Maintenance of the 33-year-old bar screens at the Kalamazoo (Mich.) Water Reclamation Plant was stressing the operators. Shear pin failures occurred often, and almost always on weekends.
The worn and corroded frames allowed chain guides to wobble, requiring tension adjustments. When some 1-inch screen rack bars broke, they weren’t replaced because of their difficult location and the unit’s age. Operators worried that rags slipping through the larger gaps would clog pumps and flood lift stations. With one screen worn out and the other two not likely to continue working, they feared a catastrophe.
To research replacement options, a team that included design
