Open top ram wood grinder guarrding

[mishi]

I have an open top hydraulic wood grinder that utilizes a ram to push the material through cutting teeth.
The grinder is located approximately 5' below the floor level of the plant on the outside of the building.
Three of its sides are protected by brick walls and therefore have no access.
The fourth side is inside the building and since it is lower than the floor we pitch the wood into the grinder below or utilize forklifts to dump hoppers into it.
There is a 5' wall in front of the opening to prevent someone from falling in.
My question is this proper or do I need to do more?

 

[chicopee]

protect all four sides of opening with a guard rail so that no one can step thru the opening; also have warning signs about the danger of the grinder on the guard rail, post requirements for personal protective equipment such as safety goggles and ear muffs, and instruct not to drop hard objects such tool and debris such as rocks.