referring to the drawings in particular , the invention embodied therein comprises the process for cleaning the inner and outer tubes of it vertically arranged rows in a heat exchanger such as a trash incinerator or a wasted boiler following a trash incinerator generally designated 1a which has a heating gas inlet 1d in a discharge 12 . fig1 shows a waste heat boiler following a trash incinerator , as disclosed by german pat . no . 23 41 444 . this waste boiler has a bottom 1 and the two front and back walls 2 , 3 , as well as a cover 4 and the side walls 5 . tubes 7 and 8 are suspended in the interior 6 of the boiler , which are designed in the present case as finned tubes , with the longitudinal edges of the finned tubes being connected to one another so that the adjacent tubes 7 and 8 in each case form a wall of finned tubes . the tubes 8 are displaced downward from the tubes 7 in the longitudinal direction , so that respective intermediate spaces 7a and 8a are produced in each case at the upper end of the tube 8 , and its fins ; and at the lower end of the tube 7 and its fins . this can be bounded by suitable walls 9 and 10 , or otherwise . the flue gases therefore flow in the direction of the arrows a and follow a meandering course , with the fluid gases flowing through the gaps 11 formed between the walls of finned tubes 7 and 8 . the flue gas leaves the boiler at 12 . instead of the finned tubes , other types of tubes can also be provided with a different arrangement and with different flow of the gases entraining the clinging particles , for example , individual tubes that are suspended in the interior 6 of the the boiler . it is important for the vertical tubes 7 and 8 in question to be freely movable in the directions of the double arrows over their entire length notwithstanding the distribution and header lines to be described in detail below , in order to achieve the purpose of the invention . ( a movable section of the tubes as a consequence of thermal expansion with means of compensation is not meant here ). in the example shown , the tubes 7 open into a bottom distribution line 13 that is connected to a boiler drum through a downpipe ( not shown ), and into an upper header line 14 that is connected in the same way through a riser to the boiler . the tubes 8 are connected in the same way to a lower distribution line 15 and an upper header line 16 and are connected through a downpipe and a rise to the boiler drum . the upper horizontal header lines 14 and 16 , parallel to one another , together with the tubes 7 and 8 suspended on them , and the lower , likewise parallel horizontal distribution lines 13 and 15 , forms a unit that is movable in the longitudinal directions of the pipes ( cf . arrow s in fig1 ). in the example illustrated , the two ends 14a and 16a of each header line 14 and 16 are supported on a lifting and supporting device with the general reference symbol 17 ( fig3 ). for this purpose , the ends of the lines 14a and 16a have a shoulder 18 at their bottom sections , which extends between the face 14b and 16b of the line 14 and 16 and the first tube 7b and 8b adjacent to this wall . this shoulder 18 preferably has a slightly concave arched bottom 18a ( fig2 and 3 ). against it rests the correspondingly arched section 19a of the circumference 19 of a cam plate 20 , that with its drive represents the lifting device of the two ends of the lines 14a and 16a of each header line . the cam plate 20 can preferably be actuated from the outside of the heat exchanger by rotating its carrying shaft 21 . the circumference 19 of the cam plate forms an offset or a shoulder 20 . during the rotation of the cam plate 20 in the direction of the arrow k in fig3 the header lines 14 and 16 are lifted until the moment when the edge 23 of the offset of of the shoulder 22 slips off of the shoulder 24 of the section 19a of the cam plate 20 with the largest radius . this sliding off produces an abrupt drop of the header line 14 and 16 since the lifting and support device 17 is operated synchronously at both ends of the lines 14 and 16 . the thickness of the shoulder 18 is larger than that of the offset or of the shoulder 22 , so that the shoulder 18 rests on the circumference 19 of the cam plate 20 directly next to or in the vicinity of the offset or of the shoulder 22 . the rotary motion of the cam plate 20 can be repeated as often as desired ; the tubes 7 and 8 are kept in the raised position by stopping the cam plate in