Type of equipment
Industrial pumps
Delivery type
International delivery
There are three common sealing methods for fine sand recovery slurry pumps: packing seal, impeller + packing seal, and mechanical seal.
Let's analyze the advantages and disadvantages of these three sealing methods.
Packing seal: This is the most common sealing method. It is a sealing assembly consisting of 4 pieces of packing at the shaft seal. It is now composed of a water seal ring, a stuffing box, a positioning sleeve and other accessories. This sealing method is to enter the shaft seal water with a certain pressure and flow rate, and evenly enter the gap between the packing and the shaft sleeve through the front water seal ring, thereby preventing the slurry in the pump cavity from flowing out. The advantages of this seal are: durable and low replacement cost. The disadvantage is: it requires high-pressure shaft seal water (the shaft seal water pressure is 0.2-0.3MPa higher than the pump outlet pressure), and there will be leakage during pump operation.
Impeller + packing seal: This is also a commonly used sealing method for slurry pumps. It is composed of an impeller + 2 fillers. It mainly relies on the pressure generated by the secondary impeller that is synchronized with the main impeller to prevent slurry leakage. In this sealing method, you can connect the water seal tube to the shaft seal water, or you can use an oil cup with butter inside. If it is not convenient to add shaft seal water on site, you can use this seal and fill the seal with butter. However, this kind of seal must be installed by reverse pouring. For the transportation of slurry with a weight concentration of no more than 15%, the positive pressure at the pump inlet cannot exceed 10% of the pump outlet pressure. Otherwise, the gas-liquid separation surface cannot be formed and the seal cannot be achieved. Effect. The advantage of this seal is that, like the packing seal, it is durable and has low replacement cost. It is not necessary to add high-pressure shaft seal water. Disadvantages: There are certain restrictions on working conditions. If the concentration is greater than 15%, it cannot be used. It doesn't work if the pouring height is too high. There will be dripping when the pump is stopped.
Mechanical seal: Mechanical seal is often used in sites with high sealing requirements. It can be made completely leak-free. Its structure is relatively simple, which is a sealing assembly composed of a mechanical seal, a mechanical seal box, and a mechanical seal sleeve. There are also three types of mechanical seals: external flushing mechanical seal, internal flushing mechanical seal, and waterless mechanical seal. For external flushing of the mechanical seal, flushing water needs to be added, usually clean water, and there are corresponding requirements for pressure and flow. It has two water seal tubes, one is used to receive flushing water, and the water circulates in the machine seal and is drained away from the other water seal tube. Internal flushing mechanical seal: There is only one water seal pipe to receive flushing water. The flushing water will directly reach the pump chamber and be pumped out together with the slurry. Mechanical seal without flushing water: This kind of mechanical seal uses the slurry itself to cool the mechanical seal, so there is no need to add flushing water. The advantage of this sealing method is: the site is clean and there is no dripping. The disadvantage is that water cannot be drained, and draining water can easily cause dry grinding of the machine seal. Dry grinding of the machine seal will soon cause damage, and the replacement cost is high.
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