Hoisting & Rigging

The ability to safely move materials from one location to another is a vital part of many activities at Princeton. Hoists are often used when materials are too heavy or bulky to be safely moved manually. Because hoists rely upon slings to hold their suspended loads, slings are the most commonly used materials-handling apparatus.

Slings, chokers, shackles and hoists are are available in many different materials and styles. Slings are commonly used in combination with a lifting device, such as an overhead crane, hoist, or forklift. The four main types of slings are:
  • Wire Rope: The most commonly used sling. Used in the construction and other applications where heavy loads and rugged conditions exist.
  • Chain: Combines superior strength, ease of handling and durability. The combination of heavy loads, elevated working temperatures and severe lift conditions usually dictate that an alloy chain sling be used.
  • Mesh: Wire and Chain. Excellent in lifting objects that are hot or have sharp edges, such as bar stock or plate steel. Mesh slings usually have wide load bearing surfaces that greatly enhance load balancing. Machine shops and steel warehouses typically have applications requiring mesh slings.
  • Synthetic: Both web and round-slings are used where loads must be protected from damage. Their light weight and flexibility reduce fatigue and strain on the rigger.

The sections below serve as a guideline when hoisting or rigging at Princeton University.

Basic Hoisting and Rigging Guidelines

The following basic guidelines must be followed for all types of rigging:
  • It is essential to determine the proper style, size, length, diameter and thickness of sling needed for the application prior to use. Select the sling best suited for the job.
  • Never tie knots in slings.
  • Rigging equipment must not be loaded in excess of its safe working load.
  • Hooks must be provided with safety latches.
  • Know the limitations of the lifting device
  • Determine the center of gravity of the load.
  • Protect sling from sharp surfaces.
  • Protect load from rigging, if necessary.
  • Allow for increased tension caused by sling angles.
  • Equalize load on multiple leg slings.
  • Maintain load control. If required, attach tag lines prior to lift.
  • Keep personnel clear of lift area.
  • Lift load a few inches and check rigging.
  • Start and stop the lift slowly.
  • Watch for obstructions and power lines. Maintain at least 10 feet from energized power lines at all times.
  • Use proper hand signals when communicating with crane operators.

Safe Lifting Practices

Selection of the sling is only the first step in the rigging process. The next step is learning how to safely use it to hold and move a suspended load. There are four primary factors to consider when lifting a load safely. These are:
  • Load Size, Weight, and Center of Gravity – The center of gravity of an object is that point at which the entire weight may be considered to be concentrated. To make a level lift, the hoist hook must be located directly above this point. If the hook is too far to either side of the center of gravity, dangerous tilting will result, causing unequal stress in the sling legs. Load imbalances must be corrected immediately.
  • Number of Legs and Angle with the Horizontal – The smaller the angle between the sling legs and the horizontal, the greater the stress on the individual sling legs. This increased stress effectively decreases the weight that can be safely lifted with any given sling size. Large (heavy) loads can be safely moved by keeping this angle as large as possible and, when necessary, distributing the weight of the load among more sling legs.
  • Rated Capacity of the Sling – The rated capacity of a sling varies depending upon the type of material the sling is made of, the size of the sling, and the type of hitch. Workers must know the capacity of the sling, and can obtain this information through charts or tables available through the manufacturer. The rated capacity of a sling must not be exceeded, under any circumstances.
  • History of Care and Use – Mishandling and misuse of slings are the leading causes of sling failure. Following the manufacturer’s recommendations for proper care and use are essential for maximum sling service life and safety.

Selection, Use, and Inspection of Slings

Workers involved in hoisting and rigging must exercise care when selecting and using slings. The selection of slings should be based upon the size and type of the load, and the environmental conditions of the workplace. Slings should be visually inspected before each use to ensure their effectiveness. Improper use of hoisting equipment, including slings, may result in overloading, excessive speed (e.g., taking up slack with a sudden jerk, shock loading), or sudden acceleration or deceleration of equipment.

Factors to consider when choosing the best sling for the job include size, weight, shape, temperature, and sensitivity of the material being moved, and the environmental conditions under which the sling will be used. The following guide may be useful in selecting the appropriate sling:

Alloy steel chains are strong and able to adapt to the shape of the load. Care should be taken when using chain slings because sudden shocks will damage them. This may result in sling failure and possible injury to workers or damage to the load.

Chain slings must be visually inspected prior to use. During the inspection, pay particular attention to any stretching, nicks, gouges, and wear in excess of the allowances made by the manufacturer. These signs indicate that the sling may be unsafe and must be removed from service immediately.

Wire Rope
Wire rope is composed of individual wires that have been twisted to form strands. Strands are then twisted to form a wire rope. When wire rope has a fiber core, it is usually more flexible but less resistant to environmental damage. Conversely, wire rope with a core that is made of a wire rope strand tends to have greater strength and is more resistant to heat damage.

