Vibrational Analysis of Industrial Fans

Vibrational Analysis of Industrial Fans

Just like any other appliance, industrial machinery – especially industrial fans – need to be maintained regularly. How so? By measuring its quality and performance at all times, checking for any machinery issues and imbalances that might shorten the lifespan of your hardworking industrial fan. It’s crucial to constantly make sure that everything about your industrial fan is in peak working condition.

People usually do this by running quick maintenance tests on their machinery, keeping an eye out for issues ideally before they need heavy repair, or before any of the components are permanently broken and need replacement. Luckily, there usually is just one main test that can run a simple health check on your machine – a vibrational analysis.

But first, what is a vibrational analysis? Let’s get into its definition, its process, how it is done, and its importance in keeping industrial fans in tip-top shape.

The definition of vibrational analysis
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Vibrational analysis is exactly what its name entails – it is the action of analyzing an item’s vibrations.

Vibrations are defined as a “mechanical phenomenon” where oscillations occur in an equilibrium point. It is also “the alternating mechanical motion of an elastic system, with components of which are amplitude, frequency and phase.”

But since we’re talking about industrial fans, this pertains to the specific process of measuring the vibration levels of the machinery, as well as its frequencies. The stats learned in this in-depth analysis will help determine the overall status of the fan overall, as well as the health percentages of its vital components and how well they all still work together.

Manufacturers are on the lookout for a fan’s amplitude and frequency. Amplitude is defined by how far the rotating body moves from its center axis, while the frequency is the number of cycles that happen in any given period of time. This information is crucial in determining if something is wrong with your fan.

Since industrial fans usually have heavy-duty blades and extra-strong pumps for cooling, exhaust, and circulation functions, the vibrations emitted are strong, which make it even more important to analyze on a regular basis.

It’s important to note that there are many factors that can affect the vibrational level of an industrial fan – its wheel balance, rotational speed, motor operations, components, and even wiring.

A vibrational analysis of how strong or weak the vibrations are could easily detect early signs of machinery errors, missing or loose parts, shaky bolts, improper installation, unbalance between components, not enough lubrication, and many other issues – so it’s best to do it as soon as possible before it wrecks permanent damage onto your machinery.

Example, if a fan blade is missing within, the fan will emit strong vibrations, due to the imbalance happening inside the system of the fan. A quick check-in inside will reveal the missing fan blade. Once added, the vibrations would lessen, making for a smoother experience. Even a loose bolt or an exposed hole inside would generate a loud and strong vibration. Hence, it’s a great method for maintenance, for testing the performance and condition of an item, and for ensuring the length of its lifespan.

How a vibrational analysis is done

Vibrational analysis, a form of predictive technology, can detect unbalance in your piece of machine using an accelerometer. This accelerometer uses a voltage signal equal to the amount of vibration being emitted by the machine and its frequency. It can also find out how much time per second the vibration happens. This data is then analyzed by either a trained analyst or a computer program, which can then conclude the diagnosis of your machine.

First and foremost, you have to mount and prep your fan for vibration testing, before it gets analyzed. The fan is placed on a supported installation or flexible bed. Each one must have a natural frequency above the running speed. Then, the tri-axial accelerometer is used, both in the horizontal, axial, and vertical directions, which then measures the vibrations per direction. Two kinds of vibrations are recorded – filter-in and filter-out.

A filter-in vibration reading is detected only at one frequency (fan rpm), while the filter-out vibration measures the vibration over a wide frequency range.

Velocity and amplitude testing, as mentioned, are also sought out in vibrational analyses. A velocity measurement detects the severity of vibrations, while the amplitude reveals the

Vibration testing guidelines
Air Conditioner ventilation system on building rooftop. Aerial view to AC system on skyscraper.

The vibration testing happens when the fan is operated at the design speed, to see if the unit performs below or above the maximum vibration. For it to be of high-quality standards and ready to sell, the fan’s vibration level must be within the ideal, acceptable range. Anything above or below normal level after the analysis will be further inspected and the necessary components will be either fixed or replaced during appropriate balancing and vibration elimination processes.

The usual cause is lack of balancing, which leads to excessive vibrations. Balancing is defined by the additions or removal of mass from the fan shaft to fix the center of gravity of the fan, to its normal axis of rotation.

This is why a vibrational analysis is so important – it can easily and swiftly detect excessive vibration or peaks by figuring out the specific frequency when vibration happens. When vibration peaks suddenly during normal fan speeds, that could be a sign of unbalance in the wheel. A possible remedy could be trim balancing. It could also mean a motor pulley imbalance.

If the vibrational analysis shows two sudden spikes happening consecutively within a short period of time, that could mean a lot for the frequency of the fan – loose bolts, misalignment, poorly-placed or bent shafts. There are so many factors to consider, that is why it is highly-recommended to have a trained analyst with good after-sales services to look after your machinery. They would know that so many components make up the overall vibration level and health of an assembled fan – accessories, base, fan, motor, and many others.

After which, a thorough post-vibrational analysis report by a skilled professional will usually be presented to the client. This report usually contains a detailed series of statistics per segment, giving an accurate diagnosis on the overall condition of your fan. The report includes identification of the assets, an introduction on the state of your fan, current operational conditions, reading points, readings, analysis of said readings, an expert’s diagnosis, and recommendations.

Addressing fan vibration problems
Industrial cooling towers or air cooled chillers on building rooftop

Don’t worry if your fan is experiencing fan vibration problems – these could merely be a result of a normal build-up of material due to normal use. However, if not addressed right away, this could cause graver problems, or reveal a deeper root cause – if the structure wasn’t designed properly, or if it’s insufficient to cater to your operating needs or environment. If not diagnosed, this could lead to irreparable outcomes, or very expensive repairs.

Performing a thorough vibrational analysis is fairly simple, very useful, and also very accessible, making it a chosen go-to diagnostic method for maintenance and assurance of smooth-running machinery. It’s also very cost-effective, depending on the size of your machinery, and will save you a lot of money in the long-run. It’s a worthy, comprehensive test to have done on your machinery regularly, and a great example of engineering excellence.

Do you need industrial fans? If yes, check out our fans here. You can also contact us to receive a free consultation.

Ferrari Ventilation has been manufacturing top quality industrial fans since 1963.

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