Sheffield Crown Court heard how on 10 December 2015 36-year-old David Beresford was employed by R K Civil Engineers Ltd working at the EON Renewable Energy Plant in the city.
He was one of two workers unloading large heating pipes weighing 840kg each from a trailer to place them into containers at the site.
The pipes were being lifted and moved using an excavator and were incorrectly stacked above the top edge of the stillages.
During the positioning of the pipes, two of the pipes rolled off and fell into a gap between two stillages. Mr Beresford was standing within this gap and the second pipe fell onto him.
R K Civil Engineers Ltd of Manchester was found guilty of safety breaches and was fined £1,000,000
R K District Heating Ltd of Sheffield was also found guilty and fined £1,000,000.
Companies House records show R K Civil Engineers went into administration in June 2016 while R K District Heating went into liquidation in March 2017.
After the hearing, HSE inspector Mark Welsh commented: “This was a wholly avoidable incident, caused by the failure of both companies to follow safe systems of work, and a failure to identify the risks.
“This tragic incident led to the avoidable death of a young man. There was a lack of planning for the work carried out and, as a result, inadequate controls put in place.”