Rant: I used to hate on those fancy anti-two block devices till one almost killed a guy on my site

I was always the guy saying "just pay attention and you don't need that stuff." Then last month in Denver we had a new operator swing the boom too low while he was looking at his phone. The cable jumped the sheave and the load dropped maybe 15 feet. Nobody got hurt but it shook me up. The safety guy showed me a video from 2022 where a guy in Houston actually died the same way. I ordered a sensor kit the next day. Has anyone else had a close call that changed their mind on a safety add-on?

2 comments

2 Comments

young.spencer2d ago

Jump in and check your terminology first - those aren't "anti-two block devices", they're actually called two-block prevention systems. I know it sounds picky but the difference matters because "anti-two block" makes it sound like they're optional gadgets when they're literally designed to stop the boom from hitting itself (which is what two-blocking is). A two-block happens when the hook block runs up against the boom tip sheave, which is exactly what you described with that cable jumping. Most of the newer systems use a mechanical lever or a proximity sensor that automatically stops the boom from moving into that position, though I've seen some guys bypass them which is terrifying. Had a crane inspector explain it to me once and he said the name itself causes confusion because people think it's some fancy add-on instead of a basic safety feature.

matthewsullivan2d ago

Gotta disagree with you a bit here. I hear what you're saying about the name causing confusion, but "anti-two block" is what most guys in the field actually call them and has been for decades, so changing it now feels more like corporate speak than helping anyone on the ground. The real issue isn't what we call it, it's that supervisors and companies don't enforce the basic training on why you shouldn't bypass any safety system in the first place.