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Troubleshooting a 4-20mA Accelerometer System

Cal Cert Example

Fig.1

The first thing to check is that the wiring is carried out and in accordance with the calibration sheet provided with the sensor. Check polarity of the voltage power supply.

Fig.2

The next thing to check is that the accelerometer is being powered correctly. Check the cable datasheet to see which two pins to be checking the voltage across. The voltage should be somewhere between 15 and 30 volts. Many systems would typically be 24volts. If the accelerometer has an integral cable then a point along the signal path needs to be checked. The closest point to the accelerometer should be sought to check the voltage. This ensures that a check for discontinuity in the wiring is taken with as much of the signal path being checked as possible.

Fig.3

If the accelerometer is seeing the correct voltage then the next check is to see if the accelerometer is generating a current that is at least 4 mA . To do this the multi-meter needs to be in series with the accelerometer. The circuit wiring needs to be disconnected at some point along the signal circuit and the meter inserted. If the machine on which the accelerometer is mounted is off you would expect 4mA. (No vibration condition). If the machine is running and vibration is being generated you would expect to see anywhere from 4 to 20 mA depending on the level of machine vibration. If you have 15-30V of power and you are seeing less than 4mA then the accelerometer is defective. If you are seeing greater than 20mA then the vibration levels are saturating the sensor or the sensor is defective.

Fig.4

If at least 4mA of signal is being generated then the accelerometer is most likely functioning correctly. If the accelerometer is showing more than 20mA and the machine is running then the machine vibration might be saturating the accelerometer and a lower sensitivity sensor is required. To check for this disconnect the sensor and repeatedly hit it with a light object. This should cause the mA current to increase. The Hansford Sensors 4-20mA sensors have a 5 second averaging circuit so ensure the light tapping of the sensor is repeated for at least 10 seconds to register above 4mA. If the accelerometer remains at 20mA or above despite being disconnected from the vibration then the accelerometer is likely defective.

 

If you have any questions, please contact us at sales@gvsensors.com.au or view our product range here

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How to select the right vibration sensor

With so many different types, shapes and sizes to choose from, selecting the right vibration sensors (otherwise known as accelerometers) for your operations can be a challenging task. It is, however, essential. To ensure you specify correctly, there is a number of important factors you need to consider.

Vibration range and sensitivity – The range of vibration varies greatly from operation to operation. You should always specify vibration sensors to measure the maximum vibration range of your specific application. In a standard application (80g range), the sensitivity of a typical vibration sensor is 100mV/g, while in low vibration applications (16g) the sensitivity is 500mV/G.

Vibration frequency – Knowing the frequency span you need to measure is as important as knowing the vibration range. The frequency spans are dictated by the fault frequencies of the fastest-turning component in the machinery being monitored. The frequency span of a slow turning ball mill, for example, will be narrower than that of a high speed fan.

Environmental temperature – After poor and incorrect mounting, the greatest threat to the performance of vibration sensors is the environment. High temperatures can affect the operation of the electronics. However, charge-mode accelerometers are specially designed to work in applications with very high temperatures.

Contact with chemicals or debris – This can reduce the reliability of results and should therefore be considered carefully. To ensure performance and results are unaffected by exposure to chemicals or debris, accelerometers with corrosion and chemical resistant stainless steel bodies should be specified.

Hazardous atmospheres – Hazardous environments are those that contain flammable gasses or vapours, combustible dusts, or ignitable fibres, where even the tiniest spark could cause a fire or explosion. To protect people, machinery and productivity, you need intrinsically safe accelerometers, which are specifically designed for use in hazardous areas. They deliver the same level of performance as their non-intrinsically safe counterparts, but do so by using a lower level of energy.

Immersion in liquid – The average accelerometer isn’t constructed to be waterproof. If your application requires accelerometers to be exposed to liquid, the solution is to specify vibration sensors with integral polyurethane cables. This prevents liquid infiltrating the accelerometer and affecting the electronics – whether the sensor is at minimum sprayed with water or even completely submerged in liquid on a permanent basis.

