An analysis of the causes of mechanical seal failure

Date：2022-04-22 16:52:37Views：819

The device or measure to prevent the working medium from leaking out of the pump or to prevent external impurities or air from invading into the pump is called sealing. The sealed medium is generally liquid, gas or dust. Mechanical seal, also known as end seal, has a pair of end faces perpendicular to the rotation axis. Under the action of fluid pressure and compensating the external elastic force of machinery, the end face keeps fit with the other end and slides relative to the other end depending on the cooperation of auxiliary seal, so as to prevent fluid leakage. Mechanical seal failures are generally caused by leakage, wear and torque caused by abnormal changes. The main reasons for mechanical seal failure are as follows:

1. Incorrect design and selection;

2. Installation factors or characteristics of the pump itself;

3. Seal failure.

The specific situation also needs specific analysis. The following mainly focuses on the cause analysis of seal failure. The first two points may be clearer than us, but the customer knows little about the cause of seal failure of mechanical seal. The main seal failure points are as follows:

First, corrosion causes:Under the influence of the working medium, the mechanical seal device is eroded, and a certain corrosion surface will appear on its outside. If it is not treated in time, it will become more and more serious until the corrosion penetration phenomenon occurs. At the same time, the working medium will also cause electrochemical corrosion of dissimilar metals, corrosion of the insert ring and effective fixation.

Second, causes of thermal cracking and aging:In the working state, the sealing surface is always subject to dry friction. If the cooling water is missing at this time, the impurities will contact the sealing surface, resulting in evacuation and other symptoms, which is easy to cause cracks on the outside of the ring, affect the service life of the friction ring, and the leakage problem of the sealing surface will become more and more serious.

Third, wear reasons:If the material for manufacturing the friction pair has poor quality and low hardness, its friction coefficient will inevitably increase, the equal specific pressure of the end face will also increase, and the probability of contact between the impurity and the sealing surface will increase. If the impurity is solid, the spring space will be blocked by the impurity. At this time, the wear of the sealing surface is very large, and the sealing effect is not ideal.

Fourth, causes of pump vibration and axial movement:Because the pump will produce problems such as cavitation and cavitation in the working process, as well as problems such as bearing wear during working, these problems will cause strong pump vibration and axial movement, resulting in instantaneous damage to the friction pair, resulting in the serious problem of mechanical seal failure.

Fifth, reasons for assembly, transportation and other links:Leakage occurred during mechanical seal injection and static pressure test due to unreasonable assembly.

Unreasonable assembly includes the following types:

(1) There are concave convex on the fitting surface of the dynamic and static rings, and the bumps caused by carelessness during the combination process;

(2) The size of the sealing rings of the moving and stationary rings is inappropriate and they are not compacted during assembly;

(3) Impurities exist on the surface of moving and stationary rings;

(4) The set screw is not fixed properly, and the position of the spring seat is inaccurate;

(5) The shaft sleeve seal ring is missing and not compacted.

Vi. causes during operation:

(1) The acceleration and evacuation of the pump increase the pressure on the friction pair;

(2) The spring has problems;

(3) Sudden problems of anti rotation pin and transmission pin make the sealing function lose;

(4) The sealing surface is damaged due to the sudden rise and fall of the temperature of the dynamic and static rings due to the problems of other parts;

(5) Due to the sudden change of cold and heat, the medium near the friction pair has problems such as crystallization, which makes the sealing function invalid;

(6) Under the working condition, the axial displacement of the pump impeller is too high, the running speed of the rotating shaft is unstable, and the workers use it improperly will lead to the failure of the sealing function.

The above is the introduction of the cause analysis of the failure of conventional mechanical seal. Shenzhen Chuangxin Online Testing Technology Co., Ltd. is a well-known professional testing organization for electronic components in China. It has three standardized laboratories with an area of more than 1000 square meters. The scope of testing services covers: testing and verification of electronic components, identification of IC authenticity, product design, material selection, failure analysis, function testing, factory incoming material inspection, X-ray testing of components, tape braiding and other testing items. If you have this need, welcome to consult!