When you think about vibration analysis, what comes to mind? It is becoming a very common identification method in structural engineering to identify issues with potential structural integrity, such as hidden objects or voids.
It is an effective way to identify problems with machinery that could cause catastrophic damage if left unchecked. It makes me wonder, what can vibration analysis detect?
Vibration analysis is a process by which data about the potential existence of hidden objects, voids or cracks in structures, or other anomalies can be derived through careful observation of vibration.
It is an effective way to identify structural problems and weaknesses in machinery that could cause catastrophic damage if unchecked. Vibration analysis can detect anomalies, potential cracks, and hidden objects. It is also an effective way to identify structural problems and weaknesses in machinery.
How vibration analysis works is by carefully observing vibration through various sensors such as accelerometers or embedded microphones. Additionally, engineers can use high-precision, high-speed, directly measured accelerometers called triaxial accelerometers.
Vibration analysis uses the frequency, amplitude, and direction of vibrations in structures or machines to find possible defects in them.
If a machine component fails at a resonance frequency of the whole structure, the whole machine will vibrate dangerously. Using vibrational signals, it is possible to locate anything hidden behind pieces of furniture or other objects that would otherwise be very difficult to get to.
Let's take a closer look.
Table of Contents
- Which Sensors are Used to Gather Vibration Data?
- Types of Vibration Equipment & Analysis Tools
- 5 Ways to Discover the Causes of Structural and Mechanical Problems with Vibration Analysis
- What Kind of Machinery Can We Use with Vibration Analysis?
- What Common Faults Can We Detect Using Vibration Analysis?
- Why Is Vibration Monitoring Important?
- Practical Applications for Vibration Analysis
- What Are Some Industrial Applications of Vibration Analysis?
- Motor And Structure Vibration Monitoring
- Vibration Analysis and Shaft Structure
- Can Vibration Analysis Predict Failures? - Predictive Maintenance
- What Are the Three Main Characteristics of Vibration?
- Vibration Signals
- What Are the Vibrations of an Aircraft?
- Charting Controls for Vibration Analysis
Which Sensors are Used to Gather Vibration Data?
There are several different sensors available to gather vibration data. Below is a list of some of the most common ones:
These types of sensors measure and output acceleration in one, two, or three directions. The most commonly used type is the triaxial accelerometer, which accelerates the x, y, and z axes simultaneously. To detect vibrations along a straight line, single-axis accelerometers can be used.
These sensors detect angular acceleration or rotational motion. Gyroscopes can detect vibration in any direction and can withstand high impacts and temperatures. For this reason, they are frequently used for structural vibration analysis.
These sensors convert energy from one form to another. A common use for transducers is noise and vibration analysis, where a sound vibration signal is converted into another format such as voltage or a digital signal.
These sensors can detect the direction of the sound with high precision and can therefore be used when determining the location of sounds in machine components. The signals they produce can be analyzed to determine whether there are any defects in the structure of a machine by comparing changes in vibrations over time with trends.
A typical vibration analysis system block diagram will include three main components: data acquisition, calculation, and interpretation.
Spectrometers are used to analyze the strength of signals such as acoustic or vibration signals over time. They can show the strength of a signal in a specific frequency over time, which can be useful in identifying the source of certain problems.
Image: When analyzing spectrogram data with cross-section charts, data are displayed as a heatmap along selected vertical and horizontal lines.
There are many different ways to acquire data for vibration analysis. The most common way is through an analog to digital converter, which converts the signal from a transducer into a digital format that can easily be saved and analyzed later for trends and other data.
Another way of acquiring data is through real-time acquisition (RTA), which uses sophisticated calculations to convert analog signals into digital ones in real-time.
Types of Vibration Equipment & Analysis Tools
Current solutions for monitoring vibration problems on-site use a combination of ultrasonic, accelerometers, and micro-electromechanical system (MEMS) based sensors. The high resolution from the sensors allows you to see the dynamic behavior of the machine and its components.
The process includes:
Various sources have investigated vibration analysis over the past few years, including sensitive computerized vibrometers, capable of detecting very small displacements with very little equipment, with display accuracy measured down to one-millionth of an inch or better. Computer 3D analysis tools have recently entered this market.
The needs of a vibration analyst have changed to reflect the growing importance of vibration analysis. The ability to accurately measure the vibration of an entire machine or part is becoming more important. Users must rapidly identify all sources of shock and resonance in a machine to locate problems and remedy them before damage occurs.
More recently, methods such as Digital Vibration Analysis (DVA) have been developed to help engineers and designers understand these sources better. These methods use computer software to make many very fast measurements, receiving results within seconds each time.
5 Ways to Discover the Causes of Structural and Mechanical Problems with Vibration Analysis
The first step is to find the problem using vibration analysis. Here are some tips for waveform and frequency analysis:
Vibration Analysis can help to discover the cause of structural problems in several ways:
1) Determine whether the problem is in material properties or assembly, and then determine if a change needs to be made to the material or if its assembly or configuration needs to be changed.
2) Find where on the structure there is high vibration energy, increasing wear, or producing fatigue damage. Such areas may also contribute to vibration issues.
