Hazardous Motions

The three most common hazardous motions are rotating, reciprocating, and transversing motions.

Rotating Motions

Even something as seemingly innocent as a slow-moving conveyor belt can be dangerous because of the rotating pieces. If an employee's arm, hand, or other body part or piece of clothing becomes caught in the rotation, it can put the employee at risk of severe injury. The severity of the hazard is increased even more if there are parts protruding from the rotating portion, especially at high speeds. Rotating parts can also cause in-running nip points, where the rotating pieces come into contact with another rotating piece, a tangentially moving piece, or a fixed piece. Common examples of equipment with rotation hazards are as follows:

• Meshing gears
• Shaft ends
• Flywheels
• Pulleys
• Couplings

Reciprocating Motions

Reciprocating motion refers to repeated back-and-forth or up-and-down movement. This type of motion is hazardous because the moving parts often meet with a fixed surface at the end of the movement, which can crush body parts, possibly breaking bones in the process. Common examples of equipment with reciprocating hazards are as follows:

• Pistons
• Crankshafts
• Trip hammers
• Reciprocating saws

Transversing Motions

Transversing movement is when a part continuously moves in a straight line, creating the danger of someone or something being struck or caught by the moving piece. Common examples of equipment with transversing hazards are as follows:

• Belts
• Shearing blades

To learn more about Machine Guarding visit our Machine Guarding Safety Online Training web page.