Factors affecting sealing performance
Any seal cannot be completely sealed, we will describe the following factors that affect seal performance: energy consumption, noise and leakage. These factors will be described separately, but they are closely related and must be considered as a whole. Energy consumption
There is no doubt that the rotation of the seal requires energy. The factors that cause energy consumption (ie, the energy loss of the mechanical shaft seal) are as follows:
Centrifugal suction of rotating parts: energy consumption increases significantly with increasing rotational speed (cubic relationship);
Sealing surface friction: The friction between the two sealing surfaces consists of two parts: the friction in the liquid film and the friction caused by the contact between the sealing surfaces;
The level of energy consumption depends on the seal design, lubrication conditions and sealing surface material.
Energy consumption (especially energy consumption with stuffing box seals) is an important issue, and the use of mechanical shaft seals instead of stuffing box seals saves a lot of energy.
The choice of sealing surface material is decisive for the function and life of the mechanical shaft seal. Poor lubrication conditions within the seal can cause noise when handling low viscosity liquids. The viscosity of water decreases as the temperature increases. This means that the lubrication conditions deteriorate as the temperature rises. If the pumped liquid reaches or exceeds the boiling temperature, the liquid on the sealing surface will evaporate, which leads to an exacerbation of the lubrication conditions, which have the same effect.
Pumping liquid can lubricate the sealing surface of the mechanical shaft seal. Thus, good lubrication means less friction and more leakage. Conversely, a decrease in leakage means deterioration in lubrication conditions and an increase in friction. In fact, the amount of leakage and energy loss that occurs within the mechanical shaft seal can vary. The reason is that due to the type of sealing surface, the type of liquid, and the spring load, it is impossible to theoretically quantify the factors causing the leakage.
In order to properly read the leak rate curve, the following four steps should be taken:
1. Read pressure - as shown in the example in the figure, take 5bar;
2. 30mm unbalanced shaft seal;
3. The speed is 3000 rpm;
4. The leak rate is 0.06ml/h;