A flange sealing system in combination with a pair of pipe end flanges (14a,14b) of adjoining pipes (16a,16b) joined to one another by suitable fastening, the flange sealing system comprising: an annular sealing element between the end flanges having first and second faces in sealing engagement with respective ones of the end flanges so as to provide a fluid-tight seal between the end flanges; and a centering ring (18;20;23) surrounding the annular sealing element so as to be arranged to locate the annular sealing element relative to the fastened pipe end flanges; the centering ring being discontinuous in a circumferential direction of the centering ring between two ends of the centering ring which are disconnected from one another in a mounted position between the pipe end flanges; an outer circumference of the annular sealing element being wedged within an inner circumference of the centering ring; the centering ring being flexible so as to permit insertion and removal of the annular sealing element within the centering ring; and characterised by the annular sealing element comprising a convex wedge-shaped edge on its outer circumference and the centering ring comprising a concave wedge-shaped edge on its inner circumference so as to be shaped to receive the convex wedge-shaped edge of the annular sealing element therein, the convex wedge-shaped edge of the annular sealing element being flatter than the concave wedge-shaped edge of the centering ring, wherein an outer diameter of an apex of the convex wedge-shaped edge of the annular sealing element is less than a maximum inner diameter of the centering ring at an apex of the concave wedge-shaped edge and is greater than a minimum inner diameter of the concave wedge-shaped edge of the centering ring adjacent the first and second faces of the annular sealing element. an annular sealing element between the end flanges having first and second faces in sealing engagement with respective ones of the end flanges so as to provide a fluid-tight seal between the end flanges; and a centering ring (18;20;23) surrounding the annular sealing element so as to be arranged to locate the annular sealing element relative to the fastened pipe end flanges; the centering ring being discontinuous in a circumferential direction of the centering ring between two ends of the centering ring which are disconnected from one another in a mounted position between the pipe end flanges; an outer circumference of the annular sealing element being wedged within an inner circumference of the centering ring; the centering ring being flexible so as to permit insertion and removal of the annular sealing element within the centering ring; and characterised by the annular sealing element comprising a convex wedge-shaped edge on its outer circumference and the centering ring comprising a concave wedge-shaped edge on its inner circumference so as to be shaped to receive the convex wedge-shaped edge of the annular sealing element therein, the convex wedge-shaped edge of the annular sealing element being flatter than the concave wedge-shaped edge of the centering ring, wherein an outer diameter of an apex of the convex wedge-shaped edge of the annular sealing element is less than a maximum inner diameter of the centering ring at an apex of the concave wedge-shaped edge and is greater than a minimum inner diameter of the concave wedge-shaped edge of the centering ring adjacent the first and second faces of the annular sealing element.