1. Prolong service life of components so as to reduce production cost remarkably. The service life of metal sand as filter material is extended over 3 times than conventional filter materials such as glass bead,sea sand and silicon carbide. 2. Thanks to its high degree of profile ,large specific surface and strong impurities filter capability,the use of metal sand prolongs the service life of components,reduces use of auxiliary materials(strainer and washer,etc.)related to components,cleaning expenses of components and consumption of manpower as well as loss of capacity,etc.