Chains Explained: Sizes, Grades, WLL, and Applications

HD1 Chain Kit
Selecting a Chain for Your Application

Rigging and the tools we use to do the rigging can be a new field for Firefighters. In this article we will attempt to define some of the terms used to explain chain. Many of the terms can also be used to explain performance of wire or synthetic rigging too. It is important to understand that all these tools have their limitations, and must not be taken for granted. Understanding these capacities/terms is essential to a successful and safe rescue. 

There are several “grades” of chain to select from. Due to safety concerns chain manufactures differentiate between various materials, types of chain and the specific applications they should be used for. ASTM (American Society of Testing & Materials), ASME (American Society of Mechanical Engineers) and OSHA (Occupational Safety & Health Administration) publish safety standards and regulations for the manufacturing, testing, use, inspection and repair of chain. (1)

Chain is heavy, but rugged. It doesn’t need edge protection, but can slip on hard smooth loads. Used a lot in concrete rigging, use caution when wrapping steel loads the chain can slip. Good choice for vehicle rescue, the 3/8 grade 7 or 8 has sufficient capacity to pull doors, steering wheels, stabilize large trucks and cars. Good temperature range.

Chain Grades 

The most significant way to identify chain is its “grade”. Grades (G) are based on the ultimate breaking strength of that chain. These numerical grades are; G30, G43, G70, G80 & G100. The number is derived from a mathematical formula. As an example, G80 means that the maximum stress on the chain at ultimate strength is 800 newtons per millimeter squared.

An ultimate strength test is a type of destructive test where the component is loaded to failure. An ultimate test can help determine the load at which a component will start to deform irreversibly. This figure is expressed in the in-Kilo newtons and or pounds. This is a theoretical figure at which a chain will fail in a destructive tensile test. It is tested at room temperature. (5)

Grade 30, also known as Proof Coil. ASTM specification 413, low strength carbon steel, no overhead lifting. Light weight capacity chain used for non-critical loads, not suited for rescue work.

Grade 43, also known as High Test. ASTM specification 413. Carbon steel. Used in logging, agriculture and similar work. Not for overhead lifting. Not for rescue work.

Grade 70, also known as Transport Chain. ASTM 413 specification, carbon steel. 1.46 pounds per foot. Used by truckers to secure loads, and vehicle recovery operations. This grade chain is sufficient for most rescue work, but not for overhead lifting. Typically has a gold chromate finish so Department of Transportation officials can easily identify this chain.

Grade 80, also known as Alloy Chain. ASTM specification 391. This heat-treated chain is certified by OSHA for overhead lifting. The most common grade chain for rescue work. Temperature range -40°F to 400° F. WWL 3/8 - 7100 pounds. 1.47 pounds per foot. Usually seen with a black powder coat finish.

Grade 100, also known as an Alloy Chain. ASTM specification 973, slightly lighter and much stronger than Grade 8 chain, this alloy is gaining in popularity, and is replacing grade 8. WWL 3/8 -8800 pounds. 1.44 pounds per foot. Typically has a black finish, but can be customized. ASTM requires that alloy chain can elongate no more than 20% before fracture.

 Grade 120, also known as Winner Pro. Has a blue or green powder coat for corrosion resistance. This fairly new grade does not have an ASTM specification yet, it exceeds ASTM 973. Very expensive and stronger than Grade 100.  G120 offers a design factor of 6:1 compared to G80 with 4:1. WLL 3/8 -10600. Working temperature up to 570° F. 1.75 pounds per foot. (3)

General Chain Operational Considerations 

•	All chains should be periodically inspected for cracks, gouges, wear, elongation, nicks, and suitability. Inspection standard should follow ASME publication B30.26 (10) inspection criteria.

•	Avoid lifting objects over people’s head, if necessary, only do so with grade 8 or higher.

•	Exposure to chemically active environments such as acids or corrosive liquids or fumes can reduce a chain’s performance.

•	If chains are to be used outside the recommended temperature range ( -40 °F to 400 °F), the user should first consult the chain’s manufacturer.

•	When mixing chain or component types, all should be rated at the working load limit of the lowest-rated component or chain.

•	Alloy Chain Sling shall have legible identification tag stating: (8)

o	Name or trademark of the manufacturer (often stamped on the chain), or if repaired, the entity performing repairs.
o	Grade, nominal chain size, length, number of legs if applicable.
o	Rated load for at least one hitch type and the angle upon which it is based.
o	Individual sling identification number. Usually assigned by the owner of the sling.

Terms used in describing chains and rigging.

SWL and WWL. Safe Working Load is an older term you still see, Working Load Limit is what most manufactures use, stamped/printed on their rigging products. They mean the same thing. It is the capacity you should not exceed. There will be deductions in capacity caused by certain rigging configurations, that discussion is beyond the scope of this article. (7)

Proof stress is the practical limit beyond which a material would permanently deform without breaking. With further applied stress, a material can ultimately undergo fracture. (6)

Virtually the same as proof test, yield strength of a material represents the stress beyond which its deformation is plastic. Any deformation that occurs as a result of stress higher than the yield strength is permanent. (5)

Without some familiarity in these special terms, it can be confusing to select the best chain for your application. In rescue trial and error is a poor plan and we must engineer our tools/techniques and get the job done right, the first time, by making an informed choice of tools we are better equipped to make the rescue.