Why must the seal flushing for multi-stage pumps be taken from the first-stage impeller?
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Is it a pressure issue? I don’t know the exact reason
The pressure should not be very high; it’s sufficient as long as the sealing and flushing requirements are met
It’s probably due to pressure considerations; it might also help save some rinsing water
At the first-stage impeller, the pressure is just high enough to be above that of the sealing chamber, but it’s not very high either; it’s similar to the outlet pressure of a single-stage pump. If one moves further downstream or to the last stage, pressure reduction devices are necessary, otherwise the pressure difference between this area and the sealing chamber would be too large. Flushing that is not favorable for mechanical seals
Why is a too large pressure difference unfavorable for mechanical flushing? Could you be more specific?
The flushing water for mechanical seals requires a certain pressure; when this pressure exceeds the pressure exerted by the spring, the mechanical seal fails.
This post was last edited by space ★ Xuan on 2016-9-2 09:40. Find a cross-sectional diagram of a mechanical seal with flushing functionality; assuming the sealing chamber contains 3 kilograms of fluid, and the flushing medium is injected at a pressure of 100 kilograms, think about what would happen ? ? This is why the differential pressure is high: vibration of the mechanical seal, erosion of the sealing rings, damage to the stationary and rotating rings, vaporization due to sudden pressure reduction in the sealing chamber, and so on. Think about it carefully. There is another very important reason, which is the issue of design pressure for mechanical seals.
Generally, the primary outlet pressure is slightly higher than the pressure in the sealing chamber? Is this pressure sufficient to achieve sealing flushing?
Look, in API682, version 11, section 8.3.1.6.10, it is clearly stated that it is (1.4 bar)