It seems strange that arguments about foreseeability still arise when work equipment is faulty and causes injury. But this case in point reached the House of Lords from the Scottish courts.
The claimant and his colleagues lived in accommodation provided by their employer on offshore oil rigs. The claimant was climbing into his bunk bed using a removable ladder that had not been replaced properly. It gave way and he fell to the floor.
He pleaded breaches of regulations 4 and regulations 20 of the Provision and Use of Work Equipment Regulations (PUWER) 1998. At first instance and on appeal the courts found that the accident was not reasonably foreseeable by the employer.
The House of Lords overturned this. The Lords explained that the relevance of foreseeability was only in anticipating a risk of injury at all. PUWER 1998 states a risk assessment should be carried out before work equipment is used or provided. Carelessness in the replacement of removable ladders was a risk that had to be anticipated and addressed.
To avoid the risk of injury, the ladders could have been clamped or otherwise fixed to the side of the bunks to which they were to provide access. There were breaches of regulations 4 (1) and 20.
Contributory negligence of 50 per cent was held because the claimant knew ladders were removable and frequently removed and replaced insecurely.
Robb -v- Salamis (M&I) Ltd (Formerly Salamis Marine & industrial LTS) (2006)  UKHL 56
N.B:No argument of vicarious liability was run against whoever negligently replaced the ladder because employees from other businesses, eg cleaners, had access to and removed the ladders, so it would be impossible to prove which company the negligent party had come from.
P.S. For an example of the common situation where something goes wrong with equipment, but no fault can be found in the investigation after the accident, see the Thompsons case of Butcher below in the Work Equipment section.