The operations for the depolarisation from DBDS of six transformers located at the petrochemical site of QVC (Qatar Vinyl Company Ltd.) in Doha, Qatar are under way.
To date, 21st November 2011, the operational engineers from Sea Marconi have already depolarised successfully two transformers; at the end of the works, of a total duration of two months, all the transformers shall have a concentration of DBDS below 10 mg/kg.
The selective depolarisation provided by Sea Marconi is the only countermeasure really effective against the corrosive sulfur problem and in particular, against the main responsible for the corrosivity of oils: the DBDS (DiBenzilDiSulfide).
The presence of DBDS in the oils is a problem significantly faced by utilities and industrial sites in the Gulf Countries. Cases of failures due to this phenomenon have already been reported from Saudi Arabia, Arab Emirates and Bahrain.
Sea Marconi is performing all the treatments in the on-load modality, i.e. meaning that the transformers stays in operation (energised and under load) during the entire duration of the treatment.
The technique applied by Sea Marconi (selective depolarisation – Chedcos) is performed by the use of mobile decontamination units (DMUs) developed and made entirely by Sea Marconi.
These units are connected to the transformer through two hoses. The oil present in the transformer is sucked, then flows through the DMU where it is warmed-up, degassed, filtered and, most of all, is set in contact with a solid reagent abating the presence of DBDS and other polar compounds. Finally, the oil is pumped back again into the transformer. This process is repeated in cycles until a complete depolarisation of the oil and the transformer is achieved, thanks indeed to the circulation of the oil inside it.
