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In selection of mechanical seals, gas media such as air, ethylene, propylene, and hydrogen have their own specific standards.
This is determined by characteristics of these media. Characteristics of gas media are: poor lubricating performance, large end face wear, and strong permeability; When used in stirring equipment,the equipment is mostly vertical, with long shaft, large swing and vibration, and large changes in process conditions usually occur. Sometimes it is operated under high pressure, sometimes under low pressure or vacuum; when used in compressors, the speed is high.
These characteristics determine the requirements for mechanical seals as follows: graphite impregnated sealing materials have low porosity and are suitable to make friction pairs for their wear-resistance; sealing rings have good floatability, especially for sealing of stirring equipment; when used for vacuum sealing, attention should be paid to outside air Leakage, and directionality of the mechanical seal.
Therefore, the following selection criteria are proposed for correpondent mechanical seal:1.If it is used for sealing of stirring equipment, when medium pressure is less than or equal to 0.6MPa,single mechanical seal(external type) can be used, and a cooling shell is required. When medium pressure is greater than 0.6MPa, or sealing requirements are quite strict, pressurized double mechanical seal should be used.
2. When used for vacuum sealing, pressurized double mechanical seal is often used, and vacuum oil or liquid that is difficult to volatilize is introduced as isolation fluid. Pay attention to directionality when using the V-shaped auxiliary seal.
3. For compressor sealing, if rotational speed is high, porosity of impregnated graphite ring should be reduced.
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This is determined by characteristics of these media. Characteristics of gas media are: poor lubricating performance, large end face wear, and strong permeability; When used in stirring equipment,the equipment is mostly vertical, with long shaft, large swing and vibration, and large changes in process conditions usually occur. Sometimes it is operated under high pressure, sometimes under low pressure or vacuum; when used in compressors, the speed is high.
These characteristics determine the requirements for mechanical seals as follows: graphite impregnated sealing materials have low porosity and are suitable to make friction pairs for their wear-resistance; sealing rings have good floatability, especially for sealing of stirring equipment; when used for vacuum sealing, attention should be paid to outside air Leakage, and directionality of the mechanical seal.
Therefore, the following selection criteria are proposed for correpondent mechanical seal:1.If it is used for sealing of stirring equipment, when medium pressure is less than or equal to 0.6MPa,single mechanical seal(external type) can be used, and a cooling shell is required. When medium pressure is greater than 0.6MPa, or sealing requirements are quite strict, pressurized double mechanical seal should be used.
2. When used for vacuum sealing, pressurized double mechanical seal is often used, and vacuum oil or liquid that is difficult to volatilize is introduced as isolation fluid. Pay attention to directionality when using the V-shaped auxiliary seal.
3. For compressor sealing, if rotational speed is high, porosity of impregnated graphite ring should be reduced.
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