Installation av la?glutande fingaller fo?r fra?mjande av ekologisk funktion i vattenkraftverk
En fallstudie av ett kraftverk i Umea?lven
The purpose of this bachelor degree thesis is to analyze technical issues associated with an implementation of a low sloping trash rack with narrow spacing. A hydropower plant in Umea?lven was used as a case study. The basis for the study was a model where trash racks were dimensioned for inclinations between 25 and 45 degrees. Corresponding head loss, durability and water speed through the rack were then determined for each inclination. Necessary measures are thereafter discussed for the installation. Finally some of the estimated costs and incomes regarding the installation are presented.An implementation of a narrow spaced trash rack (10 mm) with an inclination of 30 degrees will cause an exceeding of the tolerance speed through the rack 15 percent of the operational time when there is no clogging. Furthermore, the change of intake screens result in an increase of the head loss of 4.8 millimeters, which corresponds to an income loss of 25000 SEK annually due to reduced production. Complimentary measures include supporting beams, new lower attachment point and an extension of the intake walls. The final cost is strongly dependent on how the installation work is done. A high cost may occur due to an interruption in the production and when extensive arrangements for the implementation are needed, such as the construction of a cofferdam. In total a replacement of trash racks will cost at least 8 184 000 SEK, in addition to 216 000 SEK/day due to loss of production. Moreover expenses for the supporting beams and extension of the intake are added as well.