The FB chain wear gauge has been precision manufactured and accurately toleranced.
The manufacturing process includes calibration referenced back to National Calibration Standards with each unit undergoing thorough final inspection.
While the instrument cannot be adjusted for calibration, it can be checked by simply closing the slide fully and reading from the 'Percentage Wear' window the accuracy to tolerance.
In the unlikely event that the instrument moves out of calibration into the ± zones it will be as a result of wear to the moving components and should not, therefore, be used other than as a guide.
Similarly, if the 'V' jaws are damaged, the instrument may not perform accurately.
The nominal pitch of the chain must be measured over the pin centres of one of the OUTER link plates.
To assist in this the instrument is provided with three separate pairs of red arrows.
Utilise one of the pairs located on the edges and the centre of the gauge. Depending upon ease of access to the chain one pair will be more suitable than the others.
Locate the arrows over the pin centres of the chosen outer link plate and the nominal pitch of the chain will appear in the 'Pitch' window on one side of the instrument or the other.
Select and use the correct side of the gauge relevant to the measured nominal pitch as follows:
|A SCALE||B SCALE|
|1 1/2"||2 1/2"|
Once the pitch has been determined the number of pins (n) that the chain wear is to be measured over will appear in the adjacent 'Measure over Pins' window.
Identify the section of chain that regularly runs over the pulley as this part of the chain is the most susceptible to wear. Measurements must then be made in at least three separate locations on this section.
With the chain under load and using the correct scale, place one 'V' jaw of the instrument over the first pin (pin number 1) of the selected section and then extend the slide until the other 'V' jaw locates over the pin (as previously determined).
The percentage of wear will appear in the box at 0.25% (¼%) increments
Whilst viewing the 'Percentage Wear' window, ignore any readings in the 'Pitch' and 'Measure over Pins' windows.
If the instrument shows a 2% or greater elongation, the red indicator will completely fill the window. This is a warning that the chain requires replacing.
A judgement must be made, by the competent person, as to the likelihood of the elongation reaching 3% before the next thorough examination. The competent person must also specify a safe time limit to ensure renewal of the chain prior to the elongation reaching 3%.
The chain wear gauge will show wear up to 4%. Any chain used for lifting with a measured elongation of 3% or more is dangerous and must be renewed immediately.
Until the chain is renewed the equipment to which it is fitted must not be used.