Few mines use loose nut indicators, a cheap and simple device that could prevent Sheq incidents.
The indicators are simply slid over torqued nuts, to point in the same direction to create a visual pattern. As soon as a nut comes loose, the pattern is broken, allowing an operator, machinist, driver or colleague to identify and report the nut.
The markers are used in the Americas and Europe as a standard, in some states written into law.

A video clip from Fox news in the USA revealed fatal incidents cause by loose nuts. See http://www.wheel-check.com/news/wheelcheck_news.wmv