So many moving parts: Are your workers protected?

Each year, workers who operate and maintain machinery suffer approximately 18,000 amputations, lacerations, crushing injuries, and abrasions, and over 800 deaths due to unguarded or inadequately guarded machines. When the operation of a machine has the potential to injure the operator through accidental contact, or to injure others in the vicinity, the hazards must be eliminated or controlled. OSHA’s machine guarding standard at 1910.212 requires safeguarding of any machine part, function, or process that may cause injury.

Assessing equipment hazards

New equipment is usually guarded, but on-site equipment modifications often create a need for additional or modified guarding methods. The need for machine guarding is identified by conducting a hazard analysis on both new and modified machinery. The results from the analysis are then used to evaluate the need for, and the design of, machine safeguarding.

The following types of machine hazards are identified during the hazard analysis:

• Point-of-operation: These are points where work is performed on the material (i.e., cutting, boring, shaping, forming, grinding);
• Power transmission: Parts that move energy through the machine (i.e., flywheels, pulleys, belts, connecting rods, couplings, cams, spindles, chains, gears); and
• Other moving parts: These include reciprocating, rotating, and transverse moving parts; feed mechanisms; chips and flying material; sparks; etc.

These classifications often overlap. The key is to understand how the machine operates, identify the hazards, and determine how to appropriately guard for each hazard.

General types of machine guarding

Some machines can be positioned so that workers can’t come into contact with any hazards. This is called guarding “by location.” For example, an exposed gear higher than seven feet off the ground might not require shielding because it’s too far away from an employee during normal operation. The same may be true of moving parts shielded from employees because they’re against a wall and are not accessible.

If guarding by location isn’t possible, the machine must have safeguards. There are several types:

• Guards are barriers that prevent access to danger areas. They come in three types:
  • Fixed (can’t be removed easily – these provide the most protection),
  • Interlocked (shut off or disengage power when removed – these are designed to be occasionally removed), and
  • Adjustable (adjust for different machine set-ups).
• Devices stop a machine or prevent it from starting until the operator is in a safe position. They’re used mostly for point-of-operation hazards and come in five types:
  • Presence-sensing (i.e., light, radio frequency),
  • Pullback,
  • Restraint,
  • Safety controls (i.e., trip wires, two-handed trips), and
  • Gates.
• Automated feeding and ejection methods limit hazards associated with feeding stock into or ejecting material from a machine. These methods come in three types:
  • Automated feed or ejection,
  • Semi-automatic feed or ejection, and
  • Robotics.

When choosing effective safeguards, keep in mind they must:

• Prevent contact with hazardous components during machine operation;
• Not create additional hazards, such as new nip points between guards and rotating parts;
• Be secure, durable, and resistant to tampering;
• Not interfere with normal machine operation unless necessary for protecting employees; and
• Not interfere with equipment servicing or maintenance.