On commercial fans and blowers, a large portion of the spherical roller bearings are mounted pillow blocks. Pillow blocks are convenient and offer an array of options to suit most applications. In general, pillow blocks come in two types: split housed, solid housed.
Split-housed pillow blocks are shipped in pieces and require assembly. On the other hand, solid-housed pillow blocks are shipped shaft ready, which means the bearing arrives filled with grease, sealed and with bearing clearance set. All you have to do is slide it on the shaft, secure it with the attached shaft-locking device and bolt it down.
Whether you use a split-housed or solid-housed roller bearing, the performance characteristics are nearly identical as long as the bearing has been installed correctly per the service instructions.
Maybe it’s a cliché, but it’s also true: time is money, and this poses the question: “What’s best for me, split block or solid block?”
With bearing performance and capability nearly identical, the real difference is installation time. Since assembly is required, a split block can take three to four times longer to install than a solid block. A critical step in the installation of a split block is checking the bearing internal clearance of the unmounted bearing and also during installation (using feeler gauges) to make sure the bearing is secure to the shaft. Improper procedure can lead to premature bearing failure.
But that is just one step in the split-block process. You’ll also need to torque the cap bolts, install seals and C-spacers, and lubricate all critical areas. Lubrication or adding grease is extremely important. Each roller has to be hand packed to make sure there is grease on all the rolling surfaces before startup, and then, the housing cavity has to be filled. Again, failure to follow procedure can lead to premature failure.
Other items of concern during the split-block installation are lost parts and bearing contamination. The bearing needs to be unwrapped and exposed to the environment in which you are performing the installation. The bottom line? Not only does it take longer to install a split-block bearing, but there are many important steps and procedures required to ensure a successful install.
Conversely, solid-pillow blocks -- like the Rex ZAF, ZLF and P2BRN -- offer an alternative solution to complicated split-block housings. The ZAF and ZLF interchange directly with SAF22500 series split blocks. The P2BRN hard metric pillow block directly interchanges with SN500 split blocks, using a 22200 series bearing. The advantage is simplicity. These bearings come to you shaft ready, greased, sealed and with bearing clearance set.
Simply take it out of the box, slide it on, lock it to the shaft and bolt it down. Besides taking a quarter of the time to install a split block, there is no chance of incorrectly setting the bearing clearance, no chance of incorrectly lubricating, no chance of losing parts and no chance of contaminating the bearing. Fewer steps reduce the chance for error. Less chance for error leads to longer bearing life and increased uptime, which reduces your overall cost of operation.
If you have questions about solid pillow-block bearings or any other bearing-related issues, call (317)273-5781 or email [email protected]. For videos and other demos, visit our YouTube channel.
Mark Czubak
Mark Czubak is a Principal Engineer with the Rexnord Bearing business. He has spent nearly 40 years with Rexnord where he has managed all facets of engineering, including application, design and manufacturing, giving him a cradle to grave knowledge of mounted roller bearings. With this experience, Mark shares his passion and knowledge through bearing training, application assistance and installation. “Bearings are overlooked for the more expensive components of the system, but a bearing failure can cause just as much downtime as any other component so choose your bearings wisely, and save time and money.”