Analysis of the reasons why two types of turbines in the air separation unit burn thrust bearings twice every six months

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The air separation plant is equipped with two sets of 43,000 capacity air separation units, which were put into operation successively in October 2011. The air compressor is driven by a turbine; these turbines are all single-cylinder extraction condensing turbines of the ENAKS50/71/32 model. The steam inlet pressure is 9.1 MPa, the extraction pressure is 4.1 MPa, the output power is 36,421 kW, and the operating speed is 4,690 rpm. Among them, the turbine of the North Set compressor unit experienced an unexpected incident of thrust bearing damage in 2015, after the turbine wheel chamber pressure increased twice due to severe scaling ； Under basically identical operating conditions, the turbine of the South Unit showed, in the later stages, that the opening of the high-pressure control valve had reached its limit, the operating speed dropped to 4,552 revolutions per minute, and the turbine’s output became severely insufficient; however, no problem with burning out the thrust bearings occurred. When comparing the two units, the reason cited for the continuous bearing wear in the turbine of the northern unit was increased axial force due to scaling; however, the evidence and rationale provided are insufficient.