Based on qualitative analysis carried on subcritical 600 MW units for finding out the causes of salt deposition in steam turbines

through thermo-chemical test study on boilers of three units of the same type

many affecting factors for steam quality of units have been quantitatively investigated.Results show that the optimal monitoring indices of boiler water under operating condition of equilibrium phosphate treatment(EPT) should be as follows ρ(PO3-4)0.4 mg/L

DD10 μS/cm

pH value=9.30~9.5;the entrainment coefficient of steam0.1%

the change rate of unit load≤9.0 MW/min

the pressure in drum of boiler18.5 MPa

so as to enhance the steam quality of subcritical 600 MW drum boiler.Directing against the above-mentioned requirements

preventive measures for salt deposition in steam turbines of high parameter units have been put forward.