Guidelines for the proper use of lifting eyes
Lifting eyes, also commonly known as eye bolts, have widespread use in industrial plants. They are commonly used on dies, cabinets, compressors, heat exchangers, motors, molds, and other equipment to facilitate their movement, either when being installed or moved to a different plant location.
In a world increasingly conscious of product litigation, it is critically important to understand the proper selection and use of lifting eyes. It obviously pays the plant engineer to be aware of the risks when an undersized lifting eye is used; the correct size is abused, altered, or improperly loaded; or a bent wire eye is substituted for a forged one (Fig. 1). If recommended guidelines are not followed, the failure of a lifting eye can result in loss of property, personal injury, or even death in extreme cases.
Forged vs. bent wire
Whenever lifting is to be accomplished with a threaded eye bolt or lifting eye, a forged product should be used as compared to a carbon steel or bent wire eye bolt. Bent wire eyes, even if welded, are made from low-carbon steel. They can open up or stretch under load and are not designed or intended for lifting. They have no rated capacity associated with them.
Bent wire eyes are not physically tested, and because of their low carbon steel content, they exhibit very poor mechanical properties. They may be specified for nonlifting or nondynamically loaded applications, but they should never be used where product integrity and worker safety is of concern.
A situation may occur where a standard forged lifting eye that is properly sized for an existing tapped hole does not possess the rated capacity to safely handle the load to be lifted. What are the options? It may be possible to use an alloy forged lifting eye whose rated capacity is from 8% to 25% higher than a comparable standard forged lifting eye.
Using an undersized forged lifting eye or a bent wire substitute can lead to distortion of the eye, shank, or threads and is a leading cause of catastrophic failure. For this reason, manufacturers and ASTM Rated Capacity Tables (see table) state the maximum working load for various sizes of forged lifting eyes or eyebolts to aid in selection. A supplier/manufacturer of lifting eyes can supply these charts.
Never exceed rated capacity . It is a good idea to post a capacity table in work areas where lifting eyes are used and make it an active part of a safety program.
Even though the greatest load bearing capacity is in the plane of the eye and along the centerline of the shank, a properly sized but misused lifting eye can fail. It is important never to lift outside the plane of the eye. Lifting at an angle from the shank’s centerline significantly reduces the lifting eye’s capacity. Even a 45-deg angle reduces capacity. In any case, never exceed a 45-deg angle.
There are two types of capacities given for lifting eyes: Riggers and Engineering. The Riggers Capacity refers to the actual load a single lifting eye can lift. It varies with the angle between the leg of the lifting rig and the shank of the lifting eye.
Engineering Capacity refers to the allowable tension in the leg of the lifting rig as it is applied to the eye and is specifically useful when the load distribution is nonuniform, when nonsymmetrical slings are required, or when the lifting eyes are not placed on the top surface of the load.
Engineering Capacity must be calculated using trigonometry and vector analysis based on the actual loading configuration. More complete information describing how these working loads are determined may be found in ANSI B.18.15 Standard, Metric Straight Shank Lifting Eyes .
It is mandatory that the tapped receiving hole for the threads on the lifting eye have the proper major pitch and minor thread diameters, hole depth, and configuration (Fig. 2). The eye should not wobble while being screwed in nor should it take excessive force to screw in the lifting eye.
To prevent unscrewing due to twist of a cable and applied load on the hoisting device, the lifting eye should be screwed into the tapped hole with firm hand pressure and the eye aligned with washers, if necessary, so the applied load is in the plane of the eye.
Do not use a “Cheater Bar” to tighten the lifting eye. Installation instructions must be followed to ensure the initial load on the lifting eye hasn’t unseated the eye. If this happens, the eye should be unloaded and properly reseated. The hole for the lifting eye must have a counterbore to ensure snug seating of the shoulder of the lifting eye. Washers can be used to ensure snug seating of the eyebolt shoulder as long as there is a 90% minimum thread engagement.
Can lifting eyes be reused? Yes, but with caution. Before each use lifting eyes should be inspected and replaced if any of the following is detected:
Elongated or bent eye section
Elongated or bent shank
Nicks or gouges
Worn, corroded, and/or distorted threads
Cracks found by nondestructive testing, or magnetic particle inspection.
Lifting eyes that are being replaced should be destroyed by melting, crushing, or cutting clear across the eye. There are no other acceptable means of eliminating defective lifting eyes from possible reuse. The lifting eye should also be removed from service and destroyed when the name and/or trademark of the manufacturer is no longer readily identifiable to guarantee proper reference for continued usage.
Once the proper size forged lifting eye is identified, a source of supply should be determined. Beyond price and delivery considerations, insist on full compliance for proper traceability. Traceability markings should include the proper shank diameter, forging cavity number, forging code to identify manufacturing equipment used, manufacturer’s trademark, and material heat code that refers to the specific heat of steel used (Fig. 3). All of these markings are important and are an assurance of a quality supplier and product.
For highly corrosive environments, specify stainless steel forged lifting eyes. Since individual environments in this category have their own particular hazards, it is wise to consult an engineer to specify the correct material for an application.
When lifting outdoors in subfreezing weather, use a forged alloy lifting eye to reduce the chance of brittle failure. Contact a supplier for specific information on forged alloy lifting eyes.
More Info: For additional information or visual aids, contact Charles W.. Smith, President, Edward W. Daniel Company. Call toll free to 800-338-2658. Article edited by Joseph L. Foszcz, Senior Editor, 630-288-8776, email@example.com .
Lifting eye capacities
Diameter, in. Rated capacity, lbs. 0° 45° over 45° 1/4″ 500 125 Not Recommended 5/16″ 900 225 Not Recommended 3/8″ 1300 325 Not Recommended 7/16″ 1800 450 Not Recommended 1/2″ 2400 600 Not Recommended 9/16″ 3200 800 Not Recommended 5/8″ 4000 1000 Not Recommended 3/4″ 5000 1250 Not Recommended 7/8″ 7000 1750 Not Recommended 1″ 9000 2250 Not Recommended 1-1/8″ 12,000 3000 Not Recommended 1-1/4″ 15,000 3750 Not Recommended 1-1/2″ 21,000 5250 Not Recommended 1-3/4″ 28,000 7000 Not Recommended 2″ 38,000 9500 Not Recommended 2-1/2″ 56,000 14,000 Not Recommended
In general, a lifting eye must never be altered by such means as grinding, machining, or cutting. Dangerous alterations of eyebolts that can contribute to catastrophic failures include:
Machining an undercut in a shoulder lifting eye if a noncounterbore/countersunk hole is used.
Cutting undersized threads on a blank lifting eye to make it fit.
Welding another piece of metal to the eye or heating it in any way.
Rapidly loading the lifting eye in shock, especially at ambient temperatures below 30 F
Grinding the eye to make it fit a tight space.
Tips for smart lifting eye usage
Have backup inventory to ensure that the proper lifting eye is selected instead of using what’s available.
Schedule regular instructional sessions on the safe use of lifting eyes for maintenance and plant engineering personnel. Distributors and manufacturers are usually happy to put these on.
Make use of free safety posters and pocket cards are available from leading manufacturers.
Establish a regular lifting eye safety inspection schedule and procedure that is strictly enforced.
Replace all lifting eyes at least once per year.