Many countries issue their own standards which normally mirror the two international standards – ISO4347 or BS29.B.
The International ISO standard contains LL & LH (BL) and the American standard contains BL (LH). The key difference in the standards is that the ISO standard contains a minimum fatigue requirement.
Conversion of an inch in the American standard to European metric also throws up some small dimensional differences.
It is recommended that the leaf chain standards are used as a dimensional reference only, particularly for leaf chain anchors bolts slots, as this will ensure interchangeability.
While all leaf chains should meet the minimum tensile requirements of the standard, each manufacturer will have their own data which may be significantly different.
There are currently three levels of safety requirements that a leaf chain must fulfil. The first is the Machinery Directive 2006/42/EC, implemented in the UK as the Supply of Machinery (safety) Regulations 2008, which requires a minimum safety factor of 4:1.
This means that the minimum tensile strength of a leaf chain must be four times the maximum load it is used to support.
However, most leaf chain manufacturers recommend a greater safety factor.
For example, ISO 4347:2015 requires a factor of 5:1. Different legal requirements also apply to different types of machines.
Standard forklifts and telescopic handlers, for example, require a factor of 5:1; while man-up forklifts and passenger lifts require a factor of 10:1 and 20:1 respectively.
Other factors that need to be considered when selecting a leaf chain are:
- The number of load cycles
- The number and size of shock loads
- Internal bearing pressure
- The diameter of the chain roller/pulley
- Environmental conditions
All machinery supplied in the European economic area must comply with the machinery directive 2006/42/EC (with specific reference to 126.96.36.199. pulleys, drums, wheels, ropes and chains) which sets out the design requirements for leaf chain.
It’s important to bear in mind though that this directive is generic and covers all types of chain used in lifting.
For leaf and roller chain, most manufacturers would neither approve or recommend a design which uses the 4:1 safety factor contained in the machinery directive as it is a minimum standard only.
- The main standard for telehandlers is: EN1459 Rough-Terrain Trucks – Safety Requirements and Verification – Part 1: Variable Reach Trucks.
- The main standard to consider for boomed access platforms is: BS EN 280:2013+A1:2015 (which covers mobile elevating work platforms, design calculations and stability criteria.)
- The requirements for leaf chain systems are contained in sections 188.8.131.52 of EN 1459-1 and 184.108.40.206 of EN 280.
Design engineers should note however that the Mobile Elevated Work Platform (MEWP) standard refers to the leaf chain system and a decision needs to be made as to which parts of the design are included in the leaf chain system.
Many machine manufacturers take this to mean leaf chain and chain anchor bolts, supplied together, as a leaf chain assembly.