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Bearing noise
A pump Ensival Moret, drive-end bearing using SKF duplex contact angle bearing steel cage, non drive-end using SKF cylidical bearing ( NU ) polyamide cage . This pump generates lound noise at the bearings position. Oil viscosity has been incresed fron ISO VG 32 to 68. But the bearing noise is also increased ( or at lease the bearing noise remains unchanged ). Alignment figure : parallel 0,03 mm TIR, angular 0,04 mm TIR. Rotor is balance at G-2,5. Bearing housing skin temperature 70-75 deg C( after change the oil from 46 to 68 ISO VG ).
Having talk to the end user, this pump used to yield the noise louder, and this time it is pretty much improved.
But in my opinion, it should not generate the noise like this.
Any thoughs to make it quiet.
Replies to This Discussion
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Permalink Reply by MIzee on -
Noice normally come from friction, I suggest you use vibration analyzer to source for this noice as it could guide you from the spectrum reading.
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Permalink Reply by Manorom Chiewpanich on -
Vibration spectrum indicates wide broad band high frequency with several spike. While the order x 1 frequency amplitude is so low as 0.4 mm/s rms.
I expected these bearing may not be original SKF. I had experience with SKF bearing in electric motor, it give noise at the first start up. So we replaced SKF bearing with Japanese NTN bearings, resulting noise was gone.
Any one has the experience with the fake SKF bearing ?
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Permalink Reply by Manorom Chiewpanich on
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More information
We stopped this pump and dismantle for investigation(after 8 hours operation). As found : a) an outer race of NU bearing was rotated. It seems that a bearing cap was not grip( press ) to the bearing outer race. b) its roller elements indicates very high radial load or lack of lubrication. c) contact angle bearings indicates high thrust load or lack of lubricaiton. d) The tracking line(ball contact to the outer race) shows both direction of thrust load ( one side indicates extreamly high thrust load, while another side indicates mild thrust load). e) its ball element from high thrust load bearing has circumference contacted mark with micron size cracked line at the ball surface. f) its ball element from low thrust load has mild circumference contact mark.
To sum up, without knowing that it was only 8 hours operation, the speciments clearly indicates : it had been opearted for thousand hours with extream high load. In fact, it is only 8 hours running , with light load.
Shoot in the dark, it seem that either the fake bearing or the lubrication problem or both are the root cause.
Any thoughs on the possibility causes will be much appraciated.
Oopse... pump was operated with mild cavitation.
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Permalink Reply by MIzee on
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As I prefered F.A.G Bearings then S.K.F, for my side I seldomly used S.K.F and never encountered any fake one before but you could mail to S.K.F regarding this and get the info from them.
Manorom Chiewpanich said:More information
We stopped this pump and dismantle for investigation(after 8 hours operation). As found : a) an outer race of NU bearing was rotated. It seems that a bearing cap was not grip( press ) to the bearing outer race. b) its roller elements indicates very high radial load or lack of lubrication. c) contact angle bearings indicates high thrust load or lack of lubricaiton. d) The tracking line(ball contact to the outer race) shows both direction of thrust load ( one side indicates extreamly high thrust load, while another side indicates mild thrust load). e) its ball element from high thrust load bearing has circumference contacted mark with micron size cracked line at the ball surface. f) its ball element from low thrust load has mild circumference contact mark.
To sum up, without knowing that it was only 8 hours operation, the speciments clearly indicates : it had been opearted for thousand hours with extream high load. In fact, it is only 8 hours running , with light load.
Shoot in the dark, it seem that either the fake bearing or the lubrication problem or both are the root cause.
Any thoughs on the possibility causes will be much appraciated.
Oopse... pump was operated with mild cavitation.
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Permalink Reply by Jack Condon on -
i trust you have contacted Ensival Moret for recommendations. ISO 68 seems to be a low viscosity oil to me for a centrifugal pump, but the manufacturer would be the final word. if the bearing has damage putting in higher visc oil won't do much good. check with the manufacturer and get their recommendations on oil and how to proceed - they may request you send the brngs to SKF to analyse - it'll cost around $600 but you will know more than you want about the bearing and what is going on with it. They are the best at this.
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Permalink Reply by Joseph Jaigobind on
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IB casing wearing ring has too much clearance.
Manorom Chiewpanich said:More information
We stopped this pump and dismantle for investigation(after 8 hours operation). As found : a) an outer race of NU bearing was rotated. It seems that a bearing cap was not grip( press ) to the bearing outer race. b) its roller elements indicates very high radial load or lack of lubrication. c) contact angle bearings indicates high thrust load or lack of lubricaiton. d) The tracking line(ball contact to the outer race) shows both direction of thrust load ( one side indicates extreamly high thrust load, while another side indicates mild thrust load). e) its ball element from high thrust load bearing has circumference contacted mark with micron size cracked line at the ball surface. f) its ball element from low thrust load has mild circumference contact mark.
To sum up, without knowing that it was only 8 hours operation, the speciments clearly indicates : it had been opearted for thousand hours with extream high load. In fact, it is only 8 hours running , with light load.
Shoot in the dark, it seem that either the fake bearing or the lubrication problem or both are the root cause.
Any thoughs on the possibility causes will be much appraciated.
Oopse... pump was operated with mild cavitation.
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Permalink Reply by Manorom Chiewpanich on
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Finally, I have found the inducer rubbing to its inlet eye. It is strange that, at static condition, this inducer still has the radial clearance of 1 m.m. from both vertical and horizontal plane, while the shaft radial play in vertical direction. Moreover, noise & vibration yielded at the bearing location. That was why I lost the analytic process, Instead of stay cool, I jumped to conclusion on the bearings problem. The root cause of the inducer rubbing was from the poor coupling condition ( Leaf type flex coupling ). Coupling flange bolt holes diameter are oval shape. Consequently, the couple moment ( from driver torque ) at the pump DE was not symmetry, resulted the high resultant radial force occurred at DE side( coupling side ), this high radial force from DE side generated the high displacement to NDE -shaft-impeller-inducer as the cone shape at 180 phase different. After coupling flange was replaced, the problem has been gone.
I would like to close this topic, and having hope that my lesson learnt would be useful for the pump society.
Manorom Chiewpanich, Equity Services & Solutions Co., Ltd
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