Influence of Spring Stiffness on Vibration of Contact type Mechanical Seals

The working state of the mechanical seal depends on the centering error, axial vibration and angular deflection during its working process. The latter three will lead to increased wear of the end faces of the mechanical seal, increased leakage, and reduced seal life.The criteria for evaluating the performance of mechanical seals are the leakage rate and life value. In order to minimize leakage or excessive wear of the end face, it is necessary to clarify the factors that affect the vibration of the mechanical seal ring. The research shows that, in addition to the centering error, the speed of the seal ring, the spring stiffness, the angle of the end faces, the inner and outer radii of the end faces, and the medium pressure will all affect the vibration of the mechanical seal. The author of this paper will analyze the effect of spring stiffness on seal vibration through modeling for contacting face mechanical seals. And this article is a subtract of his paper.

Kinematic Analysis of Seal Ring
The mechanical seal is composed of a rotary face and a stationary seat, wherein the rotary face can rotate together with the shaft, the stationary seat is fixed on the housing, and it can float axially through the spring device behind it.When the shaft rotates, the medium pressure behind the static ring and the spring force together form the closing force of the mechanical seal, preventing the sealed medium from passing through the sealing end faces, while the liquid film pressure and contact force between the sealing end faces form the opening force, which is balanced with the closing force . 

By establishing and analyzing the graphical model of the seal ring movement of the mechanical seals, we draw the following conclusions:
(1) The increase of the stiffness value of the contact type mechanical seal makes the axial displacement and axial velocity and the rotation angle of the stationary seat to the X and Y axes change more in the early and middle stages of vibration of the mechanical seal. The greater the stiffness, the greater the amplitude of the change, and the vibration In the later stage, all the parameters are close to 0 and will not change.

(2) As the stiffness increases, the swing amplitude of the total liquid film force and contact force curves increases in the early and middle stages of vibration of the mechanical seal, and the curve fluctuations gradually disappear in the late stage of vibration. As the stiffness increases, the final stable value of the total contact force increases.

(3)In mechanical seal vibration, the greater the value of stiffness, the greater the swing of the leakage rate curve. At the initial moment of vibration, the greater the stiffness value, the smaller the leakage; when the vibration disappears, the leakage decreases with the increase of stiffness.

(4) The analysis shows that under small disturbance conditions, when the spring stiffness is in the range of 3✖10⁵ ~ 15✖10⁵  N/m, the parameters of the mechanical seal are finally stable, and the mechanical seal is stable at this time.

The above is the influence of the spring stiffness on the vibration of the contact end face mechanical seal.