What to look for when comparing quality between leaf chain suppliers

All leaf chain manufacturers will have their own ideas on the best combination of material, heat treatment and process for making good leaf chain but there are certain factors you can rely on to objectively compare quality.

Since material and heat treatment are specified by the manufacturer, we recommend comparing the following four fact-based measures of quality when looking for a new leaf chain supplier.

1. Consistent tensile strength

Each type of machinery – whether a forklift truck, telehandler or piling machine – will be made to a standard requiring a certain safety factor, usually 5:1 (where the minimum breaking load of the leaf chain is five times greater than the safe working load). The figures published for tensile strength (the resistance of a material to breaking under tension) are usually lower than those achieved during actual testing, so it is as much about consistency of test results. This can be referred to as standard deviation or dispersion.It is often better to choose a leaf chain with lower but consistent tensile strength than the strongest chain on the market with unreliable test results. The chain industry can get pretty competitive over tensile strength but as components are hardened to make chains stronger, they also become more liable to break under shock loads.

Two of the world’s largest industrial chain manufacturers have higher tensile strengths than the leaf chain standard ISO4347 requires but with test results varying by 20%. We always recommend checking the test certificate that arrives with the product and comparing it to the requirements of the original design to ensure you have a reliable quality chain that meets your safety needs.

2. High fatigue strength

Manufacturing quality leaf chain requires many different elements to be consistently correct. One of the best ways to see how all these elements combine is fatigue testing. Fatigue strength is the highest stress a material can withstand for a given number of cycles without breaking and is a measure of the chain’s ability to endure loading over time. Many chain manufacturers use high frequency machines to carry out fatigue testing but we recommend servo hydraulic test machines which better control loads

The ISO1564 fatigue test method for transmission precision roller chains describes the practice for testing a leaf chain to ISO4347;2015, which is a lengthy and complex process and produces a staircase graph. For the purposes of comparison, we recommend picking a figure at or above the normal working load of the leaf chain in your application and then running the test to three or five million cycles.

The table below give an overview of the differences: 

3. Pitch/length tolerance

High quality chains have close tolerances on the chain pitch and the bores in the link plates will be very precise. Chain that begins life as close to its nominal pitch as possible will have a long operating life as wear is measured from the theoretical starting point and it will be easy to quickly and consistently set up during assembly. If the length of your leaf chain varies dramatically between the batches provided by your chain supplier, you may find it difficult to follow the same pre-tension and installation procedures. This can result in uneven loading and over-tension once you add the calculated working loads. Measuring the parts and length of the leaf chain over a few batches will indicate any inconsistencies and give you an idea of how rigorous the manufacturer’s process control is.

4. Resistance to push out force

The nature of the applications many leaf chains operate in along with inadequate lubrication result in excess internal friction, which manifests as turned pins. Measuring the interference fit between the outer plate will show the chain’s ability to resist the turning force. 

FB Chain is not a large chain manufacturer and is not the cheapest, but you can rely us on for quality, safety and peace of mind. We pay careful attention to every detail, designing and manufacturing our leaf chain to withstand shock loads, maintain strength, minimise elongation and resist wear. Each product is issued with a test certificate and is clearly marked with a tracking or batch number, enabling it to be traced back to its raw materials. This helps our customers to operate safely, cost effectively and with maximum uptime.

Please get in touch to discuss how we can meet your leaf chain needs.