Abstract: An apparatus for building up and repairing a refractory lining of an industrial furnace by means of a rotary disc centrifugally throwing particulate refractory material against a portion of the lining to be repaired comprises a horizontal row of hollow bolts with bores to spray water into an inlet conduit of annular cross section whereby the material passing through the conduit to the disc will be uniformly wetted. Wiper elements in the conduit prevent jamming of the material therein and finely divided compressed gas is blown in the inlet funnel that supplies the material to the conduit.