Several Misconceptions in Mechanical Sealing Inspection of Sewage Pumps

Misconception 1:

New ones are better than old ones

Relatively speaking, the effect of using new mechanical seals is better than that of old ones, but the quality or material of the new mechanical seal is 

not selected at the time, and the large error in the fitting size will affect the sealing effect; in polymeric and permeable media, it is better not to replace

 the static ring if there is no excessive wear. Because the static ring is in a static state for a long time in the static ring seat, the polymer and impurities 

are deposited into one, which plays a good sealing role.

Misunderstanding 2:

The greater the spring compression, the better the sealing effect

In fact, the amount of spring compression is too large, which can cause the friction pair to wear sharply and burn instantly; excessive compression causes 

the spring to lose the ability to adjust the end surface of the moving ring, resulting in the failure of the seal.

Misconception 3:

The tighter the ring seal, the better

In fact, it is harmful to too tight the moving ring sealing ring. First, it aggravates the wear between the seal ring and the shaft sleeve, and premature leakage;

 second, it increases the resistance to adjust and move the dynamic ring axially, and cannot be adjusted in time when the working conditions change frequently; 

third, the spring is excessively fatigued and easy to damage; fourth, it deforms the dynamic ring seal ring, affecting the sealing effect.

Misconception 4:

The tighter the static ring seal, the better

The static ring sealing ring is basically in a static state, and the sealing effect will be better if it is relatively tight, but it is also harmful to be too tight. First, it 

causes excessive deformation of the static ring seal, which affects the sealing effect; second, the material of the static ring is mostly graphite, which is generally 

brittle, and excessive stress is very likely to cause fragmentation; third, it is difficult to install and disassemble, which is very easy to damage the static ring.

Misconception 5:

The tighter the impeller lock mother, the better

In mechanical seal leakage, leakage between the sleeve and the shaft (inter-axis leakage) is relatively common. It is generally believed that interaxial leakage 

means that the impeller lock mother is not locked. In fact, there are many factors that lead to interaxial leakage, such as failure of the interaxial pad, offset, 

impurities in the interaxial shaft, large morphological errors at the mating between the shaft and the shaft sleeve, damage to the contact surface, gaps between 

the components on the shaft, and excessively long threads of the shaft head will lead to interaxial leakage.

The shaft breaks from the impeller lock mother

One of the possible reasons is the improper locking degree of the lock nut

Excessive locking of the locking mother will only cause premature failure of the shaft gasket. On the contrary, locking the locking mother moderately makes 

the shaft gasket always maintain a certain compression elasticity. During operation, the locking mother will automatically lock in a timely manner, so that the

 shaft gasket is always in a good sealing state.