Diesel engine is an engine that burns diesel fuel to obtain energy release. The working process of a diesel engine is actually the same as that of a gasoline engine, and each working cycle also goes through four strokes: air intake, compression, work and exhaust. Two Cylinder 4 Stroke Diesel Engine,single Cylinder Diesel Engine,V Twin Water Cooled Diesel Engine,air cooled diesel engines Vibropac Machinery Co.,Ltd , https://www.vibropac-power.com
The diesel engine sucks pure air in the intake stroke. When the compression stroke is nearing the end, the diesel fuel is increased to more than 10MPa by the fuel injection pump, and is injected into the cylinder through the fuel injector, and mixed with the compressed high-temperature air in a very short time to form a combustible mixture. Due to the high compression ratio of the diesel engine (generally 16-22), the air pressure in the cylinder can reach 3.5-4.5MPa at the end of compression, and the temperature is as high as 750-1000K (while the mixture pressure of the gasoline engine at this time will be 0.6-1.2MPa, and the temperature will reach 600-700K), which greatly exceeds the autoignition temperature of diesel. Therefore, after the diesel fuel is injected into the cylinder, it mixes with the air in a very short time and immediately ignites and burns on its own. The air pressure in the cylinder rises sharply to 6-9MPa, and the temperature also rises to 2000-2500K. Driven by high-pressure gas, the piston moves downward and drives the crankshaft to rotate to do work, and the exhaust gas is also discharged into the atmosphere through the exhaust pipe.
Analyze and repair the skills and usage of centrifugal pump bearings
**Analyze and Repair Skills and Usage of Centrifugal Pump Bearings**
Home > Bearing Knowledge > Analyze and Repair Skills and Usage of Centrifugal Pump Bearings
Source: Bearing Network | Time: January 9, 2014
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Centrifugal pumps rely heavily on bearings for smooth and efficient operation. Proper installation, maintenance, and repair of these bearings are essential to ensure the longevity and performance of the pump. This article provides a detailed guide on analyzing and repairing both rolling and sliding bearings used in centrifugal pumps.
### Rolling Bearings
1. **Bearing Fit**: The cooperation between the bearing and the shaft follows the base hole system, while the fit with the outer casing is based on the base shaft system. The dimensions and rotational precision must comply with GB307-84 standards.
2. **Surface Finish**: The journal and inner bore of the bearing should meet the requirements of GB1031-83. The surface roughness (Ra) for the journal should be less than 1.6 μm, and for the bearing housing, it should be less than 2.5 μm.
3. **Material and Hardness**: Bearings made from GCr15 or ZGCr15 steel should have a hardness of 61–65 HRC. For GCr15SiMn or ZGCr15SiMn, the hardness should be 60–64 HRC. The hardness distribution and uniformity must follow JB1255 guidelines.
4. **Clearance**: Radial and axial clearances must adhere to GB4604-84. These measurements ensure proper movement and reduce wear during operation.
5. **Inspection**: The raceways of the inner and outer rings should not show signs of peeling, severe wear, or cracks. Balls must be free from damage, and the cage should not be deformed. Any unusual noise or vibration indicates potential failure.
6. **Tapered Roller Bearings**: For C-class tapered roller bearings, the contact between the rollers and raceways should be even. Under load, the contact marks should be continuous, with a minimum length of 80% of the roller's length.
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### Sliding Bearings
1. **Radial Thick-Walled Bearings**: The bearing clearance and bush interference should be measured using the pressure lead method or other suitable techniques. The interference between the bush and shell should be between 0 and 0.02 mm.
2. **Visual Inspection**: Check for any damage, cracks, or defects in the bearing bush. Ensure there is no peeling, porosity, cracks, or localized wear.
3. **Contact Area**: Use the color method to check the contact between the bush and the journal. The angle should be between 60° and 90°, depending on the speed. There should be 2–4 contact points per square centimeter. If the contact is poor, scraping may be necessary.
4. **Cleaning**: Clean the bearing housing thoroughly. Ensure all oil holes are unobstructed and check for cracks or leaks.
5. **Fitting**: The back and housing should be tightly and evenly fitted. The contact area should be at least 50%.
6. **Thin-Walled Bearings**: The alloy layer and bush shell must be firmly bonded without delamination. The surface should be smooth, lubricated, and free from cracks, pores, or imperfections.
7. **Fit with Housing**: The inner diameter of the bush and housing should be closely matched. For diameters under 180 mm, the contact area should be at least 85%, and for larger sizes, at least 70%.
8. **Installation Check**: After installation, use a 0.02 mm feeler gauge at the joint line. It should not pass through, indicating a tight fit.
9. **Thrust Bearings**: The thrust bush should be free from wear, deformation, or cracks. The contact area should be at least 70%, with even distribution around each tile. The thickness difference among tiles in the same group should not exceed 0.01 mm. The babbitt should be shaped into an oil wedge to aid lubrication.
10. **Gasket Adjustment**: The gasket should be flat, non-deformable, and have a thickness variation of no more than 0.01 mm. After assembly, measure the thrust clearance using the push shaft method and adjust accordingly.
11. **Positioning**: The horizontal contact surface of the bearing shell should be tight and properly positioned. Oil temperature measuring holes and tile cover eyes must align correctly, without skewing.
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