Leaf chain wear is measured manually by checking for elongation over a section of the chain.
Leaf chains, commonly used in lifting applications like forklifts, experience wear primarily in the pin and plate holes, leading to elongation of the chain. Accurately measuring this elongation is key to assessing the chain's condition and determining if it needs replacement.
The standard method for measuring leaf chain wear involves a manual measurement process focusing on the chain's pitch.
Manual Measurement Method
According to standard practices, including information from reliable sources, the accurate way to measure leaf chain wear requires measuring the chain over a significant number of pitches.
- Pitch Defined: A pitch is the distance between two adjacent link pins in the chain.
To get a reliable measurement of wear (elongation), you must measure over a series of these pitches, not just one.
Steps for Manual Measurement
Here's a breakdown of the process:
- Identify the Chain Pitch: Determine the nominal pitch of the chain. This is usually specified for the chain type (e.g., 1/2 inch, 5/8 inch, 3/4 inch).
- Select a Measurement Section: Choose a section of the chain, typically one that is subjected to the most work. For accuracy, you need to measure over a good number of pitches. A common practice is to measure over 12 or more pitches.
- Measure the Section Length: Carefully measure the total length of the selected section (e.g., the length spanning exactly 12 pitches).
- Calculate Expected Length: Calculate the original, unworn length of this section by multiplying the nominal pitch length by the number of pitches in your section (e.g., 12 pitches * nominal pitch length).
- Determine Elongation: Subtract the expected (original) length from the measured length. The difference is the total elongation over that section.
- Calculate Average Wear: To determine the average wear per pitch, divide the total elongation by the number of pitches you measured over. This calculation allows you to calculate the average wear.
Why Measure Over Multiple Pitches?
Measuring over a single pitch is not accurate because the amount of wear per pitch is very small. Wear accumulates over time across all the pins and plates in a chain. By measuring over many pitches, the small amounts of elongation from each pitch add up, making the total wear significant enough to measure accurately. This process also helps average out any minor inconsistencies in manufacturing or wear patterns along the chain.
Tool Considerations
While you can use basic measuring tools like a tape measure for this process, it's important to note that tape measures will also suffer from stretch and cheap ones are not very accurate. For the best results, specialized chain wear gauges designed specifically for this purpose or high-quality, certified measuring tools are recommended to ensure precision.
Measuring leaf chain wear is a critical part of maintenance, ensuring the safety and efficiency of equipment that uses these chains. The primary method is to measure elongation manually over a significant number of pitches and calculate the average wear.
