erensan°
“The Heating Engineer”
- 37 –
280111
gases collected in the furnace and chimney channels should be
purged out.
Whether a check-valve exists or not in the boiler outlet, the
shutting valve at the steam outlet should be tightly closed after
the flame is put out. If there are two shutting valves at the
outlet, the steam in the pipe between them should be blown
down after both are closed.
After the fuel is cut, if an atomizing medium such as steam or
pressurized air exists, the atomizing medium inlet should be
closed.
If the boiler water level is normal, feedwater pump should be
stopped. Feedwater inlet valve should be closed and if the
water level is too high, blowdown should be performed to bring
it to normal.
The cooling period of the boiler differs according to boiler type,
capacity and features. To prevent formation of differential heat,
fast cooling should be avoided. In very big boilers, additional
(short time) firings may have to be performed in the boiler
during cooling to provide equalized heat distribution.
Discharging
When the boiler is left to cool down, pressure drop is
monitored. When pressure goes down to 2-2.5 bars (2-2.5
kgf/cm
2
), the air bleed pipe should be opened to prevent parts
working under pressure. When boiler pressure becomes “0” and
water temperature drops under 90
o
C, the boiler may be
discharged.
If the boiler to be discharged operates in parallel with other
boilers, care should be shown for the discharge valve that
belongs to that boiler only. After the boiler is fully discharged,
blowdown valves should be tightly closed and warning label
should be hung on them stating that they should not be
opened.
erensan°
“The Heating Engineer”
- 38 –
280111
Inspection and maintenance preparation
• The boiler is stopped, cooled and discharged for inspection
and maintenance.
• Before entering the boiler for inspection, the main steam
outlet valve or valves should be closed. The blowdown
valve between the two valves is opened. Warning plates
are tied on the valves. Boiler feedwater inlet valve,
blowdown valves are closed and warning plates are tied
on them. If the blowdown valve of the boiler is
connected to blowdown valves of other boilers, stricter
safety measures should be provided (for example,
taking out fly wheels after blowdown valves are closed).
• All fuel inlet valves are closed and warning plates are
tied on them. To provide for the safety of the
maintenance personnel, the burner ignition pipes are
taken out and in gas fuel burning boilers, the gas line is
plugged off or part of the gas pipe is removed.
• Before entering the boiler, the combustion chamber and
chimney channels are aired and gases inside are purged.
• When personnel enter the boiler for inspection, etc.
labels or warning plates are placed at visible places to
indicate that people are working inside. Hinged doors
are fully opened and tied back before entering.
• Before stopping the boiler for inspection and
maintenance purposes, soot blowing is performed to
clean the heating surfaces. For inspection purposes, first
the soot on the heat transfer surfaces of the boiler such
as pipes, etc are swept and cleaned thoroughly.
• The mobile lamps and lining to be used for lighting in
the boiler should not be over 42 volts and the extension
cables should be faultless and thickly isolated. The
cables should be protected from crushes, cuts from
possible damaging locations (such as sharp edges, door
openings), all electrical devices to be used should be
properly grounded and devices that work with the lowest
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