Maintenance Cleaning at DONG Power Station
Carbon dust contamination of controls
For one week the power plant had scheduled a production stop. In this maintenance window AREPA was called in to take care of the removal of carbon dust contamination at circuit boards and electronic controls in four cabinets.
The reason was that the turbine protection system three times within a short period had bypassed turbine because errors of high bearing temperatures were reported. The fault was intermittent, and the errors occurred several times before the problem was located: An error on the electronics board.
The problem was due to the printed circuit boards were heavily contaminated with carbon dust. The printed circuit boards can’t be removed during operation.
The carbon layer on the circuit boards had over time been built up due to pollution from coal residuals from the production site. The carbon created electrical short cuts, which were the root cause to the malfunctions and misleading reports generated from the control units. After cleaning and change of cards the faults haven’t appeared.
The controllers in this section of the power plant are an older type compared to the other systems on site. This controller type generates more heat the demand for ventilation is higher. As more air is coming through the cabinets the amount of carbon particles will be proportional as high.
Maintenance Treatment was successful
"To carry out maintenance cleaning of more than 240 circuit board and racks in the four cabinets, we chose AREPA in Silkeborg, as we know from previous cooperation and have good experience "says Lars Jacobsen, Electronics Technician at DONG Power Plant, Esbjerg.
A team of two technicians from AREPA had in only five days cleaned all boards and racks. The cleaning methods used were both dry cleaning and wet cleaning depending on the contamination level. The control units were put in operation again and faults haven’t occurred since.
"We have been very satisfied with the assistance and cooperation with AREPA. Flexibility and know-how are essential elements of an assignment like this, and AREPAs approach towards the project were very professional. "
"In the future we will consider this kind of maintenance not only as an alternative to replacement with new components, but as a maintenance method that works well to the types of pollution, we have on site" says Lars Jacobsen.
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