High-Pressure Grinding - Maschinenfabrik Köppern2009. Redevelopment of the large mill line . High-pressure grinding roll presses (HPGRs) are emerging as an important comminution technology in the minerals processing industry. . Compared with conventional grinding, the HPGR process consumes significantly less energy, which in turn leads to a reduction in.high pressure grinding project mill site,HIGH PRESSURE GRINDING ROLL (HPGR) MACHINE CONTROL .Control Concerns: •When starting the mill, no connection between the rolls. How do you maintain speed? •While running, rolls are essentially connected by ore being crushed. How do you share load? •Rolls are not absolutely identical and can wear at different rates. How do you keep the tangential velocity the same?