Load chart mismatch almost tipped us in Tacoma last week

We were setting a 12-ton heat pump on a roof in Tacoma last Friday. My rigging list said 8,400 pounds at 35 feet, but the actual boom angle and the extra block put us at 9,100 pounds. The load cell on the auxiliary line was the only thing that caught it before we lifted. Has anyone else had a load chart that doesn't match what the computer says, and how do you double check without trusting either one?

2 comments

Log in to join the discussion

Log In

2 Comments

brown.willow2mo ago

Isn't it wild how we trust two faulty sources to cancel each other out, but they just double up on the same mistake? This reminds me of my GPS vs. my own sense of direction on long drives, both are wrong in their own special way and the real answer is usually a gas station attendant who's lived there forever. I've started treating the load cell and the chart like two kids telling different stories, they're both lying a little until I measure the boom angle myself with a protractor app on my phone. That old school tape measure and a calculator has saved me more times than any fancy screen.

10

mason8472mo ago

Read a rigging forum thread about how some older cranes show different numbers on the chart vs the computer after software updates. Honestly, I always cross check with a tape measure and a cheap angle finder before trusting either one.

4