Frequent leakage in the pump seal
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The refined oil pump in our unit leaks frequently; we once had to replace four mechanical seals in one week. The medium temperature is around 175°C, and the cooling water is in normal operation. Moreover, the self-flushing of the pump is only sent back into the sealing chamber after being cooled by water (modified by myself). Now there has been not a single leak in a month. What is the reason for this?
It is an axial flow pump; the medium is gasoline, and it is a power-frequency pump
How is the vibration of the pump? Is there a rushing sound or a sound of gas-liquid mixture inside the pump, that is, is cavitation occurring? What is the approximate temperature of the liquid returning to the mechanical seal, and what is the diameter of the flow control orifice plate in the flushing fluid pipeline? What are the pump inlet and outlet pressures? Will things get better after adding a coolant to the flushing fluid? I would like to know the answers above to facilitate problem analysis
It’s mainly due to the high temperature of the mechanical seal
Firstly, there was no vibration nor cavitation. The self-cleaning orifice plate appears to be 8 mm in size; the temperature of the medium is 175°C, while the temperature of the fluid returning for self-cleaning is around 110°C. The outlet pressure is 1.7 Mpa; increasing it improves the performance a bit, but sealing leaks still occur. The fitter at my factory thinks it’s because the cooling water for the pump is dirty; I’m puzzled by this, as the heavy oil pumps in the past didn’t have such problems either – they used the same cooling water. Is it related to the viscosity of the medium?
It may be that scaling inside the sealed chamber prevents the bellows from adjusting automatically.
It’s mainly due to the high temperature of the mechanical seal; things will get better once the flushing oil is cooled down.
Is the pump under vacuum or is the high temperature causing poor vapor lubrication?
This pump has never experienced vacuum conditions, and the liquid level at the bottom of the tower has always been normal. If scaling occurs inside the sealing chamber, it will be cleaned when the seal is replaced. There has been no leakage during this period; it’s been a month now.
Have you checked the quality of the mechanical seal? We tried it before as well; the problem was the poor quality of the mechanical seals, and installation also plays an important role.
This post was last edited by donganhj on 2011-8-31 at 22:58. Take a close look at the composition of your material; if it contains lighter components that can still vaporize at temperatures between 110 and 120 degrees, under the given inlet pressure, then increase the heat exchange area of the cooler further and reduce the temperature of the flushing fluid to between 70 and 90 degrees. I believe this will resolve your problem. Of course, the flow rate of the flushing fluid can also be reduced by decreasing the diameter of the orifice plate, which allows the temperature of the flushing fluid to be lowered without the need to replace the heat exchanger. However, too low a flow rate of the flushing fluid can also have certain effects; for example, it may fail to carry away the heat at the mechanical seal. Therefore, there is an optimal diameter for the orifice plate. This is something that must be taken into account during the renovation.