Low vacuum pump operation parameters choice of steam turbine, steam to produce high voltage impulse, double adjustment extraction condensing steam turbine unit, the second paragraph is adjustable industrial extraction, the fourth section for adjustable heating extraction. By a two level adjustment extraction, divided into high, medium and low pressure section. Unit into the largest quantity of thermal power plant on the basis of electricity, steam heat load distribution and the parameters of the system of heating in winter, and combined with the characteristics of the unit, the unit in the rated pressure of exhaust steam pressure value, this transformation units can be as high voltage frontend does medium-pressure frontend does low-pressure ChunNing machine series operation. In low vacuum operation, can be thought of high-pressure frontend enthalpy drop distribution at various levels, reaction, axial thrust and power, heat load will be the same, does not need to be restated. So low in the operation of the vacuum to the third part of the low-pressure ChunNing units accounting, this is because the initial parameters constant, low vacuum operation only cause low pressure part of the enthalpy drop cut, redistributing enthalpy drop, vacuum pump application the level of the enthalpy drop decrease, increase ratio x, reaction degree increases, the axial thrust change, need to focus on checking the resulting axial thrust change, thermal expansion changes as well as the interior of the condenser copper pipe and the sizzling uneven expansion caused by leakage. Under the calculation and analysis of the axial thrust based on the calculation of typical working condition, to analyze the reform rear axle to thrust the impact on the unit safety. Symbol design condition of low vacuum conditions after the level before the pressure level pressure differential ideal enthalpy drop reactionary reactionary degrees incremental increase axial thrust axial thrust reverse thrust always push, run note: unit design parameters and actual manufacture error is inevitable, and unpredictable; In addition, the unit run for a long time, inevitably produce aging, the health is also unable to display them with specific indicators, therefore, should be paid attention to in the actual running thrust change and influence.