Chain is ubiquitous in theatrical rigging. Motor chain, hand chain, safety chain, chain slings, and decorative chain all appear in performing arts facilities. Unlike rope, which signals its condition through surface texture, color, and fiber integrity, failing chain can look identical to serviceable chain right up to the moment it breaks. Understanding chain grades, load ratings, inspection criteria, and the critical differences between chain types that are safe for overhead rigging and those that are not is essential knowledge in the performing arts.

Chain Grades: The Critical Distinction

Not all chain is created equal. Chain is manufactured in grades that indicate the tensile strength of the steel and the working load limits the chain can safely carry. The grade is the single most important factor in determining whether a chain is appropriate for overhead rigging. The grades used in entertainment rigging are:

• Grade 80 (Alloy Steel Chain): Working load limit is calculated at approximately 80% of the proof load. Grade 80 is the standard specification for overhead lifting, rigging, and chain hoists in entertainment and industrial applications. It is manufactured with controlled alloy steel and tested to established standards. Grade 80 chain links are typically marked “8” or “80” and are commonly painted orange, though the critical identifier is the grade marking on the link, not the color.
• Grade 100 (Alloy Steel Chain): Stronger than grade 80 for the same chain diameter, allowing a higher working load limit in a smaller, lighter package. Used in chain hoists and rigging applications where load capacity per unit weight is important. Marked “10” or “100” on the links.
• Grade 120: The highest commonly available grade, used in specialized high-capacity hoist applications. Less common in general theatrical rigging.
• Proof Coil (Grade 30): Standard hardware store chain, used for non-overhead applications (decorative chain, tent stakes, bicycle locks). It has much lower tensile strength than alloy chain. Proof coil chain must NEVER be used for overhead rigging. It cannot be reliably identified by appearance alone — it may look similar to grade 80 chain but will fail at a fraction of the load.
• High Test (Grade 43): Stronger than proof coil, used for towing and tiedown applications. Still not rated for overhead lifting and must not be used for overhead rigging.
• Transport (Grade 70): Used for securing loads in transit. Not rated for overhead lifting.

The most dangerous chain in theatrical use is unmarked chain of unknown grade. Any chain without clear grade markings must be treated as proof coil (grade 30) and must not be used for overhead rigging. This includes salvaged chain, old chain with worn markings, and any chain whose source and grade cannot be verified. When in doubt, replace it.

Chain Hoists in Theatrical Rigging

Chain hoists — also called chain falls or chain blocks — are the workhorse lifting device for theatrical production. Hand-operated chain hoists use a hand chain and gear reduction to lift loads on a load chain. Electric chain hoists use a motorized drive. Understanding the difference between standard industrial chain hoists and entertainment-rated hoists is critical for anyone specifying or using this equipment.

Industrial vs. Entertainment-Rated Hoists

Standard industrial chain hoists are designed for maintenance and material-handling applications. They are not designed for the duty cycle of entertainment production (continuous operation through load-in, show, and load-out cycles, often at or near rated capacity) and they are not designed to hold a suspended load overhead for extended periods during a performance. An industrial hoist used as a theatrical flying device is being used outside its rated application.

Entertainment-rated electric chain hoists meet the requirements of ASME HST-4 (Performance Standard for Electric Chain Hoists) and are tested to the additional requirements of the entertainment industry. They incorporate safety features including:

• Dual-limit switches (upper and lower) with a secondary upper limit switch to prevent over-travel and chain jumping.
• Mechanical load brakes that hold the load if electrical power is lost.
• Overload protection to prevent the hoist from lifting loads in excess of its rated capacity.
• Slip clutches (on some models) to prevent over-tensioning of the load chain.
• Documentation of service history and load test certification.

Load Chain Inspection

The load chain is the component most subject to wear in a chain hoist. ASME B30.16 (Overhead Hoists) specifies removal-from-service criteria for chain. The most important criteria for load chain:

• Wear: a chain link whose cross-section has worn to 90% or less of the original diameter (i.e., 10% or more wear) must be removed from service. Measure link cross-section with a caliper at the point of maximum wear.
• Stretch: if a section of chain has stretched more than 3% from its nominal (new) pitch, the chain must be removed from service. Compare a 10-link section of the load chain to the manufacturer’s specification for 10-link pitch.
• Cracked, bent, or twisted links: any link showing a crack, significant bend, or twist must be removed from service. Do not attempt to straighten bent links — a bent link has been stressed beyond its yield point and cannot be reliably returned to rated strength.
• Corrosion: surface corrosion (rust) that does not pit the metal surface is typically acceptable if cleaned and lubricated. Pitting corrosion (where the rust has created surface depressions) reduces the cross-section of the link and may require professional evaluation.
• Heat damage: chain that has been exposed to fire, significant heat, or welding spatter must be proof-load tested or retired. Heat affects the temper of the alloy steel and reduces its strength in ways not visible externally.

