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.
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.
The procedures for cleaning boiler tiresides are as
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 manufacturers 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
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
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
12. Use an industrial vacuum cleaner to remove loose
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
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
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