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Mechanical seal service life and reliability
by：Lepu Seal
2022-09-13
Mechanical seal service life and reliability
1. Service life of mechanical seals Mechanical seals rarely fail due to long-term wear, and other factors tend to cause premature failure of mechanical seals. Therefore, the life of the seal should be regarded as a calculation, and it is difficult to obtain an accurate value. For example, the mechanical seals used in some sewage pumps generally use hard ring-to-hard ring end face mechanical seals. For example, at a certain time, the pump shaft moves in series and the shaft vibrates. At this time, if hard small particles enter the machine The end face of the seal will wear the end face. The effective working time of the seal depends to a large extent on the application conditions. To extend the service life of the seal, the following points should be paid attention to: 1. Establish a suitable working environment in the seal cavity, such as effectively controlling the temperature of the mechanical seal; removing solid abrasive particles; controlling the rapid fluctuation of pressure and temperature; forming between the seal faces Useful liquid film (double seal and sealing liquid if necessary). 2. The technical specifications of sealing can meet the requirements. 3. The rigidity and production precision of the pump are high. Considering the service life of the seal, not only the one-time investment of the pump (and the seal), but also the economic loss caused by the failure of the seal, including: product loss; Damage to the environment and equipment; man-hours and spare parts required to replace the seal, etc. The service life limits of seals can vary widely, from just a few days in chemical corrosion conditions to 20 years in olefin applications. 2. Reliability of mechanical seals In addition to the above-mentioned different working conditions that will make the seal life very different, the same seal will have significantly different service lives under the same operating conditions. This is similar to experiments with rolling bearings. Therefore, computational concepts are used when evaluating seal reliability. We use the following two values to calculate the reliability of the seal: 1. L10 life When the number of failures in a sample array of parts reaches 10%, the operating time is called the L10 service life. 2. Mean working life (MTBF) The mean working time is defined as the arithmetic mean of the interval time of sampling sequential failures, MTBF=(L1+L2+⋯+Ln)/n where L1, L2——single sealed Working life.
1. Service life of mechanical seals Mechanical seals rarely fail due to long-term wear, and other factors tend to cause premature failure of mechanical seals. Therefore, the life of the seal should be regarded as a calculation, and it is difficult to obtain an accurate value. For example, the mechanical seals used in some sewage pumps generally use hard ring-to-hard ring end face mechanical seals. For example, at a certain time, the pump shaft moves in series and the shaft vibrates. At this time, if hard small particles enter the machine The end face of the seal will wear the end face. The effective working time of the seal depends to a large extent on the application conditions. To extend the service life of the seal, the following points should be paid attention to: 1. Establish a suitable working environment in the seal cavity, such as effectively controlling the temperature of the mechanical seal; removing solid abrasive particles; controlling the rapid fluctuation of pressure and temperature; forming between the seal faces Useful liquid film (double seal and sealing liquid if necessary). 2. The technical specifications of sealing can meet the requirements. 3. The rigidity and production precision of the pump are high. Considering the service life of the seal, not only the one-time investment of the pump (and the seal), but also the economic loss caused by the failure of the seal, including: product loss; Damage to the environment and equipment; man-hours and spare parts required to replace the seal, etc. The service life limits of seals can vary widely, from just a few days in chemical corrosion conditions to 20 years in olefin applications. 2. Reliability of mechanical seals In addition to the above-mentioned different working conditions that will make the seal life very different, the same seal will have significantly different service lives under the same operating conditions. This is similar to experiments with rolling bearings. Therefore, computational concepts are used when evaluating seal reliability. We use the following two values to calculate the reliability of the seal: 1. L10 life When the number of failures in a sample array of parts reaches 10%, the operating time is called the L10 service life. 2. Mean working life (MTBF) The mean working time is defined as the arithmetic mean of the interval time of sampling sequential failures, MTBF=(L1+L2+⋯+Ln)/n where L1, L2——single sealed Working life.
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