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Articles: Vibration Analysis

How is Machine Vibration Described?

By Commtest Instruments

To analyze the condition of a machine you first need to accurately describe the behavior or symptoms of the machine.

How can vibration symptoms be described accurately?

How do vibration analysts describe the condition of a machine?

In this section we present the basic methods of describing machine vibration.

After reading this section you will:

• Know the two most important methods of describing machine vibration
• Understand the term ‘amplitude’
• Understand the term ‘frequency’
• Understand what a spectrum or waveform is

 

 

How is Vibration Measured?

By Commtest Instruments

In the last section we identified the most important vibration analysis tool as the spectrum. When we measure machine vibration we usually measure vibration spectra, since the spectrum of a vibrating component tells us a great deal about the condition of the component as well as about the cause of vibration. Naturally it is vital that the spectrum, which gives such valuable information, be obtained accurately.

What guidelines must be observed to ensure measurements are accurate? How should measurements be taken and for which machines should they be taken?

Identifying the Motor Rotor Bar Related Peaks in a Spectrum

By Alan Friedman, DLI Engineering Corp
The motor bar peak in a spectrum appears at a frequency equal to the number of motor bars multiplied by the shaft rate of the machine. Although initially, most analysts will have no idea how many motor bars there are, identifying the peak that relates to the motor bars is fairly simple to accomplish. The reason for this is that the motor bar peak will have peaks on either side of it, spaced 120 Hz away (100 Hz where electrical line frequency is 50Hz).

If the Bearing is Hot: (It might be greased or not)

"Vibration analysis" is commonly used to assess bearing condition however, although the vibration data can appear ok, there are other conditions which can exist or be unknowingly created to open the door for potential failure.

I am referring to bearing lubrication. This is an area where although, information by the bucket full can be easily obtained, Practicing the art of proper bearing lubrication tends to be ignored, not practiced or severely misunderstood. Usually, one step in a PM requires maintenance personnel to grease the bearings. This practice has become acceptable because we all know what happens when there is not enough grease so...we apply the old rule of thumb that is; "better to have too much grease than not enough" right? The problem is... we really aren't sure how many times or the last time a bearing on a particular machine got greased. It has been said over and over again that over greasing can cause more damage. Unless some system has been put into place to record the greasing activity, we can never be 100% sure. I will demonstrate through the use of infrared technology what the outcome will be if over lubrication happens.

Measuring Shock Pulse another approach to Front Line Condition Monitoring

Downtime in a paper mill or any 24/7 facility is very expensive in maintenance costs, but even more so in the impact to profit because of production loss. In this article we will explain the Shock Pulse Method, why it's a good choice for frontline vibration measurement and show the resulting savings that the Hallsta Mill in Sweden realized from utilizing it as the primary component of its Condition Based Maintenance Program.

Hallsta personnel determined these calculations when they looked at the number of incidents in which they were able to perform maintenance in a planned shutdown, instead of taking the equipment (and production line) down.

Condition monitoring should always start with a list of machine faults, specific for each machine. Only if you know exactly what you expect from the monitoring method, can you apply it efficiently and correctly. Otherwise, there is a danger that you will simply be collecting data. And data is of no use unless it is converted to useful information that you can act upon to realize your true goal of maintaining plant equipment in good working order.

Monitoring the Performance and Health of a Shredder Plant

In today’s difficult business conditions, it is more important than ever to know how your recycling plant is performing. It is also vital to avoid sudden expensive breakdowns, and to keep plant downtime to a minimum. This is particularly difficult in the scrap auto recycling industry, where all the machinery must be capable of handling large vehicles with a high throughput; the machinery takes a battering, and sooner or later it must be maintained or it will break down. While it is possible to build some redundancy into an operation – such as having spare scrap handling cranes – there is often only one shredding machine at the heart of an auto shredding plant. If the shredder is working well, then the plant is productive; and if the shredder is not working, then the plant is inoperative.

Refined SPM method saves money at Hallsta Paper Mill

Since April, 2009, Hallsta Paper Mill in Roslagen, Sweden has been engaged in a successful project together with SPM Instrument, where bearing condition has been measured on four twin wire presses using the SPM^®HD measuring technique.

Refining a Refiner with 4-20 mA Monitoring

by Ed Nisbett, Tim Gilliss and Tom LaRocque

In their mill that is located in East Millinocket, ME (“The Town that Paper Made”), Katahdin Paper Company, LLC, produces pulp, which is used in the production of directory paper, from two paper machines.  Prior to paper production, the characteristics of the wood pulps are adjusted accordingly by passing them through a refiner with patterned rotating plates (see Figure 1).

Reliability Leadership Interview with Jim Berry

Terrence O'Hanlon interviews James Berry, President, Technical Associates of Charlotte.

Reliability Quiz - Detecting the severity of bearing defects

Test your knowledge with this quiz sponsored by Commtest.

Reliability Quiz - Tools and Terms for an Effective Reliability Program

Test your knowledge with this quiz sponsored by Commtest.

Standardization of Absolute Vibration Level and Damage Factors for Machinery Health Monitoring

An attempt has been made to study the vibration level of various machine tools to explore the possibility of establishing the standard vibration level. Till today no vibration standards are available for determining the acceptable vibration level for specific machine tools. However there are some standards available that gives an indication of machinery health based on overall vibration level like ISO 2372 (RMS velocity in the frequency range 10 Hz to 1kHz) and Canadian specifications (RMS velocity in the frequency range 10Hz to 10kHz). But these standards are made for general purpose machinery like pumps, motors, generators and so on. The present study is aimed at establishing the vibration standards for precision machine tools. The machine tools are first segregated and then their vibration data are analyzed for determining the normal vibration level and damage factors (DF). After refining and fixing the vibration standards obtained, they can be used to assess the machinery health.

Structural Failures in Vibrating Screeners at a Petrochemical Plant

Finding A Cure for Troubling Failures

by Maki Onari and Eric Olson

Successful Solution to the Challenge of Low RPM Bearing Monitoring

By Tim Sundström

Low RPM applications have been notoriously difficult to monitor with traditional vibration-based techniques. The energy involved at RPMs below 50 is very low, making it a difficult task to extract meaningful information from the measured signal.

The Challenges of Automated Spectral Analysis

Reflections on eighteen years of development by Jason Tranter, Managing Director, Mobius Institute

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