726 Introduction to Machine Guarding

Program Elements

Types of Safeguards

Machine safeguards are essential for protecting workers from injuries caused by dangerous machine parts. Each type of safeguard has a specific purpose and application depending on the machine and work process. Properly selecting and using these safeguards reduce the risk of accidents and ensure compliance with safety standards.

The types of safeguards in this workplace and their application discussed below:

• Fixed Guards:
  • These are permanent physical barriers that enclose moving parts or hazardous areas.
  • They are ideal for machines or areas where no operator access is needed during operation.
  • Examples include sheet metal covers over gears or machine casings enclosing dangerous parts.
  • Fixed guards are simple, reliable, and require little maintenance once installed.
• Interlocked Guards:
  • These guards are connected to the machine’s control system to automatically stop or disengage the machine when the guard is opened or removed.
  • They are perfect for machines that require frequent access for loading, adjusting, or maintenance.
  • Examples include hinged doors with safety switches on presses or packaging machines.
  • Interlocked guards help prevent operators from bypassing safety measures because the machine cannot run without the guard in place.
• Adjustable Guards:
  • Adjustable guards can be moved or resized manually to accommodate different sizes or shapes of stock.
  • They maintain protection while allowing flexibility in the operation of machines with varying material sizes.
  • Examples include sliding or rotating covers on saws and feed tables that change position based on the stock.
  • Operators must be trained to properly adjust these guards for safe use.
• Presence-Sensing Devices:
  • These use optical, pressure, or other sensor technologies to detect the presence of an operator near the danger zone.
  • When the sensor is triggered, the machine automatically stops or will not start until the area is clear.
  • Examples include light curtains, pressure mats, and laser scanners used on presses, robotic cells, or cutting machines.
  • They provide protection without physical barriers, improving visibility and access but require precise setup and maintenance.
• Pullback and Restraint Devices:
  • These mechanical devices attach to the operator’s hands or arms and pull them back or restrict movement away from the danger area during machine operation.
  • They are commonly used on machines like punch presses or stamping machines where hand placement is critical.
  • Examples include cables or straps connected to the operator’s wrists and linked to the machine cycle.
  • These devices reduce the risk of hand injuries but must be used with caution and proper training.
• Safety Trip Controls:
  • Safety trip controls are pressure-sensitive devices like trip wires, mats, or bars that stop the machine when activated by the operator or an object.
  • They add an extra layer of protection by allowing immediate machine shutdown if a hazardous situation arises.
  • Examples include emergency stop trip wires along conveyor belts or safety mats around robotic work cells.
  • Trip controls must be regularly tested to ensure proper function.

Important Note: Makeshift or unauthorized safeguards must be prohibited as they often do not meet safety standards and may increase the risk of injury. Always use approved and properly designed safeguards following safety regulations and manufacturer guidelines.

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