Vertical roller mill dam ring – Grinding Mill China. function of dam ring in vertical roller mills. Ohio's Old Mills by CountySciFiCincinnati. Because Ohio has numerous old mills that at one time functioned as a flour mill, let's try to understand the basic. Pendulum Roller Mills, Vertical Ring-Roll Mills.Vertical cement mill is a kind of vertical roller mill, also known as VRM cement mill, mainly used in the grinding production of cement clinker. Our company absorbs the latest grinding technology from Europe and combines with the market demand of grinding industry to develop a new and improved vertical cement mill.