b if it is desired to terminate the purging without restarting fuel flow a valve in line 22 upstream from the equipment shown in the figs may be closed but if it is desired to re fire the burner immediately upon completion of purging operating mechanism 19 is actuated in the opposite direction to close valve 24 completely and then open valve 23 to restore fuel flow the equipment is thus returned to the configuration shown in fig1 a from the foregoing it can be seen that by sequencing the operation of valves 23 and 24 the opportunity for the fuel to back mix or cross over into the purge line is substantially eliminated as is the chance for the purge fluid to work its way into fuel line 21 upstream of valve 23 a burner system employing three valves is shown in fig2 a and 2b burner 25 is of the media assist atomizing type in which steam or air is mixed with the fuel oil to propel it voilently through the burner nozzle to break the fuel up into fine streams or particles fuel is fed to the burner through line 26 and purging media through line 27 purge media is introduced through line 28 which branches into both.