PREVENTER RAM

FIELD: sealing or packing boreholes or wells, particularly blowout preventers used for sealing well head during ground or underwater oil and gas well drilling. ^ SUBSTANCE: preventer ram comprises body made as semi-ring with insert arranged inside the body. The insert is provided with sealing member including inner semi-ring to cooperate with pipe to be sealed and two outer semi-rings arranged along insert height. The outer semi-rings have sealing surfaces to cooperate with preventer body. Outer semi-rings have different heights and curvilinear surfaces. Radial part of semi-ring cross-section has center offset towards inner semi-ring. Convex area of radial part is above insert surface, edges thereof are below insert surface. Edge located from outer side is located below another edge. Convex radial part area of one outer semi-ring projects over insert surface for distance equal to at least one axial gap between ram and preventer bodies. Convex radial part area of another outer semi-ring projects over insert surface for distance equal to at least two axial gaps between ram and preventer bodies. ^ EFFECT: simplified structure and increased operational reliability. ^ 4 dwg