Two Floormen were working in the substructure approximately 4 metres (13.4 feet) above the ground and removing the bell nipple from the top of the blowout preventer (BOP). The flow line had been disconnected from the bell nipple but was still attached to the winch on the drill floor when it was raised unexpectedly. The flow line flange knocked the bell nipple from the BOP seating and it fell to the ground. The Floormen had moved from one side of the Bell Nipple (v-door side) to the other side (draw works side) where they had just connected a soft sling to secure the Bell Nipple. One Floorman (#1 in picture below) had attached his shock absorbing lanyard to the Bell Nipple (approx 300 kg) and he was pulled down and fell to the ground. The other Floorman (#2 in picture below) was knocked off balance and fell backwards to the extent of his shock absorber lanyard before coming to rest suspended upside down with the unused work platform stopping his fall any further. His lanyard did not extend far enough to activate the shock absorber. Both workers were standing on the BOP lifting bracket. Both workers received soft tissue injuries and returned to work the next day.