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GVS News News

A Case Study: Motion Amplification Analysis of a Drum Drive Gearbox

A manufacturing plant located in WA recently encountered a significant issue related to a critical drum drive gearbox. The Asset Management and Reliability Team noticed excessive vibrations and sought to identify the root cause of this problem. To address this issue, the Iris M™ Motion Amplification® technology was utilised. This case study outlines how Motion Amplification® technology successfully captured, quantified, and qualified the operational vibration characteristics and identified the root cause of the problem.

Problem Identification:

The manufacturing plant initially detected unacceptable levels of vibration in the drum drive gearbox of their machinery, which they had yet to identify. This vibration had the potential to disrupt operations and, if left unaddressed, could lead to costly equipment damage.

Motion Amplification Analysis:

Upon implementing Iris M™ Motion Amplification® technology, the plant’s Asset Management and Reliability Team conducted real-time data analysis, revealing several crucial findings:

  1. Vibration Frequencies: The analysis showed that the majority of the vibration in the drum drive train occurred at three distinct frequencies:
    • Motor running speed: 25.76Hz
    • Pinion gearmesh frequency: 7.69Hz
    • 2x pinion gearmesh frequency: 15.38Hz

The presence of the 2x pinion gearmesh frequency indicated a classic symptom of gear misalignment and uneven wear across the gear teeth.

  1. Phase Difference: There was a noticeable phase difference between the motor and gearbox input, which is a typical indicator of offset misalignment across the coupling.
  2. Vertical Orientation: The vibration analysis also revealed that the vertical orientation of the inner side of the drum drive gearbox’s base frame exhibited higher levels of vibration compared to the outer side.

Recommendations:

Based on the observations and analysis using the Motion Amplification® technology, the following recommendations were made to address the identified issues:

  1. Pinion Inspection and Realignment: Given the presence of gear misalignment and uneven wear across the gear teeth, it was recommended that the pinion be inspected thoroughly. Any misalignment should be corrected and worn gear components should be replaced.
  2. Torque Arm Connection Inspection: The connection between the torque arm and the base frame should be inspected for any signs of damage or misalignment. Any issues found in this area should be promptly addressed.
  3. Motor-to-Gearbox Realignment: To resolve the phase difference identified between the motor and gearbox input, realignment of the motor to the gearbox is necessary. Proper alignment will ensure that power is transmitted efficiently and reduce unnecessary stress on the machinery.

The implementation of Iris M™ Motion Amplification® technology proved to be instrumental in diagnosing and identifying the root causes of unacceptable vibrations in the drum drive gearbox. Through this analysis the plant was able to mitigate the vibration complications and prevent potential equipment damage, ensuring the continued smooth operation of their machinery.

 

 

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GVS News News

Techniques for Effective Condition Monitoring of Low-Speed Machines

Condition monitoring of low-speed machines, operating at speeds typically below 600 RPM, demands a systematic approach due to the inherent challenges that slow speed operation carries. Here we review some of the techniques utilised for successful monitoring of slow-speed machinery.

The unique characteristics of low-speed machines give rise to a series of challenges when establishing a condition monitoring program:

·         Lower frequencies of interest

·         Lower impact amplitudes (vibration signals)

·         High ambient noise

Lower frequencies of interest:

The slower rotational speeds mean that the fault frequencies of interest in condition monitoring (e.g. bearing ball pass frequency) typically occur at much lower-frequencies and vibrations and dynamic signals, complicating the task of identifying anomalies and irregularities.  Lower rotating speeds result in lower amplitudes in the impacts that are often key indicators used in vibration or ultrasound analysis to detect early stage bearing faults.  Slow rotating machines are often found in crushing, milling, grinding and other processes, where there are high levels of ambient noise and vibration. The presence of these external noise sources, lowers the signal-to-noise ratio, making it challenging to extract relevant data.

To tackle the complexities of monitoring low-speed machines, a comprehensive approach integrating various complementary methods is preferred. This multi-pronged strategy enhances data accuracy and dependability, facilitating a thorough understanding of the machine’s health.  Here are the key techniques commonly employed:

1.    Vibration Analysis: Vibration analysis remains a cornerstone technique for low-speed machinery monitoring.  Through the utilisation of high sensitivity sensors, longer time waveforms and advanced signal processing algorithms, low level faults associated with operational abnormalities can be detected. Proper sensor selection- and placement, as well as good data collection parameter configuration, are pivotal for optimal data acquisition and analysis.

 

2.    Oil Analysis: Lubricating oil analysis serves as a valuable diagnostic tool for slow-speed machines.  By monitoring contamination and wear debris, insights into potential component issues can be gained early.  Regular oil sampling and analysis are critical for the early detection of deterioration.  It is recommended that analytical ferrography or filtergrams be specified as part of the analysis package of slow speed machines as these methods provide more accurate wear particle and contamination information for monitoring slow speed machines.   The latest developments in online oil condition sensors show significant promise for slow speed machine monitoring.

 

3.    Thermography: Thermal imaging is adept at identifying overheating problems and abnormal temperature distributions within machinery. In low-speed machines, where temperature changes might manifest more gradually, thermal imaging helps pinpoint localised heat irregularities or cooling inefficiencies.  It should be noted that thermography is typically a late stage indicator of faults and cannot be relied upon for early detection of developing problems.


