ANALYSIS OF THE TYPES AND USES OF CHEMICAL PUMP SEALS

In the chemical field, the sealing system of the chemical pump is very important, which not only affects the normal operation of the pump, but also affects the safety and reliability of the chemical production process. The following is a detailed introduction to the main types of chemical pump seals and their respective uses.

1. Gasket seal

The gasket is the basic component of the static seal of the centrifugal pump, and it is widely used. The mechanism of gasket sealing is leakage, that is, the medium flows from the inside of the limited space to the outside, or enters the inside of the limited space from the outside. The leakage occurs through the interface of the internal and external space, that is, the sealing surface. The root cause of the leakage is that there is a gap on the contact surface, and the pressure difference and concentration on both sides of the contact surface are the driving force of the leakage. To reduce leakage, it is necessary to maximize the contact surface, that is, reduce the cross-sectional area of the leakage channel, increase the leakage resistance, and make it greater than the leakage driving force. 

Applying a compression load to the sealing surface to generate compression stress can improve the contact degree of the sealing surface. When the stress increases enough to cause obvious plastic deformation on the surface, it can fill the gap of the sealing surface and block the leakage channel. The purpose of using the gasket is to use the characteristics that the gasket material is easy to produce plastic deformation under the pressure load, so that it can fill the small unevenness of the flange sealing surface, so as to achieve sealing. When the chemical pump conveying medium is not high for temperature and pressure, non-metallic sealing gaskets are generally selected; when the conveying medium of chemical pump is medium and high temperature, non-metallic and metal combination gaskets are selected. Non-metallic gaskets are most commonly used in pumps, and their materials are generally paper, rubber and polytetrafluoroethylene. 

When the temperature does not exceed 120℃ and the pressure is below 1.0Mpa, green shell paper or molded paper gasket is generally selected. If the conveying medium of the chemical pump is oil and the temperature is -30~110℃, butadiene rubber with good aging resistance is generally selected. When the chemical pump conveys the medium at -50~200℃, it is more appropriate to choose fluorine rubber. Because in addition to oil and heat resistance, its mechanical strength is also its main feature. With the wider use of chemical pumps, there are more and more and more types of media to be transported. Therefore, when choosing the gasket material, you should consult the relevant materials or make a correct choice after passing the experimnt.

2.  Mechanical Seal

Mechanical sealing is the most widely used form of sealing in chemical pumps. It consists of a pair or several pairs of end faces that slide relatively perpendicular to the axis. Under the action of fluid pressure and the elastic force (or magnetic force) of the compensation mechanism, it maintains the fit and is equipped with auxiliary sealing to achieve the purpose of leakage resistance.

The mechanical seal has the advantages of good sealing performance, small leakage and long service life. It is suitable for conveying chemical pumps with high temperature, high pressure, strong corrosive, flammable and explosive media. It has been widely used in petrochemical, pharmaceutical, chemical fiber and other industries.

3. Packing Seal

Packing seal is to put the compact and resilient packing into the packing box, and rely on the axial compression force of the clad to convert it into a radial sealing force, thus playing the role of sealing.

The packing seal has a simple structure and low cost, which is more suitable for situations where the medium pressure and temperature requirements are not high. However, its leakage is relatively large and requires frequent maintenance and adjustment. It is often used in general chemical process pumps, sewage pumps, etc.

4. Maze Seal

The maze seal is a series of circular sealing teeth arranged around the rotating shaft. A series of throttling gaps and expansion cavities are formed between the teeth. The sealed medium produces a throttling effect when passing through the gap of the winding maze to achieve the purpose of leakage blocking.

Maze seals are often used in high-speed, high-temperature and high-pressure chemical pumps, especially for preventing gas leakage. For example, it is widely used in centrifugal compressors, steam turbines and other equipment.

5. Magnetic Seal

Magnetic sealing uses the magnetic field force of magnetic materials to attract the rotating shaft and stationary parts to achieve sealing.

Magnetic seal has the advantages of no leakage, no lubrication, no pollution, etc. It is suitable for chemical pumps with extremely high requirements for sealing, such as transporting toxic, harmful and valuable liquids.

6. Corrugated Pipe Sealing

The bellows seal adopts a bellows structure in the auxiliary sealing part of the moving ring or static ring. The bellows have good elasticity and compensation ability, and can effectively adapt to the vibration and pendulum of the shaft.

The bellows seal is suitable for chemical pumps under high temperature, low temperature, high pressure and other harsh working conditions, especially in situations where the reliability of the seal is high.

In short, different types of chemical pump seals have their own characteristics and scope of application. In practical application, it is necessary to comprehensively consider the suitable sealing form according to the working conditions of the chemical pump, the nature of the conveying medium, the process requirements and other factors to ensure the safe, stable and efficient operation of the chemical pump and ensure the smooth progress of the chemical production.