Exit and profile – The exit and profile of a vibration sensor has minimal impact on performance, but if not considered can become a frustration for those responsible for maintenance. Depending on where the vibration sensor is located, you can choose between a top exit, side exit or low profile connection to allow maintenance engineers easy, safe access.

By taking these factors into consideration you can make the right choice in vibration sensor specification for the requirements of the average application or an industry specific use. If you need further assistance or require advice on special applications, GVS is here to help and can assist you in selecting the ideal vibration sensor. Get in touch today, or view our full range of vibration sensors, cables and accessories. 

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Ultrasound Inspection On Rotating Assets

front page

GVS Reliability Products in conjunction with SDT Ultrasound Solutions is proud to present the below case study, Ultrasound Inspection On Rotating Assets, submitted by Mike Halls.

Mike is Technical Officer of Condition Monitoring at Rio Tinto’s Yarwun alumina refinery where he has held this position for over seven years. Mike has over 20 years working in the condition monitoring field, utilising popular technologies such as VA, Thermography and Oil Analysis. And now Ultrasound for the last 2 years!

Mike’s years of experience have given him a unique perspective on using ‘alternative’ condition monitoring tools such as the SDT 270 PROthe world’s flagship ultrasound inspection device. With the SDT 270 delivering reliable, repeatable and calibrated ultrasound data and, with the power of signal analysis using SDT’s UAS software, Mike has been able to clearly demonstrate that ultrasound inspection should be the technology of choice for certain applications.

When using Ultrasound inspection technology in a harmonious relationship with other condition monitoring inspection devices, plant coverage increases, as does the overall reliability and availability of monitored assets. This then translates into greater production capacity and therefore overall profitability of an enterprise/company.

A portion of this case history was first published in The Industrial Eye: The official journal of the Australian Institute for Non-Destructive Testing – Condition Monitoring Issue – March/April 2017. 
It has since been edited and rectified to give further information regarding the case.

Read on for Mike’s ultrasound inspection success story…

Case History: Mike Halls – Rio Tinto Yarwun – 16-10-2017

Bearing Life Extension using SDT 270 Contact Ultrasound measurement

vaccum pump

Equipment Details

Equipment: P2620Vacuum Pump

Bearings: Tapered Roller Bearings

Pump Speed: 222 RPM

Motor: 630Kw – 6 Poles

Number of Vacuum Pumps on Site: 21

Costs associated with bearing failure

Overhaul cost due to a bearing failure: $120K
Total Replacement cost: $300K
Costs due to lost production or downtime: Currently there is some redundancy (as long as there are not too many other problems…). This may change in the near as further production demands are made on the plant.

History

Previous vacuum pump equipment failure modes and RCA’s have revealed that there has been an increase in bearing internal clearances & cage wear resulting in premature bearing failure. Due to the nature of these machines, vibration spectral analysis only revealed bearing defects in the later stages of the failure mode. Vibration analysis identified advanced propagation of fatigue due to surface cracks and spalling of the bearing raceway surfaces which were already resulting in unsatisfactory equipment performance.

Contributing factors to consider when using a vibration analysis approach are

a) a relatively low operating speed and

b) fluctuating ‘flow related’ vibration

Both of the above plant characteristics have the tendency to mask the early stage, low level amplitude bearing defect fault frequencies which, had they been detectable, would have indicated sub-surface bearing raceway defects and/or lubrication related anomalies. See the vibration analysis plots below as reference.

Vibration Analysis Plots

Below is the vibration Acceleration & PkVue spectral data taken the day after the acoustic vibration route was collected and, prior to any maintenance or lubricant/greasing intervention. Vibration analysis of the spectral plots indicates that the dominant frequencies relate to the vacuum pump pressure pulse fundamental & related harmonics. Neither of the plots indicates incipient bearing anomalies or lubrication related issues.

vibration analysis_1
vibration analysis_2

Challenge

With traditional condition monitoring technologies being limited in their capacity for detection of the early stages of the bearing failure modes, trending of the degradation process was not possible. Without being able to detect and trend the early stages of the failure modes, this left the plant exposed when needing to determine a projected planned maintenance window. So, once the later stage defects were finally identified, the asset was already at a critical crossroad in

a) needing immediate attention or

b) risk plant failure with consequent potential safety hazards or production loses.

