Analysis of the Causes of Sealing Failure in Mechanical Seal Parts

In pump mechanical seals, the effectiveness of mechanical seal parts directly relates to the operational efficiency and reliability of the equipment. Despite well-designed mechanical seals, leakage issues frequently occur, mainly in five critical areas: the seal between the shaft sleeve and the shaft, the seal between the rotating ring and the shaft sleeve, the seal between the stationary rings, the seal between the stationary rings and the stationary ring seat, and the seal between the seal end cover and the pump body. This article will analyze the causes of failure of these mechanical seal parts to help users better maintain their equipment.

Leakage Problems During Static Pressure Testing of Mechanical Seal Parts

After the mechanical seal installation is completed, conducting static pressure testing is an important step to detect leakage. If a small amount of leakage is found during the test, it usually indicates a problem with the sealing rings of the rotating or stationary ring; whereas a larger amount of leakage may suggest defects in the friction pairs of the rotating and stationary rings. Observing changes in the amount of leakage during the test is crucial.

If there is no significant change in the amount of leakage during manual rotation, it can generally be judged as a problem with the sealing rings of the stationary and rotating rings; but if the amount of leakage changes significantly during rotation, it likely indicates a problem with the friction rings of the rotating and stationary rings. If the leaked medium sprays along the axial direction, the likelihood of rotating ring seal failure is high; while if the leaked medium sprays in all directions or leaks from the cooling hole, it is mostly related to the failure of the stationary ring seal. By carefully observing and familiarizing oneself with the structure of mechanical seal parts, it is possible to effectively determine the cause of leakage and timely take corresponding repair measures.

Leakage of Mechanical Seal Parts During Trial Operation

During trial operation, after the pump mechanical seal has undergone static pressure testing, centrifugal force generated at high speeds usually suppresses medium leakage. However, if mechanical seal leakage occurs after ruling out shaft and end cover seal failures, the main cause often relates to the damage of the friction pairs of the rotating and stationary rings.

The Factors Leading to Friction Pair Seal Failure

Abnormal Operations

Under abnormal operation conditions such as emptying, cavitation, and pressure holding, the increase in axial force may lead to the separation of the contact surfaces of the rotating and stationary rings.

Excessive Compression

During the installation of the mechanical seal, excessive compression may cause severe wear or scratches on the friction end of the pairs.

Overtight Rotating Ring Seal

If the tightness of the rotating ring seal is improper, the spring cannot effectively adjust the axial float of the rotating ring, affecting the seal performance.

Loose Stationary Ring Seal

If the rotating ring exhibits axial float, and the stationary ring is loose, it may detach from the stationary ring seat, resulting in leakage.

Particles in the Working Medium

If the working medium contains particulate matter that enters the friction pairs during operation, it may scratch the sealing end faces of the rotating and stationary rings.

Design Selection Errors

If the sealing end face specific pressure is too low or the sealing material exhibits significant cold shrinkage, these design defects can also lead to seal failure.

The above issues are relatively common during trial operation. Some situations can be resolved by adjusting the stationary ring seat, but in most cases, reseating and replacing the seal are required, causing additional time and cost losses.

Through the above analysis and suggestions, users can better understand the causes of mechanical seal parts failure, thereby taking effective preventive and maintenance measures to ensure high-efficiency and safe operation of the equipment.