Working Principles of Several Mechanical Seals

What are the three sealing points of mechanical shaft seal and the sealing working principle of these three sealing points:

The seal between the moving ring and the static ring: it relies on the elastic element (spring, bellows, etc.) and the sealing liquid pressure to produce a proper compression force (specific pressure) on the contact surface (end face) of the moving ring and the static ring in relative motion, so that the two smooth and straight end faces fit closely; the end faces maintain a very thin liquid film to achieve the sealing effect. This film has the liquid dynamic pressure and static pressure, playing the role of balancing the pressure and lubricating the end face. The reason why the two ends must be highly smooth and straight is to create a perfect fit for the end face and make the specific pressure uniform. This is a relatively rotating seal.


Types of mechanical seal technology

At present, the new technologies of various mechanical seals adopting new materials and processes have made rapid progress. There are the following new technologies of mechanical seals. In recent years, slotted seal technology has opened a variety of grooves on the seal face of mechanical seal to produce hydrostatic and dynamic pressure effects, which is still being updated. In the past, zero leakage seal technology always believed that contact and non-contact mechanical seals could not achieve zero leakage (or no leakage). Israel uses slotted seal technology to put forward a new concept of zero leakage non-contact mechanical face seal, which has been used in lubricating oil pump of nuclear power plant. Dry running gas seal technology uses slotted seal technology for gas seal. The upstream pumping sealing technology is to pump a small amount of leakage fluid from the downstream back to the upstream by using a flow groove on the sealing surface.

The structural features of the above types of seals are as follows: shallow groove is adopted, the film thickness and the depth of the launder are both micron level, and lubrication groove, radial sealing dam and circumferential sealing weir are used as the sealing and bearing parts. It can also be said that slotted seal is the combination of plane seal and slotted bearing. The utility model has the advantages of small leakage (even no leakage), large film thickness, small contact friction elimination, power consumption and heat generation. The hot fluid dynamic pressure seal technology uses various deep grooves on the sealing surface to cause local thermal deformation, so as to produce the hydrodynamic wedge effect. This kind of seal with hydrodynamic bearing capacity is called thermo hydrodynamic wedge seal. Bellows seal technology can be divided into formed metal bellows and welded metal bellows mechanical seal technology. Multi face seal technology is divided into double seal, intermediate ring seal and multi seal technology. In addition, there are parallel sealing technology, monitoring sealing technology, combined sealing technology, etc.

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