Abstract: This article mainly introduces the clearance adjustment and lubrication of the 10DK9 × 2 water pump bearing underground. Through the modification of the water pump bearing adjustment and lubrication, the axial force is reduced, and the axial force borne by the motor end bearing is also reduced. This reduces the temperature of the motor end bearing, increases the service life of the bearing, reduces the labor intensity of operators, and reduces maintenance costs.
Keywords: bearings; Axial force; Adjustment; lubrication
Preface
Zhaokou Mine of Shandong Jinling Mining is one of the main ore production units of Jinling Iron Mine, responsible for nearly half of the ore production of the entire mine. Therefore, the safety production of Zhaokou Mine plays a crucial role in the development of Jinling Mining. One of the four important systems in mining production, the drainage system, plays an important role in achieving the safe operation of the entire mine production. If the water gushing from the mine cannot be discharged in a timely manner, causing a flood, the consequences will be unimaginable. The good or bad of the drainage system mainly depends on whether the water pump can operate normally. The drainage system of Zhaokou Mine adopts staged drainage, so any failure in that section will pose a threat to underground safety production.
At present, the main pump rooms of Zhaokou Mine, including the 170m pump room and the 310m pump room, share 10 sets of 10DK9 × 2 water pumps. The underground drainage of the Zhaokou mine relies on these 10 water pumps, which discharge about 13000 cubic meters of water from the underground to the surface every day, with a head of over 210 meters. The large flow rate and high head cause the water pump to generate a large load, especially for the assembly, adjustment, and lubrication of the water pump bearings. If not handled properly, it will directly affect the normal operation of the water pump (drainage time of about 18 hours per day) and affect production. Based on the actual work, some opinions on the installation, adjustment, and lubrication of bearings are discussed:
1. Adjustment of bearing clearance
In the past, the 170m water pump room 10DK9 × 2 water pump used two plates of 36318 and two plates of 6318 bearings (the outer sleeve of the 36318 bearing has a certain taper). When the water pump operates under load, axial force is generated, which is directed towards the motor direction (with a head of over 210 meters and high pressure). Due to excessive axial force, the bearing temperature rises (above 60 º C, mainly due to overheating of the motor end bearing). Long term operation of bearings at high temperatures can shorten their service life (sometimes burning out bearings), increase maintenance costs, and even affect drainage. In the past, it was always believed that the way to eliminate axial force was to reduce the adjustment pad of the motor end bearing chamber, so that the axial motor end could be aligned, and some axial force could be eliminated (this has entered a misconception). The result is that the closer it is to the motor end, the greater its axial force (because the axial motor end is aligned, the first and second groups of impellers are also aligned with the motor end, causing a change in the volume of the two impeller chambers on both sides of the pump body. The volume of the pump chamber at the motor end decreases, while the volume at the other end increases, resulting in an increase in pressure, forcing the axial motor end to move, increasing the axial force, increasing the bearing temperature, and shortening the service life.
After switching to 4-disc 6318 bearings, an adjustment pad for the motor end bearing was added. The bearing was adjusted towards the rear end (opposite to the motor), which can be adjusted to Z large (the pad can also be gradually reduced depending on the situation). At the same time, the impeller and pump axis were adjusted in the same direction, which can increase the volume of the impeller chamber at the motor end and decrease the corresponding volume at the other end. As the volume increases, the pressure also increases accordingly, causing a portion of the axial force to transfer towards the rear end (opposite to the motor). This reduces axial force and also reduces the axial force borne by the motor end bearing, causing the temperature of the motor end bearing to decrease, increasing the service life of the bearing, and reducing maintenance costs.
2. Lubrication of bearings
In the past, the lubricating grease for the bearings of the 10DK9 × 2 water pump was lubricated with turbine oil, which is not resistant to high temperatures. Due to the large flow rate and high head of the 10DK9 × 2 water pump, the load is large and it belongs to heavy-duty operation. Bearings are prone to overheating, sometimes reaching over 60 ℃. Due to the pump's own reasons, the sealing of the bearing chamber is not very tight, and water easily enters the bearing chamber. The turbine oil emulsifies quickly, and the viscosity of the emulsified lubricating oil decreases, resulting in a decrease in the lubrication of the turbine oil, which cannot provide good lubrication. Moreover, due to the moisture content of the emulsified lubricating oil, the bearings are severely corroded (after opening, there are many rust spots on the bearings, rolling elements, retainers, etc.). It directly affects the service life of bearings. When starting the pump, it is necessary to frequently inject oil into the bearing chamber, and add oil every 2-3 hours. The oil consumption is relatively high, with 5 water pumps consuming around 170kg of oil per month, and the pump is turned on for about 18 hours per day.
Now replace the lubricating oil of the pump bearings in the -310m water pump room with lithium based grease. Due to the high head, large flow rate, and slow speed of the 0DK9 × 2 water pump (-310m water pump, 1487 revolutions per minute), it should belong to low-speed heavy-duty operation. Apply high viscosity lubricating grease according to the characteristics of the water pump. Lithium based grease is a high-temperature resistant grease that can withstand temperatures up to 120 º C. It is not easily soluble in water or emulsified, and has waterproof properties. The use of lithium based grease not only provides a sealing effect, preventing water from entering the bearing chamber, but also solves the problem of oil leakage (originally liquid, now semi-solid). It is also relatively easy to inject oil. Before driving, only need to turn the oil cup cover a few weeks, and when the oil chamber is full, it can be left empty (liquid oil is prone to splashing outside during driving). The installation is also very simple, just drill a hole on the bearing housing cover and thread it to install the oil cup, without damaging the structure of the bearing housing. After more than half a year of use, the effect is very good. The bearing sound is much quieter than before. In addition, lubricating grease also has a vibration absorption effect, which can effectively reduce vibration. The replacement of bearings is not as frequent (using oil to replace bearings every 3 months, switching to grease for about a year, and so far no bearings have been replaced). Because lithium grease is a semi-solid that is not easy to leak, it can lubricate the entire bearing (oil can only be added to the rolling element below the bearing, adding too much is easy to leak, and the bearing is lubricated by the oil ring driven by shaft rotation), and the temperature of the bearing is not high, so there is no need to use water to cool down (water is often used to cool down when using oil). The process of starting the pump does not require refueling, which not only saves costs but also greatly reduces human labor intensity.
3. Conclusion
By retrofitting the installation, adjustment, and lubrication of the 10DK9 × 2 water pump bearings, the labor intensity of operators has been reduced, and the cost of use and maintenance has been reduced (5 pumps use approximately 170kg of engine oil per month at 12 yuan per kilogram, while using approximately 15kg of lithium based grease at 14 yuan per kilogram also extends the service life of the bearings). If an automatic oiling machine is installed, it can inject oil regularly, which will provide better lubrication for the equipment and greatly reduce the labor intensity of the water pump operator.
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2024-06-28