Problems and Solutions of External Gear Pumps

As one of the most widely used positive displacement pumps in hydraulic systems, external gear pumps are extensively applied in various fields such as machinery manufacturing, mining and metallurgy, agricultural machinery, and construction machinery, thanks to their advantages including simple structure, low cost, uniform flow rate, and wide adaptability. Their working principle is that a pair of intermeshing gears rotate inside the pump body, causing periodic changes in the volume of the gear meshing chambers, thereby achieving oil suction and discharge. However, affected by multiple factors like structural design, manufacturing processes, and operating conditions, external gear pumps still encounter numerous problems during actual operation, which seriously impact their working efficiency, service life, and system stability. Therefore, it is of great engineering significance to take targeted measures to solve these problems. The most prominent problem of external gear pumps is high leakage, which is also the main cause of their low volumetric efficiency. Leakage in external gear pumps is mainly classified into three types: axial leakage between the gear end faces and the pump cover, radial leakage between the gear tooth crests and the pump body bore, and meshing leakage at the contact area of the two gears. Among these, axial leakage accounts for 70% to 80% of the total leakage. The core cause of leakage is that a certain clearance must be reserved between the gear end faces and the pump cover to avoid friction during gear rotation, and the existence of such clearance will inevitably lead to the leakage of high-pressure oil to low-pressure areas. Meanwhile, insufficient manufacturing precision, aging of sealing components, and excessively high operating pressure will further exacerbate leakage, thereby reducing the pump's output flow and working efficiency while increasing energy consumption. Secondly, external gear pumps suffer from severe wear issues, which are prone to causing pump failure. Wear mainly occurs on the gear tooth surfaces, tooth crests, pump body bore, and bearings. On one hand, a certain backlash and relative sliding exist when gears mesh. If impurities are mixed into the hydraulic oil, it will intensify abrasive wear on the tooth surfaces and crests. On the other hand, the hydraulic forces generated by axial and radial leakage will cause gear displacement, leading to uneven local stress distribution and inducing eccentric wear of the gears and pump body bore. Long-term wear will result in gear tooth profile distortion and scoring of the pump body bore, ultimately causing pump sealing failure, excessive flow fluctuation, and even complete operational breakdown. In addition, external gear pumps generate high levels of noise and vibration during operation and have weak contamination resistance. Noise is mainly derived from the impact and vibration during gear meshing, pressure fluctuations of hydraulic oil in the suction and discharge processes, as well as frictional vibration between gears and the pump body, and between gears and bearings. Excessively high noise not only pollutes the environment but also indicates abnormal pump operation. The weak contamination resistance is due to the small gear clearances—solid impurities in the hydraulic oil are likely to get stuck at the gear meshing points or in the clearances, causing gear jamming, accelerated wear, and even component damage, which shortens the pump's service life. Meanwhile, external gear pumps have poor stability under low-speed and low-pressure operating conditions, and are prone to problems such as insufficient oil suction and cavitation. To address the above problems, targeted solutions can be adopted based on the structural characteristics and operating principles of external gear pumps, effectively improving their working performance and service life. For the leakage problem, the primary measure is to optimize the sealing structure by adopting automatic end face clearance compensation devices. For example, floating bushings or elastic side plates are installed on the gear end faces, and the pressure of high-pressure oil is used to push the bushings or side plates to fit closely against the gear end faces, automatically compensating for clearance changes and significantly reducing axial leakage. Meanwhile, improving manufacturing precision to strictly control the machining errors of gear end faces and pump body bores, reducing radial and meshing clearances, selecting oil-resistant and wear-resistant sealing components, and regularly inspecting and replacing aging seals can avoid sealing failure. For the wear problem, efforts should be made from both source control and daily maintenance. In the manufacturing stage, high-strength and high-wear-resistance materials are selected for gears and pump bodies, such as alloy steel treated with carburizing and quenching to improve the surface hardness and wear resistance of parts. During operation, strengthen the filtration and maintenance of hydraulic oil, select clean hydraulic oil that meets the requirements, regularly replace filter elements and hydraulic oil to prevent impurities from mixing in and exacerbating wear. Meanwhile, adjust operating parameters to avoid long-term operation of the pump under overload and high-pressure conditions, reducing eccentric wear caused by uneven gear stress. To solve the problems of high noise, vibration, and weak contamination resistance, optimize gear design by adopting profile-modified gears to reduce the impact and vibration during gear meshing and lower noise levels; design the oil suction and discharge pipelines reasonably to reduce pipeline resistance and avoid excessive pressure fluctuations of hydraulic oil; add filters and silencers to the hydraulic system to improve the cleanliness of hydraulic oil and weaken noise propagation. In addition, conduct regular inspections and maintenance on the pump, timely clean up impurities, check the wear condition of parts, and replace severely worn parts promptly to ensure the normal operation of the pump and enhance its contamination resistance and operational stability. In summary, the problems of leakage, wear, and high noise in external gear pumps mainly stem from structural design, manufacturing precision, and operation and maintenance. Through targeted measures such as optimizing the sealing structure, improving manufacturing precision, selecting high-quality materials, and strengthening daily maintenance, these problems can be effectively solved. This will significantly improve the volumetric efficiency, service life, and operational stability of external gear pumps, enabling them to better meet the working requirements of various hydraulic systems and reduce production costs and equipment failure rates.