TM 10-3950-672-10
Two-blocking MUST BE AVOIDED, to prevent damage to your crane and to avoid creating a safety hazard. Two-
blocking exists whenever the load block, headache ball, rigging, etc. come into physical contact with the boom, boom
nose, sheave, jib, etc. Two-blocking can cause hoist lines (wire rope) rigging, reeving, and other components to become
highly stressed and overloaded in which case the wire rope may fail allowing the load, block, etc. to free fall.
Your crane is equipped with an antitwo-block warning system. If the system has been damaged, removed from the
crane, or a malfunction is suspected, refuse to operate the crane if the warning system is not installed and operating
satisfactorily.
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