When selecting a wire rope sling to give the best service, there are four characteristics to consider: strength, ability to withstand fatigue (e.g., to bend without distortion), ability to withstand abrasive wear, and ability to withstand abuse.
  • Strength – Strength of wire rope is a function of its size (e.g., diameter of the rope), grade, and construction, and must be sufficient to accommodate the maximum applied load.
  • Fatigue (Bending without Failure) – Fatigue failure of wire rope is caused by the development of small cracks during small radius bends. The best means for preventing fatigue failure of wire rope slings is to use blocking or padding to increase the bend radius.
  • Abrasive Wear – The ability of wire rope to withstand abrasion is determined by the size and number of the individual wires used to make up the rope. Smaller wires bend more readily and offer greater flexibility, but are less able to withstand abrasion. Larger wires are less flexible, but withstand abrasion better.
  • Abuse – Misuse or abuse of wire rope slings will result in their failure long before any other factor. Abuse can lead to serious structural damage, resulting in kinks or bird caging. (In bird caging, the wire rope strands are forcibly untwisted and become spread outwards.) To prevent injuries to workers and prolong the life of the sling, strictly adhered to safe and proper use of wire rope slings.

Wire rope slings must be visually inspected before use. Slings with excessive broken wires, severe corrosion, localized wear, damage to end-fittings (e.g., hooks, rings, links, or collars), or damage to the rope structure (e.g., kinks, bird caging, distortion) must be removed from service and discarded.

Fiber Rope and Synthetic Web
Fiber rope and synthetic web slings are used primarily for temporary work, such as construction or painting, and are the best choice for use on expensive loads, highly finished or fragile parts, and delicate equipment.

Fiber rope slings deteriorate on contact with acids and caustics and, therefore, must not be used around these substances. Fiber rope slings that exhibit cuts, gouges, worn surface areas, brittle or discolored fibers, melting, or charring must be discarded. A buildup of powder-like sawdust on the inside of a fiber rope indicates excessive internal wear and that the sling is unsafe. Finally, if the rope fibers separate easily when scratched with a fingernail, it indicates that the sling has suffered some kind of chemical damage and should be discarded.

Synthetic web slings are commonly made of nylon, polypropylene, or polyester and have the following properties in common:

  • Strength - Depending upon their size, synthetic web slings can handle loads of up to 300,000 pounds.
  • Convenience and Safety - Synthetic web slings adjust to the load contour and hold it with a tight, non-slip grip.
  • Load Protection - Unlike other sling materials, synthetic web is less likely to mar, deface, or scratch highly polished surfaces.
  • Shock Absorbency - Regardless of the construction material, shock loading (e.g., excessive speed, rapid acceleration or deceleration) of slings should be minimized. However, it should be noted that synthetic web slings can absorb heavy shocks without damage.
  • Temperature Resistance – The lifting capacity of synthetic web is unaffected by temperatures up to 180 degrees Fahrenheit.
  • Economy and Long Life – Synthetic web slings have a low initial cost and a long service life. They are unaffected by mildew, rot, or bacteria, resist some chemical action, and have excellent abrasion resistance.

Synthetic web slings must be inspected before use and should be removed from service if found to have acid or caustic burns, melting or charring of any part of the surface, snags, tears, or cuts, broken stitches, distorted fittings, or wear or elongation beyond the manufacturer’s specifications.


Workers involved in hoisting and rigging operations should receive training in the following:
  • Sling and hitch types
  • Sling capacity determination
  • Equipment inspection, care, and maintenance
  • Load weight and center of gravity determination
  • Safe lifting techniques

Wire Ropes, Chains, and Ropes

Wire Ropes, Chains, and Ropes

  • Wire ropes, chains, ropes, and other rigging equipment must be inspected prior to use and as necessary during use to ensure their safety.
  • Defective gear must be removed from service immediately
  • Job or shop hooks and links or makeshift fasteners formed from bolts, rods, or other such attachments must not be used.
  • When U-bolts are used for eye splices, the U-bolt must be applied so that the “U” section is in contact with the dead end of the rope.
  • When U-bolt wire rope clips are used to form eyes, the following table must be used to determine the number and spacing of clips.
Improved plow steel, rope diameter (inches) Number of Clips Drop Forged Number of Clips Other Materials minimum spacing (inches)
1/2 3 4 3
5/8 3 4 3 3/4
3/4 4 5 4 1/2
7/8 4 5 5 1/4
1 5 6 6
1 1/8 6 6 6 3/4
1 1/4 6 7 7 1/2
1 3/8 7 7 8 1/4
1 1/2 7 8 9