Solution: Acoustic Vibration Monitoring Trial

Acoustic Vibration Monitoring or contact Ultrasound, are terms used when an Ultrasound inspection instrument (in this case the SDT 270 PRO), utilises a sensor to contact (touch) a surface to detect attenuated ultrasound signals. Using a sophisticated instrument such as the SDT 270 PRO, the ultrasound signals can then be acquired as either dynamic (for analysis and playback) or static measurements (for trending) and logged in SDT’s proprietary database, Ultra Analysis Suite (UAS).

Just over twelve months ago, an Acoustic Vibration Monitoring strategy was implemented on a trial basis to complement the vibration analysis program on the vacuum pump routes. This was done mainly to assist with lubrication related concerns and incipient bearing defects that vibration analysis was unable to confidently detect. After employing the ultrasound inspection strategy (with the 270), and the data analysed in UAS, a number of lubrication concerns with the vacuum pump bearings were rapidly identified. See figure 1 and 2 below.

Figure 1. Static trend

graph

Figure 2. Dynamic Signal

dynamic-signal_2

Listen to .WAV sound file at this Dropbox link.

Initial Results and Findings

The above Acoustic Vibration Analysis examples indicate a significant upward trend due to elevated ultrasound generated by the bearings. The ultrasound signal and trend indicate metal to metal contact that is identified by an outer race bearing defect. The causes for this are either inadequate lubrication or incipient bearing defect.

As already mentioned above, at these locations vibration analysis showed only high frequency data with a raised noise floor. This could be attributed to the product ‘flow’ and hence masked the true vibration signal. On the contrary (and unlike vibration), the Ultrasound signal is not affected by the ‘flow’ caused by the pump and hence did not mask/conceal the bearing condition data. Due to the clarity of this anomaly, we can call this a ‘text book case’ because in this example, increased readings in ultrasound data related directly to an inadequate bearing lubrication condition.

Due to the findings via the use of the SDT 270 Ultrasound inspection device, the recommended corrective action was; ‘grease the non-drive end bearing and re-evaluate the ultrasound values’.

Upon the recommendations being carried out in a timely manner, further readings were taken with results shown in Figure 3 and 4 below:

Figure 3. Static trend after recommended intervention

Static-Trend_alt

Figure 4. Dynamic signal after recommended intervention

dynamic-signal_alt

Note: the vertical y axis between fig 2 and 4 is different by approx. a factor of 4

Listen to .WAV sound file at this Dropbox link. 

Secondary Results and Findings

The data collected with the SDT 270 post lubrication intervention shown in figure 3 &4 showed drastically reduced static and dynamic ultrasound signals. Hence, the follow up survey indicated that the values had significantly decreased to within the acceptable ultrasound range. Further inspections were then planned to monitor the health of the asset. Through the unique attributes only available through ultrasound inspection with the SDT 270, the plant was protected.

Conclusion

Cost analysis:

Thanks to Ultrasound inspection and the access to complimentary software, a conservative estimate is that the company avoided a $120K+ cost to overhaul the pump due to a bearing failure. A catastrophic failure ($300K +) and potential compromise to personnel safety and plant production, would have seen the cost to the company far in excess of this $120K estimate.

Technology Analysis:

Ultrasound inspection has unique qualities which were instrumental in allowing condition monitoring to gain a true understanding of the health of the asset. For this application, other condition monitoring technologies were only useful once the asset was in the late stage of this particular failure mode exposing the company to high risks.

Furthermore, with the SDT 270’s ability to collect both dynamic and static data for trending and analysis, and the ability to record and analyse this data in the UAS software, the defect was easily identified and corrective actions taken.

Site Analysis and further actions:

Continued use of Ultrasound inspection technology to identify bearing condition will be employed so as to extend the reliability, availability and life expectancy of these important assets.

When using Ultrasound inspection technology in a harmonious relationship with other condition monitoring inspection devices, plant coverage increases as does the overall reliability and availability of monitored assets.

Thank you for reading.
I hope this study proved to be of use to you confirming best practice in technology integration results in determining a higher accuracy in detecting equipment failure modes.

