One or severalButterfly valveShaft end seal structure
There are many types of butterfly valves, such asAdjusting butterfly valve, Eccentric butterfly valve, connecting rod butterfly valve and so on.But as far as the shaft end seal structure is concerned, there are three basic forms:
XNUMX. Analysis of sealing structure
Applied to the blast furnaceButterfly valveThe product, the use of the medium is usually air, coal gas, flue gas and mixed gas, the temperature is 35-450 degrees, according to the actual working conditions, a reasonable selection of the shaft end seal structure sliding bearing inner packing in the outer structure of the butterfly valve, form The structure is simple and compact, but it is only suitable for occasions where the working temperature is below 200 degrees, and there is a small amount of external leakage.
The butterfly valve with the inner sliding bearing of the packing and the outer sealing structure avoids the direct effect of temperature on the sliding bearing due to the sliding bearing, and is used in high temperature occasions.However, the large axial size and the large supporting span at both ends of the main shaft result in a decrease in the rigidity of the main shaft, which affects the flexibility of valve opening and closing, and large accumulated errors cause large leakage. Therefore, the advantages and disadvantages of this structure are very prominent.
The sliding bearing has a packing seal structure on both sides of the middleButterfly valve, The sliding bearing is sealed on both sides, the front sealing packing plays the role of heat resistance and pressure reduction, and the rear sealing packing plays the final sealing role, which is a double-group multi-layer sealing structure, which is a composite sealing structure.
Therefore, the shaft end seal is better than the previous two types, and it is suitable for both high and low temperature conditions. The disadvantage is that the radial size is large and the narrow seriesButterfly valveIt is difficult to implement due to the length of the structure.Through the analysis of the three structural forms, it is not difficult for us to make a choice.
Third, the issue of external leakage
The above-mentioned three types of butterfly valve shaft end sealing structures all have the problem of external leakage of the medium, but it is only a few, and the external leakage increases with the increase of the number of opening and closing.Regular replenishment of packing or replacement of new packing can control the leakage, but a small amount of external leakage is difficult to cure.But sealing lubricant can be used as auxiliary sealing material, its effect is obvious, and it solves the problem of medium trace foreign exchange.