Mark Priestley, 34, was pinned against a skip by the beam at the firm’s Halifax factory on 31 January 2011.
The weight of the beam crushed his spine and torso, leaving him with irreversible spinal and nerve damage.
Priestley, of Claremount, Halifax, who is married with a young son, was in hospital for five months. Although he regained some movement in his legs, he is largely confined to a wheelchair, still needs intensive therapy and is unlikely to be able to work again.
Bradford Crown Court heard that Priestley had been working with a colleague to weld pin connections to the 23m long beam.
The beam had to be rotated several times so the welding could be done, which meant lifting it using chain slings.
An HSE investigation found that it was likely that one or both of the chain slings next to the beam had snagged it as it was about to be lifted in preparation for slinging.
As the chain was being raised, it caught the beam which became unbalanced and toppled sideways onto Priestley’s back as he attempted to get out of the way.
The court was told the company had failed to assess the risks for lifting operations so they were not properly planned or supervised. The chain slings and technique used were also unsuitable for the load.
Elland Steel Structures Ltd pleaded guilty to safety breaches and was fined £8,000 and ordered to pay £20,000 toward costs.
After the hearing, HSE Inspector Geoff Fletcher said: “What happened was devastating for Mr Priestley and his family. He now has a permanent disability and continues to endure significant pain.
“The incident could have been avoided had Elland Steel fulfilled its responsibilities to fully assess the risks involved with this heavy lifting, and then put measures in place to mitigate those risks.”