In a letter published on the ATA's web site, ATA Vice President of Engineering Larry Strawhorn explains to officials at the NACM that the way they assign "safety ratings" to chains actually discourages truckers from using stronger chains to secure loads.
Grade 7 chain, designed specifically for load securement, is lumped together with Grade 8 and Grade 10 chains, which are designed for heavy lifting. All three carry a "safety factor" of 4.
However, lower-strength chains not specifically designed for load securement have a safety factor of 3. This means fewer of them are required under law to secure loads.
Why? Since 1993, truckers have been required to use chains with a "working load limit" equal to 1/2 times the weight of the load. If a chain has a working load limit of 250 pounds, truckers would need one chain for every 500 pounds of load.
A 3/8-inch Grade 4 chain has a safety factor of 3 and a breaking strength of 16,200 pounds, Strawhorn says. That means the chain has a working load limit of 5,400 pounds, and one chain is required for every 10,800 pounds ofload.
In comparison, a 5/16 inch Grade 7 chain has a safety factor of 4 and a breaking strength of 18,800 pounds. That means the chain has a working load limit of 4,700 opunds and one chain is required for every 9,400 pounds of load.
A Grade 7 chain actually has a 16% greater capability than a Grade 4 chain, Strawhorn says -- but it's limited to a 13% smaller load. As a result, carriers by law must use more of the stronger chains than they would the weaker one.
"Past regulatory practice and industry experience show that, employed in conjunction with the stipulations in the Federal Motor Carrier Safety Regulations, a safety factor or 3 is appropriate for chain that is used to secure cargo," Strawhorn writes. After describing the way the safety factors penalize the use of the stronger chain, he asks that all chain be assigned a safety rating of 3 when used for load securement purposes.
ATA is asking its members to contact NACM and their chain and load securement suppliers and ask them to change the safety factor for grades 7, 8 and 10 chains when used for load securement.