Service life and reliability of mechanical seals1

The service life and reliability of mechanical seals 1. The service life of mechanical seals. Mechanical seals rarely fail due to long-term wear. Other factors often cause premature failure of seal factories. Therefore, the life of the seal should be regarded as a statistical 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, during a certain period of 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 effective working time of the seal depends on the application to a large extent to the extent of the mechanical seal of the pump. The following points should be paid attention to to prolong the service life of the seal: 1. Establish a suitable working environment in the sealed cavity, such as effectively controlling the temperature of the mechanical seal factory; eliminating solid abrasive particles; controlling the rapid fluctuation of pressure and temperature; forming between the sealing end faces Effective liquid film (use double end face seal and liquid sealing when necessary). 2. The technical specifications of the seal can meet the requirements. 3. The rigidity and manufacturing precision of the pump are high. Considering the service life of the seal, not only the one-time investment of the pump (and seal), but also the economic loss caused by the failure of the seal, including: product loss; investment in spare equipment; damage to people and environment due to fluid leakage And equipment damage; working hours and spare parts required to replace the seal. The service life limit of the seal can vary greatly, being only a few days in chemically corrosive conditions, and 20 years of effective operation in olefin applications. Second, the reliability of mechanical seals In addition to the aforementioned different working conditions, the seal life will be greatly different, and the life of the same seal under the same use conditions will also be significantly different. This is similar to the test done with rolling bearings. Therefore, statistical concepts are used when discussing seal reliability. We use the following two values u200bu200bto count the reliability of the seal: 1. L10 life The operating time when the number of failures in a part sampling array reaches 10% is called the L10 life. 2. Average working life (MTBF) The average working time is defined as the arithmetic mean of the interval between successive failures of the sample, MTBFu003d(L1+L2+??+Ln)/n where L1, L2-the working life of a single seal. Keywords: seal factory, mechanical seal factory, pump mechanical seal