Mechanical seal is by a pair of or several of the vertical axis for
relative sliding face compensation mechanism in the fluid pressure
and stretch (or magnetic) to keep under seal affixed to achieve
consolidation accompanied by supporting shaft seal leakage resistance
device.
Figure 1 Mechanical seal
Common mechanical seal structure shown in Figure 1. By the stationary
ring (stationary ring) 1, rotating ring (ring) 2, elastic element 3,
Spring Seat 4, 5, set screws, rotating auxiliary ring ring ring
supporting ring 6 and 8 and other stationary components, anti-resale
7 fixed to the lid 9 on the stationary ring to prevent rotation.
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 leakage of fluid channels may have in Figure 1, the
a, b, c, d four channels.
c, d leakage channels are stationary ring and the gland, shell gland
and the seal between the two are static sealing. b channel is the
rotation between the ring and shaft seal, when the face friction and
wear, it just can follow the loop compensation for the small amount
of movement along the axis, in fact, still a relatively static seal.
Therefore, these leaks are relatively easy to channel closure. Static
sealing, the most commonly used rubber o-ring or PTFE v-ring, but 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 the rotating ring and stationary ring seal affixed to
each other relative sliding cooperation with the dynamic seal,
mechanical seal device which is the main seal, mechanical seal
performance and determining the key to life. Therefore, the
processing requirements of the seal faces were very high, between the
seal faces in order to maintain the necessary lubrication film, must
be strictly system-side cavity surface pressure per unit area, the
pressure is too large and 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 a
sufficient life, in the design and installation of mechanical seals,
we must ensure that the pressure face value per unit area in the most
appropriate range.
Soft packing seal mechanical seal and more, has the following
advantages:
① reliable seal in the long period of operation, sealing the state
is very stable, very small leakage, according to rough statistics,
the leakage of soft packing seal generally only 1 / 100;
② long life in the oil, water, generally up to the medium class 1 to
2 years or more, usually in the chemical medium can be more than six
months; ③ friction and small power consumption of mechanical seals
friction power is only soft packing seal 10% ~ 50%;
④ shaft or bushings are basically free from wear;
⑤ maintenance cycle automatically after a long face and wear
compensation, under normal circumstances, do not need regular
maintenance; ⑥ good vibration on the rotation axis of vibration,
deflection and the deflection axis of the sealed chamber is not
sensitive;
⑦ for a wide range of mechanical seals can be used for low-
temperature, high temperature, vacuum, high pressure, different
speed, and a variety of corrosive media and sealed with abrasive
media, etc..
But its disadvantages are:
① structure is more complex and demanding manufacturing and
processing;
② too much trouble to install and replace, and require workers to
have a certain level of installed technology; ③ chance occurrence of
accidents, handling more difficult; ④ high one-time investment.
