【Daily Question No. 304】November 06, 2018

Advantages are: (1) It is particularly effective for high-temperature, high-pressure, high-speed, and large-size sealing applications； (2) It has good sealing performance, especially at high speeds ； (3) No friction between them, low power consumption, long service life ； The disadvantages are: it cannot completely prevent gas leakage, it requires high precision in tooth shaping, assembly is difficult, it wears out due to poor operation of the unit, and its sealing performance **degrades** after wear.

Advantages are: (1) It is particularly effective for high-temperature, high-pressure, high-speed, and large-size sealing applications； (2) It has good sealing performance, especially at high speeds ； (3) No friction between them, low power consumption, long service life ； The disadvantages are: it cannot completely prevent gas leakage, it requires high precision in tooth shaping, assembly is difficult, it wears out due to poor operation of the unit, and its sealing performance **degrades** after wear.

The labyrinth seal is simpler in terms of material, processing, operation, and maintenance compared to mechanical seals, but its sealing performance is inferior to that of mechanical seals, and its service life is shorter

It boasts excellent sealing performance at high speeds, requires no lubrication, has no friction, is easy to maintain, has a long service life, and does not require the use of other sealing materials. However, it has high machining precision and is difficult to assemble. It is primarily used for sealing gases, and labyrinth seals are widely employed at the shaft ends and between stages in turbines, gas turbines, compressors, and blowers. It is particularly effective for high-temperature, high-pressure, high-speed, and large-size sealing applications where ordinary seals are not suitable.

Labyrinth seal      A seal that reduces leakage by having many intricate chambers between the rotating and stationary parts. 　　A labyrinth seal consists of several annular sealing teeth arranged in sequence around the rotating shaft; gaps and expansion chambers are formed between these teeth. As the fluid to be sealed passes through these intricate labyrinthine gaps, a throttling effect occurs, thereby preventing leakage. 　　Due to the gap between the rotor and the casing in a labyrinth seal, there is no solid contact, thus lubrication is not required, and thermal expansion is allowed. This makes it suitable for applications involving high temperatures, high pressures, and high rotational speeds. This type of seal is widely used for sealing the shaft ends and stages in turbines, gas turbines, compressors, and blowers, as well as as a preliminary seal for other dynamic seals. 　　Sealing mechanism of labyrinth seals The mechanism by which fluid encounters resistance as it passes through a labyrinth, resulting in a reduction in its flow rate, is known as the “labyrinth effect”. For liquids, there are fluid dynamics effects, including hydrodynamic friction effects and flow-contraction effects ； For gases, there are also thermodynamic effects, namely the heat conversion that occurs in the labyrinth as a result of compression or expansion ； In addition, there is also the “ventilation effect,” among others. The labyrinth effect is a combined result of these effects; therefore, the mechanism of labyrinth sealing is very complex. 　　Frictional effect: As the leaking fluid flows through the labyrinth, the friction resulting from the viscosity of the liquid slows down the flow rate, thereby reducing the amount of leakage. In simple terms, the friction along the flow path and the local resistance of the fluid constitute the drag effect; the former is related to the length and cross-sectional shape of the channel, while the latter is related to the number of bends and the geometry of the labyrinth. Generally, when the flow channel is long, the bends are sharp, and the teeth are pointed, the resistance is high, the pressure drop loss is significant, and the leakage amount decreases.

Advantages: Good sealing performance, resistant to leakage. Disadvantages: High cost, difficult to repair

Within the leakage path, a labyrinthine gap composed of numerous teeth or grooves creates a throttling effect on what is to be sealed, thereby providing sealing; this type of seal is known as a labyrinth seal. It boasts excellent sealing performance at high speeds, requires no lubrication, has no friction, is easy to maintain, has a long service life, and does not require the use of other sealing materials. However, it has high machining precision and is difficult to assemble. It is primarily used for sealing gases, and labyrinth seals are widely employed at the shaft ends and between stages in turbines, gas turbines, compressors, and blowers. It is particularly effective for high-temperature, high-pressure, high-speed, and large-size sealing applications where ordinary seals are not suitable.

Advantages: Low requirements for water quality, long lifespan； Disadvantages: Complex structure, prone to leakage

Advantages are: (1) It is particularly effective for high-temperature, high-pressure, high-speed, and large-size sealing applications； (2) It has good sealing performance, especially at high speeds ； (3) No friction between them, low power consumption, long service life ； The disadvantages are: it cannot completely prevent gas leakage, it requires high precision in tooth shaping, assembly is difficult, it wears out due to poor operation of the unit, and its sealing performance **degrades** after wear.

Within the leakage path, a labyrinthine gap composed of numerous teeth or grooves creates a throttling effect on what is to be sealed, thereby providing sealing; this type of seal is known as a labyrinth seal. It boasts excellent sealing performance at high speeds, requires no lubrication, has no friction, is easy to maintain, has a long service life, and does not require the use of other sealing materials. However, it has high machining precision and is difficult to assemble. It is primarily used for sealing gases, and labyrinth seals are widely employed at the shaft ends and between stages in turbines, gas turbines, compressors, and blowers. It is particularly effective for high-temperature, high-pressure, high-speed, and large-size sealing applications where ordinary seals are not suitable.