Mechanical seal friction heat and circulation (flushing) volume-

Mechanical seal friction heat and circulation (flushing) volume
　2017-07-22　　
Mechanical seal friction heat and circulation (flushing) quantity Qx:
The temperature of the end face seal pair and auxiliary sealing element of the mechanical seal should not exceed its heat resistance limit under working conditions. In order to ensure the normal operation of the mechanical seal, simply relying on the selection of high temperature-resistant materials, sealing materials with good thermal conductivity, and a reasonable structure may not necessarily bring the expected results. What's more, for liquids with poor lubricity and volatility, there will be problems such as liquid film vaporization, which necessitates washing measures. In some occasions, the ***** is not very high, and flushing measures can also be taken to improve the working environment and prolong the service life of the seal. Generally speaking, when, flushing measures must be used. Special mechanical seal for sanitary pump
Except for high-speed and high-viscosity mechanical seals, the heat of stirring can be ignored. Under the premise of ignoring the heat of stirring, the frictional heat Qf of the mechanical seal is numerically equal to the frictional power consumption of the end face seal pair, and it is also equal to the heat taken away by the circulating (flushing) liquid. which is

When determining the flushing volume of the mechanical seal, the friction heat of the seal end face and the stirring heat of the rotating elements should be considered. However, since the stirring heat is not easy to determine, it is usually determined by the end face friction heat and the appropriate friction coefficient. Rinse volume

In the formula, the coefficient of friction, for safety reasons, take
Density of the sealed medium or flushing fluid, kg/L;
Specific heat capacity of the sealed medium or flushing fluid, J/(kg·K);
The temperature difference of the circulating (flushing) liquid at the entrance and exit of the sealed or sealed box, K.
The formula (1-27a) is applicable to the dry friction state of the seal end face (when starting and stopping), while most contact mechanical seals are in a mixed friction state. In this case, Pc can be used instead of Pg.

For water,; for oil,; for liquefied gas,; when the pressure at the sealing part is close to the vapor pressure, when the water is sealed, it is the greatest according to experience.
For volatile liquids, in order to ensure the lubrication of the liquid film, it must be considered that the temperature of the flushing liquid is likely to rise, which will cause the vapor pressure to rise.
An example is used to illustrate the calculation process of the circulation (flushing) amount Qx.
Example 1-2 There is a condensate pump, the sealed medium is water, and the sealing device adopts an internal flow contact type mechanical seal. Knowing that the water temperature is, the rotation speed of the rotating shaft is, the load factor is 0.7, and the film pressure factor, try to determine the flushing volume of the seal under dry friction and mixed friction.
Solution: Know from the meaning of the question,
.
(1) When the seal is in a state of dry friction
From formula (1-12b) we can see the specific load of the sealing surface

(2) When the seal is in a state of mixed friction
The balance of the seal end face can be pushed together
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The friction power consumption of the mechanical seal 　　 the temperature rise of the end face of the mechanical seal