Machine guarding — General

Scope

OSHA’s machine guarding standards apply to employers having employees exposed to dangerous moving parts.

Regulatory citations

• 29 CFR 1910.212 — General requirements for all machinery. (This is OSHA’s general requirement for all machinery. It is a catch-all standard requiring employers to protect employees from dangerous moving parts and to guard points of operation.) OSHA also has some machine-specific standards, which are covered elsewhere in this publication:
  • 29 CFR 1910.213 — Woodworking machinery
  • 29 CFR 1910.215 — Abrasive wheel machinery
  • 29 CFR 1910.216 — Mills and calendars in the rubber and plastics industries
  • 29 CFR 1910.217 — Mechanical power presses
  • 29 CFR 1910.218 — Forging machinery
  • 29 CFR 1910.219 — Mechanical power transmission apparatus

Key definitions

• Fixed guard: A fixed guard is a permanent part of the machine. It is not dependent upon moving parts to function. It may be constructed of sheet metal, screen, wire cloth, bars, plastic, or any other material that is substantial enough to withstand whatever impact it may receive and to endure prolonged use. This guard is usually preferable to all other types because of its relative simplicity.
• Interlock: When this type of guard is opened or removed, the tripping mechanism and/or power automatically shuts off or disengages, the moving parts of the machine are stopped, and the machine cannot cycle or be started until the guard is back in place. An interlocked guard may use electrical, mechanical, hydraulic, or pneumatic power or any combination of these. Interlocks should not prevent “inching” by remote control if required. Replacing the guard should not automatically restart the machine. To be effective, all removable guards should be interlocked to prevent occupational hazards.
• Photoelectric (light) device: The photoelectric (optical) presence-sensing device uses a system of light sources and controls which can interrupt the machine’s operating cycle. If the light field is broken, the machine stops and will not cycle. This device must be used only on machines which can be stopped before the worker can reach the danger area. The design and placement of the guard depends upon the time it takes to stop the mechanism and the speed at which the employee’s hand can reach across the distance from the guard to the danger zone.
• Point of operation: The point of equipment at which work, such as cutting, boring, or bending, is performed. With a few exceptions, the point of operation must be guarded.
• Power transmission apparatus/device: The power transmission apparatus is all components of the mechanical system which transmit energy to the part of the machine performing the work. These components include flywheels, pulleys, belts, connecting rods, couplings, cams, spindles, chains, cranks, and gears.
• Pullback: Pullback devices utilize a series of cables attached to the operator’s hands, wrists, and/or arms. This type of device is primarily used on machines with stroking action. When the slide/ram is up between cycles, the operator is allowed access to the point of operation. When the slide/ram begins to cycle by starting its descent, a mechanical linkage automatically assures withdrawal of the hands from the point of operation.
• Restraint: The restraint (hold-back) device utilizes cables or straps that are attached to the operator’s hands and a fixed point. The cables or straps must be adjusted to let the operator’s hands travel within a predetermined safe area. There is no extending or retracting action involved. Consequently, hand-feeding tools are often necessary if the operation involves placing material into the danger area.
• Self-adjusting guard: The openings of these barriers are determined by the movement of the stock. As the operator moves the stock into the danger area, the guard is pushed away, providing an opening which is only large enough to admit the stock. After the stock is removed, the guard returns to the rest position. This guard protects the operator by placing a barrier between the danger area and the operator. The guards may be constructed of plastic, metal, or other substantial material. Self-adjusting guards offer different degrees of protection.
• Two-hand control: The two-hand control requires constant, concurrent pressure by the operator to activate the machine. This kind of control requires a part-revolution clutch, brake, and a brake monitor if used on a power press. With this type of device, the operator’s hands are required to be at a safe location (on control buttons) and at a safe distance from the danger area while the machine completes its closing cycle.
• Two-hand trip: The two-hand trip requires concurrent application of both the operator’s control buttons to activate the machine cycle, after which the hands are free. This device is usually used with machines equipped with full-revolution clutches. The trips must be placed far enough from the point of operation to make it impossible for the operator to move their hands from the trip buttons or handles into the point of operation before the first half of the cycle is completed. The distance from the trip button depends upon the speed of the cycle and the band speed constant. Thus the operator’s hands are kept far enough away to prevent them from being placed in the danger area prior to the slide/ram or blade reaching the full “down” position. To be effective, both two-hand controls and trips must be located so that the operator cannot use two hands or one hand and another part of the body to trip the machine.

Summary of requirements

• Determine the types of machinery in the workplace. Then, determine if there is a machine-specific standard (e.g., 1910.213-.219), or if the equipment is covered under the “catch-all” guarding requirement of 1910.212. Follow the applicable standard.
• Provide one or more methods of machine guarding to protect the operator and other employees in the machine area from hazards such as those created by point of operation, ingoing nip points, rotating parts, flying chips and sparks. Note: Some of the machine-specific standards prescribe specific safeguarding measures.
• Ensure the point of operation of machines is guarded.
• Ensure necessary guards are affixed and secured.
• Anchor machines designed for a fixed location to prevent walking or moving.