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Monitoring saves steel rolling costs
WORLD PUMPS
Feature May 2010
White paper details As well as providing the reader with information on the basic approaches to the various types of maintenance strategy (reactive, preventive and predictive), the paper also provides useful guidance on how to set up and identify the criticality of assets in your business, including potential return on investment from implementing a predictive maintenance regime. The paper then discusses the technical benefits of using condition monitoring systems and techniques to support the predictive maintenance strategy. This includes vibration monitoring, which can be used to detect early signs of failure of rolling bearings.
benefits tend to be more immediate because of the use of highly trained staff. However, it is often more beneficial to keep the activities in house so you become more familiar with your own plant, equipment and processes which gives benefits of not only preventing unplanned downtime but enables more time to be spent on mitigating potential failure modes and improving process efficiency. The cement industry is a good example where CM has been implemented and saved money both in terms of repair costs and lost production. The failure of a large gearbox caused a three week shutdown and extensive repair costs are typically €50,000 to €100,000. To prevent such damages F’IS (FAG Industrial Services, Schaeffler Group) installed an eight channel FAG DTECT X1 system and
Detailed analysis of the various rolling bearing vibration monitoring techniques are discussed and appraised. Sections are included on frequency spectrum, envelope spectrum, Cepstrum analysis, bearing characteristic frequencies, typical bearing defects, variable compliance and bearing speed ratio. The final chapter of the paper considers various real-life scenarios of rolling bearing vibration monitoring, including detailed studies of a 250kW electric motor; an impact crusher drive shaft; a 2MW generator on a test bed; a vertical impact crusher; and the gearbox of a wind turbine. For your free copy of the white paper, please visit www.schaeffler.co.uk
trained the customer’s staff who received three months support – total cost €18,000. Detecting deterioration of the gearbox early resulted in a repair cost of €5000 saving the customer at least €27,000. More importantly, the company avoided lost production amounting to around €6000/hour. “However, with rolling bearings, characteristic vibration signatures are often generated in the form of modulation of the fundamental bearing frequencies. This can be used to our advantage and vibration condition monitoring software is designed to identify these features and provide an early warning to an impending problem. This usually takes the form of signal demodulation and the envelope spectrum, which indicates early deterioration of the rolling contact surfaces.” Q
Case study
Monitoring saves steel rolling costs By introducing a new regime of condition monitoring from scratch, a European steel rolling mill has not only avoided a number of costly breakdowns but also improved the perception of condition monitoring across the site.
L
ocated at Skinningrove near Saltburn-bythe-Sea in Northern England, the steel rolling mill is part of the Corus Group and manufactures hot-rolled steel profiles for a wide range of industries, including earth-
moving equipment, materials handling, shipbuilding and mining. Monitoring of the six pairs of spindle support bearings on the two-stand
Justifying the investment When justifying PdM the following should be taken into consideration:
• • • • • • • • • • • • • • • • • • • • • •
Direct Costs Labour Normal and overtime labour for planned repair activities unplanned repairs Materials Parts replaced Machinery replaced Indirect Costs Lost production (£/hr) Outside services Insurance costs Parts inventory Total potential cost reduction (1+2) PdM program costs Site survey Cost of capital equipment Cost of any additional labour Cost of training Initial setup and baseline Scheduled data collection (visits/yr at £/visit) Total PdM Costs for one year (3)
Contact Steve Lacey Engineering manager Schaeffler UK Ltd Tel: +44 121 313 5870 Email: steve.lacey@schaeffler.com www.schaeffler.co.uk
reversing mill was previously carried out by physical inspection on routine maintenance shutdown days. This involved two craftsmen stripping down the bearing housings and manually inspecting the bearings. If no defects were found, the same bearings were then reassembled into the original housings and refitted into the mill. The entire process is both labour and overhead crane intensive. This task was done in rotation so that each bearing pair was inspected every six weeks.