a position as shown in fig2 or just before that . preferably , all of the cam plates on one side of the exchanger are moved by a common rod simultaneously with the cam plates at the other ends of the lines . in the form of embodiment of fig6 a crossbar 27 is provided for the lines 14 and 16 of one side of the exchanger . this can be lifted while lying horizontally at each end 27a and 27b by a cam plate of the type of the cam plate 20 . each of these cam plates of the type of the cam plate 20 and 31 at the height of the cam plates , so that the lifting of the cross bars and thus of the tubes 7 and 8 can occur appropriately here also . the header lines 14 and 16 are fastened to the crossbars . the header lines 14 and 16 can be connected to the boiler drum , not illustrated , as shown in fig5 through extendable and retractable compensating pipes 32 and 33 , which in turn pass through the wall of the cover 34 and 35 of the boiler or of the heat exchanger . either the lines 32 and 33 have corresponding cross sections at both ends of the lines 14 and 16 or are arranged into several . crossbars 40 and 41 that can be mutually reinforced in a suitable way , extend between the side walls 5 of the boiler or heat exchanger at the level of the lower ends of each of the tubes 7 and 8 and thus just above the distribution lines 13 and 15 . the tubes 7 and 8 have shoulders 42 and 43 above these crossbars in their immediate vicinity . when the tubes 7 and 8 are lifted , a separation as shown in fig4 a is produced between the shoulders 42 and 43 and the crossbars 40 and 41 that is smaller than the height of the offset or of the shoulder 22 on the circumference 19 of the cam plate 20 . when the shoulder 22 of the shoulder 18 falls off of the offset or of the shoulder 22 of the cam plate 20 , the shoulders 42 and 43 strike the crossbars 40 and 41 . in this form of embodiment , the shoulder 18 or the shoulders 30 and 31 of fig6 and 7 do not lie in the vicinity of the offset or of the shoulder 22 ( fig3 ) or 28a and 29a ( fig7 ), but approximately at 45 on the circumference 19 or 28b and 29b of the cam plate , i . e ., at points with a a larger radius , so that the tubes 7 and 8 , after the shoulder 18 , 30 and 31 slips off of the offset or the shoulder 22 , 28a and 29a are again raised until the tubes 7 and 8 are suspended and held by their top ends at the circumference of the cam plate . instead of the crossbars 40 and 41 and the shoulders 42 and 43 , a stop can also be provided beneath the distribution lines 13 and 15 , which is preferred when inverted tubes or rows of tubes and tube walls are used in departure from the illustrated arrangement of tubes and of the meandering path of the gases . fig1 indicates in broken lines that instead of the wall 10 and the bottom 1 , hoppers 50 can be provided with each hopper being associated with two adjacent gaps 11 ; any other design and arrangement of the hoppers can be chosen . a cam plate like the plate 20 or the plate 28 operates by the principle of a wedge that is placed on an endless rotating chain . it is therefore possible , instead of the individual cam plates or the common cam plates for a row of tubes , to choose an endless rotating chain that carries wedges at the separation of the tubes or at the separation of the ends of the crossbars 27 according to fig6 and 7 whose diagonal wedge face points upward toward the tubes or toward the crossbar . during the rotation of the chain , the wedges on the carrying run raise the tubes and go back again into their operating position on the lower strand of the chain . in this design , additional support elements are provided for the tubes or the crossbars , on which these parts rest until the wedges cause another lifting of the tubes or of the crossbars . the shoulders on the tubes 14a and 16a or at the ends 27a and 28a of the crossbars in this case can likewise have a corresponding wedge shape , and any other suitable traction mechanism can be used instead of the chain to which the wedges , prefereably guided in shaped rails , can be attached . in the form of embodiment according to fig8 and 13 , the two side walls 5a and 5b of the waste heat boiler are lined with adjacent finned tubes 51 that form a continuous wall . these finned tubes and the side walls 5a and 5b are penetrated by the header tubes 14 and 16 for which they pass through a pipe connector 52 . the ends 14a and 16a of the header tubes extending out of the side walls 5a and 5b have a collar 