 Split bearings are tricky to diagnose when interpreting the acceleration spectrum. For diagnostic purposes, they should not be put into the same class as a normal ball bearing.
The bearing at the left is a split bearing. When using acceleration for diagnostic purposes there could be some misleading information. The information is correct, but under normal interpretation rules one would believe that there was a problem when in fact there wasn't a problem. Any technician would say that since most ball and roller bearing designs are predominantly rolling contact and not sliding contact, between the ball and raceway, any broadband vibration would be a good indication of metal to metal contact. This would be construed as a problem. |
|
 However, looking at the cross section of a typical split bearing one immediately sees that there is a lot of sliding contact happening between the bottom half of the roller sidewall, and the side of the locking collar (see red circle, picture left). In addition, there is a lot of sliding contact happening between the roller cage and locking collar. As long as there is plenty of lubricant there isn't a problem. Regardless as to the amount of lubricant, the well lubricated sliding motion is still picked up as broadband frequencies in the spectrum (picture lower left). There's also a fair amount of impacting. |
|
 |
As tricky as this bearing is to monitor, when it goes bad it generates normal bearing fault frequencies. The nonsynchronous bearing frequencies will pop up out of the mountain of broadband frequencies. |
|
There is another weakness behind this bearing and it is showcased in the article "Machine Design - Case Study No. 70: Pros and Cons of Using Split Bearings." In addition, this bearing tends to run hot and the reason is showcased in the article "Lubrication - Case Study No. 69: Eliminating Pressure Lubricated Systems and Living with High Heat." |
|
| All Pictures and Text Copyright © 2000 - 2016 Contact Mr. Adler Adler Engineering LLC of Wyoming USA
Great care has been taken in the compilation of this article. However, no warranty, expressed or implied, including without limitation, warranties of merchantability or fitness for a particular purpose, are given in connection with this article or any article archived on this website. Although this information is believed to be accurate by the author, the author cannot guarantee favorable results will be obtained from the use of this article alone. This article is intended for use by persons at their sole discretion and risk. Since the conditions of product or material use are outside of the author's control, the author assumes no liability or obligation in connection with any use of this information. The author is not liable for special, indirect or consequential damages resulting from the use of this material. No part of this article or any article archived in this website, or any part thereof, may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, without the prior written permission of the copyright holder R. H. Adler. Nothing contained in this article or any article archived in this website shall be construed as a grant of any right of manufacture, sale, use, or reproduction, in connection with any method, process, apparatus, product, composition, or system, whether or not covered by letters of patent, copyright, or trademark, and nothing contained in this article or any article archived in this website, shall be construed as a defense against any alleged infringement of letters of patent, copyright, or trademark, or as a defense against any liability for such infringement. |