The inlet and outlet piping layout of an industrial gear pump may seem like an auxiliary installation step, but it actually has a direct impact on the pump's suction performance and the risk of cavitation. Suction performance determines the pump's ability to stably pump the medium, while cavitation can cause wear of internal pump components, flow fluctuations, and even failure. The core connection between the two lies in the piping layout's impact on the medium's flow state and pressure distribution. An improper piping layout can lead to excessive pressure loss, turbulent flow, or air intrusion during the medium's suction process. This not only weakens suction capacity but can also cause local pressure to fall below the medium's vapor pressure, leading to cavitation.
The inlet piping diameter is one of the primary factors affecting suction performance. If the inlet piping diameter is smaller than the pump's inlet diameter, the medium's flow velocity within the pipe will increase significantly. This excessive flow rate is accompanied by a significant drop in pressure, making it difficult to create a sufficient vacuum at the pump's suction end to extract the medium. Especially when pumping high-viscosity media, excessive flow rates can increase friction between the medium and the pipe wall, further increasing pressure loss. Conversely, if the inlet pipe diameter is too large and the length is too long, while the flow rate will be reduced, the amount of medium retained in the pipe will increase, making it difficult to quickly expel air during startup, which may also reduce suction efficiency. Furthermore, an overly large pipe diameter may cause sedimentation due to slow medium flow, indirectly affecting suction stability. Furthermore, if the inlet pipe has a sudden change in diameter, such as from a large diameter to the pump inlet, vortexes are likely to form at the change in diameter. The pressure in the vortex area is significantly lower than the surrounding pressure. Once this pressure falls below the vapor pressure of the medium, bubbles are generated. These bubbles enter the pump with the medium and burst in the high-pressure area, causing cavitation.
The length and number of elbows in the inlet pipe also have a significant impact on suction performance and cavitation risk. Excessively long inlet pipes can lead to cumulative pressure loss along the way, especially when conveying highly viscous media or media containing small amounts of impurities. The frictional resistance of the pipe wall increases with length, causing the pressure of the medium reaching the pump inlet to be significantly lower than the pressure at the source, naturally weakening the pump's suction capacity. Excessive elbows can cause localized pressure loss. Each elbow changes the flow direction of the medium, easily creating turbulence and localized low-pressure areas. If multiple elbows are arranged consecutively, the pressure in these localized low-pressure areas may continue to drop. Once the pressure drops below the vapor pressure of the medium, the risk of cavitation increases significantly. In particular, the localized resistance of 90-degree elbows is much greater than that of 45-degree elbows. Frequent use of right-angle elbows in inlet piping can affect suction performance, even if the overall length of the piping is short.
The installation height and sealing of the inlet piping are also crucial. Industrial gear pumps have a maximum allowable suction vacuum. If the inlet piping is installed too high, exceeding the allowable suction height, gravity will make it difficult for the medium to be drawn into the pump. Consequently, the suction pressure will drop sharply, resulting in insufficient flow and potentially cavitation due to low pressure. The tightness of the inlet piping also directly impacts vacuum maintenance. Leaks at the piping joints allow air to seep into the pipe, disrupting the vacuum at the suction end and preventing the pump from effectively pumping the medium. Furthermore, this trapped air is compressed in the high-pressure area within the pump and then expands suddenly, potentially causing cavitation. This can also lead to fluctuations in the pump's outlet pressure, further impacting overall operational stability.
Although the layout of the outlet piping doesn't directly affect the suction process, it can indirectly impact suction performance and cavitation risk by affecting the pump's operating pressure. If valves in the outlet piping close too quickly, there are too many throttling elements, or there's excessive pipe resistance, the pump's outlet pressure can suddenly increase. This pressure fluctuation can be transmitted back to the pump's suction end, causing unstable pressure conditions. Excessive outlet pressure disrupts the pressure balance within the pump, potentially causing the localized pressure at the suction end to temporarily drop below the vapor pressure of the medium. This adverse effect is particularly pronounced during pump startup and shutdown, or during operating mode transitions, easily inducing cavitation. Furthermore, if the return oil path in the outlet piping is poorly designed, such as when return oil directly impacts the inlet piping, it can disrupt the flow of the inlet medium, causing uneven flow rates and, in turn, impacting suction stability.
The layout and selection of filters in the inlet piping can also impact suction performance. To prevent impurities from entering the pump and damaging gears and bearings, filters are often installed in the inlet piping. However, if the filter's flow area is too small, the filter element is too fine, or it becomes clogged due to long-term lack of cleaning, significant localized resistance can form at the filter. This causes a significant drop in medium pressure as it passes through the filter, and consequently, the pressure at the pump inlet. This not only impairs suction performance but can also cause the pressure downstream of the filter to fall below the vapor pressure of the medium due to the large pressure differential across the filter, leading to cavitation. Therefore, the filter layout must ensure that its flow capacity matches the pump's flow requirements and facilitates regular maintenance and cleaning to avoid impacting overall suction performance due to resistance in the filtration process.
Optimizing the inlet and outlet piping layout of industrial gear pumps focuses on reducing pressure loss during medium flow, ensuring a stable flow rate, preventing air intrusion, and ensuring that installation parameters are aligned with pump performance. Reasonable piping layout can not only enable the pump to maintain good suction performance and ensure stable medium transportation, but also effectively reduce the risk of cavitation, reduce the wear of pump internal components, extend the service life of the pump, and at the same time improve the operational reliability of the entire conveying system, avoiding production interruptions or equipment damage caused by improper piping layout.
