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Mechanical seal technical requirements
First, the mechanical seal failure analysis
1, the temperature caused by the failure
Mechanical seal, the temperature rise will cause failure, as a result of the temperature rise, the mechanical seal surface lubrication film vaporization, the two ends appear dry friction, due to the friction heat generated, making the wear and tear and cause thermal stress cracks Leaving the seal ring fracture or even fragmentation. Due to the temperature rise friction dip co-flow out, so that the friction and adhesion, then the temperature may exceed the limit of the material lead to the use of temperature does not allow some thermal deformation under sudden load may also lead to thermal stress cracking seal failure and seal failure . In addition, elevated temperatures may also discolour the heat-setting ring or cause the clearance to exceed the allowable value of the secondary seal. In this case, the internal pressure will squeeze the seal from the gap causing malfunction. Elevated temperature can also cause sedimentation and sedimentation impedes the sealing work. The medium used in the high-pressured boiler feed water pump is industrial water, the mechanical seal used is 831 mechanical seal, the maximum temperature in the sealed chamber is 180 ℃, so the temperature should not be too high when used. If the medium temperature exceeds the limit temperature, take appropriate measures to seal the chamber to be cooled to ensure the normal use of mechanical seals, to avoid failure.
2, moving ring burst, static ring serious wear and tear caused by failure
High pressure boiler feed pump with balanced mechanical seals are generally equipped with cooling circulation system to ensure that the sealed chamber temperature to meet the reliable use of mechanical seals. Cooler circulation system equipped with a cooler and filter, the role of the cooler to the pump cavity after the heat medium cooling medium cooler, recycled to the sealed chamber. The use of the filter is to filter the impurities in the medium cycle, if the filter is blocked or system piping leaks or switching control valve failure, will make instantaneous water seal or intermittent when the pass, then seal the end is not good Cooling, washing, the formation of temperature, causing the seal ring burst, the static ring serious wear and tear, seal leakage caused by failure. Therefore, the system should always be used when checking the pipeline, the filter should be cleaned often, to prevent the blocked heat exchanger to be fully discharged or installed in the system alarm, etc., has been to achieve timely troubleshooting to extend the service life of mechanical seals.
3, auxiliary ring damage caused by failure
Mechanical seal In addition to the end seal, in the parts in contact with the shaft and gland contact parts, the use of auxiliary seal O-ring, V-ring and U-ring seal to solve the static sealing problem. High-pressure boiler feed pump balanced mechanical seal static seal, the use of O-ring, the material for the rubber products, if the O-ring damage, but also caused a small amount of leakage failure, then the solution is to replace the O-type Seal, to prevent leakage, according to our multifaceted work experience General O-ring failure for several reasons.
3.1 pump assembly mechanical seal, due to size problems, chamfer problems or work inadvertently O-ring card is bad, in the U-ring cross-section of the diameter of the direction or axis may have stuck bad phenomenon, resulting in seal leakage.
3.2 O-type sealant itself is also a cause of defects defects, such as the O-ring seal size is not suitable for manufacturing, the relative amount of interference, the lack of section diameter of meat phenomenon, the mold die diameter due to wear and tear caused by mold Seal leakage problems may occur.
3.3 O-ring improper materials, such as the pump temperature is higher and the use of high temperature rubber ring, the use of rubber aging, resulting in static sealing failure. The company is located in:
The above measures to take the approach is to improve the quality of the assembly, to strengthen the responsibility of assembly, conscientious assembly, to avoid bad O-ring seal. In addition, to improve the quality of O-ring itself, the defective O-ring and the improper use of materials should be carefully put a good quality to prevent the occurrence of the problem.
4, the user due to improper use of the fault
Second, effective troubleshooting
There are many ways to troubleshoot, here are some common methods for reference.
1, It is necessary to monitor the temperature rise of the return water of the mechanical seal flushing water during the operation of the pump. The normal operation is the best at 40 ℃ ~ 50 ℃. When the temperature exceeds 85 ℃, the alarm will be triggered. When the temperature exceeds 90 ℃, it will trip.
2, to improve water quality. Users use the pump, the water quality must be carried out by pump and mechanical seal requirements. If necessary, increase the coarse filter coarse filter to improve water quality to avoid failure.
3, for the regular sealing system to take apart and wash, clean up dirt and impurities, in particular, magnetic filters must be regularly switched cleaning to prevent dirt clogging the filter, resulting in seal cavity water, causing the ring broken, resulting in failure.
4, before the operation of the pump must be operated according to instructions for use, good exhaust, give sealed cooling water before starting the pump. On the contrary, the operation as a result of the first start to seal the cooling water can easily lead to seals ring static burst.
5, the user in the minor repair, replace the mechanical seal should pay attention to, clean all parts of the seal, check the friction surface, not scratch, rubber O-ring is defective, there is indeed no problem before installation.
1, the temperature caused by the failure
Mechanical seal, the temperature rise will cause failure, as a result of the temperature rise, the mechanical seal surface lubrication film vaporization, the two ends appear dry friction, due to the friction heat generated, making the wear and tear and cause thermal stress cracks Leaving the seal ring fracture or even fragmentation. Due to the temperature rise friction dip co-flow out, so that the friction and adhesion, then the temperature may exceed the limit of the material lead to the use of temperature does not allow some thermal deformation under sudden load may also lead to thermal stress cracking seal failure and seal failure . In addition, elevated temperatures may also discolour the heat-setting ring or cause the clearance to exceed the allowable value of the secondary seal. In this case, the internal pressure will squeeze the seal from the gap causing malfunction. Elevated temperature can also cause sedimentation and sedimentation impedes the sealing work. The medium used in the high-pressured boiler feed water pump is industrial water, the mechanical seal used is 831 mechanical seal, the maximum temperature in the sealed chamber is 180 ℃, so the temperature should not be too high when used. If the medium temperature exceeds the limit temperature, take appropriate measures to seal the chamber to be cooled to ensure the normal use of mechanical seals, to avoid failure.
