Minnesota Power wanted to evaluate potential modifications for a paper machine at its Rapids Energy Center. The proposed tie-in would direct steam in a singular path that would allow use of desuperheaters to reduce steam temperature and provide better operating control.
After performing an initial evaluation, we suggested a review of the 50-pound steam line to determine actual pipe routing, existing turbine loading, defective support locations, and sagging piping locations. We performed 3D scanning to create a model and develop a baseline of the existing system. By conducting a pipe stress analysis, we compared existing forces and moment loads to the original allowable design loads and identified problem areas. Issues existed with pipe supports, horizontal pipe sag, and exceedances in allowable turbine force and moment loads.
Barr recommended two options for analyzing the piping system before modifying tie-ins and pipe and routing supports. We then analyzed three load-case conditions, calculated the loads, and compared them to the original design loads. We also presented two support options with pipe-routing and turbine-nozzle load variations.
In the project’s second phase, Barr conducted pipe stress analysis for both support options. We then designed the new piping system, verified piping changes, and sized new supports. Minnesota Power proceeded with tie-in modifications to the paper machine, following piping and support-hanger modifications recommended by Barr.