We have recently delivered to a ship owner a boiler tubes cleaning system for cleaning the EGB ( economizer ) tubes with ID 44 mm x 2500 pieces; during the PUTZMAUS trial test on board, needed about 30-40 seconds for one tube with perfectly clean result! see above picture.
The darker tubes are cleaned, the surrounding brown ones are still full of soot. Back to “as new” condition with one return pass of the putzmaus with the soft cleaning brush. The tubes on the outer rim needed the harder reconditioning brush due to bigger deposits but still only a single return run to go back to “as new” condition!