Method and apparatus for detecting deposits in a pipe system of an apparatus

A method for detecting deposits in a pipe system (10) of an apparatus that is flowed through by a fluid,

• wherein at least one microwave probe (100) is introduced into the pipe system (10) in such a way that the fluid flows against a window (102) of the microwave probe (100) that is transparent to microwave radiation, and wherein microwaves are coupled into the pipe system (10) by way of at least one microwave probe (100) through the window (102) which is transparent to microwave radiation, wherein the microwaves coupled into the pipe system (10) propagate in the pipe system (10) in the same way as in a hollow conductor, wherein
• a.) a reflection measurement is carried out, in which reflections of the microwaves radiated by the at least one microwave probe (100) are received again by the respective microwave probe (100), cut-off frequencies being determined, wherein for determining the cut-off frequencies of the microwaves coupled into the pipe system (10), the frequency of the microwaves is varied in a preset region and for each frequency the intensity of the reflected microwave radiation is determined, and a comparison with a reference or a previous measurement being used to deduce a constriction in the surrounding area of the microwave probe (100), wherein cut-off frequencies indicating constrictions are detected and the free cross-section at the constriction being determined from this constriction indicating cut-off frequency, and/or
• b.) a reflection measurement is carried out, in which reflections of the microwaves radiated by the at least one microwave probe (100) are received again by the respective microwave probe (100) at a constriction, the distance between the respective microwave probe (100) and the constriction in the pipe system being ascertained by taking account of a signal runtime, and/or
• c.) at least two microwave probes (100) are introduced into the pipe system at a distance from one another and a transmission measurement between two microwave probes (100) is carried out, the arrangement of the two microwave probes (100) defining a pipe system segment, cut-off frequencies of the pipe system segment being determined, wherein for determining the cut-off frequencies of the microwaves coupled into the pipe system (10), the frequency of the microwaves is varied in a preset region and for each frequency the intensity of the reflected microwave radiation is determined, and a comparison with a reference or a previous measurement being used to deduce a constriction in the pipe system segment, wherein cut-off frequencies indicating constrictions are detected and the free cross-section at the constriction being determined from this constriction indicating cut-off frequency,
• wherein the detection of a constriction is used to deduce the presence of deposits.