The invention relates to a continuous process for converting carbonaceous material contained in one or more feedstocks into a liquid hydrocarbon product, said feedstocks including the carbonaceous material being in a feed mixture including one or more fluids, said fluids including water, the process comprising converting at least part of the carbonaceous material, and further in a state of cleaning the pressure and temperature is set to a predetermined desired level; where prior to the cleaning, the inflow of feed mixture is terminated and the system is filled with a fluid, where the temperature and the pressure are altered to the predetermined level at a predetermined rate and where the pressure is constantly kept at a level above the saturation pressure for the fluid at a given temperature, where the inflow of at least one cleaning fluid is initiated and the at least one cleaning fluid is circulated in the system for a predetermined time; where upon reaching the predetermined time for the cleaning fluid circulation, the temperature and pressure is altered to the operational pressure and temperature at a predetermined rate, where the pressure is constantly kept at a level above the saturation pressure for the fluid at a given temperature; and where upon reaching the operational conditions the inflow of the fluid/cleaning fluid is terminated and the inflow of feed mixture is initiated.