TOUT LUI FAUT OPERATIONS

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1 Equipment Failure Date: 22 November 2007 Location: 100 Unit Equipment Name: E-107A Fan Motor Asset Number: EP-107A Failed Component Name: Front Bearing Damage Condition Possible Cause Pro-Active Maintenance Electromotor of E-107 filled Grease outlet of motor bearings Provide outlet for grease with grease plugged with setscrew Proper packing of grease cavity Discussion Bearing housings design There are two basic bearing housing designs used in most motors with regreasble rolling element bearings. 1

2 Figure 1 Flow-Through Design (open bearings) Figure 2 Same-Side Fill & Drain More motors are manufactured with a same-side design (Figure 2) than a Flow-Through design. Figure 2 shows that the drain plug is the only external path for the grease to exit the grease cavity. Flow-Through is used only for open-faced bearings. The other arrangement is suitable for open, single-shielded and double-shielded bearings. The motor of the E-107 fan has a Same-Side Fill and drain design as showed in Figure 3. Figure 3 Bearing Cover Plate E-107 motor 2

3 Lubricating Mechanism Grease consists of a soap which contains lubricating oil; the heat generated by the moving parts will release the oil from the grease, which forms the lubricating film. Lubricant Starvation Occurs when the grease cavity is not packed with the proper amount of grease during bearing installation (25% of cavity), when the bearing is not re-greased at the appropriate interval with the proper amount or when the oil is removed from the base of the grease by bearing overheating. Over pressurization of the bearing shields When grease is added to a grease cavity, grease volume and cavity pressure increase. Damage can occur to the shield on a single- or double-shielded during regreasing if the grease is added too fast. When the motor is placed into service, the grease will thermally expand. If the grease cavity is full damage can occur to the shields and bearings, and/or the excess grease can find Figure 4 Bearing Housing his way into the motor, causing winding insulation failures. Overpressure protection Grease guns are hydraulic devices that can easily create pressures up to psi, which is more than the average 500 psi limits on the shields. A pressure cut-off-grease nipple does not allow additional grease to be added to the grease cavity when the pressure exceeds 20 psi. The plunger drain opens the center of the grease relief nipple at 1-5 psi to purge excess grease and pressure. Figure 5 Grease Relief Valves 3

4 Sealed bearings Are greased for life Limited to a maximum of 10 Hp and 3600 RPM Light loads and intermittent use Keep contaminants out of the bearing Typical life is 2 4 years depending on the application Heat will accelerate the oxidation of the contained grease Single-Shield Bearings The shield facing the grease supply serves as a baffle, and keeps contamination out of the bearing The shield-to-inner race annulus meters in oil from the grease The shield facing the motor facilitates grease flow to the bearing, while keep helping grease out of the motor Re-lubrication can be done while the motor is running, or while it is idle The drain port should be cleared of any hardened soap that may be causing blockage Double-Shielded Bearings Shields prevent excess amounts of grease (and contamination) from being forced into the bearing, causing churning and heat Oil seeping from the grease will revitalize the lubrication of bearings over time. Oil flows at annulus between the shields and the inner race 4

5 Recommendations Provide outlet for grease on motors, when installing new motor, always check for factory installed setscrews which must be removed. When difficult accessible, provide piping for inlet and outlet. Pack the overflow cavity with 25% of grease volume. Literature: 1. ALERT, Advanced Equipment Reliability Training Series, Lubrication Training, Staatsolie, How to Design an Electric Motor Regreasing Program, Machinery Lubrication Magazine, 3. Lubrication for Industry 2 nd Edition, Kenneth E. Bannister, Industrial Press INC Greasing Double Shielded Bearings Steven van Els 5