4.   Ultrasound Condition Monitoring: Ultrasound monitoring has emerged as a preferred technique for slow-speed machines. Ultrasound waves can detect subtle changes in machinery, such as friction, impacting, cavitation, and leakage. Ultrasound provides a powerful means for optimising lubrication doses in grease lubricated machines. Ultrasound monitoring techniques enhance early fault detection even in low-speed conditions and supports predictive maintenance efforts.

By integrating a spectrum of condition monitoring techniques, maintenance teams can achieve a comprehensive understanding of machine health. These preferred methods enable the efficient and accurate monitoring of slow-speed machinery, facilitating timely interventions and assisting in ensuring the equipment reaches its intended lifespan. 

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Industry News News

Screen Monitoring with Waites Wireless – Iron Ore Mine WA

An iron ore mining client in Western Australia was experiencing repeated failures on their vibrating exciters. These failures had resulted in production losses and were a health and safety hazard.

The site strategy for monitoring the screens was to use vibration analysis. To do so, the clients historically used hard-wired industrial piezoelectric accelerometers. A condition monitoring technician would then routinely (monthly or greater) manually collect vibration data onto a portable device and review the signals for signs and faults.

The original solution:

Increased frequency of the vibration analysis survey to weekly in order to provide earlier detection.

Whilst the vibration data collection and analysis method is proven to detect faults, there are three problems that make this method ineffective or unreliable for screen exciters.

1. The cable of the hard-wired sensors often fatigues due to the harsh environment (oscillating screen) which meant vibration data could not be collected.

2. A bearing can go from ‘normal’ to ‘severe’ condition within days. When failures do occur, they are normally catastrophic destroying shafts, gears, weights and exciter cases. Given the nature of the rate of deterioration, even a fault detected early on in its failure mode, a routine survey would need a very high frequency of measurements to provide an accurate report of the assets’ health to operations/maintenance.

 3. Weekly inspections are demanding on vital condition monitoring human resources.

All of the above problems meant a labour intensive, seven-day inspection routine was unsatisfactory for plant reliability and personnel safety.

With the above challenges being a constant source of concern, the client engaged GVS Reliability Products and installed the Waites Wireless online condition monitoring system. This overcame the challenges of collecting higher frequency, important asset health data, was a cable free solution and did not require a technician to walk around and manually collect the data.

To the customer, this meant overcoming all three challenges listed above.

The below case study highlights the versatility of moving to wireless technology, which ultimately proved its worth in detecting both the initial fault and the rapidness of the failure, preventing significant secondary damage and reducing down-time.

Case Study

The Waites Wireless SM1-1150 motes were installed one on each exciter across a few screens to monitor and detect the signs of early bearing faults. Exciter temperatures, acceleration and velocity levels were trended and time waveform and FFT data were captured and stored in the cloud for ease of access and analysis. The Waites Wireless ‘ImpactVUE’ feature was also utilised for the early bearing fault and impact detection ability.

The trends of the exciters (see below – Figure 2), show the steady operation with acceleration levels for over three months. Over this period the alarm sets were tailor-made to suit the machine and its operating condition at the site.

A few months after an outage in December, the trend of the drive-end exciter can be seen slowly increasing (see below – Figure 3). In early February, the hourly acceleration readings on the screen exciter began to spike breaching alarm levels. At the triggering of the ‘caution’ alarm, Waites Wireless automatically sent notifications to the Condition Monitoring team.

The triggering of the ‘caution’ alarm gave the onsite Condition Monitoring Team the chance to inspect the asset, diagnose the issue and provide early notice to the Operation Team of the fault and machine condition. 

The Waites Wireless ‘ImpactVUE’ FFT shows (see below – Figure 4) the inner race fault frequencies clearly defined.

The site team used their onsite data collector which clearly showed similar data to the Waites Wireless platform (see below – Figure 5). 

Shortly after this data was collected, the vibration amplitudes dramatically increased, and the decision was made to shut the screen and plant down (see below- Figure 6).

By neutralizing the threat, secondary damage to other components was avoided, greatly reducing the costs of the rebuild/repair. While the failure was fast moving, Waites Wireless provided sufficient time for maintenance to be organised with necessary parts, prior to the shut-down. By giving time for maintenance to be organised and ready, Waites reduced the overall downtime and the financial impact to the company of this impending failure.

Two days later, another completely different screen monitored by Waites Wireless hardware, sent their condition monitoring team alarms that indicated similar signs of rapid failure while the other screen was under maintenance. The trend increased dramatically on the 4th of February (see below – Figure 7). 

The Waites Wireless condition monitoring system was able to prevent catastrophic secondary damage on two screens in quick succession. This success story is achieved for the customer by the intelligent use of Waites Wireless high frequency data sampling intervals and a good practical alarm set configuration.

Reach out to your local GVS Reliability Products representative via sales@gvsensors.com.au for more information on how to easily monitor your own vibrating screens (and other rotating equipment) with the Waites Wireless condition monitoring hardware.