Leaf chain is a type of chain found most commonly on telehandlers and forklift trucks. In both applications it plays a crucial role. Failure of a leaf chain component can result in catastrophic consequences – leading to a loss of production with associated financial implications or even worse, serious injuries to an operator.
Whatever the role of a leaf chain, it will inevitably wear, and this wear, if unchecked, will lead to failure. It is vital to take steps to prevent as much wear as possible and essential to monitor leaf chain wear so problems can be addressed before a major incident occurs. You should be aware that as well as measuring leaf chain wear to avoid any potential financial loss, it is also a legal requirement.
What affects leaf chain wear?
There are a number of factors that can lead to leaf chain failure, with the environment that the leaf chain operates in being a major factor.
Environmental effects include the following:
- Excessive moisture – this may lead to rusting, pitting and cracking
- Low temperatures or fluctuation between extremes of temperature can cause a leaf chain to become brittle
- Corrosive chemicals or vapours – perhaps not surprisingly – can cause deterioration in a leaf chain at a microscopic level.
- Abrasive materials such as sand or grit can also wear away at the moving parts of the leaf chain, causing wear that is not easy to spot with the naked eye.
In addition to environmental factors, the amount and frequency of use experienced by a telehandler, forklift (or any other machinery that uses leaf chain) affects leaf chain wear. Heavily used equipment – especially where it is used on multiple shifts – will hasten the speed of wear. Sudden increased loads or shocks caused by operating over uneven ground will also increase wear rates.
Although the operating environment can be a big factor in leaf chain wear, over 60% of all leaf chain defects are caused by poor lubrication. A properly lubricated leaf chain will last an estimated sixty-times longer that a dry-running leaf chain.
Lubrication can help to avoid the following problems:
- Noisy operation
- Surface rust
- Oint rust
- Stiff joints
- Twisted pins
- Loose pins
- Broken link plates
- Broken pins
- Unacceptable leaf chain elongation
Symptoms of leaf chain wear
There are many ways a leaf chain can wear including:
- Worn contours
- Worn surfaces
- Tight joints
- Missing parts
- Protruding or turned pins
- Cracked plates
- Fractured plates
- Arc-like cracked plates
- Enlarged holes
- Corrosive damage
- Worn anchor bolt connecting pins
Not all of these are visible to the naked eye.
How to check and measure leaf chain wear
Although important, a visual inspection of the leaf chain will only spot a few of the potential problems that can affect the safe working of a leaf chain. On its own, an inspection is unlikely to indicate whether the leaf chain is worn through normal use. The only way to be sure how much wear has taken place, and therefore whether the leaf chain is safe to use, is by measuring the chain.
Before going out and measuring a leaf chain, it’s important to recognise that like any set of components made of metal, a leaf chain will stretch slightly under load and will return to its normal length once that load is removed. This means that if you are measuring for wear, you will get different results if you measure the chain under load or without load.
To correctly measure leaf chain wear, you should measure it when it is under a small load equivalent to 1% of its tensile strength.
Measuring leaf chain wear by eye with a tape measure or steel rule is not recommended. (Bear in mind tape measures will also suffer from stretch and cheap ones are not very accurate) To measure leaf chain wear with any sort of accuracy you would need to measure over a good number of pitches (a pitch is the distance between two adjacent link pins) and then calculate the average wear.
The difference between a new chain and a normal leaf chain could be less than a millimetre and the markings on a steel rule or tape measure are almost as wide as this, making an accurate reading very difficult. A manual measurement can also suffer from inaccuracies due to parallax errors when viewing from different angles.
In addition, a calculation is required to assess the percentage of wear, which again is prone to error. The acceptable range of this percentage of wear is also small – less than 2% is acceptable but at 3% the leaf chain needs replacing.
Potentially, five different people measuring the same leaf chain might get five different results, and what’s worse, an unsafe chain may be incorrectly diagnosed as worn within acceptable limits.
Using a gauge
A more accurate reading is given if a measuring tool is used. Some of these are a little better than using a tape measure or steel rule, and many will still require some form of calculation.
Some give you a result of worn or not worn but give you no idea how worn an acceptable chain currently is. This is an issue because it gives you no idea of a timescale for replacement. Suddenly you will find yourself having to replace a leaf chain, disrupting production if you have no replacement part ready, along with the pain of an unplanned expenditure. Better to have an idea of how worn a leaf chain currently is, so you can plan for a programmed replacement.
The FB Professional Chain Wear Gauge
Probably the easiest way to measure wear accurately and painlessly is with a professional chain wear gauge like the one we have produced which is based on our many years of expertise in manufacturing, measuring and replacing leaf chain.
With many types of measurement, you have to know the pitch of the chain before you begin, but the FB Gauge will tell you this with a simple, quick check. Then it is easy to use the gauge to measure the leaf chain and display an instant percentage result without any calculation involved.
Apart from the legal requirements, knowing how worn a leaf chain on a telehandler or forklift is will give you an idea of a timescale for replacement and will avoid the unnecessary expense of a chain failure or the potential for serious operator injury. The use of a gauge, and in particular the FB Professional Chain Wear Gauge makes this a quick, efficient and easy task.