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The last article took the the melamine slurry tank agitator mechanical seal of a Chinese enterprise as an example to analyze the cause of the damage of the mechanical seal. According to it, various optimizing measures are proposed in this article to extend the life of mechanical seal and improve the production and processing efficiency of enterprises.
2.1 Optimize the transfer equipment
Due to the stiffness of the slurry tank is relatively low, the staff added a annular reinforcement plate to its content. On the one hand,the reinforcing plate of three layers of flat steel ring is welded with the radian on the inner wall of the device, whose width is 12.6 cm, and thickness is 1.6 cm. The distance before the bottom of the equipment is usually 200 cm, and the average distance between the three layers of reinforcing plate is 150 cm. This strengthening of the equipment as a whole can better avoid the occurrence of the resonance phenomenon during the operation. On the other hand, the corresponding reinforcing plate is welded on the inner wall near the flange takeover port of the mixer, and the corresponding vertical bars are welded near the vicinity to further improve the stiffness of the connecting pipe.The following measures will target the agitator mechanical seal.
Due to the stiffness of the slurry tank is relatively low, the staff added a annular reinforcement plate to its content. On the one hand,the reinforcing plate of three layers of flat steel ring is welded with the radian on the inner wall of the device, whose width is 12.6 cm, and thickness is 1.6 cm. The distance before the bottom of the equipment is usually 200 cm, and the average distance between the three layers of reinforcing plate is 150 cm. This strengthening of the equipment as a whole can better avoid the occurrence of the resonance phenomenon during the operation. On the other hand, the corresponding reinforcing plate is welded on the inner wall near the flange takeover port of the mixer, and the corresponding vertical bars are welded near the vicinity to further improve the stiffness of the connecting pipe.The following measures will target the agitator mechanical seal.
2.2 Adjust the stationary seat size
The inner diameter of the stationary seat of the agitator mechanical seal is usually 6.7 cm. The outer diameter of the shaft sleeve is 6.6 cm, and its spacing is 0.05 cm. In order to solve the problem of stationary seat fragmentation, the content of the stationary seat should be adjusted to 6.8 cm, resulting in the spacing between the two increased by 0.1 cm each side, and enhance the restricting function of the stationary seat to prevent too much swing of the mixing axis & the friction of the mixing axis on the stationary seat of the mechanical seal.
The inner diameter of the stationary seat of the agitator mechanical seal is usually 6.7 cm. The outer diameter of the shaft sleeve is 6.6 cm, and its spacing is 0.05 cm. In order to solve the problem of stationary seat fragmentation, the content of the stationary seat should be adjusted to 6.8 cm, resulting in the spacing between the two increased by 0.1 cm each side, and enhance the restricting function of the stationary seat to prevent too much swing of the mixing axis & the friction of the mixing axis on the stationary seat of the mechanical seal.
2.3 Do Innovations about rotary face and stationary seat processing materials
In the past practice, the stationary seat of the mechanical seal is made of diamond sand whose toughness is relatively small, and the fragmentation chances due to friction and extrusion with the mixing axis are greater. Therefore, the staff can use tungsten carbide to make the stationary seat to further strengthen its toughness. In the past, the rotary face is made of carbon graphite, but there are a large number of particles in the medium, resulting in serious wear, so tungsten carbide can be used to process the rotary face of the mechanical seal, and the soft vs soft combination of mechanical seal friction pair is changed to hard vs hard match.
In the past practice, the stationary seat of the mechanical seal is made of diamond sand whose toughness is relatively small, and the fragmentation chances due to friction and extrusion with the mixing axis are greater. Therefore, the staff can use tungsten carbide to make the stationary seat to further strengthen its toughness. In the past, the rotary face is made of carbon graphite, but there are a large number of particles in the medium, resulting in serious wear, so tungsten carbide can be used to process the rotary face of the mechanical seal, and the soft vs soft combination of mechanical seal friction pair is changed to hard vs hard match.
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2.4 Stationary seat rabbet and positioning device
In the past, the centricity of the shaft sleeve and the static ring seat is adjusted according to the positioning clamp ring of the mechanical seal. Its main function is to preset the compression amount of the bellows during the installation, and to specify whether the shaft and the static ring seat are concentric according to the positions of positioning clamp ring and the static ring seat and the lock ring. The positioning clamp ring shall be removed at the end of the mechanical seal installation. However, there are corresponding distances between the shaft and the shaft sleeve, the shaft sleeve and the lock ring,the above method will cause week accuracy of the mechanical seal, and under the influence of other factors, the error is usually 0.2 mm to 0.4 mm. Therefore, the structure of the static ring seat should be adjusted, and the bump rabbet device should be added, so that the unilateral distance between the static ring seat rabbet and the sealing cavity of the mechanical seal is 0.05 mm, and the O-type static ring seat gasket should be used, its diameter should be 0.3 meters.