53 that has a supporting rib 54 . this is connected to pivot by a pin 55 to a fork 56 , which in turn is connected to the piston rod 57 of a suspended pneumatic piston cylinder unit 58 , which hangs from a traverse 60 or the like by suitable means 59 , for example . the two piston cylinder units 58 on each side of the waste heat boiler , i . e ., outside of the side walls 5a , 5b of the boiler , are connected to one another through a common line 61 that leads to a valve 62 , whose supply and discharge lines have the reference symbols 63 , 64 . this valve 62 determines the pressure ratios in the piston cylinder unit 58 for lifting or lowering the header tubes 14 , 16 and the tubes 7 , 8 suspended on them , and is controlled hydraulically , pneumatically , or electrically through lines 65 , 66 . in this way , the header tube 14 , 16 of each row of tubes consisting of the tubes 7 , 8 can be raised uniformly , and likewise can be lowered uniformly . the catching device for the collar 53 gives the general reference symbol 67 and the ends of the tubes 14a , 16a are placed at the level of the collar 53 , below it . this is attached to a suitable crossbar 68 and has several layers of superimposed metallic or other type of plates 69 . these hold a yoke 70 that is formed from a central section 71 and two jaws 72 , 73 . the jaws on the arms 74 , 75 of the yoke have a curvature at their concave tops sloped toward one another that matches the curvature of the circumference of the collar 53 . the two jaws are displaced in height from the plates 59 and the crossbar 68 . thus , the jaw 73 has a central height &# 34 ; a &# 34 ; from the crossbar 68 , while the jaw 72 has a central height &# 34 ; b &# 34 ; that is significantly larger than the height &# 34 ; a &# 34 ;. when the collar 53 strikes the yoke 70 when the header tubes 14 , 16 drop , the row of tubes with the header tubes 14 , 16 is given a sudden lateral motion in the direction of the arrow f in fig1 in addition to striking the yoke 70 . the pivot suspension of the rib 54 on the piston cylinder unit 58 , which can additionally be mounted to pivot through a linkage 58a , serves this purpose . when the header line 14 and 16 is lifted to its upper position by the piston cylinder unit 58 , the row of tubes pivots with the tubes 7 and 8 back into the starting position shown in fig1 in which the collar 53 stands symmetrically above the yoke 70 . the header lines 14 and 16 with the tubes 7 and 8 suspended on them are subject to the action of gravity when the piston cylinder unit is depressurized , so that a sudden lowering of the parts is produced . if this lowering is to be additionally accelerated , the piston cylinder units 58 are connected to the lines 83 when the counterline 61 is depressurized . so that not only the upper section of the rows of tubes consisting of the tubes 7 and 8 and the upper header lines 14 and 16 are given a sudden lateral displacement when the rows of tubes are lowered , when the piston cylinder units 58 are depressurized , one or more devices can be provided along the length of the rows of tubes consisting of the tubes 7 and 8 as shown in fig1 and 13 . the fins 76 of the tubes 51 ( cf . also fig8 ), which line the wall 5a , have a continuous rib or fin 77 over the length of the tubes 7 and 8 for this purpose . ( only one rib or fin 77 for one row of tubes is shown in fig1 . such a rib or fin is associated with each row of tubes ). opposite this rib or fin , the tubes 7 and 8 adjacent to the tube wall 5a also has a rib or a fin 78 that is continuous over the length of this tube . the rib or fin 77 surrounds the edge 78a of the rib or fin 78 with its edges 77a and 77b with these edges having a slip fit on one another . the rib or fin 78 at its edge 78a has profiled projections 79 at uniform longitudinal distances that have the wedge surfaces 80 . the edge 77c of the rib or fin 77 carries shoulders 81 with wedge surfaces 82 at the same interval as the projections 79 , off of which the diagonal wedge faces 80 of the profiled projection 79 slip when the row of tubes consisting of the tubes 7 and 8 is raised or lowered with the header line 14 and 16 in the direction of the arrow k ( fig1 ). the tubes are suddenly displaced laterally parallel to one another in the direction of the double arrows k by the projections 79 and the shoulders 81 . the tube wall 5b opposite the tube wall 5a ( cf . fig8 ) is designed to conform to the tubes 7 and 8 adjacent to this wall .