A small question about finding time!
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Vacuuming in a single-stage pump can damage the mechanical seal, while vacuuming in a multi-stage pump can cause the shaft to break. How did all of this come about? Please explain in detail. Thank you
Before starting a single-stage centrifugal pump, if the pump is not filled with liquid, air enters the system, the liquid level is insufficient, or a large amount of the fluid vaporizes, the outlet pressure of the centrifugal pump drops significantly and fluctuates violently. This phenomenon is known as cavitation. In terms of performance, this is manifested as the discharge pressure approaching zero or being close to the pump’s inlet pressure. The parts in contact within the pump and the friction pairs of the mechanical seal suffer wear and failure due to dry or semi-dry friction, thereby damaging the mechanical seal. Excessive vibration can cause the shaft to jump out of place, and in severe cases, it may lead to the shaft breaking in a multi-stage pump.
When a centrifugal pump experiences cavitation, dry rotation occurs within the pump, and there is no liquid to provide lubrication between the stationary and rotating rings of the mechanical seal, resulting in dry friction. Additionally, the temperature rises, and since there is no fluid to carry away heat, the mechanical seal will get damaged over time. At the same time, after the pump is evacuated, its vibration increases and the unbalanced forces rise; this is especially true for multi-stage pumps, where shaft breakage can occur
When the pump transports dirty media, the aggregation of such media can easily lead to blockage at the inlet; as a result, the pump gets clogged. Once blockage occurs, the pump loses pressure suddenly, creating a local vacuum in its pumping chamber. A small amount of medium present can cause cavitation, which increases the vibration of the pump, raises the shaft displacement, accelerates wear on the bearings and seals, and may even lead to the seals being damaged due to dry friction resulting from the loss of fluid. Over time, the pump’s impeller and other components can suffer severe damage as a result of these issues.
The issues that arise are, first, dry friction occurring at the seal, and second, damage to the seal surface due to collisions between the sealing surfaces； Take the time to increase the pressure ratio to boost the axial force.
There is no liquid between the stationary and rotating rings of the mechanical seal to provide lubrication and cooling