Abstract: A closing arrangement for a conveyor line for a mixture containing an abrasive solid is composed of a fluid-tight valve and of a solid-tight auxiliary closing part which acts in the direction of flow in front of the valve and can be closed before the valve in time to protect it. According to the invention the auxiliary closing part is formed by a casing arranged inside the valve which casing is movably guided in the direction of the movement of the valve disk. This casing protects the valve seat from the flowing medium in a direct end position which it assumes when the valve is open. During the closing movement the valve disk contacts the casing edge before it reaches the valve seat. This essentially blocks off at least the abrasive part of the flow medium, so that the valve disk can approach the valve plate under protected conditions, while at the same time the casing is pushed against an elastic force.