Safe Rigging Begins with Eye Bolts

Sept. 28, 2010
Eye Bolt Capacity in Angular Lifts

Several components make up an effective yet safe rigging system. One slight mistake could spell disaster, resulting in the loss of an expensive load, lifting equipment, or even the life of a crew member.

One of the most misunderstood pieces of rigging gear is also perhaps the most commonly used: the eye bolt. With only a loop on one end and threads on the other, this balloon-shaped anchor looks harmless, but riggers must follow the appropriate operating guidelines and review the load chart for each type of eye bolt before attaching them to a load.

Schooling means safety

Training is the first step to assembling a rigging system complete with eye bolts. Without the proper education, riggers cannot grasp the small details that add up to a safe and successful lift.

"Most riggers are unaware of the capacities of eye bolts," says Howard Kaplan, safety and training director at Southwest Industrial Rigging. "Eye bolts are marked with size, not capacity, and as long as the eye bolt doesn't bend or break, usually riggers think everything is fine."

A mistake common among untrained riggers is the use of a shackle capable of lifting more than the eye bolt to which it's attached. If, for instance, the shackle has double the capacity of the eye bolt, then the eye bolt likely is overloaded by a 2:1 ratio.

Some riggers also fail to make the distinction between standard and shouldered eye bolts. Standard eye bolts are designed only for straight, vertical lifts. Shouldered ones, which are fitted with a "skirt" below the eye to resist bending, can be used in angular lifts but at reduced capacities.

"If it's not a shouldered eye bolt, most manufacturers don't recommend any kind of angular pulling unless it's a very miniscule amount," Kaplan says. "If you add any kind of angle, the capacity drops so quickly."

"Even with a shouldered eye bolt, you don't want to go below 45 degrees. If you do, you always have to look up the manufacturer's capacities," he says.

Before making a lift

Fifteen years ago, Southwest Industrial was contracted to hoist a heavy stamping press, nearly 75,000 pounds. The rigging crew thought they could successfully and safely lift it because it was attached to large, high-capacity eye bolts. "It bent," Kaplan says, referring to one of the eye bolts in the midst of the lift. However, the press was not too heavy for the eye bolt. The eye bolt bent because the crew failed to properly seat the shoulders of the eye bolt. Dust, dirt and grit had built up in the tapped hole of the load, and the crew neglected to clean it out.

"At 75 degrees, there was just enough angular pull that the failure to seat the shoulders at near-capacity lift bent the eye bolt," he says.

Fortunately, no one was injured and the load was intact. "But an eye bolt could have pulled out, and we could have lost the load," Kaplan says. "The lesson learned was to take a second look. Had they just cleaned out the tapped holes and run the eye bolts in completely and accurately by seating the shoulder, they would never have had that issue."

Tapped holes for eye bolts must be capped or plugged when not in use. If cleaning out the eye-bolt hole does not help to properly seat the shoulders, use washers or spacers to ensure a secure fit.

Another rule is never to reuse a bent eye bolt. They might appear sturdy, but actually bent eye bolts have been structurally compromised.

"I often use the analogy of the paper clip: If you bend it one time, what happens to the paper clip? It doesn't break. But it does if you keep bending it," Kaplan says.

Eye bolts could also bend if they are not aligned with the sling line during a lift. The load should be in the plane of the eye, according to The Crosby Group, a manufacutrer of rigging gear.

A safer alternative

More and more, riggers are taking advantage of swivel hoist rings as an alternative to eye bolts. Unlike eye bolts, which are immobile when attached to the load, swivel hoist rings have a bail that can pivot and move up and down, eliminating many of the issues and structural weak points that plague standard and shouldered eye bolts.

There are a few downsides: They are more expensive, heavier, and they have to be torqued down. "But you have consistent capacity anywhere you want. You can spin it, turn it, rotate it, and it retains the same capacity regardless of the angle," Kaplan says.

Swivel hoist rings worked perfectly when Kaplan's company was contracted to lift — from vertical to horizontal — a decommissioned nuclear reactor in Idaho, he says.

Kaplan advises riggers using swivel hoist rings for the first time to thoroughly read the instruction manual that comes with the hoist ring, as there are a few key differences from a standard eye bolt. For instance, with swivel hoist rings, riggers should turn the ring so that the eye is perpendicular with the load, unlike with eye bolts where the eye should run parallel with the load.

Now is the time to learn how to use these rigging tools safely, Kaplan says. Don't wait until after an accident happens.

Shouldered eye bolts are designed to handle angular lifts, but pulling at an angle greatly reduces the eye bolt's load capacity. When pulling at an angle of up to 45 degrees, several eye bolts can hoist only 30 percent of the rated working load. Pulling at an angle of up to 90 degrees further decreases that capacity to 25 percent of the working load. Always check the manufacturer's load chart to determine the eye bolt's capacities for both straight and angular lifts.

Eye bolts can bend or become loose if not seated and installed properly. For eye bolts with a shank diameter that is narrower than the depth of the load, one hex nut must be added. Two hex nuts are required when the load depth is shallower than the shank diameter of the eye bolt.

One of the biggest rigging mistakes is using a single sling to make an angular lift with two eye bolts. If you insert one sling through both eye bolts and then lift, the resultant loads on the eye bolts will be at a deeper angle, meaning reduced capacity. Instead, use two shackles to firmly attach the eye bolts to two slings.

Shims must be added to an eye bolt if applying a load perpendicular to its eye, and angular pulls reduce the capacity of the eye bolt. But swivel hoist rings offer added versatility. Because they have a bail that can rotate and turn in multiple directions, swivel hoist rings can withstand a consistent load capacity regardless of lift angle and load alignment.