Trillium Lifting Lug Bushing

Ontario Power Generation Internship project:

Project Background:

Another project I worked on during my internship at OPG was to design a low-cost solution that will fix the lifting lugs on the Trillium package.

The lifting lugs used to transport a radioactive waste package called the "Trillium Transportation Package" were poorly designed and severely damaged after a prolonged time of usage (Figure 1). There are two issues with the shackle/lug interface. First, the lug plate is thin compared to the inside width of the shackle bail at the pin. It will prevent the shackle from being centred, causing the lug to twist by the shackle when lifted. Second, the shackle pin diameter is much smaller than that of the hole in the lug. The lug hole gradually deformed over time due to the small contact area.

OPG did not want the lugs to be removed or changed, as it might raise the concern of relicensing the entire package. This process is expensive and time-consuming. My job was to design a viable solution capable of maintaining the original lugs and solve the issue at hand. The design must be inexpensive, durable, and can withstand different weather conditions without rusting.

Design Ideas:

I developed numerous innovative solutions capable of reducing the stress acting on the lugs and protecting them from bending (see Figure 2). All of the proposed solutions are then systematically evaluated using a decision matrix based on weighted design criteria. (full presentation)

Design Process:

Design four, "the threaded bushing" had the best score and was approved as the optimal solution by my manager. This design is similar to a bolt and nut mechanism. It fills the void space between the shackle and the lug and increases the contact area. I used the detailed design drawings of the lug and sketched it on SolidWorks to customize the size and fit of the bushing. I then used the thread pitch chart to design threading for the nut. To ensure that the fit and thread size was correct, I printed 3D models of the design and tested them on the lugs. I calculated the bearing stresses acting on the lugs while accounting for the lifting angle. The material selected to manufacture the bushing was stainless steel. It was sufficient to withstand rust, and its yield strength was adequate to withstand the bearing stresses on the lugs. Finally, I made detailed 2D drawings of the parts and wrote a design report outlining the assumptions, limitations, and calculations used to analyze the bushing. Full calculation report.

Results:

Twelve bushing components were manufactured and are currently used as a permanent solution to transport the Trillium packages (see Figure 3). Loctite is used to permanently lock and seal the threaded fasteners. The final design reduced the bearing stress acting on the lugs and prevented them from twisting.