In the past, the centricity of the shaft sleeve and the static ring seat is adjusted according to the positioning clamp ring of the mechanical seal. Its main function is to preset the compression amount of the bellows during the installation, and to specify whether the shaft and the static ring seat are concentric according to the positions of positioning clamp ring and the static ring seat and the lock ring. The positioning clamp ring shall be removed at the end of the mechanical seal installation. However, there are corresponding distances between the shaft and the shaft sleeve, the shaft sleeve and the lock ring,the above method will cause week accuracy of the mechanical seal, and under the influence of other factors, the error is usually 0.2 mm to 0.4 mm. Therefore, the structure of the static ring seat should be adjusted, and the bump rabbet device should be added, so that the unilateral distance between the static ring seat rabbet and the sealing cavity of the mechanical seal is 0.05 mm, and the O-type static ring seat gasket should be used, its diameter should be 0.3 meters.
2.5 Improve the shaft sleeve length and reduce the deflection
For the large mixing shaft deflection problem caused by short shaft sleeve and the small transmission support bearing spacing, the staff can innovate and adjust the gearbox shaft sleeve. The inner diameter of the shaft sleeve is increased to 7.7 cm, and the shaft sleeve length coupled with the actual installation conditions and the space needs are detected as the basis of the production of the new shaft sleeve. The previous shaft sleeve is installed together with the new shaft sleeve to further reduce the deflection of the mixing shaft. The surplus fit method shall be used where the surplus shall be 0.05 mm, and then the shaft sleeves shall be installed. At the same time, at the contact position of the new and the old shaft sleeve section，four points around the core should be welded to raise the connection degree. The new sleeve end shall be fitted with three threaded holes at the circumference point and secure the new sleeve against the shaft with three M14 top wires during installation. During the shaft sleeve locking period, the staff shall make the meter measurement to ensure the accuracy of the concentricity of the shaft and the shaft sleeve. After locking, use three top wire to tighten the nut to avoid the top wire shedding during its operation. At the same time, ,the main function of the pushing plate and its central screw is to restrict the movement of the stirring shaft in the direction of the impeller shaft. Among them, the push plate mainly constrains and controls the movement of the stirring shaft along the direction away from the impeller shaft. However, due to the installation of the new shaft sleeve, the push plate cannot be installed normally, so the push plate should be adjusted to increase its outer diameter to 9.6 centimeters, and the center hole of the newly produced and processed thrust plate cannot be changed, and Add four holes evenly on the circumference of 7.6 cm. At the same time, the hole diameter should be 0.9 cm. The screw at the center position cannot be changed in the past. In addition, four M8 screws are used to attach the new thrust plate to the previous bushing according to the newly added 4 holes. Fix it on the top to further prevent the reverse movement of the stirring shaft.
For the large mixing shaft deflection problem caused by short shaft sleeve and the small transmission support bearing spacing, the staff can innovate and adjust the gearbox shaft sleeve. The inner diameter of the shaft sleeve is increased to 7.7 cm, and the shaft sleeve length coupled with the actual installation conditions and the space needs are detected as the basis of the production of the new shaft sleeve. The previous shaft sleeve is installed together with the new shaft sleeve to further reduce the deflection of the mixing shaft. The surplus fit method shall be used where the surplus shall be 0.05 mm, and then the shaft sleeves shall be installed. At the same time, at the contact position of the new and the old shaft sleeve section，four points around the core should be welded to raise the connection degree. The new sleeve end shall be fitted with three threaded holes at the circumference point and secure the new sleeve against the shaft with three M14 top wires during installation. During the shaft sleeve locking period, the staff shall make the meter measurement to ensure the accuracy of the concentricity of the shaft and the shaft sleeve. After locking, use three top wire to tighten the nut to avoid the top wire shedding during its operation. At the same time, ,the main function of the pushing plate and its central screw is to restrict the movement of the stirring shaft in the direction of the impeller shaft. Among them, the push plate mainly constrains and controls the movement of the stirring shaft along the direction away from the impeller shaft. However, due to the installation of the new shaft sleeve, the push plate cannot be installed normally, so the push plate should be adjusted to increase its outer diameter to 9.6 centimeters, and the center hole of the newly produced and processed thrust plate cannot be changed, and Add four holes evenly on the circumference of 7.6 cm. At the same time, the hole diameter should be 0.9 cm. The screw at the center position cannot be changed in the past. In addition, four M8 screws are used to attach the new thrust plate to the previous bushing according to the newly added 4 holes. Fix it on the top to further prevent the reverse movement of the stirring shaft.
