By Greg Fenrick

Although I’ve tightened, loosened, and in some cases twisted off a few rusty bolts in my younger years, I never worried about how tight they were. All I was told to do was “make them as tight as you can”, and that’s what I did. That was until I got a call from Philomena Clark of the Valley Forge & Bolt Manufacturing Co. In about ten minutes, I knew more about bolts than I knew what to do with.

So what are load indicating fasteners and how can they reduce mill costs? Here's what Valley Forge says on their website:

The SPC4™ load indicating fastener allows users to install a bolted assembly with confidence. The user can constantly monitor the clamp load of any SPC4™ bolted joint whether static or dynamic, by attaching a probe to the datum disc located on the end of the fastener and reading the value on a hand held battery powered digital monitor. Optional data gathering and storage of the bolted joint are available.

After my lesson on the difference between bolt torque and bolt tension, Ms. Clark quickly pointed me to Kemess Mine's testimonial on their experience with load indicating fasteners.

Kemess Mine was experiencing a major amount of downtime and production availability as a result of some flanges in their ball mills not being mated well. This was causing them to break flange bolts almost daily. As a result they were loosing at least four hours of production each time they installed new flange bolts. This downtime and production loss was costing Kemess a minimum of $9,000.00 per hour. After measurements were taken and the bolts were replaced, Valley Forge & Bolt was able to save Kemess Mine over twenty million dollars in downtime and maintenance costs. It’s clear that more mill operations with similar maintenance problems should give Valley Forge & Bolt Manufacturing Co. a call. I’m sure they would be happy to put a quote together for you.