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Types of Sleeve Bearings & Sleeve Bearing Repair

Bearings account for about 51% of all electric motor failures and the most common sources of failure involve normal wear and tear, lubrication issues, contamination, or electrical damage that affects the bearing surfac es. While rolling element bearings are the most common type of bearing, sleeve bearings are found most often in larger motors that require a bearing life that rolling element bearings simply cannot achieve.

Purpose of Sleeve Bearings

Sleeve bearings go by several different names, including Babbitt bearings, bushings, journal bearings and plain bearings, and are crucial to the correct operation of rotating equipment that they are part of. They can serve multiple purposes at the same time: constrain motion, serve as a guide, provide support, and reduce friction. They work with linear, rotating, and oscillating motion. Sleeve bearings are cylindrical in shape and are straight, as opposed to tapered or conical.

Considerations for Purchasing a Large Electric Motor



For some reason, you've found yourself in a position where you need to purchase a large electric motor -- as in a motor that is not a standard "NEMA" electric motor. It may be that some new equipment is being installed at your location, you may be in search of a surplus motor, or the time has come to replace one. Regardless of why you need a large electric motor, there are some key things to keep in mind. But first, let's define what we mean by large.

Large Electric Motors

These are not your everyday, on-the-shelf motors that every PT (Power Train) house and motor shop has in stock.

The kind of motors under discussion here are typically built specifically for your application and although some large motors may provide hundreds of horsepower (400+ hp), the kind I'm talking provide thousands of horsepower. These are typically referred to Above-NEMA or A-NEMA motors and they can be far more challenging to purchase than a standard motor.

The Basics of Bidding Out an ANEMA Motor

First, start with the basics which include information such as ...

  • Horsepower
  • Speed
  • Voltage
  • Full load amps
  • Enclosure
  • Frame
  • Mounting
  • Bearing type
  • NEMA design
  • KVA code
  • and quite a few more!

You also want to include any other information you have about the original motor and its application. This can include frame dimensions, speed vs. torque curves, data packets, and schematics.

B-Stage vs. VPI Insulation Systems for 13.2KV/13.8KV Large Electric Motors


Higher voltage (Medium voltage) Insulation systems have been developed over many years, with a recent interest in newer vacuum pressure impregnation (VPI) insulation systems that have a perception of being newer and better but not with an improvement in longevity or quality. The newer VPI insulation systems today are promoted by some manufacturers and vendors as being better than the older systems that have lasted for the last 50+ years with great success. The main reason for the VPI processing of newer design large motors is for economics. The newer motors are smaller in physical size and have higher temperature rises. The use of VPI in these motors allows the manufacturer to reduce costs for manufacturing purposes… but not necessarily for longevity. This trend has now been incorporated into older machines with the same reasons: for lower costs to process but not necessarily for longer lasting service. 

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