The wire rope running on most cranes terminates in an asymmetric wedge socket. This cone-shaped device wraps a loop of wire rope around a wedge that slots inside it.

Wedge sockets are perfect for cranes because they are self-tightening, says wire rope designer Roland Verreet, of Germany-based Wire Rope Technology. “The more you pull, the more you pull the wedge into the socket, the more resistance there is against the forces.”

Verreet continues: “The problem is when there is a sudden unloading. Then rope force is in the opposite direction, and that might shoot out the wedge. When the crane then starts lifting, it pulls the wedge back in, but the rope might have shifted a little bit. If that happened several times, every time the rope slipped a few millimetres, one day the rope will escape out of the termination. In order to prevent that, you put a wire clip at the end of the rope at its exit.”

The problem is, most wire rope clips are too wide to clamp down securely over just one wire rope. As a result, dead ends are sometimes:

• clipped back on themselves

• clipped to a spare piece of rope

• clipped through an extended wedge
socket (the patented Crosby Terminator),

• clipped to the live end with a special sliding double clip

• clipped to the live end with a standard fastener.

Standards in North America and Europe suggest that clipping dead to live with a standard fastener is a bad idea. ASME B 30.5:1994 and EN 13411-6 say that only clipping the dead end back on itself, or clipping the dead end to a spare piece of rope are acceptable. An informational appendix (E) to Canadian crane standard Z150-98 suggests four methods, including the two ASMEmethods plus using an extended wedge and a special sliding double clip. In the Crane Safety Association of Ontario Rigging Manual, a drawing of the dead end clipped to the live end is marked ‘WRONG’. There are currently no ISO standards on the subject.

But the Japanese Construction Code for Cranes does not prohibit clipping the dead wire back to the live one, according to Shigeichi Kiyota of the Japan Crane Association.

Clipping the dead end to live appears to be common practice in Japan, according to at least one observer in Southeast Asia. “From my experience, most mobile cranes imported into the Philippines from both Japan and Singapore terminate their rope by securing the dead end side of the rope to the live end at the wedge socket. Cranes originating from the UK, US, or Europe do not seem to have this issue,” says Tom O’Connor, executive vice president of Philippines-based Inspection Consultants International.

Engineers in Europe and the USA argue that there are two major problems with clipping dead line to live.

There is a typical sequence of failure when the dead end is clipped to the load side rope, says Crosby chief product fittings engineer Ron Garrett. “First the load side rope starts stretching and reducing in diameter from the applied load. The dead end does not see as much load and does not stretch as much. As the load side rope moves relative to the dead end, it starts pulling the clip saddle (or U-bolt) with it, and creates a misalignment between the saddle and U-bolt. This misalignment causes both sides of the rope to bend or crimp, creating a stress riser and reducing the strength of the load-side rope.”

Roland Verreet argues that if the dead end clips to the live end, then it begins to share the load.

“The rope force will go the shortest path. Whichever of the two ends is shorter, that’s the direction the force will take, and that means the rope force in live rope will pass through the clip and up the dead rope. Then the full rope load is at this clip; this is very detrimental.” He added that it would be very hard to ensure that the dead end is longer than the live end when clamping the rope.

Kiyota says that in Japan clipping dead wire to live wire is only allowed when the saddle of the clip is connected to the live wire and the U-bolt with the dead line. Because it is flatter, the saddle does not bite so much into the live rope.

Verreet agrees with this analysis. “Okay, out of the two solutions, this is the better one, but it is not neccessary at all.”

Kiyota argues that there is a precedent for clipping dead rope to the live one. ASME B30.5-1994 allows this for creating eye sockets (5.1.7.3(b)). Several clips grip the dead rope to the live one and hold a loop around a grommet.

Verreet argues there are two problems with this logic. First, there are usually four or five clips holding wire rope around an eye socket, and each takes a portion of the load. Second, he says, eye sockets are not generally permitted as permanent end connections. “People assume that you will take them apart, reclamp them in different positions. Wedge sockets are assumed to be permanent, so there are people who never open it again. That means that if the dead end were clipped to the live end in a temporary eye socket, the clip would stay at the same point, and fatigue damage would occur at the same point for the whole rope life.

Another concern for Verreet is that users are putting the rope in wedge sockets the wrong way around. “If you come in on the wrong side of the wedge, the wedge has to align itself, and it will rotate around bolt, in order to be in line with the rope tension. In doing so, it will bend the rope at the exit of the pocket. Wire rope is made to bend over sheaves 20 times the rope diameter, not a little radius. And then you get low cycle fatigue: a limited number of bends will break the rope.”

“I drive home and pass the same construction site every day. I am used to looking at cranes as I drive. One day, I noticed that the wedge socket was installed the wrong way on one of the cranes at the site. But by the time I am passing, it’s always too late to stop. One day, I left earlier than normal, and stopped, and told the workers on the job site. They didn’t believe me, so I said, let’s put the boom down. Not only was the rope coming in the wrong way, but it was 50% damaged. This thing would have come down a week later. The crane operator thought I was an inspector. “Will I get a fine? he asked me. “No,” I said, “Say thank you: I just saved your life.”


Rope fed through a wedge socket can gradually work its way out over many load cycles. Most wire rope clips are intended to clip two ropes together, not one. The problem: Rope fed through a wedge socket The Crosby Terminator wedge socket has an extended wedge that the rope clips into Recommended solution: Wire rope termination with rope clip tied into extended wedge socket Wire rope fed through a wedge socket, looped back on itself and clipped Recommended solution: Wire rope fed through a wedge socket, looped back on itself and clipped Wire rope exiting a wedge socket clamped to a spare piece of rope Recommended solution: Wire rope exiting a wedge socket clamped to a spare piece of rope Dead end of wire rope from a wedge socket clamped to the live rope, with the saddle on the live wire Solution not recommended: Dead end of wire rope from a wedge socket clamped to the live rope Wire rope terminated in a wedge socket tied to the live (load-bearing) line Wire rope terminated in a wedge socket tied to the live (load-bearing) line