sensor is experiencing disturbance and measurements are definitely compromised
Red when disturbance is so severe that the meter has entered a fault state.

Selecting a Coriolis flow meter robust enough to stand up to your operational environment is the best means of mitigating noise and vibration, and ensuring accurate measurements in the long-term.

Chances are you’ve heard the expression, “It ran like a well-oiled machine.” There’s a reason why this figure of speech is so often used. Simply put, proper oil flow is essential to making heavy machinery and equipment run the way it is supposed to.

This is why successful plant managers know how important it is to maintain consistent flow measurement. Monitoring oil flow ensures that oil is where it needs to be, when it needs to be there.

Let’s look at 5 tips that can help you make sure you are measuring your flow accurately.

Understand the basic equations

Of course, there is plenty of equipment that will automatically calculate flow measurement. Even so, it is good to have a basic grasp of the calculations behind the measurement.

When calculating volumetric flow in a pipe, the basic equation is Q = V * A where Q stands for the volumetric flow rate of the liquid, V is the velocity of the fluid and A is the cross-sectional area of the pipe. Simply put, volumetric flow is calculated by multiplying the speed of the liquid by the area of the hole the liquid is flowing through.

Mass flow is a little more involved as density must be taken into account. The basic equation for mass flow is M = Q x D, where D is density. The volumetric flow is multiplied by the fluid density to provide a weight or mass of fluid passing through the pipe.

Know what resources are available to you

That said, there’s no need to despair if mathematics wasn’t your best class at school. With the help of online calculators, you can easily determine flow measurement just by filling in certain parameters.

Use a flow meter

While it is important to understand the math behind the measurements, most flow measurements are generated by a flow meter. Flow meters are a great investment for any industrial manufacturing or production plant. They provide consistent and accurate measurements with easy-to-read displays.

Volumetric flow meters are perfect for fluids where the volume matters. For flow measurements where mass is important (most gas measurements are made using mass because of varying pressure conditions and liquid sold by weight has to be measured in mass), Coriolis meters really shine. Coriolis meters can measure both volume and mass, and to very high precision. At Rheonik, our Coriolis meters come in sizes ranging from 1/4″ to 12″. No matter what the needs of your machinery are, we have a meter that can fit them.

Make sure your flow measurement meter is properly calibrated

That said, while flow meters are great tools, they must be correctly set up and maintained. If the flow meter is not properly calibrated, it won’t provide accurate readings.

To ensure accuracy, make sure to run periodic tests and check diagnostics often so that you know your meters are functioning properly.

Ensure your flow meter is installed properly

Even with proper calibration, flow meters can perform poorly when they are not properly installed. Following a few basic guidelines can ensure the best performance out of your flow meter. Make sure it’s installed in a place where it will always be full of liquid (or empty of liquid in gas applications). Gas or vapor in a liquid flow meter (and vice versa) can affect the meter’s ability to make accurate calculations. Don’t install a meter close to elbows or other flow disturbing features in the piping. If the meter is too close to these irregularities, it may not be able to calculate flow properly. For nearly all volumetric meters, it’s best that the meter is installed at a location where there is sufficient straight piping on either side of the meter. Coriolis meters are more forgiving and in many cases can be installed without straight piping runs – a real advantage in tight places.

Coriolis meters are becoming more and more common in many process control schemes, often because of their inherent accuracy and their low maintenance requirements. However, responsible plant maintenance managers know that despite the trouble free performance they get from their meters, it is important to check calibration just to make sure. In a nutshell, simple routine maintenance and testing are non-negotiable. Ignoring these needs can lead to instrument failure; plant downtime, quality issues, even situations dangerous to personnel.

We’re breaking down what tests to regularly perform to verify the calibration of your Coriolis flow meter.

In Situ Testing

Coriolis flow meters have come a long way since their inception, and today many offer some form of in-situ testing opportunity. This kind of testing relies on built-in diagnostic tools that allows end users to conduct a quick review to verify instrument health and functionality. The benefits here are twofold. First, this testing is user-friendly, meaning any user/operator can run these tests without help from an outside party. Secondly, this type of check [often] doesn’t require process interruption while it is being carried out.

In-situ testing tries to compare an earlier version of a meter’s diagnostic values to current values at the time of the test. Repetition of these values provides confidence that the meter is operating as expected and that there is no reason to believe that the meter is operating at anything other than optimal.

Changes in the diagnostic values can indicate a change in the meter condition – maybe the meter internals are dirty and coated, or some abrasion/corrosion of the internal parts has occurred. Changes in diagnostic values might be interpreted to suggest general maintenance is needed, recalibration is necessary, or maybe there is an issue with the unit itself. Whatever the cause of the change, it’s clear that the meter may not be working at peak performance and may be adding cost to production of your product. It might also be a potential safety issue. Diagnostic values and their interpretation varies by manufacturer but there are several common values such as drive gain, frequency and stability.

Vendor Testing of Your Coriolis Flow Meters

In situ testing can often only identify that there is a potential problem with the meter. That is, you’ll know that your reading may not be accurate, but you won’t have the power to correct the issue right there and then. This is particularly true where process material can corrode the inside of your Coriolis flow meters, and this can be the cause of an abnormal reading despite the presence of correct, known calibration settings. Vendor testing allows an independent party (your device manufacturer) to fully test your meter and recalibrate to factory standards. This will require removing your meter from line and shipping it to the test laboratory, so make sure to plan this type of maintenance ahead of time. Vendors should perform a density test and calibration, full pressure testing (critical where corrosion may be an issue), full electronic checkout and live calibration in a certified flow loop. The vendor may also perform other proprietary tests as needed. This full testing suite should also satisfy compliance concerns for those industries that have an oversight body and regulatory standards. Anytime you are unable to validate performance based on your in situ diagnostics review, you should suspect something is amiss with your Coriolis flow meter and schedule other maintenance or outside testing.

In Conclusion

Running regular tests on your Coriolis flow meters is essential to maintaining an efficient, safe and highly functioning operation. Proper testing starts with the operator or maintenance manager, and extends into third party testing if required. Don’t become complacent. Your flow meters have sensitive components that won’t guarantee accuracy after normal wear and tear. Stay diligent about monitoring your components and you will have no issues verifying the calibration of your Coriolis flow meters. Prevention is a best value case for any processing plant environment.