CRANE CRITIQUE
TERMINATING WIRE ROPE WITH A BECKET AND WEDGE
A monthly crane and rigging informative column for all personnel directly or indirectly involved with crane safety. Each month we will attempt to explain a different technical issue pertaining to crane operations here on Guam, addressing the sometimes overlooked or misunderstood topics by management and operators alike. By Dave Barnhouse
I have discussed the topic of correct becket and wedge use previously in this column and have received some positive feedback on the subject. However, sitting at a stop light and observing a boom truck in the next lane with what looks like an accident waiting to happen because of the crimped wire at the termination, I cringe and ask myself if maybe some operators are not getting the message. I feel partly responsible for an ill conceived termination on any crane or boom truck, mostly because chances are the operator is in possession of an operator qualification card issued by me and I probably inspected the crane he is operating. I have approached operators in the past about an improper termination on their crane and the answer is always the same: ‘Oh, the mechanics, or helpers did that’. My response to them is: ‘Hand over your operator’s card’. Since when do you operate in an unsafe condition because of someone else’s incompetence? Isn’t that why we do a daily inspection? Doesn’t the operator have authority to stop operations if any hazards or unsafe conditions are found? And as a competent person doesn’t he have the responsibility to confirm a qualified person corrects this condition? If you are unfamiliar with becket and wedge use and why they are considered a critical area, know this: at the point where the wire rope enters the becket is the weakest link on the entire wire rope. This is true even when first terminated and there are no kinks or corrosion to consider. The reason for this is the nature of wire rope, it just does not like to be bent tightly around a wedge nor to be constantly wearing against the sharp edge of the becket. Add to this some corrosion or the fact that the operator crimped the cable with two cable clamps and tightened the nuts as if the clamps are holding the load and you end
22 | JUNE2015
up with a wire rope capacity with a fraction of the original safe working load. So, what is the right and wrong way to terminate a wire rope in a becket? There are a few correct methods and as much or more incorrect methods. If you are not sure what you are looking at when you look at wire rope termination using a becket and wedge than you are no doubt not the person to be inspecting this assembly. Briefly, the following is an explanation how a properly terminated wire rope works and what it should look like. First, realize that the loaded end of the wire rope is referred to as the ‘live’ end, the unloaded end of course is referred to as the ‘dead’ end. The goal is for the live end to load the becket pin in as much as possible a direct and perfect line. This is accomplished by assuring the live end is exiting on the straight
CONSTRUCTION NEWS BULLETIN
side of the becket as opposed to the tapered side. There should also be no wire rope clips on the live end, an issue that is difficult for many operators and mechanics to comprehend, see photo 1. The common misconception is that somehow this cable clamp supports part of the load, whereas in reality in supports exactly zero portion of the load and lifts could be made perfectly fine without any clamps of any kind. Just look at a dragline bucket with two inch or bigger cable terminations at the drag chains pulling the bucket, there are no clamps and it holds without slipping just fine. Why the clamps than? A clamp is required on lift cranes on the deadend only to prevent the wedge from becoming dislodged from the becket in the event there is a sudden unloading of the live end such as the wire rope or the block striking the ground, etc. If the wedge is free in the becket there is no reason why the wire will slip under normal www.guamcontractors.org