• Carmen Zajicek

How to Prevent Your Crane Operator from Two Blocking Your Crane


a yellow tower crane

Allison Marine Contractors conducted a crane lift operation in 1997 to move liquified oxygen containers for scrap usage. The operator held the crane’s main hoist line with slings that had an 18-inch headache ball. 


As soon as the operator boomed the line down, the ball hit the boom tip, separating the crane’s lifting line and resulting in a two-block accident. Tragically, the ball fell 50 feet, instantly killing an employee.


Two-blocking is a common crane incident that usually occurs due to improper signaling and rigging, leading to the crane’s hook coming in contact with its boom tip, breaking apart the hoist line. In fact, 2% of crane-related deaths in 10 years were due to two-blocking incidents. A snapped hoist line can cause havoc on an industrial site with workers and costly building materials.


An ideal way to prevent two-blocking incidents is through anti-two-blocking systems, which are essential crane safety systems that guarantee protection from such incidents. Here’s everything you should know about them.


What are Anti-Two-Blocking Systems?

An anti-two-blocking system is a safety device that prevents two-blocking accidents. It’s now mandatory for crane operators to install anti-two-blocking systems to all the cranes manufactured after 1992, as per ASME (American National Standards for Mobile and Locomotive Cranes) Regulations.


It’s a technologically advanced hardwired or wireless device with built-in sensors that warn the operator about the escalating risks of two-blocking accidents, helping them take preventative measures to quickly stop the crane operation. 


Wireless vs. Hardwired ATB Warning Systems

Two of the most popular variations of this safety device are wireless ATB systems and hardwired ATB systems.


While crane safety system manufacturers offer two variations of ATB systems, i.e., wireless and hardwired, most people prefer wireless ATBs. They are easier to operate, install, and easily work with cranes of any size or boom type.


An anti-two-blocking system works by triggering an audio-visual alarm on the crane’s display to alert the crane operator as soon as the crane’s hook reaches its maximum height. It ensures that the operator no longer needs to extend the hoist line to hit the boom tip.


While wireless systems are more efficient and advanced, hardwire anti-two-blocking systems are also excellent for cranes with fixed boom tips. They alarm the operator before the hook can reach the boom tip providing the crane operator with the necessary guidance for a safe croperation.

 a tower crane operation

Why You Should Get It

Evidently, an ATB warning system can benefit you significantly. It helps crane lifting personnel ensure crew safety and human life preservation, which is a top priority during all lifting operations. It ultimately leads to a secure work environment with increased confidence, productivity, and efficiency.


Furthermore, crane operators must ensure the safety of all the heavy equipment and building materials they’re loading. An ATB warning system guarantees the safe and timely transportation of materials without damage.


Finally, OSHA requires all certified crane operators to install an anti-two-blocking system on their crane. Therefore, installing one not only lets you comply with these regulations but will also reduce your insurance cost.


a construction worker

If your looking to install a reliable and efficient wireless A2B system on your cranes? Feel free to get in touch with us at Crane Warning Systems Atlanta for all your crane safety needs. We distribute advanced Rayco Wylie crane safety devices in the U.S. and offer everything from wireless crane anemometer to load monitoring systems. Contact us for more information today!

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