Unplanned downtime, or time spent performing maintenance on machines that fail unexpectedly, can cost a company a lot in terms of time, lost processes, and human resources. A vibration monitoring system is a tool to look for irregularities and other anomalies in machine health by measuring vibration levels. It helps protect facilities, processes and people. The system can identify anything from unbalance and misalignment to loose parts and help prevent machine downtime. Vibration monitoring systems, even single-channel vibration monitoring systems, are one of the most effective ways to predict potential machine problems and provide early warning of machine failures. For many industries, security and keeping processes running are critical.

How does the vibration monitoring system work?

Vibration monitoring systems work using a method called vibration trend analysis. Vibration trend analysis is a process of monitoring the abnormal vibration characteristics of a machine. When the vibration amplitude rises or falls significantly under steady-state conditions, it usually indicates that something has changed inside the machine. The total amplitude is the main indicator of machine failure and is ideal for output 4-20 mA to control systems (PLC, SCADA, RTU, etc.). The overall amplitude includes the various individual frequencies and amplitudes produced by machine components, their rotational or reciprocating motion, and/or process issues. Some monitoring systems record vibration waveforms and identify potential machine problems by revealing anomalies in the recorded vibrations.

Characteristic of vibration

The main characteristics of vibration are amplitude, frequency, phase, form, and when using proximity sensors, position. Amplitude refers to the severity of the associated vibrations. Frequency helps pinpoint the source of vibration. Changes in vibration frequency independent of changes in machine speed may also indicate a problem. Paying attention to frequencies can quickly identify specific problems. Phase helps determine when and where vibrations occur. When studying the waveform of a given vibration, the varying amplitude and frequency can reveal a great deal about the machine in question. The amplitude measured by the vibration monitoring system can show the difference in movement from the time the machine starts running to the specific moment when a part may have a problem or problem. The use of proximity sensors, the position of the rotor in the bearing clearance, or the axial movement of the rotor, may be observed and is important when assessing the condition of the machine. In most cases, vibration monitoring systems use total amplitude to compare with vibration limits or alarm values.

How are vibrations measured?

Although vibration is recorded using frequency and amplitude, it is measured in terms of acceleration, velocity, and displacement. These characteristics can be monitored with sensors and vibration analysis equipment. The device may vary in what elements it measures, and how it measures.

For example, machines with rolling bearings (REBs) are often monitored using seismic vibration sensors (speed sensors or accelerometers). REB machines operating at frequencies below 60 Hz typically use speed sensors. Machines with oil film bearings (journal bearings or sleeve bearings) are usually monitored using proximity probe sensors.

Accelerometers typically use piezoelectric crystals (PZT sensors), which generate an electrical charge when any change in acceleration, pressure, or force is detected. Accelerometers can also be designed to use MEMS (micro-electro-mechanical System) technology to measure acceleration. Speed sensors can take an amplified accelerometer output (piezoelectric or MEMS), integrate the signal, and then output the speed signal. In high temperature applications, moving-coil speed sensors are often used to measure vibration using speed. Proximity probes are used to measure the relative motion between the rotor surface and the bearing, usually with oil-film bearings. The proximity probe measures vibration, axial position, and rotor speed. The vibration signal from the sensor can be digitized and recorded for trend analysis.

Popular vibration monitoring methods

1. Walking/periodic vibration collection

This type of monitoring usually uses an accelerometer to record the vibration level of each radial and axial bearing of the machine on a regular basis, usually monthly or quarterly. It does not use transient data (start and close data) and is best equipped with vibration switches (electrical or mechanical), which helps prevent machine failure between each periodic data run.

2. Walk Around Vibration Data Collection (with waveform or transient data)

This is usually performed after a problem is found during the patrol data collection process, or when a vibration switch turns off the machine.

3. Continuous vibration monitoring (no waveform or transient data)

These monitoring systems are often equipped with alarm and shutdown functions to help prevent machine failures. This type of monitoring uses transmitters that provide 4 to 20 milliamps (mA) signals connected directly to the control system to monitor vibration data.

4. Continuous vibration monitoring (with process data correlation, no waveform or transient data)

This monitoring concept combines alarm and shutdown functions to help prevent machine failures and identify abnormal trends. Data is sent using 4 to 20 mA transmitters connected directly to the control system, which has been connected to the "plant information Network" to associate with process information (load, flow, level, pressure, temperature, etc.). The vibration data, together with the process data, provides a higher degree of understanding of the actual operation of the machine.

5. Continuous vibration monitoring (related to process data)

Single - or multi-channel monitoring devices with alarm and stop functions help prevent machine failures and easily identify vibration trends. When you have the right sensor suite, this type of monitoring also allows you to perform diagnostics on the machine. Vibration, speed, thrust position and impact data are usually included in the data suite.

6. Continuous vibration monitoring (with process data correlation and waveform and transient data)

This type of monitoring has the same functions as above, allowing you to identify abnormal trends and prevent machine failures under normal processing conditions. You can also run machine diagnostics on demand and use sensors integrated with factory process data. This is the highest form of mechanical vibration monitoring.

Common applications of vibration monitoring systems

Vibration monitoring systems can be used for a variety of different applications. Here are some of the most common industrial uses:

It is important to note that the number of vibration sensors used on rotating or reciprocating machines depends on how critical the equipment is. Critical equipment, which can cost more than $100,000 if shut down for just one day, should be fitted with XY vibration sensors on each radial bearing, thrust sensor, and at least one phase trigger. If the machine is less important and the impact is less than $10,000 per day, perhaps a vibration sensor on the load side bearing closest to the coupling is sufficient. Between these two jiduan, it is necessary to judge the best way to monitor the machine so that the factory can get a return on investment (ROI), which may be one or two sensors with an on-off function (alarm/off).

1. Rotating machinery

Rotating equipment and machinery such as motors, fans, turbines and transmissions are the most common places for vibration monitoring systems. Because several different parts rotate simultaneously and create vibration patterns, vibration monitoring is essential to ensure that all components are working properly. For rotating equipment, a problem can lead to equipment damage and catastrophic failure. Vibration monitoring can help identify misalignment, unbalance, friction, bearing failure and even resonance problems in rotating machinery.

2. Bearings and gears

In the bearings and gears of the machine, various vibrations occur at different frequencies, which is why vibration monitoring systems are so common. With gears, a number of different vibration modes are generated when the device performs its desired task. These varying vibrations are too difficult to monitor by humans alone, and the use of a monitoring system for early warning is essential for the continued functioning of the machine.

3. Reciprocating compressors, engines and pumps

Equipment such as reciprocating compressors, engines, and positive displacement pumps have multiple components within them that actively vibrate. Reciprocating machinery is special in that its parts move in two ways: rotation and straight line. Monitoring the vibrations of these different components helps identify potential failures before they cause damage to the machine.

4. Bridges

Vibration monitoring is crucial in ensuring the structural integrity of Bridges. Vibration trends can help establish a baseline for the behavior of an undamaged and healthy bridge, and then detect when it may be experiencing structural problems. If the bridge begins to exhibit abnormal vibration behavior, maintenance personnel can perform the necessary inspections to determine the source of the problem.

5. Plumbing

Vibration monitoring systems are essential for pipelines that may be prone to problems caused by vibration. Monitoring systems not only help alert when problems start to appear, but also help find the root cause of problem areas. In this way, high-risk areas on the pipeline can be monitored for potential problems.

Install vibration monitoring system

Taking steps to ensure that machines and equipment work properly and can be used for as long as possible is essential to bi for any business. Using a vibration monitoring system to measure any anomalies and alert you to potential problems, you will be able to help your machine run more efficiently for longer without causing major damage.