Analysis of external causes affecting mechanical seals for hydraulic pumps

The external reasons that affect the mechanical seals for hydraulic pumps are mainly reflected in the following five aspects. Dalan Hydraulics will analyze it with you.

1. The axial volume of the pump shaft

1 The sealing surface of the mechanical seal must have a certain specific pressure (0.4 ~ 0.6MPa), so as to achieve the purpose of sealing, the tightness of the two end faces can be adjusted by the spring.

2 In order to ensure this specific pressure, the pump shaft is not required to have too much enthalpy (generally ≤ 0.5mm), but in actual production, the pump shaft often produces a large amount of enthalpy.

2, the deflection of the pump shaft is too large

The linear displacement of the cross-sectional area along the axis perpendicular to the axis when the 1-axis is bent is called the deflection, and the mechanical seal requires uniform force between the two sealing end faces.

2 Due to the unreasonable design of the pump product, the deflection generated at the mechanical seal installation is too large, so that the force at the seal is uneven, and the sealing effect is lost. This phenomenon is mostly found in horizontal multistage centrifugal pumps.

3, no auxiliary flushing system or auxiliary flushing system design is not reasonable

1 The auxiliary flushing system of mechanical seal is very important. It can effectively protect the sealing surface and play the role of cooling, lubricating and washing away debris.

2 Sometimes the design is unreasonable and the sealing effect is not achieved.

3 Some design auxiliary systems, but due to impurities in the rinsing liquid, the flow rate and pressure of the rinsing liquid are not enough, the design of the rinsing port is unreasonable, etc., and the same effect is not achieved.

4, the vibration is too large

The mechanical seal vibration is often not the cause of the mechanical seal itself, but the pump shaft design is not reasonable, the machining accuracy is not enough, the parallelism of the back wheel is large, and the radial force is large.

5, pump cavitation

1 The inlet of the centrifugal pump impeller is the place where the pressure inside the pump is the smallest. When the pressure here is equal to or lower than the saturated vapor pressure of the liquid to be delivered at the working temperature by 1px, the liquid will boil and vaporize, generating a large number of bubbles. At the same time, bubbles originally dissolved in the liquid will also precipitate.

2 These bubbles bubble and condense as the liquid flows to the higher pressure in the impeller. During the condensation process, due to the sharply reduced volume, the surrounding liquid rushes to the entire condensing space at a great speed, causing shock vibration and noise inside the pump.

3 Under the continuous impact of a liquid pressure with a large pressure and a high frequency, the metal surface is gradually destroyed by fatigue, and this damage is called ablation. At the same time, active gases such as oxygen dissolved in the liquid also cause corrosion of the metal. Due to the combined action of chemical corrosion and mechanical ablation, the speed of metal damage is accelerated, and the impeller is destroyed, which is cavitation damage.







----- Editor-in-Chief: Dalan Oil Pump Motor 02-Procurement Consultant

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