Unless idle boilers are stored properly,
they can corrode badly. Wet layup of a boiler is possible as long as the
ambient temperature remains above freezing. Before wet storage, the boiler
should be inspected, cleaned if necessary, and refilled to the normal water
level with deaerated feedwater. Add the correct dosage of treatment and
apply heat for one hour.
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If the superheater is drainable or the
boiler does not have a superheater, allow the boiler to cool slightly after
firing. Then, before a vacuum has a chance to form, completely fill the
unit with deaerated feedwater. After filling the boiler completely, connect
a surge tank, such as a 55 gallon drum containing a solution of Alken®
Treatment J-677, or a nitrogen tank at 5 psig pressure, to the steam drum
vent. This supply will compensate for volumetric changes due to temperature
variations. Leave the drain between the non-return and main steam stop valves
open wide. Tightly close all other drains and vents.
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| Test the boiler water once a week from
the shut-down boiler, and add extra treatment, as necessary, to maintain
minimum levels. When chemicals are added, use an external pump to circulate
the boiler water or reduce the water level to the normal operating level
and steam the boiler for a short time. Then follow the above directions
to lay it up again. If the superheater cannot be drained, fill it with deaerated
water and treat it in the same proportion as the boiler. |
