I am very familiar with OSHA standards and rock crushers. I have 8 years of experience working at an engineering company that designed and furnished heavy rock crushing systems (including impact crushers). This crusher is designed in a very consistent way with other types of impactors. The key issues in this case are machine guarding, lockout, and tagout. OSHA standards are generic in terms of lockout and tagout; the principles apply across different types of machinery. Typically jams occur when something goes through the machine that is oversized. There are spring releases in the rock crusher that keep the machinery from destroying itself. Then, the worker needs to unplug the machine. Workers receive sets of instructions to operate the machinery. The biggest question for me is if the worker followed these instructions, unplugged the rock crusher and the rock crusher malfunctioned and went into operation. If everything was done correctly by the worker, and the rock crusher was locked out and tagged out, then you have a control/programming issue.