Difference between packing seal and mechanical seal

First, the packing seal of the pump has simple structure, cheap price and convenient maintenance. But the leakage is large and the loss of power consumption is large. Therefore, the packing seal is used to transport general media, such as water; Generally not suitable for petroleum and chemical media, especially can not be used in valuable, explosive and toxic media.

The selection of centrifugal pump fillers should consider the following conditions:

1, There is a certain plasticity, under the action of compression force can produce a certain radial force and contact with the close axis.

2, There is enough chemical stability, does not pollute the medium, the filler is not inflated by the medium, the impregnating agent in the filler is not dissolved by the medium, and the filler itself does not corrodes the sealing surface.

3, The packing self-lubrication performance is good, wear resistance, small friction coefficient.

4, When the shaft has a small amount of offset, the packing should have enough floating elasticity.

5, Simple manufacturing, easy to fill.

To this end, it is necessary to adjust the compression degree of the pump packing frequently, and it is necessary to replace the packing regularly. In addition, in order to maintain the liquid film and take away the friction heat, it is also necessary to intentionally allow a small amount of leakage at the pump filler.

The problems existing in the use of packing filler in the pump: from the principle of packing seal, there are three channels that the fluid can leak in the sealing chamber: one is that the fluid penetrates the fiber material to cause leakage; The second is leakage between the packing and the packing box; The third leakage is between the packing and the shaft surface. Therefore, the most critical measures to prevent pump leakage are: reasonable selection of sealing filler; A reasonably designed sealing cavity; Adjust the appropriate seal compression force.

Second, the sealing effect of mechanical seal (also known as end seal) is good, the leakage is small, the life is long, but the price is expensive, and the processing, installation and maintenance are higher than the general sealing requirements. The mechanical seal of the centrifugal pump is suitable for conveying petroleum and chemical media, and can be used for a variety of media with different viscosity, strong corrosion and particles.

Centrifugal pump mechanical seal leakage reasons:

1, Seal end face failure: wear, heat cracking, deformation, damage (especially non-metal seal end face).

2, Spring failure: relaxation, fracture and corrosion.

3, The failure of the auxiliary sealing ring: the failure of assembly has fallen, cracks, bruises, curling and distortion; Non-assembly faults are deformation, hardening, cracking and deterioration.

Centrifugal pump mechanical seal failure in the operation performance of vibration, heating, wear, and finally appear in the form of medium leakage.