According to the different types of coal machine, such as: hydraulic support, roadheader, bolt machine, slag machine, etc., the filter elements installed have obvious difference. For the Hydraulic support: the filter elements installed are mostly stainless steel backwash filter, spray filter, pilot filter, etc., they are usually installed in the backwash valve used. For the roadheader, bolt machine as well as other downhole running machinery: the hydraulic filter elements are usually installed.