This series belongs to the pilot valve piston valve. From the main valve and pilot valve composed of two parts. Mainly by the main valve seat, the main valve plate, piston, cylinder, spring and other parts. Mainly by the pilot valve seat, disc, diaphragm, spring, adjusting SPRINGS. Adjusting the spring pressure by adjusting the outlet pressure setting, the use of changes in outlet pressure sensing diaphragm, through the pilot valve opening and closing the main valve piston adjusting throttle flow area the size of the site to achieve vacuum regulator function. 
 This product is mainly used for steam pipes, from the vacuum regulator role.