The roller press adopts the high-pressure material layer crushing principle to crush the material, which is a one-time input of high energy. In order to achieve continuous industrial production operations, a pair of oppositely moving rollers (one fixed roller and one movable roller) are used

The roller press adopts the high-pressure material layer crushing principle to crush the material, which is a one-time input of high energy. In order to achieve continuous industrial production operations, a pair of oppositely moving rollers (one fixed roller and one movable roller) are used. The hydraulic pressure acts on the material pulled between the two rollers through the movable roller, and it is compacted and crushed. Roller press, as a grinding equipment for brittle materials, is suitable for grinding cement clinker, cement raw materials (limestone, sandstone, etc.), gypsum, coal, quartz sand, iron ore, blast furnace slag, and other materials. The dry goods shared by the master today are an example of bearing fault diagnosis for the cement roller press gearbox of a cement factory under a large cement group.

PART. 1 Equipment alarm

On February 16, 2023, the equipment intelligent operation and maintenance management platform was officially launched in the cement plant. On May 2nd, the system showed that the acceleration peak and envelope peak of multiple measuring points on the gearbox of the cement plant's roller press exceeded the high alarm threshold, resulting in abnormal equipment operation.

Figure 1 System Warning Details

PART. 2 Fault Diagnosis

On May 10th, on-site personnel from the cement plant discovered abnormal noise from the gearbox during their inspection, and immediately contacted the diagnostic engineer Zhang Gong from the company. Zhang checked the system and analyzed the equipment data.

Basic information of the cement roller press gearbox:

Gearbox model: JGR3240 Rated speed: 1487r/min

Input shaft front bearing model: QJ236N2MPA

Input shaft middle bearing model: NU236EM1C3

Input shaft rear bearing model: NU236EM1C3

From the linkage of the V-envelope peak values at the driving end of the first axis of the fixed roller gearbox (Figure 2), it can be seen that the envelope peak value of this measuring point is too large, exceeding the high alarm threshold. There is a significant frequency impact in the time-domain diagram, and in addition to 1x frequency and its harmonics, there are also fault frequencies and harmonics in the inner ring of the non driving end bearing of the input shaft in the envelope spectrum.

Figure 2 Three Diagram Linkage of V-Envelope at the Drive End of Axis 1 of the Fixed Roller Gearbox

After analysis, Mr. Zhang believes that there is a significant fault in the input shaft bearing of the gearbox of the roller press. It is recommended that the magnetic rod and iron filings of the gearbox be inspected at the site if there is time.

PART. 3 Disassembly Verification

On May 11th, the cement plant was shut down for maintenance. Equipment personnel inspected the magnetic rod on site and found a large amount of iron filings and small iron blocks on the magnetic rod.

Figure 3 Maintenance site magnetic rod condition

On May 13th, the gearbox was replaced on-site. After restarting, the device's operating data returned to normal (Figure 4). On June 7th, during the on-site inspection of the offline gearbox, it was found that there was a large area of peeling off on the inner ring of the non drive end bearing of the input shaft (Figure 5).

Figure 4 Linkage of the V-envelope of the Drive End of Axis 1 of the Fixed Roller Gearbox after Maintenance

Figure 5: Large area of peeling on the inner ring of the bearing

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