A method for reducing the temperature of the fifth bearing of a hydraulic coupler

Abstract

This invention relates to the field of nuclear power plant equipment, and in particular to a method for reducing the temperature of the fifth bearing of a hydraulic coupling. The method includes: Step 1: Measuring and adjusting the journal lift of the motor shaft; Step 1.1: Measuring the journal lift of the bearings at both ends of the motor; Step 1.2: Adjusting the journal lift of the bearings at both ends of the motor so that the journal lifts are the same but in opposite directions; Step 2: Adjusting the alignment of the motor coupling wheel and the hydraulic coupling wheel opening; Step 3: Adjusting the bearing clearance of the fifth bearing of the hydraulic coupling; Step 4: Increasing the diameter of the oil inlet plate of the fifth bearing of the hydraulic coupling. This method, through shaft lift adjustment and coupling wheel center optimization, can reduce the load on the fifth bearing of the hydraulic coupling, thereby reducing the heat generation of the fifth bearing; by increasing the diameter of the oil inlet plate of the fifth bearing, the oil intake of the fifth bearing is increased, ensuring sufficient cooling of the fifth bearing; and by increasing the bearing clearance of the fifth bearing, the minimum oil film thickness of the fifth bearing is effectively increased, thereby improving the operational safety of the fifth bearing.

Description

Technical Field

[0001] This invention relates to the field of nuclear power plant equipment, and in particular to a method for reducing the temperature of the fifth bearing of a hydraulic coupler. Background Technology

[0002] The main feedwater pump set (APA pump set) is a crucial auxiliary equipment in a nuclear power plant. Its safe and reliable operation directly impacts the power output of the nuclear power unit. As the most important pump set in the conventional island of a nuclear power plant, the main feedwater pumps are responsible for supplying water to the secondary loop evaporators. Each unit in a nuclear power plant is equipped with three 50% capacity APA pump sets. Each APA pump set consists of a booster pump, a pressure stage pump, a hydraulic coupling, and a motor. The hydraulic coupling is a critical component of the main feedwater pump set. The hydraulic coupling serves three main functions for the APA pump set: speed regulation, speed control, and vibration isolation. The reliability of the hydraulic coupling directly affects the stable operation of the entire APA pump set.

[0003] In the existing technology, the hydraulic couplings of million-kilowatt and ten-million-kilowatt nuclear power units have experienced multiple temperature alarms and wear failures of the No. 5 bearing during the rapid start-up process. This invention proposes a method to reduce the temperature of the No. 5 bearing of the hydraulic coupling in order to meet the requirements of rapid start-up of the APA pump unit. Summary of the Invention

[0004] This invention provides a method for reducing the temperature of the fifth bearing of a hydraulic coupler, which solves the problems of temperature alarm and wear failure of the fifth bearing during the rapid start-up process of the hydraulic coupler in the prior art.

[0005] The technical solution of the present invention is as follows: This invention proposes a method for reducing the temperature of the fifth bearing of a hydraulic coupling, the method comprising: Step 1: Measure and adjust the motor journal lift; Step 1.1: Measure the lift of the bearing journals at both ends of the motor; Step 1.2: Adjust the journal lift of the bearings at both ends of the motor so that the journal lift is the same but the direction is opposite; Step 2: Adjust the motor coupling and the hydraulic coupling to align their openings; Step 3: Adjust the bearing clearance of the fifth bearing of the hydraulic coupling; Step 4: Increase the diameter of the oil inlet plate of the fifth bearing of the hydraulic coupling.

[0006] In some embodiments, in step one, a hydraulic coupling and a pre-pump are connected to the two ends of the motor respectively. Step 1.1 specifically includes: removing the bolts of the bearing seats at both ends of the motor, removing the upper cover of the bearing seats at both ends of the motor, removing the upper bearing, and re-measuring the journal lift of the motor using a level.

[0007] In some embodiments, the specific requirements for adjusting the journal lift of the bearings at both ends of the motor to make the journal lift the same in step 2 are as follows: the journal lift at the end where the motor is connected to the hydraulic coupler is not lower than the journal lift at the end where the motor is connected to the pre-pump, and the deviation of the journal lift of the bearings at both ends of the motor is not greater than 0.05mm.

[0008] In some embodiments, step two, adjusting the alignment of the motor and hydraulic coupling wheel openings, specifically includes: using the motor journal lift as a reference, adjusting the hydraulic coupling pump-side set screws to lift the hydraulic coupling pump side until the vertical deviation between the motor and hydraulic coupling wheel openings is no greater than 0.05mm.

[0009] In some embodiments, in step two, the upper and lower opening deviation between the motor coupling and the hydraulic coupling is not greater than 0.05mm, and the upper gap between the motor coupling and the hydraulic coupling is required to be less than or equal to the lower gap.

