can be cleaned simultaneously the overall cleaning duration can thereby be further reduced the measuring device 16 is described in more detail below with reference to fig2 to 9 fig2 shows a measuring device 16 connected for example to a steam line 4 1 for example the high pressure steam line 4 1 a or the temporary steam line system 4 1 b via a mounting 20 designed as a saddle mounting the measuring device 16 is fastened rigidly to the tubular steam line 4 1 so that relative movements are avoided by means of the measuring device 16 what is known as a blow out level also called a u201c baffle plate u201d is introduced as a measuring apparatus m inside the steam line 4 1 during continuous operation this is a polished metal strip for example an aluminum copper or steel strip the measuring apparatus m is in this case introduced into the steam line 4 1 transversely with respect to the flow direction the degree of purity of the medium is observed visually and judged during the blow out operation by means of particle impacts impinging onto the measuring apparatus m the measuring apparatus m is designed as a baffle plate change device so that it can be changed during operation that is to.