Proposed changes to ISO 4347 – the international standard governing the manufacture of the type of leaf chain used by forklift truck manufacturers to operate a lift truck’s mast – will require chain manufacturers to demonstrate that their products offer high levels of ‘fatigue’ resistance (dynamic strength).
At present, chain suppliers – who provide chain to original equipment manufacturers (OEMs) as well as forklift dealers, who replace worn or damaged lift truck chain – are only required to demonstrate that their products comply with ‘breaking load’ guidelines.
A chain’s ‘breaking load’ (ultimate tensile strength) indicates the stress or force that can be applied to a chain before it breaks or ruptures.
By introducing an element of fatigue resistance testing to ISO 4347, the International Standards Committee will require that chains are manufactured with good endurance levels as well as high breaking loads.
This combination will ensure that chain users can specify products for use on their materials handling equipment and other machinery that is fit for purpose and will provide the longest life and – therefore – the lowest operational costs.
"A high breaking load alone does not indicate that a chain will have a long life," says Jim Cameron, technical director of FB Chain Ltd and a member of the International Standards committee tasked with overhauling the current guidelines.
The proposed changes to ISO 4347 will require chain manufacturers to show that their chain will withstand a minimum dynamic load for at least 3 million cycles.
Jim Cameron adds: "A chain’s ability to provide good ‘fatigue’ resistance whilst maintaining high breaking loads is a far more accurate guide to the chain’s quality and suitability.
"Most good chain manufacturers will know the fatigue limits of their products and engineers looking to design in or replace a lift truck chain should be taking fatigue limits into consideration as well as breaking loads.
"Anyone tasked with acquiring new leaf chain should ensure that what they are buying has been thoroughly tested for both ‘breaking load’ and ‘fatigue resistance’."
The changes to ISO 4347 are expected to be adopted within the next 12 months.