For PDF download please view here Ultrasound-inspection-for-Rotating-assets-case-study-by-Mike-Halls-1.pdf

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Case History: Generator Stator Coolant Pump

RDI’s Motion Amplification (TM) provides visualisation of a structural fault on a Generator Stator Coolant Pump that has gone unresolved for more than 10 years!

RESULTS

  • Captured Motion Amplification (TM) (MA) videos and diagnosed the fault in the field within 1 hour
  • Visualisation of the root cause (structural fault) of the high vibration that has been undiagnosed for more than 10 years
  • Simple and inexpensive remediation work during a scheduled outage reduced the high vibration by more than 70%
  • The pump was returned to duty service rather than stand-by
  • Solution implemented at a fraction (1%) of the cost of previous attempted corrective actions

COMPANY

AGL Loy Yang


LOCATION

Latrobe Valley, 165 kilometres south east of Melbourne, Victoria, Australia

3

PROBLEM

There are two (duty and stand-by) Stator Coolant Pumps (SCP) critical to the operation of each 500+ megawatt turbo generator at the Loy Yang Power Station. One of the two SCPs for Unit 1 turbo generator has had a long history, more than 10 years, of high lateral vibration, sometimes reaching 20 mm/sec RMS. There have been many attempts to remedy the problem at an estimated material cost of AU$160k. This does not take into account the estimated labour cost of 500+ man-hours and loss of power generation revenue. Some of the attempts to remedy the problem include laser alignment, base frame spot welds, bracing of pipework, fitment of flexible bellows to the pump suction and discharge pipework, pump replacement x2, motor replacement, coupling replacement.

1


SOLUTION

Optical Motion Technologies (OMT) were contracted to apply RDI’s Motion AmplificationTM (MA) technology to solving the long running problem on 1-SCP-2. From arriving at the location of the SCPs in the power station, setting up the video camera acquisition system and then collecting nine MA videos took less than one hour. This hour included the time to analyse the results all of which was done in the field. The process involved taking wide angle ‘whole of machine’ videos, analysing them in the field and then honing in with zoomed videos on the root cause of the problem. It was clear from the MA videos that the problem was a soft foot condition between the pump base frame and skid base plate. In fact, there was a twisting operational deflection shape of the pump base frame. During a scheduled outage, a series of fillet welds were made across the suction end the pump base frame to the skid base plate. When the pump was returned to duty service the high lateral motion and vibration had been reduced by more than 70% and was now less than 5 mm/sec RMS. The solution to this problem was achieved through the application of RDI’s Motion AmplificationTM technology for a fraction of the time and cost already incurred.

View the full case study at http://opticalmotion.com.au/case-studies/

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Memorable Demo day for Motion Amplification

GVS Reliability Products and Optical Motion Technology recently held a Demo day for Motion Amplification at the Metro Hotel in South Perth.

The purpose of the day was to help educate engineers and professionals on the ground breaking new technology called ‘Motion Amplification’.

For those that do not already know, Motion Amplification is a process whereby using a video camera and the proprietary software, movement can be detected and amplified so that it can be seen. This kind of visualization technology has previously been the domain of ODS only. It truly has to be seen to be believed!

And that is exactly what our guests on the 30th of September did. They saw and they believed!

‘A very impressive development for machinery and structural health monitoring’

‘A fault visualization tool that is in a class of its own. The advantages that I see are Non-contact and diagnose/visualize in the field without having to travel back to an office to analyse data. Outstanding. Thanks GVS and OMT’

‘Great presentation. The technology is impressive. Our company could use a tool like this in so many different areas.’

Just some of the fault types that can be visualised and easily interpreted with the Motion Amplification technology are

If you would like to learn more about Motion Amplification and how it can help you, get in touch with our sales team today.

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Vibration Monitoring with Video. GVS presents Revolutionary New Technology

It’s Time to Open Up the World of the Unseenintroducing Vibration Monitoring with Video.

