Thanks to its unique structural design, the double-suction split-case centrifugal pump demonstrates certain advantages in terms of axial force balance, with its axial force being smaller compared to ordinary multistage pumps. However, during actual operation, it is usually difficult to achieve complete balance of axial forces in both directions. In particular, during the pumping process of liquids, fluctuations in parameters such as flow rate and pressure will cause significant changes in axial force, which makes shaft endplay a tangible problem. Generally speaking, if the bearing endplay is excessive, it is likely caused by deviations in the positions of components during installation. But in addition to that, there are various other factors that can lead to this phenomenon. Below, we will introduce in detail the causes and treatment measures for excessive bearing endplay in double-suction split-case centrifugal pumps.
1.Unlocked Bearings
Bearings play a key supporting role in the operation of centrifugal pumps. Once they are not locked, they cannot provide stable positioning for the shaft, which in turn leads to excessive shaft endplay. There are various situations that cause the bearing to be unlocked. It may be due to quality problems of the bearing itself, such as damage to the locking structure of the bearing; or it may be that the bearing rear cover is loose, causing the bearing to gradually deviate from the correct position during operation.
Treatment method: First, conduct a comprehensive inspection of the bearing, carefully check whether the locking structure of the bearing is intact, and whether components such as rolling elements and raceways are worn or deformed. At the same time, check the tightness of the bearing rear cover. If looseness is found, tighten the relevant bolts in time to ensure that the bearing can be firmly installed on the pump shaft.
2.Improper Operation, Working Conditions Far from the Designed Conditions of the Pump
Centrifugal pumps are designed with a specific range of working conditions, including parameters such as flow rate, head, and rotational speed. If in actual operation, operators do not operate in accordance with the design requirements, such as randomly adjusting the valve opening, changing the nature of the conveyed medium, etc., it will cause the pump's operating conditions to deviate from the designed conditions. When the working conditions deviate too much, the hydraulic balance inside the pump will be broken, resulting in additional axial force and causing excessive bearing endplay.
Treatment method: Operators must strictly operate in accordance with the pump's operating procedures, pay close attention to the pump's operating parameters, and ensure that it operates within the designed working range. When it is necessary to adjust parameters such as flow rate, correct methods should be adopted to avoid drastic changes in working conditions. At the same time, regularly train operators to improve their operating skills and understanding of the impact of working condition changes.
3.Unsmooth Balance
Double-suction split-case centrifugal pumps are usually equipped with a balancing device to balance the axial force, and the balance pipe is an important part of the balancing device. Its function is to guide the high-pressure liquid at the pump outlet to components such as the balance disc to achieve the balance of axial force. If the balance pipe is blocked, leaking, or has other problems, the balancing device will fail to work normally, resulting in unsmooth balance. In turn, the axial force cannot be effectively balanced, causing excessive bearing endplay.
Treatment method: Regularly inspect and clean the balance pipe to ensure it is unobstructed. Check whether the connection parts of the balance pipe are tight and whether there is any leakage. If leakage is found, replace the seals or repair the pipeline in time. In addition, a filter can be installed on the balance pipe to prevent impurities from entering the balance pipe and causing blockage.
4.The Materials of the Balance Plate and Balance Plate Seat Do Not Meet Requirements
The balance plate and balance plate seat are key components in the balancing device. They rub against each other during operation and bear a certain axial force. If their materials do not meet the requirements, such as insufficient hardness, wear resistance, strength and other indicators of the materials, it will cause the balance plate and balance plate seat to wear quickly during operation, thereby destroying the balancing effect of the balancing device and causing excessive bearing endplay.
Treatment method: Replace the materials of the balance plate and balance plate seat with those that meet the requirements. When selecting materials, according to factors such as the pump's working pressure and the nature of the conveyed medium, materials with sufficient hardness, wear resistance and strength should be selected, such as high-quality cast iron, alloy steel, etc. At the same time, ensure that the replaced balance plate and balance plate seat have undergone precision machining to ensure their fitting accuracy and working performance.
5.The Bearing Installation Is Not Horizontal
The levelness of bearing installation is crucial to the normal operation of the centrifugal pump. If the bearing is not installed horizontally, the pump shaft will be inclined, resulting in uneven distribution of the load borne by the bearing, increasing bearing wear and axial endplay. Long-term operation will seriously affect the service life of the bearing and cause a series of failures.
Treatment method: Correct the installation levelness of the double-suction oil pump bearing. Tools such as a level can be used to measure the levelness of the bearing seat. According to the measurement results, adjust the levelness of the bearing by adjusting the gaskets at the bottom of the bearing seat, etc., so that the bearing meets the requirements of horizontal installation. During the correction process, repeated measurements and adjustments are required to ensure that the levelness error of the bearing is within the allowable range.
In conclusion, excessive bearing endplay in double-suction split-case centrifugal pumps is a problem that requires attention, and its causes involve many aspects. In the actual operation and maintenance process, we should strengthen the inspection and maintenance of the pump, promptly discover and deal with various problems, so as to ensure the normal operation of the pump and extend its service life.