As the driving shaft through the inside and outside of the equipment, a circumferential gap exists between this axis and the equipment, equipment of medium leak out through the gap, if the equipment inside the pressure below atmospheric pressure, air leakage to the equipment, so there must be a to prevent leakage of the seal device. Many seal species, due to mechanical seal has the advantages of small amount of leakage and long life, it is one of the world’s most main shaft seal.
Mechanical seal is mainly the radial seal into axial sealing through a series of parts, interaction of the spring and the medium pressure, due to the axial caused equipment running wear can timely compensation, the axial seal always. The sealing performance and service life depends on many factors, such as selection, the precision of the machine and the installation, before the start, operation and outage maintenance operations such as [ 1 ].
Mechanical seal according to the working conditions and the medium properties are different, high temperature resistance, low temperature resistance of mechanical seals, mechanical light hydrocarbon resistance of granules medium mechanical seal and adapt to easy vaporization of the seals, should be based on the mechanical different use different structure and materials of sealing. To select the machine according to the requirements of the accuracy of mechanical seal in installation and use, according to the rotation shaft always choose the left and right, spring.
2 installation [ 2 ]
Types of installation method with mechanical seal, the machine will be different, but the installation are almost the same, installation procedures and precautions are as follows:
2.1 installation size determine the correct.
2.2 into the front, shaft ( sleeve ), gland should be free of burrs, bearing in good condition; seals, shaft seal chamber, capping should be cleaned. To reduce friction, shaft mechanical seal parts to be coated with a thin layer of oil, to lubricate, considering the compatibility of rubber O ring, should not be oil, can be coated with soap and water. Floating type static ring without a stop pin structure, not oil, should be dry in the gland.
2.3 the static ring and the cover is mounted on the shaft and the shaft, careful not to touch, and then the moving ring assembly load. The spring seat or the driving seat screws should be divided into several evenly tightened.
Preparation work before the start of the 3 and the matters needing attention
3.1 comprehensive inspection of mechanical seal, mechanical seal before the start of the hydrostatic test, check whether there is leakage phenomenon.
3.2 before the start should be kept sealed cavity filled with liquid. To deliver solidified medium, application of steam seal cavity heated to melting according to medium pump rotary turning, check whether a uniform. Such as the disk hard or not, it should check whether the assembly dimension error, installation is reasonable.
4 run in maintenance
4.1 when the transmission medium temperature too high, too low, or contain the impurity particles, flammable, explosive, toxic, must take the corresponding sealing, flushing, cooling, filtering and other measures.
4.2 before the operation of hand turning, pay attention to the torque is too large, there is no eraser brush up against abnormal sound.
4.3 pay attention to whether the rotation, coupling, lubricating oil additive bearing parts of the appropriate, piping is correct.
4.4 operation before the first medium, cooling water valve open, check the seal cavity of the gas discharge is caused by static pressure, prevent leakage, and then start running.
4.5 drive is normal and stable, there is no abnormal because of the torque shaft rotation caused, and the abnormal noise and overheating.
5.1 for the pump mechanical seal of the seal oil system, should first start the oil sealing system. Finally stop the seal oil system of parking.
Can’t stop cooling water sealed oil chamber and the 5.2 oil pump seal after the shutdown, should be the end seal oil temperature dropped to 80 degrees below, can stop the cooling water, so as not to damage the sealing parts .
6 new technical transformation [ 4 ]
In order to improve the reliability and service life of mechanical seal, reducing wear, there appeared a variety of machinery and the use of new materials and new technology of sealing technology. Machinery at present advanced seal technology mainly seal technology, control balance ratio sealing technology, sealing technology and controllable mechanical seal technology, can change the performance of mechanical seals.
The following main sealing surface modified technology. Sealing surface modified technology is through the various forms in the seal groove on the end surface to improve lubrication, long-life operation so as to realize the mechanical seal, it is the high-tech field in mechanical seal.
6.1 dry gas seal technology 
Dry gas seal is to be slotted sealing technology for gas seal, which belongs to the non-contact seal. In the dry gas seal of a sealing ring face outside processing with uniformly distributed 2.5-10um dynamic pressure groove, when the east ring rotates, the fluid dynamic pressure groove of the high-pressure gas pump isolation outside into the seal face, increases gradually from outside to the groove root gas film pressure, since the groove roots to the inner diameter of gas film pressure gradually decreased, because the film pressure increases the formation of Del opening force is greater than the effect on the sealing ring closing force, to form a layer of film is very thin in the friction between, so that the flour in a non-contact state, gas film formed by completely blocking the relatively low pressure sealing medium leakage channels, to realize zero leakage sealing medium.
The sealing operation and no wear, power consumption is small; a small amount of leakage, can realize zero leakage; the structure is relatively simple, without the need of oil seal system complex, installation and maintenance costs low; system is reliable, can realize the long term stable operation.
Groove dry gas seal is divided into single rotation direction and double rotation to two. Single spiral groove can only be used in unidirectional rotational equipment, it can generate downward opening force in rotation, such as inversion produces the opening force and may lead to negative seal damage. But compared to the trough to the double spiral, it can form a larger opening force and stiffness of gas film, produced more stable and more reliable to prevent end contact. It can also be used in low speed and large vibration, is widely used in the current. Bidirectional groove without rotation to requirements, positive inversion can be used. Reversal not rotor seal damage caused by. The range of use a single rotation direction groove width, but its stability, anti-interference ability is unidirectional rotation difference.
The 6.2 upstream pumping seal
The working principle of upstream pumping seal and dry gas seal is similar, with the fluid sealing ring section positioned at the inner side of dynamic pressure groove in a rotating viscous shear conditions to pump liquid into the seal between the liquid film pressure increases, and separated the two seal; and dry gas seal is different, face the liquid upstream pumping seal dynamic pressure groove type from the high voltage side to the low pressure side of the seal leakage of liquid to the inverse transmission of high side, to eliminate the seal leakage of medium to low voltage side of the high pressure side.
6.3 on the end surface of deep groove of hydrostatic mechanical seal
Deep groove on the end surface of hydrostatic mechanical seal is the seal out of several groups of depth of a few millimeters in grooves or holes and the pressure medium into a hole, the sealing fluid or external lubricating fluid into the seal face, so as to fully lubrication and cooling of the seal face. In the structure of self pressure groove type and external pressure groove type etc.. Since the annular groove communicated pressure groove type in non peripheral rotating opened with a plurality of holes and face out, thereby the pressure medium is sealed into the seal; and pore pressure groove type non rotating ring is communicated with the outside the sealing medium, while the fluid source and external lubrication are interlinked, the outside introduction of a fluid seal for lubrication and cooling. Deep groove on the end surface of hydrostatic mechanical seal, because the pressure medium into a face, balance the closing force, so that both ends of the surface is divided into a non-contact type mechanical seal leakage, despite the relatively large, usually several hundred per hour ml, far larger than the conventional mechanical seal leakage, but still widely used in high voltage, high speed, high temperature a common mechanical seal, the difficult conditions.
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In order to reveal the law of mechanical seal, to improve the reliability of surface parameters and test of mechanical seal is the key. The special properties of nanomaterials will help to improve the mechanical seal lubrication state, the development of nano material and nano mechanical seal flushing fluid will be short-term goal of mechanical seal. With the development of sound and technical experience, mechanical seal will be more and more mature, gradually moving towards zero leakage, long term stable operation.