Chain Slings

Chain slings are assemblies of alloy chain with hardware (hooks, links, and master links) used to create a rigging sling for lifting loads. Chain slings are rated for different configurations:

• Vertical hitch: the simplest configuration, with the load suspended straight below the attachment point. The working load limit of the sling equals the rated capacity of the chain in this configuration.
• Choker hitch: the sling is looped around the load and back through itself (or its own hook). The choker hitch reduces the working load limit to approximately 75% of the vertical hitch rating due to the angle at the choke point.
• Basket hitch: the sling goes under the load and both ends attach to the lifting hook. The working load limit depends on the angle the sling legs make with the vertical. At 0 degrees (both legs vertical), each leg carries half the load. As the angle increases (legs spread further apart), the tension in each leg increases dramatically — at 60 degrees from vertical, each leg carries the full rated load and the total lift capacity is reduced to the single-leg vertical rating.

The angle effect on sling tension is one of the most commonly misunderstood concepts in rigging. At a 45-degree angle from vertical (the sling legs form a 90-degree included angle), each leg is carrying approximately 141% of what it would carry in a straight vertical pull. At 60 degrees from vertical (120-degree included angle), each leg carries 200% of the vertical tension. Sling angles greater than 60 degrees from vertical (120-degree included angles) create tensions that exceed the vertical working load limit and are not recommended.

Safety Chain in Theatrical Applications

Safety chain is a secondary retention device, not a primary rigging device. Safety chains catch items that have failed their primary attachment; they are not designed to support the load under normal circumstances. Using a safety chain as the primary rigging device is always incorrect. Safety chains in theatrical applications:

• Equipment safety chains (on lighting instruments, for example) use chain sized to catch the instrument’s weight with a short fall. They are not rated for the full rigging design factors required for primary overhead loads.
• Motor chain safety loops (dead-end clips that prevent the motor chain from falling if the master link fails) are a required safety feature on entertainment chain hoists used in overhead applications.
• Decorative chain (used as a set piece, costume element, or prop) must be segregated clearly from rigging chain and must not be repurposed for load-bearing use.

Inspection and Retirement Program

Chain used in theatrical rigging must be inspected before each use and formally inspected on a scheduled basis. The formal inspection should be conducted by a qualified rigger and documented in writing. Retirement criteria:

• Any chain whose grade cannot be confirmed is retired or relegated to non-overhead use.
• Any chain link showing the wear, stretch, cracking, or heat damage criteria described above is retired from overhead use.
• Chain hoists should be load-tested to 125% of rated capacity annually or per the manufacturer’s schedule.
• Documentation: each chain and chain hoist used in theatrical rigging should have a tag or record showing its rated capacity, last inspection date, and any maintenance performed.

Key Takeaways

• Only Grade 80 or Grade 100 alloy chain may be used for overhead rigging. Proof coil (Grade 30), high test (Grade 43), and transport (Grade 70) chain must never be used overhead.
• Unmarked chain of unknown grade is treated as proof coil and not used for overhead rigging.
• Load chain must be inspected for wear (10% wear = retire), stretch (3% stretch over 10 links = retire), cracks, bends, twists, corrosion pitting, and heat damage.
• Sling angles matter: a sling leg at 60 degrees from vertical carries double the tension of a vertical lift. Do not exceed 60-degree sling leg angles from vertical.
• Entertainment-rated chain hoists are not the same as industrial hoists. Entertainment hoists include safety features (dual limits, mechanical brakes, overload protection) required for overhead theatrical use.
• Safety chain is secondary retention only. It must never serve as the primary rigging element.

References

American Society of Mechanical Engineers. (2021). ASME B30.16: Overhead hoists. ASME.

American Society of Mechanical Engineers. (2022). ASME B30.9: Slings. ASME.

American Society of Mechanical Engineers. (2014). ASME HST-4: Performance standard for electric chain hoists. ASME.

Occupational Safety and Health Administration. (n.d.). Slings. 29 CFR 1910.184. U.S. Department of Labor.

Entertainment Services and Technology Association. (2019). ANSI E1.6-1: Entertainment technology: Powered hoist systems. ESTA.

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