hot water. The steam should be wet and at a pressure of 70 to 150 psig. The unit must be dried out immediately after lancing is completed. Sweating Fireside slag can be removed from the convection superheaters by forming a sweat on the outside of the tubes. Cold water is circulated through the tubes. and moisture from the air condenses on the tubes to produce sweat. The hard slag is changed into mud by the sweat, and the mud can be blown off by an air or a steam lance. A large tank filled with water and ice can be used as the cold-water  source.  Steam  can  be  blown  into  the  area around the tubes during the cold-water circulating period to provide adequate moisture in the air. Cleaning Procedures The procedures for cleaning boiler tiresides are as follows: 1. Remove the boiler from service and allow it to cool. Make sure the boiler is cool enough for a person to enter. Someone must be standing by whenever a person is in the boiler. DO NOT force-cool the boiler. 2.  Disconnect  the  fuel  line  openings.  Secure  all valves, and chain. lock. and tag all fuel lines to the burner and  install  pipe  caps. 3. Disconnect the electrical wiring. Secure and tag the electrical power to the boiler. Disconnect the burner conduit and wiring. Mark and tag all electrical wiring to ensure  proper  reinstallation. 4.   Open the boiler access doors by loosening all nuts and dogs and swing the door open. Be careful not to damage the refractory door lining. 5.  Remove  the  burner  from  the  boiler  openings. Follow  the  manufacturer’s  instructions  for  specified burners. Wrap this equipment with plastic, rags. or other suitable protective coverings. Remember. soot and loose carbon particles must be kept out of the moving parts of the burner  because  they  can  cause  the  burner  to  malfunction. 6.  Provide  all  spaces  with  free-air  circulation  by opening  doors  and  windows,  or  provide  fresh  air  by mechanical  means.  An  assistant  should  be  stationed outside the opening and be ready at all times to lend a hand or to be of service in case of a mishap. 7. Cover the floor area around the tube ends with drop  cloths  to  catch  soot.  Position  a  vacuum  cleaner  hose at the end of the tube being cleaned. Keep soot from contacting wet areas because soot and water form carbonic acid. 8. Remove tube baffles where possible and pass a hand lance or rotating power cleaner brush through each tube  slowly  and  carefully  so  no  damage  occurs  to personnel  or  equipment. 9. Inspect tube surfaces for satisfactory condition before continuing on to the nest tube. Use a drop cord or flashlight  for  viewing  through  the  entire  length  of  a  tube. Wire brush all tube baffles either by hand or use of power tools. 10. Apply a light coat of mineral oil to all cleaned surfaces. To do this, fix an oil soaked rag to the end of a brush or rod long enough to extend through the tubes and thoroughly swab each surface, including baffles. Mineral oil is the only lubricant that prevents rusting and also burns off  freely  without  leaving  a  carbon  deposit. 11.   Clean all flat surfaces by brushing with the hand or power  tools.  Make  sure  that  powered  equipment  is grounded. 12.   Use an industrial vacuum cleaner to remove loose soot. CLEANING BOILER WATERSIDES Any waterside deposit interferes with heat transfer and thus causes overheating of the boiler metal. Where waterside  deposit  exists,  the  metal  tube  cannot  transfer the heat as rapidly as it receives it. What happens? The metal becomes overheated so that it becomes plastic and blows out, under boiler pressure, into a bubble or blister. The  term  waterside  deposits  include  sludge.  oil, scale. corrosion deposits. and high-temperature oxide. Except for oil. these deposits are not usually soluble enough to be removed by washing or boiling out the boiler. The  term  waterside  corrosion  is  used  to  include  both localized pitting and general corrosion. Most, if not all, is probably electrochemical. There are always some slight variations (both chemical and physical) in the surface of boiler metal. These variations in the metal surface cause slight differences in the electric potential between one area of a tube and another area. Some areas are ANODES (positive  terminals). Iron from the boiler tube tends to go into solution more rapidly in the anode areas than at other points on the boiler  tube.  This  electrolytic  action  cannot  be  completely prevented in any boiler. However, it can be reduced by maintaining the boiler water at the proper alkalinity and 1-36