Imagine having a video camera where every pixel becomes a vibration sensor. This is now a reality with a brilliant new technology called Motion Amplification developed by RDI Technologies. Research, Development, Innovation (RDI) Technologies is headquartered in Knoxville, Tennessee. RDI was founded by Dr Jeff Hay, the inventor and patent holder of the technology which originated in research funded by the U.S. Department of Homeland Security at the University of Louisville in Kentucky. The research project, led by Dr Hay, aimed to find a fast, noncontact method for the assessment of critical infrastructure that could assist first responders during emergencies.

The unique benefits of the technology are listed below;

• Measure deflection, displacement, movement and vibration
• Reveal movement not visible to the human eye
• Every pixel in the video becomes a sensor
• See the bigger picture
• Non-contact measurement
• Visualisation of vibration data
• Complementary CM tool
• Revolutionises ODS analysis
• Set up, acquire and visualise in minutes not days
• Applications: Up to your imagination!

Seeing is believing.

Click videos below to see Motion Amplification in action

Optical Motion Technologies (OMT) is the authorised distributor for RDI Technologies (RDI) in Australasia. OMT is a provider of revolutionary Optical Motion Technologies and Technical Services to the Industrial Predictive Maintenance (PdM) and Structural Health Monitoring (SHM) industries across the region. Together with our authorised channel partner, GVS Reliability Products (GVS), we offer to you our extensive knowledge, experience, expertise and customer service for you to reap the benefits of this innovative and revolutionary technology.


OMT was formed with the express objective of bringing RDI Technologies to Australasia. The prospect of bringing RDI’s innovative and revolutionary technologies to the Australasian PdM and SHM industries was so compelling to warrant the foundation of a dedicated company in OMT. The founders of OMT, Andrew Gale – Technical Director and Nathan Osborn – Sales Director, have been working in the PdM industry for decades with extensive experience and expertise in instrumentation, service, training, and customer support.

Get in touch with the GVS team for more information about this revolutionary technology for the reliability industry.

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Level 1 Ultrasound Inspector at GVS

Do you have questions about using Ultrasound to improve the reliability of your plant? GVS has the expertise to meet your needs.

Recently, Tim King of GVS Reliability Products completed the level 1 inspectors course with SDT. This course was designed in accordance with the guidelines of ASNT Recommended Practice Number SNT-TC-1A. SDT’s Level 1 is a 3-day comprehensive mix of practical experience and theory and provide maximum transfer of information, skills, and abilities.

The course follows strict guidelines governed by ASNT. Tim, who successfully complete the curriculum, received an accreditation certificate from SDT and is now eligible to receive 1.8 Continuing Education Units (CEU’s) from the American Society of Non-Destructive Testing (ASNT).

GVS intends to host many more of these courses. Should you choose to attend one in the future you Will Learn

Level 1:

  • The principles of ultrasound applied to predictive maintenance
  • How to organize conduct and air leak survey program
  • How to quickly find leaks in any industrial environment
  • The principles of AVM – Acoustic Vibration Monitoring
  • How to establish a condition monitoring program for rotating equipment
  • The principles of AVM as applied to condition based lubrication of bearings
  • How to inspect steam systems and trouble shoot hydraulic systems
  • Ultrasound techniques for safe inspection of electrical systems
  • Equipment and sensor selection for specific tasks
  • Route creation and data management
  • Instrumentation review and maintenance best practices

The Level 1 Ultrasound inspectors course is a sure-fire way to make your ultrasound hardware put money back into your business. If you would like to know when the next course is in your area, please don’t hesitate to get in touch with the sales team.

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New HS-429 vibration switch protects critical assets

GVS Reliability Products is excited and proud to introduce into Australia, New Zealand, and the Pacific region the new Hansford Sensors HS-429. The HS-429 is a new compact vibration switch, designed to protect machinery against unexpected shutdown and repair costs. The HS-429 automatically trips in the event of detected excessive vibration, allowing critical systems to be shut down before damage can occur.

The distinct advantage of the HS-429 is that it is one of the most compact vibration switches on the market, thus enabling continuous monitoring and protection of assets that were once restricted by tight spaces. The HS-429 is designed to transmit a 4-20mA signal, features an adjustable false trigger delay of up to one minute to prevent error trips (which may occur at machine start up) and is overload protected to a maximum shock of 100g.

