At the moment many hydropower units, HPU, in Sweden are to be renovated and due to the typically long life of HPU the staff that designed and commissioned them are no longer available to consult. In order for the units to operate in a similar or improved matter after renovation as prior to it, Vattenfall and Statkraft has together complied a document called Nordic Generator Technical Requirements, NGTR, where appendix 4 states demands on the mechanical dimensioning of HPU that are to be seen as guidelines when renovating a HPU.The section on rotor dynamics is evaluated in this thesis as to check if these guidelines can be met with typical designs why two HPU, Harsprånget G2 and Midskog G2, are analyzed. The RAPPID v.3.20 software supplied by RSR is used throughout this thesis.A method for conducting a sensitivity analysis called the elementary effects method is applied and the results give information to novice designers of hydropower units as to what parameters have the strongest effect on the end results. The parameters that were tested during the sensitivity analysis were mainly bearing parameters that are typically changed during design but also the added mass from co-rotating water in runner. As the sensitivity analysis was run using a large number of simulations, all of these simulations were evaluated using the NGTR requirements to look for designs were these criteria were met. As none of these designs fulfilled the criteria an optimization scheme typical for renovations was setup to further improve the designs.Neither one of these optimized designs met the criteria why it is concluded that it is not possible to dimension these two HPU according to the guidelines in NGTR Appendix 4 without a more significant design change than what was done in this thesis.