Challenges This maintenance regime presented the engineering team with a number of challenges. As Scott Boyd, Operations Engineer, Mechanical points out: “It is not good practice to tie up valuable labour for a full day disassembling and then reassembling bearings when they could be working on other areas of the plant and freeing up valuable resources.” www.worldpumps.com
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Feature WORLD PUMPS
May 2010
of the six spindle support bearing sets, with a plan to connect the two spare sensors to the pinion box. “By using the online condition monitoring system we have been able to gain a much better understanding of the plant,” says Taylor. “When we began to analyse the first set of data, we realised that interference from other general plant equipment was masking the true bearing defects. We therefore needed to eliminate this in order to obtain true readings.”
Monitoring of the six pairs of spindle support bearings was a time-consuming process. The spindle support bearing housing (shown here) had to be stripped down and the bearings inspected manually.
Not only were these increased manning levels an issue for the engineering team, but there was also the risk of introducing new problems as a result of human intervention. Boyd continues: “Due to the harsh environment in which the mill operates, there is an increased risk of particulate contamination within the bearings during the dismounting and remounting process. We also had to ensure that when we refitted the bearings we did so to the correct bearing clearance, and this all takes time.” Following a request from Skinningrove at the beginning of 2008, Corus’ Plant Condition Monitoring (PCM) team carried out patrol monitoring on the bearings. By using a portable vibration monitoring device to obtain data on bearing defect frequencies they were able to report on some interesting findings. “We found that we could obtain some very reliable data from our handheld device which allowed us to understand the condition of the six pairs of bearings and determine when a failure was imminent,” comments Ian Taylor, Business Development Engineer, PCM at Corus. “However, for health and safety reasons, the manual approach was not practical in the long term,” adds Taylor. “Rather than sending our engineers into the working steel mill to obtain this data on a regular basis, it was agreed to install an online condition monitoring system.” In September 2008, an eight-channel FAG DTECT X1 vibration monitoring system from Schaeffler UK was installed on the rolling mill. One sensor was fitted to each www.worldpumps.com
Once this issue had been resolved, the FAG DTECT X1 system discovered two bearing faults on two separate occasions within the first week of operation. The engineers were able to plan the outage of the failed bearing and avoid a breakdown, which would have resulted in a significant plant stoppage on each occasion to allow time for stripping down and replacing the failed bearings. As Boyd points out: “By preventing two potential plant stoppages, the system has already paid for itself. Early detection means that we are in control of our plant. Not only are we spending less time and manpower removing and replacing perfectly good bearings, or trying to identify which bearing has failed and why, but we are also avoiding the added risks that human intervention brings.”
Future plans Asked what the future plans are for condition monitoring at Skinningrove, Boyd
The FAG Detector III handheld vibration monitoring device. Handheld devices allowed the maintenance teams to determine when a failure was imminent.
The FAG DTECT X1 is a fixed/online condition monitoring system. By using an online condition monitoring system, the maintenance team was able to gain a much better understanding of the plant.
confirmed that the company intends to further utilise such techniques and technology on other critical pieces of plant. “People now believe in this technology,” concludes Boyd. “This has changed the perception of condition monitoring as they can now clearly appreciate the benefits to be gained from using the system. We are still on a learning curve, having only introduced this regime earlier in 2008, but I am confident that we will obtain a greater understanding of the bearings.” The DTECT X1 series is a cost effective range of online monitoring devices that enables permanent frequencyselective monitoring. The advantage of the DTECTX1 system is that it includes features that are usually only available in far more expensive online systems. The basic model is available as a two-channel or eight-channel version with external multiplexer. All commonly used acceleration, speed and displacement sensors can be connected to the system. Depending on the version used, process quantities such as speed, temperature, torque and pressure can be recorded. The signal measured by the sensor is broken up into its frequency components using Fast Fourier Transformation (FFT), which enables monitoring of amplitudes for previously specified threshold values within very narrow, defined frequency bands, including the triggering of an alarm if these values are exceeded. Therefore, damage can be detected at an early stage by means of frequency-selective monitoring. Q
Feature May 2010
White paper details As well as providing the reader with information on the basic approaches to the various types of maintenance strategy (reactive, preventive and predictive), the paper also provides useful guidance on how to set up and identify the criticality of assets in your business, including potential return on investment from implementing a predictive maintenance regime. The paper then discusses the technical benefits of using condition monitoring systems and techniques to support the predictive maintenance strategy. This includes vibration monitoring, which can be used to detect early signs of failure of rolling bearings.
