Hi! It’s Friday, May 3, 2013 and time for a Virtual Field Trip at ClickSchooling!
Age Range: 9 and up (approximately, with parental supervision)
At this website you can watch a five-minute video on how bolts are manufactured.
You may know that the building of a new San Francisco Bay Bridge, the world’s largest single-tower, self-anchored suspension span, is underway. You may have also heard that one third of the 96 bolts (threaded steel rods that are 3 inches in diameter and 17-24 feet long) broke after workers placed them in March 2012. The bolts were used to connect the bridge at the pier to help control swaying and seismic uplift during an earthquake.
Metallurgy experts suspect that galvanizing the steel bolts trapped hydrogen atoms beneath the zinc coating causing the bolts to become brittle.
Interestingly, the company featured on today’s website, declined to submit a bid on manufacturing the Bay Bridge bolts because of the riskiness of the galvanizing requirement. (Galvanizing this kind of bolt is prohibited in the Caltrans bridge design manual – but engineers opted to do it anyway! They haven’t explained why.)
When you get to the website, you can read about the history of the Portland Bolt & Manufacturing Company. Scroll down to the end of the page to find the video, “How It’s Made: Portland Bolt.” Then click on the arrow to watch the video that includes:
- Hot-Dip Galvanizing
- Caustic Soda Bath
- Sulfuric Acid Bath
- Flux Bath