When measuring vibrations in heavy industry, the Coriolis mass flow meter is one of the most accurate instruments available. A Coriolis mass flow meter benefits over other measuring devices, such as measuring minimal flow changes and high resolution. However, every measuring principle has challenges, as does the Coriolis principle.
The main challenge when using a Coriolis instrument in low-flow applications is that it can be difficult to deal with vibrations. This can be incredibly challenging when working in heavy industry with many vibrations, such as those caused by machinery or people walking around inside your facility.
THE CORIOLIS PRINCIPLE
If you’re in the industry and need to keep track of the flow of your products and materials, then Coriolis mass flow meters are what you need. The Coriolis principle is crucial because it prevents errors caused by the physical properties of the fluid. This is a massive advantage over other measuring devices, which can measure mass but not directly. Coriolis instruments are accurate, have high repeatability, have no moving mechanical parts, have high dynamic range, etc.
DOES VIBRATION AFFECT THE MEASUREMENT ACCURACY OF A CORIOLIS MASS FLOW METER?
Vibrations can affect the accuracy of a Coriolis mass flow meter. The sensor tube that measures the mass flow is a vibrating element, and when it is vibrating in phase with the fluid, it produces accurate measurements. However, its output will be inaccurate when the sensor tube vibrates out of step with the fluid.
Vibrations can be caused by external forces such as changes in wind speed or direction, changes in temperature or pressure, or even shaking from nearby machinery. This type of vibration can be minimized by using a proper design for your Coriolis mass flow meter and ensuring that you have built-in safeguards to prevent unwanted vibrations from affecting your data. Manufacturers of Coriolis flow meters do their best to reduce the influence of vibrations on the measured value by use of standard technical solutions, such as using:
- Higher driving frequencies.
- Dual sensor tubes.
- Different sensor shapes.
- Mass inertia.
- Passive and active vibration compensation.
Yes, vibration can affect the measurement accuracy of the Coriolis flow meter, but only if the vibration has a frequency close to the resonant frequency. Unfortunately, that is not always easy to determine from the data. First, you need to know what kind of vibration it is and how fast it moves.
Vibration can be defined as the frequency of oscillation of a system or a periodic variation in force or displacement over time. Vibration can be generated by any force, such as wind, gravity, and pneumatic pressure. However, the most common vibration is caused by mechanical forces acting on objects like trucks, trains, and machines.
 THREE MAIN TYPES OF VIBRATIONS
ENVIRONMENTAL VIBRATIONS
Environmentally related vibration sources include truck transportation, rail transportation, and industry activities. They can be generated by moving these vehicles or equipment through an area, causing them to vibrate against their surroundings in a predictable pattern. The most common environmental vibration sources are trucking companies and freight trains.
BUILDING BASED VIBRATIONS
Building-based vibration sources include mechanical installations like air conditioning units and electrical installations like motors. These systems are often installed in large buildings with multiple floors and ceilings that interact at various frequencies, creating noise levels that vary from location to location depending on how they interact with each other and their surroundings.
USAGE-BASED VIBRATIONS
Usage-based vibrations: these are caused by equipment and machines used within a facility, typically pumps, conveyor belts, or similar machinery. Vibrations are a problem in Coriolis flow meters that can cause incorrect measurements. These vibrations travel through a medium like a floor, in the air, pipes, or the fluid itself. Therefore, the measured flow could be somewhat incorrect if these vibrations disturb the Coriolis frequency.
It is helpful to identify these sources to minimize the effects of vibration. It is sometimes possible to move the flow meter slightly and rotate it (Coriolis flow counters are in most cases less susceptible to vibration if the counter is rotated 90 degrees), use of a more significant mass block, use flexible tubes or U-bend metal tubes or use suspension alternatives.
HOW TO CHECK THE PERFORMANCE OF A CORIOLIS FLOW METER?
The performance of a Coriolis flow meter can be tested by using a measuring system with a high-precision measurement capability and a developed controller. If your application requires heavy industrial vibrations, you should test the flow meter before using it in your process. Be careful when filtering the measurement signal. In some cases, this makes sense (when a quick response isn’t required), but if you want to test the performance of a flow meter, filtering could blur your judgment. If your Coriolis flow meter is not performing as expected, you may see a shift in the process output. For example, an application of dosing color to a detergent can result in differences in product color by incorrect dosing and unexpected measuring signal behavior. In these cases, checking the raw measuring signal (without filters!) makes sense because it will give you a good insight into the flow meter’s performance. Then, ask your flow meter manufacturer to switch off all signal filtering.
STANDARDS REGARDING VIBRATIONS
Two standards are helpful concerning vibrations: IEC60068-2, Environmental testing for electronic equipment regarding safety, and MIL-STD 810, Environmental engineering considerations regarding shock, transport, and use.
- IEC60068-2 is mainly focused on electronics manufacturers and their products. It defines environmental conditions under which electronic equipment shall be tested. The primary focus is on shock and vibration testing; however, it also covers temperature and humidity testing.
- MIL-STD 810 is a standard written by the U.S. Department of Defense (DoD) that defines environmental conditions under which military equipment shall be tested. It also covers temperature and humidity testing; however, it does not mention vibration testing specifically. As a user of Coriolis flow meters, it is crucial to understand your application and how it might be affected by external vibration sources.
With in-house test facilities, BCST can conduct special vibration tests on Coriolis flow meters to ensure they meet your specific needs. And with the experience, knowledge, and expertise gained from working with our customers to develop custom solutions for their needs, we constantly strive to improve our products to provide you with the best performance possible.