Redesign of Shaft Seal Running Ring and Fastener Testing
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Date
2016-12-07
Authors
Morrish, Eric
Harper, Mihskakwan James
Skorpad, Andrew
Qin, Yang
Yao, Shenghui
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Abstract
Manitoba Hydro’s Jenpeg generating station wasexperiencing difficulties with their turbine shaftfrom corrosive river water conditions. Revisiting Manitoba Hydro’s initial shaft seal solution, found that deflection ofa running ring,whilebeing installedduring the repair,wasexcessive.They had also determined that the running ring was exhibitingcorrosion concerns. Manitoba Hydro has requestedthat Generation Solutions redesign the running ring of the shaft seal to simultaneously improve alignment, installation times, and corrosions concerns. They have also asked us to create a standard system that can determine the Nut factor k of fasteners.Following the completion of a rigorous design process and finite element analysis,Generation Solutions has successfully increased the stiffness of the running ring. The change in vertical diameter of the running ring was reduced from 0.033”to 0.007”, corresponding to an improvement of 77.3%. Generation Solutions and Manitoba Hydro were hoping to achieve a deflection value of 0.005”in order to conform to assembly tolerance, however the achieved value will significantly reduce the defection despite not meeting our goal.Researchconducted byGeneration Solutions determinedthatchanging the material of the running ring from ASTM A516 Gr 70 steel to 410 stainless steel will reduce the corrosion of the running ring from greater than 0.050” peryear to less than 0.020”peryear. Through extensive detailed design and optimization, we have created an apparatus that both the team and the client are happy with. We have created a procedure for how to use the apparatus to determine the Nut factor, along with its correspondinganalysis program. We have received acceptable results from our apparatus, with an average Nut factor value of 0.177 for a 5/8” x 5”stud under 5.2”of tension with Loctite applied undergoing 0.010” elongation length with a standard deviation of0.0263 and a confidence level of 85%.Given the many different sources of error with regards to determining the Nut factor, we believe that our results are acceptable and well within the scope of the project.