benefits tend to be more immediate because of the use of highly trained staff. However, it is often more beneficial to keep the activities in house so you become more familiar with your own plant, equipment and processes which gives benefits of not only preventing unplanned downtime but enables more time to be spent on mitigating potential failure modes and improving process efficiency. The cement industry is a good example where CM has been implemented and saved money both in terms of repair costs and lost production. The failure of a large gearbox caused a three week shutdown and extensive repair costs are typically €50,000 to €100,000. To prevent such damages F’IS (FAG Industrial Services, Schaeffler Group) installed an eight channel FAG DTECT X1 system and
Detailed analysis of the various rolling bearing vibration monitoring techniques are discussed and appraised. Sections are included on frequency spectrum, envelope spectrum, Cepstrum analysis, bearing characteristic frequencies, typical bearing defects, variable compliance and bearing speed ratio. The final chapter of the paper considers various real-life scenarios of rolling bearing vibration monitoring, including detailed studies of a 250kW electric motor; an impact crusher drive shaft; a 2MW generator on a test bed; a vertical impact crusher; and the gearbox of a wind turbine. For your free copy of the white paper, please visit www.schaeffler.co.uk
trained the customer’s staff who received three months support – total cost €18,000. Detecting deterioration of the gearbox early resulted in a repair cost of €5000 saving the customer at least €27,000. More importantly, the company avoided lost production amounting to around €6000/hour. “However, with rolling bearings, characteristic vibration signatures are often generated in the form of modulation of the fundamental bearing frequencies. This can be used to our advantage and vibration condition monitoring software is designed to identify these features and provide an early warning to an impending problem. This usually takes the form of signal demodulation and the envelope spectrum, which indicates early deterioration of the rolling contact surfaces.” Q
Case study
Monitoring saves steel rolling costs By introducing a new regime of condition monitoring from scratch, a European steel rolling mill has not only avoided a number of costly breakdowns but also improved the perception of condition monitoring across the site.
L
ocated at Skinningrove near Saltburn-bythe-Sea in Northern England, the steel rolling mill is part of the Corus Group and manufactures hot-rolled steel profiles for a wide range of industries, including earth-
moving equipment, materials handling, shipbuilding and mining. Monitoring of the six pairs of spindle support bearings on the two-stand
Justifying the investment When justifying PdM the following should be taken into consideration:
• • • • • • • • • • • • • • • • • • • • • •
Direct Costs Labour Normal and overtime labour for planned repair activities unplanned repairs Materials Parts replaced Machinery replaced Indirect Costs Lost production (£/hr) Outside services Insurance costs Parts inventory Total potential cost reduction (1+2) PdM program costs Site survey Cost of capital equipment Cost of any additional labour Cost of training Initial setup and baseline Scheduled data collection (visits/yr at £/visit) Total PdM Costs for one year (3)
Contact Steve Lacey Engineering manager Schaeffler UK Ltd Tel: +44 121 313 5870 Email: steve.lacey@schaeffler.com www.schaeffler.co.uk
reversing mill was previously carried out by physical inspection on routine maintenance shutdown days. This involved two craftsmen stripping down the bearing housings and manually inspecting the bearings. If no defects were found, the same bearings were then reassembled into the original housings and refitted into the mill. The entire process is both labour and overhead crane intensive. This task was done in rotation so that each bearing pair was inspected every six weeks.