[0010] In some embodiments, the bearing gap of the fifth bearing of the hydraulic coupling is adjusted to be 0.18mm-0.20mm.

[0011] In some embodiments, in step four, the diameter of the fifth bearing oil inlet plate of the hydraulic coupling is increased by 1 mm.

[0012] In some embodiments, the diameter of the bearing oil inlet plate is enlarged to 7.7 mm.

[0013] In some embodiments, step three, adjusting the bearing gap of the fifth bearing of the hydraulic coupling, specifically includes: adjusting the bearing gap by scraping the bearing gap, and using red lead powder to color and inspect the bearing.

[0014] In some embodiments, the method for enlarging the diameter of the oil inlet orifice plate in step four specifically includes: removing the oil inlet orifice plate, measuring the diameter of the oil inlet orifice plate, clamping the oil inlet orifice plate on a drilling machine, and enlarging the orifice plate using a 7.7mm drill bit.

[0015] The implementation of this invention has the following beneficial effects: This invention proposes a method for reducing the temperature of the fifth bearing bush in a hydraulic coupling. This method reduces the load on the fifth bearing bush by adjusting the shaft lift and optimizing the coupling center, thereby reducing the heat generation of the fifth bearing bush. Increasing the diameter of the oil inlet plate and the oil flow rate of the fifth bearing bush ensures sufficient cooling. Increasing the bearing clearance effectively improves the minimum oil film thickness of the fifth bearing bush, thus enhancing its operational safety. The significant advantage of this comprehensive method is its ability to effectively reduce the temperature of the fifth bearing bush in the hydraulic coupling, meeting the requirements for rapid start-up. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the main feedwater pump set for a method to reduce the temperature of the fifth bearing of a hydraulic coupler according to an embodiment of the present invention. Figure descriptions: 1. Pressure stage pump; 2. Hydraulic coupling; 3. Motor; 4. Pre-pump. Detailed Implementation

[0017] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] like Figure 1 As shown, this invention proposes a method to reduce the temperature of the fifth bearing of a hydraulic coupler. The method aims to reduce the temperature of the fifth bearing of the hydraulic coupler 2 so that during the rapid acceleration of the pump unit after the hydraulic coupler 2 starts, the temperature of the fifth bearing does not exceed 90°C, and during rated operating conditions, the temperature of the fifth bearing does not exceed 75°C. Figure 1 As shown, the main feedwater pump unit consists of a pre-pump 4, a pressure stage pump 1, a hydraulic coupler 2, and a motor 3. The pressure stage pump 1 is connected to the hydraulic coupler 2, the hydraulic coupler 2 is connected to the motor 3, and the motor 3 is connected to the pre-pump 4. This invention reduces the temperature of the fifth bearing of the hydraulic coupler 2 by measuring and adjusting the journal lift of the motor 3, optimizing the center of the motor 3 and the coupler coupling, adjusting the bearing clearance of the fifth bearing of the hydraulic coupler 2, and increasing the diameter of the oil inlet plate of the fifth bearing of the hydraulic coupler 2.

[0019] This invention proposes a method for reducing the temperature of the fifth bearing of a hydraulic coupling, the method specifically comprising: Step 1: Measure and adjust the lifting of the motor's three journals.

[0020] Step 1.1: Measure the journal lift of the bearings at both ends of motor 3. Specifically, this includes: removing the split bolts on the bearing seats at both ends of motor 3, removing the upper cover of the bearing seats at both ends of motor 3, removing the upper bearing shell, and re-measuring the journal lift of motor 3 using a level.

[0021] Step 1.2: Adjust the journal lift of the bearings at both ends of motor 3 so that the journal lift is the same in magnitude but opposite in direction. The journal lift at the end of motor 3 connected to hydraulic coupler 2 should not be lower than the journal lift at the end of motor 3 connected to the pre-pump 4, and the deviation of the journal lift at both ends of motor 3 should not exceed 0.05mm. Because the load on bearing #5 of coupler is relatively large, the adjustment of the journal lift of motor 3 needs to consider the need to reduce the load on bearing #5. The journal lift at the end of motor 3 connected to hydraulic coupler 2 should have a positive deviation, that is, the journal lift at the end of motor 3 connected to hydraulic coupler 2 should not be lower than the journal lift at the end connected to the pre-pump 4, but the difference should not exceed 0.05mm. After adjusting the lift, the elevation of bearing #5 of coupler can be reduced, thereby achieving the purpose of reducing the load on bearing #5.

