Cleaning tubesheets of heat exchangers

A heat exchange system comprising:

• a shell having an interior with an inlet and an outlet wherein a first fluid circuit is defined from the inlet, through a heat exchange volume within the interior of the shell, to the outlet;
• a tubesheet mounted within the shell dividing between the heat exchange volume and a plenum of a second fluid circuit within the interior of the shell;
• a set of tubes extending through the heat exchange volume, a respective interior passage of each tube being in fluid communication with the plenum through a respective opening though the tubesheet, wherein the second fluid circuit includes the plenum and interior passages of the tubes;
• a spray nozzle mounted in the plenum of the second fluid circuit with a spray outlet directed toward the tubesheet for cleaning the tubesheet with a submerged impingement jet issued from the spray nozzle, wherein the spray nozzle includes a mechanism configured to move the spray outlet through a procession of angles rotating in a first direction relative to the tubesheet about a first axis and rotating in a second direction about a second axis different from the first axis, to move the impingement jet over an area of the tubesheet;
• and
• wherein neither of the first and second axes is fixed normal to the tubesheet.