Mechanical seal Principle Overview

Mechanical seal is by one pair or several pairs perpendicular to the axis relative to the sliding face in the fluid pressure and compensation institutions elastic ( or magnetic ) to keep under seal affixed to achieve the merger with auxiliary shaft seal leakage resistance device .
Mechanical seal used by the stationary ring ( stationary ring ) 1 , rotating ring ( ring ) 2 , the elastic member 3 , the spring seat 4 , set screws 5 , 6 rotating ring secondary seal , and the stationary ring secondary seal 8 and other components composition, anti-rotation pin 7 is fixed to prevent the gland 9 stationary ring is rotated . Rotating ring and the stationary ring often also according to whether they have the ability to compensate for axial cyclic or compensation is also referred to as compensation .
Mechanical seal possible leakage of fluid channels are A, B, C, D four channels.
C, D leakage channels are stationary ring and the gland , the gland seal between the housing , the two are static seal . B channel between the rotary shaft sealing ring and , when Friction and wear , it can follow the compensation ring only for a small amount of movement in the axial direction , in fact, still a relatively static seal .
Therefore, these leak paths are relatively easy closure. The most commonly used static sealing rubber O-ring or PTFE V-ring , and as compensation or stationary rotating ring ring ring secondary seal , sometimes using both elastic elements feature rubber, PTFE or metal bellows structures.
A channel is a rotating ring and the stationary ring opposite end faces sliding Lamination dynamic seal , it is the mechanical security seals device of the main seal , mechanical seal in determining the performance and life of the key.
Thus , the processing requirements of the seal face is high , while the sealing end faces in order to maintain the necessary lubrication film , the system must be strictly the end surface of the cavity pressure per unit area , the pressure is too large, difficult to form a stable lubricating film , will accelerate the end wear ; pressure is too small , increase of leakage . Therefore, to obtain good sealing performance and enough life , in the design and installation of mechanical seals , we must ensure that the pressure per unit area of ​​face value in the most appropriate range.
Mechanical seal and soft packing seal comparison , has the following advantages: ① sealing is reliable in the long period of operation, the sealed state is very stable, very small leakage , according to rough statistics, the leakage is typically only soft packing seal 1/100 ;stainless steel cable ties ② long life in oil, aqueous medium, generally up to 1 to 2 years or more, usually in the chemical medium can be more than six months ; ③ friction power consumption is small mechanical seal friction power only soft packing seal 10% to 50%.