[0022] Step Two: Align the opening of the motor 3 wheel pair with that of the hydraulic coupler 2. After adjusting the journal lift of the motor 3 shaft in Step One, use the journal lift of the motor 3 shaft as a reference to adjust the jacking screws on the pump side of the hydraulic coupler 2 to lift the pump side of the hydraulic coupler 2 until the upper and lower opening deviation between the motor 3 and the hydraulic coupler 2 is no greater than 0.05mm. However, an upper opening is not allowed; that is, the upper clearance between the motor 3 wheel pair and the hydraulic coupler 2 wheel pair should not be greater than the lower clearance. Adjusting in this way can further reduce the elevation of the No. 5 bearing and further reduce the load on the No. 5 bearing.

[0023] Step 3: Adjust the clearance of the fifth bearing of the hydraulic coupling 2 to between 0.18mm and 0.20mm. The clearance is typically adjusted by scraping. The bearing is scraped to increase the clearance, and red lead powder is used for staining to ensure that the contact point between the bearing and the journal meets the standard requirement of 70%.

[0024] Since the original fifth bearing clearance of the hydraulic coupling 2 was designed to be 0.14–0.22 mm, this invention conducted a survey and statistical analysis on the original fifth bearing clearance of the hydraulic coupling 2 in various power plants, as detailed in the table below: Table 1. Statistical Analysis of the Clearance of the Fifth Bearing of Hydraulic Coupler 2 The statistics show that the clearance of the fifth bearing of the coupler in each plant is within the design range. Several pump units in each nuclear power plant have no abnormal wear on the fifth bearing clearance, which is within the lower limit of the qualified range. However, the multiple coupler bearing wear failures in nuclear power plants all occurred when the bearing clearance was within the lower limit of the qualified range, while no abnormalities have been found in the couplers with larger bearing clearances. Statistical results show that the probability of wear of the fifth bearing is higher when the clearance of the fifth bearing is at the lower limit of the design range. However, the fact that the clearance of the fifth bearing is at the lower limit of the design range does not necessarily lead to bearing wear. Therefore, the fact that the clearance of the fifth bearing is at the lower limit of the design range is not the root cause of bearing wear. Many failures of the fifth bearing occurred when the pump was started and rapidly loaded under low lubricating oil temperature. It is highly likely that the journal and bearing expanded asynchronously, causing the bearing clearance to decrease further and exceed the design range. In winter, when the coupling housing is shut down, the overall temperature is low, and the journal and bearing expand slowly, which will limit the bearing expansion. However, when the load is rapidly started, the journal temperature reaches the design temperature and expands normally. Therefore, the journal and bearing expand at different rates, resulting in a momentary decrease in the bearing clearance. The specific expansion parameters of the bearing and journal are shown in Table 2.

[0025] Table 2. Analysis of journal expansion during wear of the fifth bearing of hydraulic coupling 2. Ideally, both the shaft and the bearing expand freely outward in the radial direction, and their expansion amounts are similar, so the bearing clearance remains basically unchanged. However, the actual thermal expansion of the bearing is also limited by the bearing chamber and bearing seat on the hydraulic coupler 2 housing, and the thermal expansion of the bearing chamber and bearing seat is mainly affected by the overall temperature of the hydraulic coupler 2. Before pump startup, the overall temperature of hydraulic coupling 2 was low. After rapid loading, the shaft and bearing rapidly heated up, while the housing of hydraulic coupling 2 heated up more slowly. The large temperature difference between the bearing and bearing seat caused the radial outward expansion of the bearing to be restricted by the bearing seat, directly compressing the bearing clearance. Under asynchronous expansion conditions, this is equivalent to a direct reduction of 0.031mm in the bearing clearance (the journal expansion minus the bearing seat expansion in Table 2, i.e., 0.063 - 0.032 = 0.0031mm). Assuming the clearance of the fifth bearing was 0.15mm during installation, the instantaneous clearance of the fifth bearing upon heating was only 0.119mm, far below the design lower limit of 0.14mm. Therefore, this analysis suggests that the asynchronous expansion of the journal and bearing caused by rapid loading after pump startup at a low lubricating oil temperature is one of the main causes of bearing wear, necessitating optimization of the bearing clearance. The design clearance of the fifth bearing bush is 0.14–0.22 mm. Statistical analysis shows that during rapid startup, the fifth bearing bush of couplers exhibiting high temperatures consistently had clearances between 0.14 and 0.15 mm. While this clearance meets design requirements, it is at the lower limit. During rapid startup, the journal temperature rises quickly, and the bearing bush expansion, constrained by the housing, causes a momentary reduction in the clearance, resulting in the fifth bearing bush's clearance momentarily failing to meet design requirements. Calculations indicate that the reduction in clearance is due to different expansion rates. This can be prevented by increasing the clearance. The fifth bearing bush is scraped to achieve a clearance greater than or equal to 0.18 mm, with a maximum of 0.20 mm. Increasing the clearance by 0.04 mm from the minimum clearance of 0.14 mm increases the minimum oil film thickness, preventing the adverse effects of different expansion rates during rapid startup.

