Leaf chain environmental conditions
The various environments in which materials handling forklift truck chain and leaf chain mechanisms operate differ widely. Forklift truck chain may be exposed to normal outdoor moisture or even highly corrosive industrial atmospheres. Forklift truck chain may also be subject to abrasion from sand or grit.
Some of the key environmental challenges for forklift truck chains are listed below.
Moisture – Produces corrosive rusting. This reduces the strength of the leaf chain through pitting and cracking.
Temperature – Low temperatures can make a forklift truck chain brittle. If a lift truck’s daily activity involves constantly moving in and out of cold stores, condensation will form on the outer and bearing surfaces of the chain. This moisture will cause stiffness and eventually corrosion fatigue cracking. This reduces the service life of a forklift truck chain.
Chemical solutions or vapours – Chemical solutions and vapours will corrode leaf chain components, anchor pins, anchor bolts, anchor blocks and typically cause microscopic stress cracking. According to the extent of exposure, cracks will propagate across the forklift truck chain leading to complete and abrupt failure.
Abrasives - Accelerated wearing or scoring of the pin surfaces and link plate apertures will also lead to reduced forklift chain strength. Because the bearing surfaces of these articulating members are not readily accessible, the wear is not usually visible. As a result, the extent of chain wear should be regularly inspected using a precision tool such as the FB Professional Chain Wear Gauge.
Each specific forklift truck chain application should be evaluated for risk according to the extent of exposure to the above and an assessment of the particular area of operation. Leaf chains should be frequently inspected and a schedule for the replacement of worn leaf chains should be established to avoid potential forklift truck chain failure. Leaf chains should be inspected more or less frequently depending on the type of environment the forklift truck is operating in and the particular hazards it is exposed to. However, the frequency of forklift truck inspections must always 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. It is also recommended that forklift truck users are familiar with all the relevant Health and Safety guidance notes and particularly PUWER 98. Others guidance documents published by the British Industrial Truck Association (BITA GN15 & GN28) and the technical bulletins of Fork Lift Truck Association (FLTA TB 02, 05, 08 & 09) should be noted as well.
Inspection procedure development for leaf chain should continue until a projected time of replacement can be estimated. By its very nature a forklift truck leaf chain should be viewed as an expendable item and a safe leaf chain replacement schedule established.
In addition, it is advisable for forklift truck chains that operate in arduous, harsh or aggressive environments (including cold stores, marine, corrosive chemical, metal manufacturing or processing, cement/ aggregate processing and brine processes) to have their leaf chains and leaf chain anchor pins replaced after no more than 4000 operating hours or two years (whichever is the shorter). Furthermore, if a lifting mechanism uses a single leaf chain (e.g. free lift section), any leaf chain anchor bolts should be replaced together with the chain.