The difference between single mechanical seal and double mechanical seal

A pair of sealing end faces consists of a single-end seal (see Figure 29.7-7a), and a pair of sealed end faces consist of a double-face seal (see Figure 29.7-7bc). The single-end sealing structure is simple, easy to manufacture and install, generally in the condition that the medium itself has good lubricity and allows a small amount of leakage. It is a commonly used sealing type. When the medium is toxic, flammable, explosive and has strict requirements on leakage, it is not suitable. use.

The double end seal has an axial double seal and a radial double seal. The double-end sealing structure arranged in the radial direction is tighter than the axial double-end sealing. Double-face seal is suitable for the medium itself, poor lubricity, toxic, flammable, explosive, volatile, abrasive particles and gas.

The axial double-face seal has a structure of face-to-face or back-to-back arrangement. During operation, a sealing liquid higher than the medium pressure of 0.05-0.15 MPa is introduced between the two pairs of end faces to improve the lubrication and cooling conditions between the end faces, and the medium is isolated from the outside. It is possible to achieve a "zero leak" of the medium.

Figure 29.7-7 Single-end and double-faced mechanical seals

a) single end type; b) axial double end type; c) radial double end seal