Abstract
The shafting of large steam turbine generator set is composed of several rotors which are connected by couplings. The computing method of shafting with different structure under specific installation requirement is studied in this paper. Based on three-moment equation, shafting alignment mathematical model is established. The computing method of bearing elevations and loads under corresponding installation requirements, where bending moment of each coupling is zero and there exist preset sag and gap in some couplings, is proposed, respectively. Bearing elevations and loads of shafting with different structure under specific installation requirement are calculated; calculation results are compared with installation data measured on site which verifies the validity and accuracy of the proposed shafting alignment computing method. The above work provides a reliable approach to analyze shafting alignment and could guide installation on site.
Highlights
The shafting of large rotating machinery is a multibearing rotor system
Giving the elevations of the 5th and 6th bearing as 0 mm, bearing elevations and loads distribution of single bearing support shafting are calculated and compared with installation data measured on site
This paper has established the mathematical model of shafting alignment, and computing methods of bearing elevations and loads under corresponding installation requirements, where bending moment of each coupling is zero and there exist preset sag and gap in every coupling, are proposed, respectively
Summary
The shafting of large rotating machinery is a multibearing rotor system. Shafts are manufactured separately and connected by rigid or flexible couplings. The main purpose of these shafting alignment methods mentioned above is to decrease the gap and sag of every coupling These methods are efficient to deal with the alignment of small rotating machinery which does not pay attention to the influence of bearing elevation for bearing load. For the shafting alignment of large rotating machinery, such as steam turbine generator set or ground-based heavy-duty gas turbine generator set, bearing elevations significantly influence bearing loads distribution. It was shown that bearing elevations and loads gained from the second assumption are more reasonable through comparison The latter calculation method based on the second assumption does not apply to shafting in addition to double bearing support, because the catenary curve of every double bearing supported rotor is calculated firstly and each bearing elevation is adjusted to make each coupling fulfill the zero to zero condition. Through calculation by means of programming, bearing elevations and loads of shafting with single bearing support, with double bearing support, and with synchro-self-shifting clutch under different installation requirements, were obtained, respectively
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