3) For complex structures, it can frequently locate where resonant frequencies exist in multiple component groups that interact with each other.
4) Vibration analysis can also be useful because it can detect potential structural problems resulting from a component failure. In this way, mechanical vibration analysis can be used to discover mechanical problems that may be detrimental to safety, reliability, and functionality.
5) Vibration analysis can also reveal problems with complex mechanical assemblies – for instance, an incorrect number of connections between components or the failure of a component itself.
Vibration exposure tests (VET) are a common example that has not been listed above. VETs are often performed on bridges and should be mandatory whenever a tall structure may experience high stresses due to wind loadings (e.g., bridge design issues).
What Kind of Machinery Can We Use Vibration Analysis?
A wide range of machinery can be used for vibration analysis, including:
- Automatic machines and equipment such as pneumatic tools, hydraulic lifts, and automatic controls on industrial presses.
- Equipment used in the oil industry, such as oil drilling rigs.
- Metal castings and forgings such as large external combustion engine components or internal combustion engine cylinder heads.
- Oil drilling rigs and pipelines.
- Coating machines that coat surfaces with paint or wax after repair work so that the surface is stable.
- Machinery is used in construction for drywall fabrication or flooring installation after repairs or enables new products to be produced.
What Common Faults Can We Detect with Vibration Analysis?
All of the following faults can be found using vibration analysis:
- Defective bearings or gears
- Unbalanced rotating machines or masses to which the bearing is attached
- Loose bolts, nuts, and other parts
- Cracks and fractures in metal castings and forgings or faulty welds on metal joints or bolted assemblies.
If a machine component fails at a resonance frequency of the whole structure, the whole machine will vibrate dangerously. Depending on the industry using the machinery, it can have varying implications and use cases.
Why Is Vibration Monitoring Important?
Today, the use of sound vibration technology is interpreted in many different ways. However, everyone agrees that it can be a valuable tool for communication and analysis. Even more importantly, it can help save money and help prevent damage to machinery or structures.
Vibration monitors are extremely important because they allow us to hear all possible sources of noise that could have hidden issues within them. They allow us to discover unusual sounds such as hollow notes or ticking clocks, indicating a serious structural integrity issue within the machine or structure itself.
Vibration monitors can also monitor other machines and environments that could pose a risk to life and property if not checked regularly. There are several different types of monitors that can be used for different purposes, including the following:
- Duty Cycle Monitors are commonly used to monitor high energy consumption equipment such as a conveyor belt.
- Motion Monitors allow users to evaluate sharp movements, which could lead to damage.
- Vibration Monitors can also detect and record noise within a machine or structure.
Practical Applications for Vibration Analysis
Vibration analysis is used in many different projects and applications to identify issues with potential structural integrity. Some of the most common types of projects are:
Researching practices involving vibrations that are new or untested, such as recycled plastic in oil drilling, prevent oil spills.
Finding structural issues with machinery, such as the ability of an excavator to handle a heavy load.
Identifying structural issues with buildings such as a building on the verge of collapse.
Checking for potential weaknesses with shipping containers and bridges, which could cause catastrophic damage if unchecked.
Some examples of vibration analysis applications:
- Detection and analysis of defects within the bearings used in construction machinery such as trucks, cranes, and bulldozers.
- Detecting problems with rotating equipment such as generators due to unbalanced rotating masses in which they are installed.
- Identifying areas where maintenance must be performed on systems that use vibration, such as trolley systems or service lifts.
Small Tools Used For Vibration Analysis Include:
- Microphones – these are small devices that pick up vibrations and convert them into sound. They can be handheld or mounted on the end of a boom. The use of these is not limited to vibration analysis; they can be used for monitoring.
- Portable Vibrometer – this device is similar to a seismograph which measures earthquake waves in an environment to determine the source of the disturbance and any potential damage that could occur if unchecked.
- Acoustic Autopilot – this device allows people to record sound using its onboard microphone for hearing what goes on underneath them or within their machines.
- Automated Acoustic Monitoring – a computerized system that uses vibration analysis methods to monitor and detect changes in surroundings. It could lead to problems such as structural integrity issues. At the same time, it stores the data for later retrieval and review.
- Noise Meter – Like a portable Vibrometer, this device measures sound levels in areas where noise is produced. It can be used both indoors and outdoors.
- Seismograph – a seismograph is used to record earthquake activity worldwide to determine its source and potential damage if not checked.
Image: Understanding vibration analysis can change a run to failure system to a condition-based, proactive maintenance program.
What Are Some Industrial Applications of Vibration Analysis?
In oil and gas extraction, vibration analysis accurately determines the ground conditions at a well site. Firstly, this will determine if the well that is being drilled is in a rock formation with large amounts of elastic energy. This energy typically means that oil and gas are present at the drilling site.
To determine these conditions accurately, engineers use vibration analysis, combined with seismic imaging and fractal analysis.
Once vibrations are measured, they can be converted into a depth map. As mentioned earlier, this will help determine how deep underground the oil or gas deposits are located. Typically, wells will have either 5 or 7 layers of rock for extraction.
