Built-up deposits on the top surface of a tubesheet and on adjacent tube sections in a tube bundle heat exchanger are removed by inducing vigorous turbulent flow of cleaning liquid radially along the surface of the tubesheet by repetitively and periodically injecting gas pulses into the liquid to form...http://www.google.de/patents/US4972805?utm_source=gb-gplus-sharePatent US4972805 - Method and apparatus for removing foreign matter from heat exchanger tubesheets
