During geothermal energy use serious difficulties are faced due to scaling from geothermal fluid. The first step to avoid these problems is studying and modelling scaling processes. A computer modelling program has been developed and a laboratory scale device was constructed to test the program. This equipment was suitable to determine experimental conditions of equilibrium solubility investigations before the construction of a pilot-plant scale modelling equipment. Solubility-scaling investigations were also scheduled in the pilot-plant scale equipment with the help of these experiments.