2, moving ring burst, static ring serious wear and tear caused by failure
High pressure boiler feed pump with balanced mechanical seals are generally equipped with cooling circulation system to ensure that the sealed chamber temperature to meet the reliable use of mechanical seals. Cooler circulation system equipped with a cooler and filter, the role of the cooler to the pump cavity after the heat medium cooling medium cooler, recycled to the sealed chamber. The use of the filter is to filter the impurities in the medium cycle, if the filter is blocked or system piping leaks or switching control valve failure, will make instantaneous water seal or intermittent when the pass, then seal the end is not good Cooling, washing, the formation of temperature, causing the seal ring burst, the static ring serious wear and tear, seal leakage caused by failure. Therefore, the system should always be used when checking the pipeline, the filter should be cleaned often, to prevent the blocked heat exchanger to be fully discharged or installed in the system alarm, etc., has been to achieve timely troubleshooting to extend the service life of mechanical seals.
3, auxiliary ring damage caused by failure
Mechanical seal In addition to the end seal, in the parts in contact with the shaft and gland contact parts, the use of auxiliary seal O-ring, V-ring and U-ring seal to solve the static sealing problem. High-pressure boiler feed pump balanced mechanical seal static seal, the use of O-ring, the material for the rubber products, if the O-ring damage, but also caused a small amount of leakage failure, then the solution is to replace the O-type Seal, to prevent leakage, according to our multifaceted work experience General O-ring failure for several reasons.
3.1 pump assembly mechanical seal, due to size problems, chamfer problems or work inadvertently O-ring card is bad, in the U-ring cross-section of the diameter of the direction or axis may have stuck bad phenomenon, resulting in seal leakage.
3.2 O-type sealant itself is also a cause of defects defects, such as the O-ring seal size is not suitable for manufacturing, the relative amount of interference, the lack of section diameter of meat phenomenon, the mold die diameter due to wear and tear caused by mold Seal leakage problems may occur.
3.3 O-ring improper materials, such as the pump temperature is higher and the use of high temperature rubber ring, the use of rubber aging, resulting in static sealing failure. The company is located in:
The above measures to take the approach is to improve the quality of the assembly, to strengthen the responsibility of assembly, conscientious assembly, to avoid bad O-ring seal. In addition, to improve the quality of O-ring itself, the defective O-ring and the improper use of materials should be carefully put a good quality to prevent the occurrence of the problem.
4, the user due to improper use of the fault
High-pressure boiler feed pump in use there is a certain use of technical requirements, if not according to the manufacturer's technical requirements, the use will have to fault.
4.1 If the pump is installed, it can not be properly installed according to the installation manual, causing the pump to vibrate so that the end face of the mechanical seal in the pump is not good enough or the end face is opened to cause the seal to leak.
4.2 The pump is running due to inadequate exhaust or other causes of the gas sealed chamber, the operation of the sealing chamber pressure under the action of the friction pair instantly open open seal leakage caused by failure.
4.3 The system is not clean or dirty cleaning filter, poor water quality, foreign body, mud, etc., so that the friction surface can also cause serious wear and tear failure. Such as Anhui Huainan Power Plant, due to poor water quality, cooling cycle is not good, heat transfer performance decline.
4.4 In addition, when the pump is running due to sudden pressure fluctuations, pulse pressure or frequent start-up may make the transmission parts, anti-rotation parts of the weak link damage, resulting in mechanical seal failure. Therefore, when users use high-pressure boiler feed pump, we must first solve the correctness of the power plant process flow, minimize the pressure fluctuations during the operation of the process, and reduce the frequency of frequent start-up. In addition, in the design of a mechanical seal, the calculation of the strength and the avoidance of wear should be taken into account when the wear torque is transmitted from the moving ring to the shaft and from the stationary ring to the pump stator, and from the transmission of the driving force from the shaft to the moving ring Produce the above problems.
Second, effective troubleshooting
There are many ways to troubleshoot, here are some common methods for reference.
1, It is necessary to monitor the temperature rise of the return water of the mechanical seal flushing water during the operation of the pump. The normal operation is the best at 40 ℃ ~ 50 ℃. When the temperature exceeds 85 ℃, the alarm will be triggered. When the temperature exceeds 90 ℃, it will trip.
2, to improve water quality. Users use the pump, the water quality must be carried out by pump and mechanical seal requirements. If necessary, increase the coarse filter coarse filter to improve water quality to avoid failure.
3, for the regular sealing system to take apart and wash, clean up dirt and impurities, in particular, magnetic filters must be regularly switched cleaning to prevent dirt clogging the filter, resulting in seal cavity water, causing the ring broken, resulting in failure.
4, before the operation of the pump must be operated according to instructions for use, good exhaust, give sealed cooling water before starting the pump. On the contrary, the operation as a result of the first start to seal the cooling water can easily lead to seals ring static burst.
5, the user in the minor repair, replace the mechanical seal should pay attention to, clean all parts of the seal, check the friction surface, not scratch, rubber O-ring is defective, there is indeed no problem before installation.
