THERMOELECTRIC POWER PLANT
Demolition of the GVR plant, the metal chimney and the related pipe-rack
Armofer tackles the decommissioning of a Thermoelectric Group, inside the A2A power plant in Cassano d'Adda. A steam generator, the associated 100 m high chimney and the pipe-rack serving the plant itself are completely dismantled. The interventions foreseen within the industrial decommissioning are the remediation of environmental liabilities (FAV insulation ) and the mechanical demolition of steelwork structures implemented with a top-down technique.
METAL CHIMNEY DEMOLITION
Deconstruction by controlled disassembly using self-propelled cranes.
La procedura operativa prevede, terminate le bonifiche a terra, la realizzazione di tutte le asole per il l’imbrago dei conci da svarare. Le asole, realizzate sottoflangia, sono 4 per ciascun concio e rispettano perfettamente la simmetria dell’oggetto per garantire la corretta distribuzione dei pesi rispetto al baricentro durante le operazioni di svaro.
Armofer's executive design includes 17 cuts for as many ashlars. The first double-barrel hot cut takes place at an elevation of + 97 m, with personnel at height operating from the personnel basket suspended from a dedicated crane (all terrain, 400 ton).
Working in two shifts Armofer has subsequently planned for up to four crane pulls per day; of course if weather conditions of wind speed at altitude, which are constantly monitored, allow.
Sectioning is done hot, with oxyacetylene flame, by running the personnel basket with technicians around the circumference of the chimney. The ashlar is already secured to the four crane chains and held lightly by the dedicated crane (750-ton Liebherr). When the cut is complete, the ashlar remains hanging from the crane chains and is hauled to the ground. The "flight" lasts only a few minutes and deposits the ashlar in the dedicated site area so that dismantling, sectioning, and carpentry cutting can proceed.
There is constant radio contact between all operators , crane drivers, and technical management of ground operations.
STEAM GENERATOR DECOMMISSIONING
The steam generator of the decommissioned plant has remarkable dimensions: the inclined mouth, the main body up to 35 m high. The double metal structure is fully insulated with mineral wool. Therefore, it is necessary to carry out remediation by preparing static and dynamic confinement of the whole object. Inside, personnel, equipped with all the appropriate PPE proceed manually and by mechanical means to remove the metal sheets and then the FAV wools. Once the dismantling is finished, the metal harps contained inside are disassembled and then the external metal structure of the artifact is sectioned.
The huge harps hanging inside the structure are one by one grabbed by the excavator, cut at height to detach them from their housing; then literally "slipped "whole from the mouth of the steam generartor . In the field, Andrea Cinerari on the brand new Liebherr 960 retrofitted to have great gripping and cutting power on the boom and hydraulic shear that grabs and cuts such structures. Outside, off-site, secondary demolition continues, hot and/or cold, up to ready-made cutting of the resulting iron.
The pipe-rack serving the facility needs to be reclaimed. In order to safely access the structure, an access and material handling slab was erected and supported by provisional works. The pipe rack structure was fully insulated, statically confined, in order to properly remediate the environmental liabilities within it.