Motor And Structure Vibration Monitoring
Any equipment with a motor, a motor carrier, and a drive train are susceptible to motor vibrations. These vibrations are minute, but they occur in the same manner as earthquakes; the well has mini bursts of quakes that happen over time. They can be strong enough to ruin equipment, lead to safety issues and add extra stress on the personnel working around them.
The first step in monitoring for vibrations is by monitoring them with a vibrometer. It is also referred to as a shake table; it will record any movement that occurs when any of its motors are turned on.
The next step would be creating graphs of all this data to see if there are any significant changes when the motor is turned off or on (check out this site for some more information).
Vibration Analysis and Shaft Structure
A continuous vibration inspection was conducted on a large conveyor silo in north China. The shaft was examined by measuring the shaft vibration during the normal operating state. The Fourier power spectrum analysis demonstrated that the frequency of interference exists in the vicinity of 2~3 times per revolution.
This interference phenomenon will increase stress in the bearing, resulting in the short service life of the bearing or excessive vibration and wear of other machine components, such as gears, shafts, couplings, and bearings.
Image: Real-time charts from vibration waveform data, power spectrum, and spectrogram.
Can Vibration Analysis Predict Failures? – Predictive Maintenance
Depending on the industry, vibrations can also be used as a predictive tool for future failures. It can range anywhere from industries such as oil and gas extraction to other industries like mining, water treatment, power generation, and transportation.
Vibration engineers have been known to use vibration analysis in many different ways, including the following:
- To predict or prevent failure of machines and equipment under high-stress conditions;
- To understand the dynamic behavior of machines and equipment;
- To detect an early warning system of impending failure
If your project requires vibration analysis visualizations, check out our charting controls for vibration analysis and download a free trial.
What Are The Three Main Characteristics of Vibration?
There are three main characteristics of vibration. These include frequency, amplitude, and direction. Frequency is the number of vibrations per second. Frequency is measured in Hertz (Hz).
Amplitude or intensity refers to how much the vibration fluctuates from its normal state, from weak to strong. Amplitude is measured in units of displacement such as inches or meters. Direction refers to whether the vibration moves in linear, circular, or other non-linear patterns like a sine wave.
Interestingly, if plotted on charts, these measurements can visually show engineers the faults we talked about in this article.
A signal is a vibration that is significant enough to be recorded by an instrument, and in the case of vibration, this will usually be a vibrometer. When a vibrometer captures a vibration signal, it will then be sent to an oscilloscope for further analysis. It can be done either with the use of analog or digital methods.
Analog methods involve measuring how much the tip of the moving probe moves in response to the motor's vibrations. Different rates of movement are then displayed on an oscilloscope's screen.
Digital methods involve creating a mathematical formula that models how the tip moves (i.e., in response to motor vibrations). The speed that the tip moves at can then be calculated, and this speed is displayed on an oscilloscope's screen.
The second step that is performed after creating graphs from the data collected by a vibrometer will involve using trend analysis to determine any vibration levels over time. When doing this, the engineer will write down any significant or abnormal changes as they happen.
It can include when abnormal events occur, such as when surface noise levels change and the motor starts to vibrate abnormally. The engineer will also record any times that the vibration level drops, indicating a decrease in efficiency or a possible defect in machinery.
What are the vibrations of an aircraft?
The vibrations of aircraft have become an important part of daily life. It is used for checks on airfields, flights, controls in aircraft and helicopters. The essential use of testing is to detect any irregularities before a flight with a more intensive analysis after the flight. The equipment used to test aircraft vibrations is often vibrometers, but there are also other instruments that can detect vibrations.
Tests are performed on all kinds of aircraft, and they include the following:
- Static test – this test checks for loose bolts or rivets that may act as loose pieces during flight. It also tests engines installed in the fuselage for loose nuts or bolts that will cause vibrations when accelerated by fuel or engine power.
- Cold test – this test requires the operation of an aircraft's engines at low power to check for air leaks and also to reduce stress on the structure.
- Hot test - is done while the aircraft is in flight to check vibrations and excessive stress on different parts of the aircraft exposed to high airspeed and pressure changes.
- Rolling test - this checks for any irregular or excessive movement of different parts of a plane that may cause structural damage over time.
- Engine test - is typically done before take-off or after landing, where it checks for any damage caused by dust, sand, gravel, or other particles that could get into the engine when in flight.
Charting Controls for Vibration Analysis
Vibration analysis is not just for detecting hidden objects, voids, or cracks in structures. It is also an effective way to detect structural issues with machinery that could cause catastrophic damage if left unchecked, such as bearings and gears, the basis for predictive maintenance.
The industries we mentioned in this article - structural and mechanical industries, motor industries including aerospace and motorsport, and building industries all benefit from vibration analysis implemented in different case studies.
Using software to plot the vibrations caused by the machine or structure, i.e., making it visual, adds to the faster detection of irregular vibrations.
It is possible today. If you need to visualize vibration data for huge data sets in real-time, check out our charting controls for vibration analysis and download a free trial.