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Decommissioning
Decommissioning means shutting down the system via
the circuit breaker at the control panel. The duration of
the shutdown determines the preservation measures
described in this chapter.
What preservation is for
A depressurised boiler system is at risk from idle-time
corrosion. Preservation measures prevent such corro-
sion.
Preservation measures are carried out in areas on the
flue gas side and on the water side of a boiler system.
The type of preservation depends on the type and
duration of the interruption in operation.
Type of preser-
Effect
vation
Wet preservation Keeps oxygen away from the boiler
system.
Dry preservation
Keeps moisture in the boiler system
to a minimum.
Tab. 4
Brief interruption in operation
Treatment on the water side
Operating
Measures
condition
The boiler is
Add oxygen binder to the feedwater 1
switched off.
hour before switching off. Dosing: 2
to 3 times the standard dose
The boiler re-
Maintain the boiler system pressure
mains on.
and temperature.
Tab. 6
Treatment on the flue gas side
■
Keep heating surfaces dry.
■
Remove severe contamination as it binds moisture.
Interruption in operation
Treatment on the water side
Dry preservation
Note
Restarting the system quickly is not possible.
A short-term shutdown is not recommended, as every
start-up process subjects the boiler to additional
stresses. For a period of up to 72 hours, e.g. over a
weekend, the boiler should be left to continue operat-
ing.
Interruption in operation
Duration
≤
>
Tab. 5
Basic rule
VdTÜV datasheet TC 1465 "Preserving the water side
of steam boilers"
Recommendation
If using preservation methods that include chemicals
other than those stated here, please consult the chem-
ical manufacturers.
3 days
≤
Preserving agents: Ammonia or nitrogen
■
■
■
3 days
>
Applications:
■
■
Notes on decommissioning and preservation
Recommendation
3 days
Maintain the positive pressure in the boil-
er system incl. all boiler-related equip-
ment (thermal water treatment, etc.).
3 days
Select type of preservation.
A technically demanding form of preservation.
Consult the chemical manufacturer before use.
The operator must compile system-specific operating
instructions.
Prolonged boiler idle periods
Risk of frost
See chapter "Using antifreeze in boiler systems"
in the technical guide
15
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