Challenges This maintenance regime presented the engineering team with a number of challenges. As Scott Boyd, Operations Engineer, Mechanical points out: “It is not good practice to tie up valuable labour for a full day disassembling and then reassembling bearings when they could be working on other areas of the plant and freeing up valuable resources.” www.worldpumps.com
33
34
Feature WORLD PUMPS
May 2010
of the six spindle support bearing sets, with a plan to connect the two spare sensors to the pinion box. “By using the online condition monitoring system we have been able to gain a much better understanding of the plant,” says Taylor. “When we began to analyse the first set of data, we realised that interference from other general plant equipment was masking the true bearing defects. We therefore needed to eliminate this in order to obtain true readings.”
Monitoring of the six pairs of spindle support bearings was a time-consuming process. The spindle support bearing housing (shown here) had to be stripped down and the bearings inspected manually.
Not only were these increased manning levels an issue for the engineering team, but there was also the risk of introducing new problems as a result of human intervention. Boyd continues: “Due to the harsh environment in which the mill operates, there is an increased risk of particulate contamination within the bearings during the dismounting and remounting process. We also had to ensure that when we refitted the bearings we did so to the correct bearing clearance, and this all takes time.” Following a request from Skinningrove at the beginning of 2008, Corus’ Plant Condition Monitoring (PCM) team carried out patrol monitoring on the bearings. By using a portable vibration monitoring device to obtain data on bearing defect frequencies they were able to report on some interesting findings. “We found that we could obtain some very reliable data from our handheld device which allowed us to understand the condition of the six pairs of bearings and determine when a failure was imminent,” comments Ian Taylor, Business Development Engineer, PCM at Corus. “However, for health and safety reasons, the manual approach was not practical in the long term,” adds Taylor. “Rather than sending our engineers into the working steel mill to obtain this data on a regular basis, it was agreed to install an online condition monitoring system.” In September 2008, an eight-channel FAG DTECT X1 vibration monitoring system from Schaeffler UK was installed on the rolling mill. One sensor was fitted to each www.worldpumps.com
Once this issue had been resolved, the FAG DTECT X1 system discovered two bearing faults on two separate occasions within the first week of operation. The engineers were able to plan the outage of the failed bearing and avoid a breakdown, which would have resulted in a significant plant stoppage on each occasion to allow time for stripping down and replacing the failed bearings. As Boyd points out: “By preventing two potential plant stoppages, the system has already paid for itself. Early detection means that we are in control of our plant. Not only are we spending less time and manpower removing and replacing perfectly good bearings, or trying to identify which bearing has failed and why, but we are also avoiding the added risks that human intervention brings.”
Future plans Asked what the future plans are for condition monitoring at Skinningrove, Boyd
The FAG Detector III handheld vibration monitoring device. Handheld devices allowed the maintenance teams to determine when a failure was imminent.
The FAG DTECT X1 is a fixed/online condition monitoring system. By using an online condition monitoring system, the maintenance team was able to gain a much better understanding of the plant.
confirmed that the company intends to further utilise such techniques and technology on other critical pieces of plant. “People now believe in this technology,” concludes Boyd. “This has changed the perception of condition monitoring as they can now clearly appreciate the benefits to be gained from using the system. We are still on a learning curve, having only introduced this regime earlier in 2008, but I am confident that we will obtain a greater understanding of the bearings.” The DTECT X1 series is a cost effective range of online monitoring devices that enables permanent frequencyselective monitoring. The advantage of the DTECTX1 system is that it includes features that are usually only available in far more expensive online systems. The basic model is available as a two-channel or eight-channel version with external multiplexer. All commonly used acceleration, speed and displacement sensors can be connected to the system. Depending on the version used, process quantities such as speed, temperature, torque and pressure can be recorded. The signal measured by the sensor is broken up into its frequency components using Fast Fourier Transformation (FFT), which enables monitoring of amplitudes for previously specified threshold values within very narrow, defined frequency bands, including the triggering of an alarm if these values are exceeded. Therefore, damage can be detected at an early stage by means of frequency-selective monitoring. Q