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. 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. 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. For dry layup, the boiler should be drained, cleaned and dried out. Place an absorbent material, such as hydrated lime or silica gel in trays inside the boiler and seal it to prevent air from seeping into the boiler. Periodic replacement of the drying agent may be required during a logn storage period. |
