HD Technology Case Study:

Transcription

1 CASE STUDY HD Technology Case Study: Bearing monitoring of Autogenous Mill at Aurubis Bulgaria AD By Dobromir Dobrev and Nikolay Nikolaev SPM Instrument Bulgaria EOOD November, 2017

2 2 (10) Contents 1 Introduction Conclusion and summary Application description System setup Measuring equipment Measuring techniques Condmaster setup Case description Appendix... 9

3 3 (10) 1 Introduction This case study describes online condition measurements on a pinion drive-end bearing in Autogenous Mill No. 2 at a flotation plant. The measurements were carried out using the SPM HD shock pulse technology. The customer, Aurubis Bulgaria AD, is a leader in the non-ferrous metals business in Bulgaria and a leading copper producing plant in southeastern Europe. The company s main activity is the production of copper anodes and copper cathodes, as well as byproducts such as sulfuric acid and iron silicate. The pinion gear shaft of the autogenous mill which is the subject of this case study works at low rotational speed (178 RPM). Both bearings are subjected to heavy loads and surrounded by sources of strong ambient noise. To the customer, long forewarning time for gearbox and pinion bearing failures is essential. From a mechanical perspective, autogenous mills operate in a similar way to ball mills but use different media to break or grind the ore. Autogenous mills use larger rocks of ore instead of grinding balls made of steel or other materials to grind the ore. 2 Conclusion and summary At the Aurubis plant, the online system Intellinova Compact INS06 is installed with the SPM HD and EVAM measuring techniques monitoring the mechanical condition of critical equipment. For the pinion drive-end bearing (measuring point no. P430MG02-PN-09), the SPM HD level graph shows a growing HDm trend and large fluctuations in the shock pulse amplitude from the beginning of the measurements on January 1 st, 2015 until machine stoppage for bearing replacement on August 5 th, HDm/HDc levels reach 35/-8 db. This fluctuation is most likely related to dirt or load shocks. Over a period of eighteen months, HDm increased from 0 to 35 db. Analysis of spectrum, time signal, and Colored Spectrum Overview shows bearing damage with accurately matching outer race symptom (BPFO). The installed bearing type is SKF CA.

4 4 (10) 3 Application description Autogenous mill 2 consists of an electrical motor, a two-stage gearbox, a pinion gear, and the drum with a girth gear. Fig 1. Autogenous mill 2-3D graphic. P430MG02-PN-09 Pinion - DE bearing Measuring points Measuring point no. Position Sensor type P430MG02-EM-01 Electrical motor - NDE bearing Shock pulse P430MG02-EM-02 Electrical motor - DE bearing Shock pulse P430MG02-EM-22 Electrical motor - DE bearing Vibration P430MG02-GB-03 Gearbox - DE bearing/1st shaft Vibration P430MG02-GB-06 Gearbox - NDE bearing/2nd shaft Vibration P430MG02-PN-09 Pinion - DE bearing Shock pulse P430MG02-PN-10 Pinion - NDE bearing Shock pulse

5 5 (10) Fig 2. Autogenous Mill 2. Fig 3. Autogenous mill 2 - measuring point locations, measuring point numbers, and installed sensors. Vibration sensor Shock pulse sensor P430MG02-PN-09 - Bearing damage 09 RPM measurement SPM Instrument Bulgaria ЕООD Str. Hadzhi Stamat Siderov 35/А 9000 Varna, BULGARIA 03 spm.office@mbox.contact.bg Tel.: , Fax: Company 1967/1995 SPM CS_016B

6 6 (10) 4 System setup 4.1 Measuring equipment - Online monitoring system: Intellinova Compact INS06 - Shock pulse transducers: 4 x Vibration transducers: 2 x SLD144S - Analog vibration transmitter: 1 x SLD733C (4-20 ma) - RPM sensor: 1 x proximity switch on motor drive side 4.2 Measuring techniques SPM HD is the appropriate measuring technique for this application, because the monitored object is a low-speed machine with sources of strong ambient noise, making shock pulse analysis necessary. 4.3 Condmaster setup Settings used in Condmaster Nova for the actual measuring point are as follow. The measuring technique used is SPM HD. - Measuring time: Same as FFT measurement - Short / long time memory: Time signal and FFT - Upper frequency: 100 Orders - Lines in spectrum: Symptom enhancement factor: 5 - Max RPM = Min RPM = Case description Measuring point P430MG02-PN-09 Pinion - DE bearing - SPM Measurement took place from January 1 st, 2015 to October 26 th, From January 1 st, 2015 to May 1 st, 2016 the level graph shows increasing HDm levels and large fluctuations in the amplitudes of shock pulses. HDm/HDc levels reach approximately 35/-8 db. There were big fluctuations in the Delta level; on average from 7 db to 27 db. The reason for these fluctuations is most likely related to dirt or load shocks.

7 7 (10) Fig 4. SPM HD trend graph HDm/HDc, from January November Bearing damage Bearing replacement Fig 5. SPM HD Spectrum on April 30, 2016 before bearing replacement. SPM HD Spectrum shows high HDesv levels and a perfect match with bearing symptom BPFO for outer race damage.

8 8 (10) Fig 6. SPM HD Time Signal and Circular plot diagram on April 30, 2016 before bearing replacement. Time signal and Circular plot diagrams show very clear peaks. HD 2 esv level reached values around (for comparison, before the damage HD 2 esv levels were around 60). The time signal clearly shows 9,73 peaks per 1 rev. Fig 7. SPM HD Colored Spectrum Overview. Bearing replacement Colored Spectrum Overview shows BPFO match from the beginning of the measurements and rising levels over time. There are some periods with lower amplitudes which are probably the result of reduced load on the mill. The green arrow shows the time of bearing replacement.

9 9 (10) 6 Appendix Below are pictures of the dismounted bearing. On the outer race surface, there are visible signs (scratches) of bearing damage. Fig 8. Outer race. Fig 9. Outer race.

10 10 (10) Fig 10. Outer race. Fig 11. Outer race.