Intermittent valves for manual or automatic and programme-controlled removing of boiler sludge from land or marine installations, particularly if these installations are operated without constant supervision in accordance with TRD 604. Sludge sediments, which are accumulated precipitates from boiler water that settle at the bottom of the boiler, will be removed from the steam boiler with the the aid of valves PA and MPA. These valves give the boiler a short blow at regular intervals, thereby discharging accumulated sludge and sediments.