Mechanical seal is the number by a pair or perpendicular to the axis of relative sliding of the end for the fluid pressure and the compensation mechanism in the elastic (or magnetic) to keep under seal affixed to achieve combined together with the auxiliary shaft seal leakage resistance device.
Common mechanical seal structure shown in Figure 1. From the stationary ring (stationary ring), and turn the ring (ring) 2, elastic element 3, 4 spring seat, set screws 5, 6 rotating secondary seal ring and stationary ring seal 8 and other auxiliary components, anti-resale 7 fixed to the gland to prevent the stationary ring 9 on the turn. Rotating ring and stationary ring often can be compensated according to whether they have the ability to axial or non-compensation is also known as the compensation ring.
Mechanical seal in the fluid may leak through the following in Figure 1 A, B, C, D four channels.
C, D leak channels are stationary ring and the gland, the seal between the shell gland, the two are still sealed. B-channel is the axis of rotation between the ring and the seal, when the face friction and wear, it is only able to follow the compensation loop for micro-movement along the axis, in fact, still a relatively static seal. Therefore, these leaks are relatively easy to channel block. Static sealing element most commonly used rubber O-rings or PTFE V-ring, and as compensation, or stationary rotating ring ring ring secondary seals, sometimes functionality using both the rubber elastic element, PTFE or metal bellows structure.
A channel is a rotating ring and stationary ring face each other Lamination dynamic sliding seal, mechanical seal is the main seal, mechanical seal performance and determining the key to life. Therefore, the sealed end of the processing requirements were very high, between the seal faces in order to maintain the necessary lubrication film, the system must be strictly chamber-side surface of the unit area pressure, the pressure is too large and difficult to form a stable lubricating film, will accelerate the end wear; pressure is too small, leakage increases. Therefore, to obtain good sealing performance and a sufficient 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 with relatively soft packing seal, has the following advantages: ① reliable sealing in the long period of operation, sealing the state is very stable, very small amount of leakage, according to rough statistics, the amount of leakage is typically only a soft packing seal 1 / 100; ② long life in oil, water media category in general up to 1 to 2 years or more, usually in the chemical medium can be more than six months; ③ power consumption of a small mechanical friction and the friction power is only a soft seal packing seal 10% ~ 50%; ④ largely unaffected by the shaft or sleeve wear; ⑤ face wear after a long maintenance cycle can be automatically compensated, under normal circumstances, without regular maintenance; ⑥ good vibration vibration of the axis of rotation , deflection and the deflection axis of the sealed chamber is not sensitive; ⑦ can apply a wide range of Mechanical Seals for low temperature, high temperature, vacuum, high pressure, different speeds, and a variety of corrosive media and abrasive media, such as with the seal. But its disadvantages are: ① structure is more complicated, the manufacturing process requires high; ② cumbersome to install and replace, and require workers to have a certain level of technology installed; ③ chance accident occurred when the treatment more difficult; ④ high one-time investment.
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