The body of Victor Nicholl, who had worked for FP McCann for 19 years, was found beside a dumper truck at Knockloughrim Quarry, Magherafelt, on 13 March 2015.
The company pleaded guilty to breaching Art 4(1) by virtue of Art 4(2) of the Health and Safety at Work (Northern Ireland) Order and reg 6(1) of the Quarries Regulations (Northern Ireland).
At Belfast Crown Court, the judge handed down a £75,000 fine for each of the two offences.
The prosecution was brought by the Health and Safety Executive for Northern Ireland (HSENI), whose investigation found the Aveling Barford dumper truck Nicholl was operating to move material from a crushing and screening plant to a stockpile area was in poor repair.
Nicholl was found lying on the ground next to one of the front wheels of the truck, which were wedged in the safety berm -- a form of edge protection used in quarries -- around the stockpile area.
The vehicle had several faults, including low break efficiencies, no parking brake, no emergency steering and no working seatbelt.
Edge protection in the stockpile area was also found to be below the recommended height of 1.5 m, although it was enough to stop the vehicle on this occasion, the HSENI said.
Its principal inspector, Anne Boylan, said: "The vehicle that Mr Nicholl was driving on the day of the incident had not been maintained in a safe condition and was not fit for use in a hazardous environment such as a quarry.
"Employers must ensure that work equipment, including work vehicles, undergo regular planned maintenance. Failure to do so may result in unsafe vehicles, leading to potentially serious or even fatal accidents."
She added: "Robust systems must be in place to check that maintenance schedules are adhered to and vehicles are in a safe condition at all times."
