The Dry Gas Seal Technology And Its Application In The Compression Unit In Refinery

The shaft end seal is the main component of rotating equipment. The reliability of shaft end seal plays a very important role in assuring the long life and the maximum economic benefit of the equipment. The conventional shaft end seal contains labyrinth seal, floating-ring seal, mechanical seal and etc, before the use of dry gas seal. In the recent years, with the development of sealing technology (especially the shaft end sealing technology), the dry gas seal technology has been applied widely. The dry gas seal device depends on the fluid hydrodynamic effect to build a rigid fluid film which is set up to make the two seal faces non-contact between the two seal faces. Meanwhile, the medium leakage rate of the seal apparatus is controlled under an acceptable level (or even zero leakage).The technology of dry gas seal is originally developed and applied forms the developed countries. The products that used in the early stage mainly relied on import. The researches on dry gas seal technology in our country that started by some corporations and individuals with the development of dry gas seal, although getting a great improvement but just at the beginning stage. Also the system of development, design and manufacture of dry gas seal product has not yet been wholly set up. Consider about the usage of imported dry gas seal products, the performance of dry gas seal, the failure type and supplementary system are investigated in this thesis, which is helpful for the reliable operation of the dry gas seal in centrifugal compressors.Compared with the conventional shaft end seal (includes labyrinth seal, floating-ring seal, mechanical seal and etc) the dry gas seal have some advantages, such as small leakage rate, little surface abrasion, low frictional power consumption and long operation life. Nowadays, dry gas seal, especially the spiral groove gas seal, is widely applied to the rotating equipment to deliver fluid (centrifugal compressor, expansion machine, gas turbine, centrifugal pump, and so on).The main research contents and results are summarized as follows.The distribution of pressure in the gas film, the leakage rate and the axial thrust namely opening force are obtained. Meanwhile, based on load capacity and leakage rate, the influence of the operation conditions and the spiral groove geometrical parameters on the performance of sealing apparatus is analyzed. The optimal values of these parameters are acquired. The experimental investigation of a spiral groove dry gas seal is also conducted on a high-speed test device, and a series of leakage rate data are obtained. The test results are nearly in agreement with that of numerical simulation. In order to improve the reliability of a high-pressure dry gas seal used in the hydrocracker, the failure causes of the dry gas seal are analyzed, and there are then reconstructed for it.