Wear Debris Analysis

The clinker hammer crusher is one of the main pieces of equipment in cement production and is used for the crushing of clinker, the main product of cement kilns, into smaller parts for the preparation of grinding. At CEMEX Egypt, the bearings used in the clinker crusher are spherical roller bearings. These bearings are lubricated with a lithium complex thickened grease with a synthetic base oil designed for high-temperature applications.

Clinker Hammer Crusher

At the CEMEX plant, bearing failures can lead to a halt in cement production. To maintain continuous operation, it is critical for the bearings to operate smoothly. As part of the predictive maintenance program, vibration analysis is used to monitor the condition of the crusher.

A grease sample to analyze wear debris was taken at the first shutdown of the clinker crusher as part of a new program to monitor the performance of equipment. Vibration monitoring of the outboard bearing in the third clinker crusher line at a speed of 360 RPM provided no warning signals. During the next scheduled shutdown, the bearing was opened and a sample of grease was taken. Wear debris analysis was performed on the grease sample to find the cause of the bearing failure that occurred.

Wear Debris Analysis
Wear debris analysis was carried out on used greases by extracting magnetic particles from the sample using a magnet. Microscopic analysis of the sample identified numerous small and large spherical particles. Research has shown that spherical wear debris can reveal the severity of rolling-contact fatigue wear. Because large spherical particles (50 microns) are the product of high metal-to-metal contact and high frictional temperature, their presence is considered a supporting symptom for assessing the wear severity levels.

52ZM Stereoscopic Zoom Microscope

Wear particles were considered to be a critical alarm indicating the need to change the bearing before a forced outage occurs.

Follow-up Inspection
During shutdown, the crusher's outboard bearing was replaced. To check for potential defects, the bearing was opened and visually inspected. A close look of the outer race of the defective bearing showed signs of severe wearing.

Large and Small Spherical Particles Found in a Bearing Grease Sample

Magnet Used to Extract Wear Debris

Defective Bearing Shows Signs of Severe Wear

This case study illustrates the efficiency of condition monitoring based on the detection of debris in grease, which can be a resourceful tool in controlling machine condition and should integrate diagnostic devices.

References

1. Sabrin Gebarin and Jim Fitch. "Origin of Spherical Particles in Lubricants." Practicing Oil Analysis magazine, March 2005.

2. Ray Garvey. "Enhanced 5200 Minilab Offers Improved Oil Analysis." Practicing Oil Analysis magazine, July 2005.

3. Jian Ding. "Determining Fatigue Wear Using Wear Particle Analysis Tools." Practicing Oil Analysis magazine, September 2003.