What Are Slings?
The lifting component that connects the hoisting device to the load is called a sling. While a textile fiber choker is often looped around a load to actually look like a sling, wire rope and chain are considered slings too. A chain sling generally consists of a master link, a chain leg (the smaller links), and some type of terminating fitting such as a hoist hook.
What Are The Chain Sling's Advantages?
Slings fabricated from chain are capable of combating against a load's sharp edges that can be abrading to other sling materials. They are suitable for harsh environments such as steel mills, foundries, and machine shops. Chain slings are the most flexible type of sling and are easily repaired in the event of damage.
CAUTIONARY NOTE Repaired slings require proof testing and re-certification.
The Chain Material
For obvious reasons, chains are fabricated from steel. The steel is highly alloyed. This means that additional elements are added to plain carbon steel to improve the mechanical characteristics. For greater strength the alloyed steel is heated then cooled. This is called heat treating and tempering.
What Are The Standards For Chain Materials?
The National Association of Chain Manufacturers (NACM) has developed welded steel chain specifications that establish nine different grades of chain. OSHA guidelines indicate that chains for overhead lifts be manufactured and tested in accordance with ASTM (American Society for Testing and Materials) standards. These are ASTM A391 for Grade 80 and ASTM A973 for Grade 100. ASTM A906 covers rating and testing.
What Is The Difference in Grade 80 and Grade 100?
Namely, strength. The numbers represent 10% of the metric tensile (breaking) strength of the chain in megapascals (MPa). In U.S. English units these two tensile strengths are approximately 115,000 and 145,000 pounds per square inch for Grade 80 and Grade 100 respectively.
CAUTIONARY NOTE Only chain slings of the same type and grade should be used in combination with hoisting fittings of equal rating.
How Are Chains Marked?
According to OSHA, welded alloy steel chain slings must have permanently affixed durable identification stating size, grade, rated capacity, and sling manufacturer.