The HS-429, which features a MEMS (Micro-Electro-Mechanical System) accelerometer integrated onto the I.C. (Integrated Circuit) microchip, with the maximum RMS velocity set point and response delay time adjustable using two rotating setup dials, it is quick and simple to set up. With sealing of IP67 and designed to perform reliably within a temperature range of -25 to +80 degrees Celsius, the HS-429 is ideal for use in a range of sectors from: 

  • Mining and minerals processing
  • Bulk handling 
  • Pulp and paper 
  • Metals manufacturing
  • Utilities
  • Automotive
  • Water 
  • Building services
  • Pharmaceutical
  • etc…

Chris Hansford, Managing Director at Hansford Sensors, explains: “Minimising machine downtime and maintenance costs are essential for the productivity and profitability of manufacturers. The HS-429 provides a simple, cost effective method of continuous monitoring for protecting motors, generators, engines, pumps and fans, ensuring greater machine availability and increased output.”

If you would like to learn more then please follow this link or contact us here at GVS reliability products.

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GV-700 Vibe Port Wireless Vibration & Temperature Transmitter

gv-700-work

GV-700 Vibe Port Wireless Vibration & Temperature Transmitter

OVERVIEW:

This paper is an application review of the GV-700 Vibe Port Wireless vibration & temperature transmitter (refer GV700 VIBE PORT FLYER for the unit’s technical specifications, available on request from GVS)

APPLICATION: 

Wireless GV-700 Vibe Port was fitted to a shuttle pulley in a screen house, this critical to production shuttle pulley traversed across the screen house with the conveyor pulley rotating around 91 RPM. The system was set up and manual data was collected via condition monitoring personal on a routine basis. This pulley is critical to the throughput of the plant, and being in an awkward location (on top of the screen house), it is also critical due to the resources required to be arranged for a change out.

gv-700-cut

ANALYSIS:

The vibration data (on page two) clearly indicated a cracked inner raceway, plans were then put into place to change the pulley out. This included: – sourcing the third party lifting equipment and resources – writing the controlled safety plan to change out – scheduling the change out at the next planned maintenance slot …so as to not disrupt the production schedule.

Maximize Production – Minimize unnecessary Maintenance

VIBRATION DATA:

The PeakVue Acceleration spectrum displays a fundamental with harmonics that match the calculated defect frequency for the bearing inner raceway, this is also side banded by running speed harmonics.

VIBRATION DATA:

The PeakVue Acceleration time waveform displays a regular impact for each revolution of the shaft.

INSPECTION:

On dismantling of the conveyor pulley it was evident that the inner raceway had a through crack and had started to spin and pick up on the shaft.

Inspection

Simplifying Wireless, No Software

SUMMARY:

The wireless GV-700 Vibe Port enabled detection of the failure of a bearing prior to catastrophic unplanned shutdown. It is estimated that if this had failed without prior knowledge this would have disrupted production schedule throughput by around 150,000 tonnes. This excludes extra costs involved with deploying contractors in a breakdown situation and the increased safety risk exposure in a breakdown situation.

GOOD VIBRATION SENSORS – contact GVS Sales Team TODAY to discuss your requirements

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KING OF VIBRATION

Earlier this year GVS Reliability Products put out a challenge to our subscribers to demonstrate how vibration analysis is a dominant force in predictive maintenance.

Entrants were requested to submit the following

  1. Picture of a failed bearing
  2. Snapshot of VA data
  3. Description of the analysis process to prove how the fault was found.

The Winners prize is a $100 gift voucher and the prestigious title of the ‘King of Vibes’.

We were inundated with entries but alas, there can be only one winner. And that was Ben Hardy from Noble Engineering. We believed Ben’s entry was a great example of how vibration analysis is such a powerful tool in determining the health of a bearing / machine.

His entry below –

SymptomsAcceleration data showed increasing levels over time with harmonics of the inner raceway defect frequency and impacting indications increasing in the waveform.

Other Maintenance / Operational Information: This motor pump set up is a vertical type unit with this top bearing being the axial load carrier.

This pump unit had been in service for a number of years also.

Plots/Images