[0026] Step 4: Increase the diameter of the oil inlet plate of the fifth bearing bush in hydraulic coupling 2. Adjust the diameter of the oil inlet plate to 7.7mm. The oil inlet plate is located at the inlet of the lubricating oil channel of the bearing bush and is used to control the amount of lubricating oil entering the bearing bush. Enlarge the diameter of the oil inlet plate of the fifth bearing bush by 1mm from the current diameter of 6.7mm, aiming to adjust the diameter to 7.7mm. This will increase the oil flow to the fifth bearing bush and reduce its temperature. The specific method for enlarging the diameter of the oil inlet plate is as follows: First, remove the oil inlet plate, measure its diameter, place the plate on a drilling machine and clamp it, and enlarge the hole using a 7.7mm drill bit.

[0027] This method comprehensively considers the effects of load, bearing clearance, and lubricating oil flow on bearing temperature. By adjusting the shaft lift and optimizing the wheel center, the load on the fifth bearing of the hydraulic coupler 2 can be reduced, thus reducing the heat generation of the fifth bearing. Increasing the diameter of the oil inlet plate of the fifth bearing increases the oil intake, ensuring sufficient cooling. Increasing the bearing clearance from the lower design limit to the middle design value effectively improves the minimum oil film thickness of the fifth bearing, preventing adverse effects caused by different expansion rates during rapid start-up, thereby improving the operational safety of the fifth bearing. In summary, the significant effect of using this comprehensive method is that it effectively reduces the temperature of the fifth bearing of the hydraulic coupler 2. During the rapid acceleration of the pump unit after the coupler starts, the temperature of the fifth bearing does not exceed 90℃, and during rated operating conditions, the temperature of the fifth bearing does not exceed 75℃.

[0028] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for reducing the temperature of the fifth bearing of a hydraulic coupling, characterized in that, The method includes: Step 1: Measure and adjust the journal lift of the motor (3), with the hydraulic coupler (2) and the pre-pump (4) connected to both ends of the motor (3); Step 1.1: Measure the journal lift of the bearings at both ends of the motor (3), specifically including: removing the bolts of the bearing seats at both ends of the motor (3), removing the upper cover of the bearing seats at both ends of the motor (3), removing the upper bearing, and re-measuring the journal lift of the motor (3) using a level. Step 1.2: Adjust the journal lift of the bearings at both ends of the motor (3) so that the journal lift is the same and the direction is opposite. Specifically, the journal lift of the end of the motor (3) connected to the hydraulic coupler (2) is not lower than the journal lift of the end of the motor (3) connected to the pre-pump (4), and the deviation of the journal lift of the bearings at both ends of the motor (3) is not greater than 0.05mm. Step 2: Adjust the motor (3) to align the gear and the hydraulic coupling (2) with the gear opening; Step 3: Adjust the bearing gap of the fifth bearing of the hydraulic coupling (2), specifically 0.18mm-0.20mm; Step 4: Increase the diameter of the fifth bearing oil inlet plate of the hydraulic coupler (2), increase the diameter of the fifth bearing oil inlet plate of the hydraulic coupler (2), expand the diameter of the bearing oil inlet plate by 1mm, and the diameter of the bearing oil inlet plate after expansion is 7.7mm.

2. The method for reducing the temperature of the fifth bearing of a hydraulic coupler according to claim 1, characterized in that, The second step of adjusting the opening of the motor (3) and the hydraulic coupler (2) is specifically as follows: taking the journal lift of the motor (3) as a reference, adjust the pump side set screw of the hydraulic coupler (2) to lift the pump side of the hydraulic coupler (2) until the upper and lower opening deviation of the motor (3) and the hydraulic coupler (2) is not greater than 0.05mm.

3. The method for reducing the temperature of the fifth bearing of a hydraulic coupler according to claim 2, characterized in that, In step two, the upper and lower opening deviation between the motor (3) wheel and the hydraulic coupler (2) wheel should not exceed 0.05mm, and the upper gap between the motor (3) wheel and the hydraulic coupler (2) wheel should be less than or equal to the lower gap.

4. The method for reducing the temperature of the fifth bearing of a hydraulic coupler according to claim 1, characterized in that, The third step of adjusting the bearing gap of the fifth bearing of the hydraulic coupling (2) specifically includes: adjusting the bearing gap by scraping the bearing gap, and using red lead powder to color and inspect the bearing.

5. The method for reducing the temperature of the fifth bearing of a hydraulic coupler according to claim 1, characterized in that, The method for enlarging the diameter of the oil inlet orifice plate in step four specifically includes: removing the oil inlet orifice plate, measuring the diameter of the oil inlet orifice plate, clamping the oil inlet orifice plate on a drilling machine, and enlarging the orifice plate using a 7.7mm drill bit.

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