A driller was operating a top drive drilling unit. There was a stand of drill pipe clamped in the slips and the top drive was raised and held on the brake. The driller saw a roughneck step into the hazardous area and therefore went to reach for the microphone to tell the roughneck to step back.
As the driller reached for the microphone, he released pressure on the brake slightly. The top drive descended, bending the drill pipe which fortunately did not spring out. A 27kg pipe-guide fell 90 feet to the floor, narrowly missing the roughneck.
Apply good quality management of change process to avoid incremental change.
Use an ergonomist to advise on what people will be physically capable of in different situations.
Speak up if there is equipment which is difficult to use.
Get experienced end-users involved in the design and commissioning of plant.