the holes however if holes and fittings are plugged cleaning can take place simply by blowing steam through the cleaning pipes 5 the installation shown in fig4 comprises a conveying pipe 1 in which the steam pipes 4 are connected to a steam supply pipe 6 the cleaning pipes 5 in this case are connected to a cyclone 7 for separating fibers from the steam stop valves 8 are located in the cleaning pipes 5 the pulp is heated as described above by steam supply via the steam pipes 4 if for some reason pulp should penetrate out through the inlet holes 3 to the fittings 2 cleaning can be effected by opening one or more of the valves 8 the steam supplied in this manner will then flow through the corresponding fitting 2 out through the cleaning pipe 5 to the cyclone 7 the pulp thereby follows along and the inlet holes 3 are exposed in the cyclone 7 the pulp is then separated from the steam the cyclone 7 thus begins to operate only during cleaning of the apparatus by blowing this installation renders it easy to clean the apparatus even when it is in operation the stop valves 8 for example can be opened one at a time for cleaning as soon as there is a tendency of plugging thereby reducing interruption of the operation to the smallest possible.