Service life and reliability of mechanical seals

Service life and reliability of mechanical seals 1. Service life of mechanical seals Mechanical seals rarely fail due to long-term wear and tear, and other elements can promote premature failure of mechanical seals. Therefore, the life of the seal should be regarded as a computational quantity, and it is difficult to obtain an accurate value. For example, the mechanical seals used in some sewage pumps generally use a mechanical seal with a hard ring on the end face of the hard ring. For example, at a certain time, the pump shaft moves and the shaft vibrates. At this time, if hard small particles enter the machine The end face of the seal will wear out the end face. The useful working time of the seal depends to a large extent on the operating conditions. Pay attention to the following points in extending the service life of the seal: 1. Establish a suitable operating environment in the sealed cavity, such as effectively controlling the temperature of the mechanical seal; eliminating solid abrasive particles; controlling the rapid fluctuation of pressure and temperature; forming between the sealing end faces Useful liquid film (use double end face seal and sealing liquid if necessary). 2. The technical specifications of the seal can meet the requirements. 3. The pump has high rigidity and high precision. Considering the service life of the seal, not only consider the one-time investment of the pump (and seal), but also consider the economic loss caused by the failure of the seal, including: product loss; investment in spare equipment; Damage to the environment and equipment; working hours and spare parts required to replace the seal. The service life limit of the seal can vary greatly, only a few days under chemical corrosion conditions, and 20 years of useful operation in olefin applications. Second, the reliability of mechanical seals In addition to the aforementioned different working conditions will make the seal life different, the same seal under the same operating conditions, its operating life will also be significantly different. This is similar to the experiment done with rolling bearings. Therefore, the calculation concept is used when commenting on the reliability of the seal. We use the following two values u200bu200bto calculate the reliability of the seal: 1. L10 Lifetime When the number of failures in a part sampling array reaches 10%, the operating time is called L10 service life. 2. The average operating time (MTBF) is defined as the arithmetic mean of the time interval between successive failures of the sample, MTBFu003d(L1+L2+...+Ln)/n where L1, L2——single sealed Job life. Keywords: mechanical seals, mechanical seals