Some signs of leaf chain wear are obvious. Turned pins, for example, are easy to spot and are an indication that a leaf chain will need to be replaced as a matter of urgency.
But other forms of leaf chain wear, may be less visible, which means leaf chain needs to be routinely measured to ensure that it is not exceeding the accepted percentage of elongation.
At the same time it is important to bear in mind that there can be an over-reliance on leaf chain elongation when conducting a leaf chain inspection. What is important is to take into account all the operational factors that can have an impact on leaf chain wear.
In this blog post we discuss some of the key considerations that will help to guide your leaf chain inspections and to ensure the safe and consistent operation of your materials handling equipment.
Leaf chain elongation
A leaf chain is considered to have worn beyond its safe service life when the nominal pitch length has been extended by between 2% and 3%.
A leaf chain that is elongated by 2% is a sign that the dynamic life of the leaf chain has been impacted and the ultimate breaking strength has been reduced. At this stage of wear, the leaf chain is considered to be becoming dangerous which means that the designated competent person will need to determine the safe time limit for its replacement.
If the extent of leaf chain elongation has exceeded 2%, but is less than 3%, then the competent person will either choose to recommend immediate replacement, or will set out a time limit for renewal within three months of the date of examination.
When a leaf chain has elongated by 3%, or more, it is considered to be dangerous and will need to be replaced straight away. And until such time as the leaf chain has been replaced, any equipment to which that leaf chain is fitted will also be deemed unsafe to use.
How quickly a leaf chain will wear depends upon that leaf chain’s operating environment and the number of duty cycles it is required to undertake.
In order to conduct a thorough assessment of wear, it is important that the technician is mindful of all the following factors:
- The general condition of the leaf chain
- The rate of deterioration since the leaf chain was last examined
- The nature of the loads that the leaf chain is required to carry
- The type of surface that the specific form of materials handling equipment is operating on
- How long it is till the next examination regime will be carried out
- Evidence of local damage or wear
- The quality and frequency of the maintenance that has been previously carried out
- The frequency of work or duty cycles per day/week that are expected of the leaf chain
- Whether the leaf chain is working at, or close to, its maximum operational capacity
- The condition of the travelling surfaces over which the equipment is required to operate
- The nature of the working environment, for example whether the conditions are wet, dry, dusty, hot, cold, abrasive or corrosive
Industry guidelines and specifications
For an independent reference of recommendations on leaf chain wear, it is always advisable to refer to the following leaf chain standards:
ASME B29.8 Leaf Chains, Clevises and Sheaves – this is the international chain standard of prescribed specifications which requires that leaf chain is manufactured to specific guidelines and minimum tensile values. The standard also includes supplementary information on maintenance and lubrication.
BITA Guidance Notes GN15 – produced by the British Industrial Truck Association (BITA), this is a detailed technical publication that clarifies specific and vital aspects of safe fork-lift truck operation.
The Safety Assessment Federation (SAFed) MLCC01 – which provides guidance on the in-service inspection procedures for lifting equipment.
The frequency of forklift truck inspections must also comply with the minimum legal requirement as detailed in LOLER 98, regulations 9, 10 and 11, for the Thorough Examination and Inspection of Industrial Truck Leaf Chain.