【2026 Rotating Equipment】Can the seal flushing water be turned off when the pump stops operating?
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Can the seal flushing water be turned off after the pump is stopped? This is an important issue related to equipment maintenance, operational safety, and efficiency. A mechanical seal is a key component in rotating equipment such as centrifugal pumps; its function is to prevent the leakage of the medium and ensure the proper operation of the pump. During pump operation, the mechanical seal requires flushing water supplied from the outside to maintain its proper functioning, including for cooling, lubrication, and cleaning. However, when the pump stops operating, deciding whether to turn off the seal flushing water requires considering multiple factors.
Firstly, from the perspective of the protection and maintenance of the mechanical seal, turning off the flushing water immediately after stopping the pump may have an adverse effect on the mechanical seal. Because during pump operation, the mechanical seal generates heat due to friction; if the flushing water is stopped immediately after the pump is shut down, this heat cannot be dissipated effectively, resulting in an increase in the temperature of the mechanical seal. High temperatures not only accelerate the aging of seal materials but can also cause the seals to fail, leading to issues such as leaks. Therefore, to protect the mechanical seal and extend its service life, it is generally recommended to keep the flushing water flowing for a period of time after the pump stops, to ensure that the mechanical seal is adequately cooled and cleaned.
Secondly, from the perspective of operational safety, closing the seal flushing water after stopping the pump also requires careful handling. In some cases, such as when pumping crystalline or highly viscous fluids, turning off the flushing water immediately after stopping the pump can cause the fluid to crystallize or solidify at the seal area. This not only increases the resistance during startup but may also damage the seal. Therefore, in this case, the flow of flushing water should be maintained for some time after the pump is stopped, to prevent the medium from crystallizing or solidifying at the mechanical seal.
However, this does not mean that the flushing water cannot be turned off after stopping the pump in all cases. In certain special situations, such as when the pump is not in use for an extended period or is under maintenance, it may be necessary to turn off the flushing water. But even in such cases, appropriate measures should be taken to protect the mechanical seal, such as regularly turning the pump shaft manually to maintain its mobility, or using a specialized protective fluid instead of flushing water.
In summary, there is no fixed answer as to whether to turn off the seal flushing water when stopping the pump; it depends on the specific operating conditions and equipment requirements. Under normal circumstances, to protect the mechanical seal and extend its service life, it is recommended to keep the flushing water flowing for a period of time after the pump stops. However, in special circumstances, such as when the pump is not in use for an extended period or is under maintenance, the flushing water can be turned off and appropriate protective measures taken. In short, the correct approach is to analyze each situation based on the actual operation of the equipment, in order to ensure its safe and efficient operation.
Why must mechanical seals be flushed? Because the sealing medium in the sealed chamber contains particles and impurities, the precipitation of these particles and impurities due to crystallization causes the moving and stationary rings of the mechanical seal to lose their ability to float, leading to the failure of the springs. The entry of particles and impurities into the friction pair increases frictional wear, leading to rapid failure of the mechanical seal.
Purpose of mechanical seal flushing: Flushing helps to control temperature and can extend the service life of the mechanical seal. The purpose of flushing is mainly to remove heat, lower the sealing temperature, prevent vaporization of the liquid film, improve lubrication conditions, and avoid dry operation, accumulation of impurities, and formation of air bubbles.
API 682 self-flushing: There are 26 different schemes for the seal assistance systems as specified in the API682-2004 standard; among these, the schemes used for flushing the medium side of mechanical seals are 01, 11, 12, 13, 14, 21, 22, 23, 31, 32, and 41. The most commonly used schemes are 11, 21, 23, and 32. In these schemes, 11, 21 (Figure 1), and 23 involve self-flushing using the medium delivered by the equipment, a process commonly referred to as self-flushing.
API 682 External flushing: Figure 2 shows the use of an external medium to flush the side where the sealing medium is located; this is commonly referred to as external flushing. The advantage of self-flushing is that it does not affect the composition of the material transported by the equipment, thus ensuring that the composition of the medium remains unchanged. External flushing, on the other hand, can alter the composition of the medium; if this affects product quality, separation or removal of such components is necessary in subsequent stages.