What are the rated loads for chain slings used in hot-dip galvanizing?

The American Galvanizers Associations (AGA) Galvanizing Note, Steel Chain for Hot-Dip Galvanizing, details a study performed to determine the type of chain that will provide the best performance for overhead lifting use in a galvanizing facility. The study focuses on finding the breaking strength of chain at the elevated galvanizing temperature and at the end of life condition.  The end of life condition, or EOL, was defined as a fifteen percent loss in diameter of the chain due to use in the hot-dip galvanizing process. A Galvanizing Guideline, Chains for Overhead Lifting, was produced based on the results of this study and gives specific procedures for determining the working load limit of chain slings in a galvanizing plant. The article presented here is meant to summarize this Galvanizing Note for quick reference. If non-members would like access to either of these notes, please contact your local galvanizer. 

Table 1 (below) is from the guideline, Chains for Overhead Lifting, and does an excellent job of summarizing the rated loads of given chain and sling types to be used in a galvanizing plant. A rated load is the amount that can be safely lifted according to OSHA standards and the study conducted by the AGA. Information about the strength of chains at their end of life condition determines the rated loads listed in the chart. 

Based on the AGAs study, the working load limit of chains at elevated temperature depends on the nominal chain size and the material (grade) of chain being used. This information, coupled with the type of sling being used and the horizontal angle formed between the inclined leg and the horizontal plane of the load, yields the rated load for chain slings used for hot-dip galvanizing. To better understand this table, we will go through each one of these factors, and discuss how they affect the rated load.

Chain manufactures classify the diameter of each chain link as the nominal chain size. The galvanizing procedure reduces the diameter of the chain in time, but the nominal chain size remains the same and will be used to describe the same chain through the end of life conditions. With a given chain material, the chain strength will increase as the nominal chain size increases. Table 1 (above) associates nominal chain sizes with rated loads. 

The fact there are two different chain materials listed on the table means each nominal size is listed twice. It is important to make sure the correct row is associated with the correct nominal size and chain material. The blue columns in the chart highlight where the nominal chain sizes are found in both standard and metric measurements. 

The strength of the material used to make a chain determines the grade of the chain. Stronger materials receive a higher grade rating. Findings from the AGA study recommend not using grade 63 and higher chains in a galvanizing environment due to the potential development of hydrogen embrittlement. Therefore, the table only lists two grades of chain to be used in hot-dip galvanizing operations. The green rectangle highlights the rated loads of grade 30 chains, while the yellow rectangle highlights the rated loads of grade 43 chains.

Every pairing of nominal chain size and chain material can be used in combination with every sling type listed in the table. The geometry of the sling type and horizontal angle between the chain and the load determine the force applied to each length of chain. The results of the AGAs study on steel chains for overhead lifting and the given geometry of slings determine the rated loads listed in Table 1.  

The horizontal angles are highlighted in orange. Each sling type, with corresponding rated loads, is outlined by a red rectangle. The highlighted chart in this article is a quick reference for checking what rated loads can be used with what chain size, chain strength, sling type, and horizontal angle in the hot-dip galvanizing industry. This should not be used as a complete reference, rather, it is merely a supplement to the AGAs Galvanizing Guideline Chains for Overhead Lifting. The Guideline itself is the complete reference which includes operating practices, sling identification, inspection and repair procedures, and record keeping with a sample chain log. Read the entire Guideline for a better understanding of chains for overhead lifting used in a hot-dip galvanizing operation.