Common mechanical seal cooling and flushing methods2

The mechanical seal cooling and flushing method is an indispensable operation point during the use of the product, but although many users know this operation, they do not understand the specific operation point, so the following will introduce it in detail.

Due to the friction of the end face, a large amount of friction heat will be generated, which will increase the temperature of the friction pair ring. At the same time, if the temperature of the sealing medium itself is high, it will make the end face of the friction pair always run at a high temperature. In this case, if the flushing and cooling measures are not taken, it will make:

(1) Dry friction occurs due to the evaporation of the liquid film between the end faces;

(2) The auxiliary sealing ring made of rubber and plastic materials will age, crack and even fail;

(3) Accelerate the corrosive effect of the sealing medium on the sealing parts;

(4) Deformation of dynamic and static rings;

(5) The wear of the end face is aggravated;

(6) Serious leakage at the end face.

From this point of view, the purpose of using flushing oil and cooling water for seals is to reduce the temperature during friction, ensure that there is a complete liquid film between the friction surfaces, reduce friction loss, reduce power consumption, and ensure that the liquid film is not damaged due to high temperature vaporization. destroyed. Therefore, the flushing and cooling measures of the seals are an indispensable and important link to ensure that the seals have good sealing performance and long service life.

See below for common mechanical seal flushing and cooling

Direct injection of liquid into the high-pressure side of the double-end or single-end seal is called 'flushing'. General pumps should be flushed, especially light hydrocarbon pumps. The purpose of flushing is to seal, cool and lubricate:

(1) The external circulation of liquid compatible with the medium is introduced into the sealed sealing cavity, so as to: prevent high temperature, toxic and precious media from leaking from the pump shaft; prevent the medium containing solid particles from leaking into the sealing cavity and wear the sealing surface; Prevent the medium that is easy to vaporize and freeze (such as liquefied gas) from leaking into the sealing cavity to generate gas, causing friction and wearing the sealing surface; preventing the medium that is easy to crystallize from leaking into the sealing cavity, and the sealing surface is worn due to the formation of crystallization due to cooling; under negative pressure to prevent air and flushing fluid from leaking into the pump.

(2) Cooling prevents the high temperature medium from entering the sealing cavity; guides the frictional heat generated when the moving ring and the static ring work.

(3) Lubrication keeps a layer of liquid film between the sealing surfaces for lubrication.

1. Self-cleaning

Features: Using the sealed medium as the flushing liquid, a small part of the liquid is drawn from the pump outlet side, directly injected into the high pressure side of the sealing end face, flushed, and then flows into the pump cavity.

Uses: It is suitable for occasions where the pressure in the sealing chamber is less than the pump outlet pressure, greater than the pump inlet pressure, the medium temperature is not high and the temperature is less than or equal to 80C), and there are no impurities.

2. External flushing

Features: Use another flushing fluid, the flushing fluid should be:

(1) Clean, non-corrosive without solid particles, low temperature (usually 40'C).

(2) It has a certain lubricity and does not affect the quality of process products.

(3) It is not easy to vaporize under operating conditions.

Uses: When the temperature of the sealed medium is high, it is easy to vaporize and the impurity content is high, the pressure of the god lotion is 0.1~0.2MPa higher than the pressure of the medium in the sealed cavity.

3. Cyclic flushing

Features: With the help of the impeller in the sealing cavity, the liquid in the sealing ring is circulated. The heat taken away is the heat generated by the mechanical seal, and compared with self-flushing, the cooling water consumption is less.

Application: Due to the small lift of the impeller in the pump, it is suitable for occasions where the pressure difference between the inlet and outlet of the pump is small.