Specialist leaf chain supplier FB Chain regularly receives queries from forklift owners, struggling to calculate mast chain wear using a tape measure. In response the company has developed its own easy-to-use gauge that eliminates measurement and calculation errors.
Measuring leaf chain for wear is a vital part of the thorough examination required to meet LOLER and PUWER regulations for lifting equipment. If a chain has elongated by as little as 3% due to wear it is neither safe nor legal and could break at any time. Yet many service technicians fail to carry out this safety-critical task with a sufficient level of accuracy.
“A tape or steel rule is the traditional tool for measuring chain wear but it is fraught with difficulties,” says Peter Church, managing director of FB Chain. “The measurements involved are so small – 0.25% wear is only 0.75 mm over 300 mm (12 inches) – that even a slight misalignment can have a significant impact on the result.”
First it may be difficult to hold the rule steady and secondly it may be difficult to line up both start and end points at the same time. The position of the individual inspector’s eyes can also affect the reading – this is known as parallax error.
“To use a tape or steel rule accurately, you would need to be ambidextrous, have three hands and two pairs of eyes,” adds Church.
A large (20 inch plus) vernier calliper can help measure length more accurately as it can be locked into place but its size and weight also have their downsides.
Grade A in Mathematics
Even if an inspector has successfully passed this first stage, he or she now needs to perform some arithmetic to convert the increase in chain length into percentage wear. For example, a 5/8” pitch chain (15.875 mm) is measured over a length of 18 pitches and judged to be 286.7 mm.Using the following formula, wear is calculated at 0.33%.
X = ((L – (P x N)) x 100
(P x N) 0.33% = ((286.7 – (15.875 x 18)) x 100
X = percentage wear; L = measured length; P = pitch of chain and N = pitches measured.
“The calculation isn’t difficult but there is plenty of scope for errors, especially regarding the measuring distance,” says Church.
The easiest and most accurate way of measuring and calculating chain wear is to use FB Chain’s specially-designed chain wear gauge.
“Most chain manufacturers can supply gauges but these are typically flimsy promotional items. Others made of hard plastic or steel just show whether a chain is worn or not worn, which again is not especially helpful,” says Church. “Only the FB Professional Chain Wear Gauge can reliably help maintenance staff to plan service intervals and replacements.”
The FB Professional Chain Wear Gauge is a ‘how much worn’ gauge showing wear in 0.25% wear increments from 0-4% worn with a red warning box appearing at 2%. It is suitable for measuring wear on all leaf chains from 3/8 to 3 inch pitch.
Each gauge comes complete with a protective case and a set of comprehensive instructions detailing how to determine the nominal pitch of a chain and the correct measurement procedure. The straightforward design and positive pin location allow the FB Professional Chain Wear Gauge to be used as effectively by both skilled practitioners and novices.
Church concludes: “The patented FB Professional Chain Wear Gauge is now considered the industry standard and is used extensively by maintenance engineers and insurance inspectors all over the world. It’s not a giveaway item but, for a reasonable price, it adds a professional instrument to the armoury of any technician who understands the importance of recognizing precisely the amount of wear in a safety-critical lifting chain.”