With the rapid development of modern industry, the new technology of China mechanical seals has higher and higher requirements for sealing, and a single seal is sometimes difficult to meet harsh working conditions. Combining several kinds of seals and making full use of their respective advantages has become a widely used technology in the sealing industry.
There are many types of combined mechanical seals, but they are no more than two types of non-contact seals and contact seals, or contact seals and contact seals. In the case of high parameters or harsh conditions, mechanical seals and floating ring seals, spiral seals or labyrinth seals are used to form a combined seal. In the combined seal, the mechanical seal mainly plays the role of leakage prevention, while other types of seals play the role of throttling and blocking.
In medium and low pressure process gas turbine compressors, it is an important technological development to replace the traditional floating ring seal with the combined seal of the mechanical seal and the floating ring seal. According to statistics, since the 1970s, there have been more and more mechanical-floating ring combined seals in large-scale petrochemical plants imported from abroad, involving fields such as fertilizer, oil refining, ethylene, and chemical industry. Mechanical-floating ring combined seal, the former can restrain internal leakage, while the latter can withstand high pressure. Such seals are produced by the Sichuan Institute of Sealing in China and are widely used in centrifugal compressors. In addition, Chinese pumps also use mechanical-labyrinth-screw combined seals, mechanical-packing combined seals, and mechanical-screw combined seals.
The mechanical-dry gas combination seal is mainly used under medium and high pressure conditions. The first-stage seal is a mechanical seal, the sealing medium is liquid, the second-stage seal is a dry gas seal, and the sealing medium is the trace medium leaked from the first-stage seal and the external Inert gas introduced. Its characteristic is that the mechanical seal acts as the main seal to seal the process medium, and the dry gas seal acts as the auxiliary seal.
