All machines consist of three fundamental areas; the point of operation, the power transmission device, and the operating controls. Despite all machines having the same basic components, their safeguarding needs widely differ due to varying physical characteristics and operator involvement.

The point of operation is where work is performed on the material, such as cutting, shaping, boring, or forming of stock.

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.

Other moving parts refers to all parts of the machine which move while the machine is working. These can include reciprocating, rotating, and transverse moving parts, as well as feed mechanisms and auxiliary parts of the machine.

Guards are barriers that prevent access to danger areas. There are four general types of guards:

• Fixed;

• Interlocked;

• Adjustable; and

• Self-adjusting.

Fixed

As its name implies, a fixed guard is a permanent part of the machine that provides a barrier. 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.

Advantages are that it can be constructed to suit many specific applications; in-plant construction is often possible; it can provide maximum protection; usually requires minimum maintenance; and it can be suitable to high production, repetitive operations.

Its limitations are that it may interfere with visibility; can be limited to specific operations; and machine adjustment and repair often require its removal, thereby necessitating other means of protection for maintenance personnel.

Interlocked

When an interlocked 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 hazards.

Advantages are that it can provide maximum protection, and allows access to the machine for removing jams without time consuming removal of fixed guards.

Limitations are that hands may enter the danger area — protection may not be complete at all times; it may require frequent maintenance and/or adjustment; the guard may be made ineffective by the operator; and it may interfere with visibility.

Adjustable

Adjustable guards are useful because they allow flexibility in accommodating various sizes of stock.

Advantages are that they can be constructed to suit many specific applications, and can be adjusted to admit varying sizes of stock.

Limitations include hands may enter danger area - protection may not be complete at all times; may require frequent maintenance and/or adjustment; the guard may be made ineffective by the operator; and it may interfere with visibility.

Self Adjusting

The openings of self-adjusting 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.

Advantages are that off-the-shelf guards are often commercially available.

Limitations are that they do not always provide maximum protection; may interfere with visibility; and may require frequent maintenance and adjustment.

The safeguard must prevent hands, arms, and any other part of a worker’s body from making contact with dangerous moving parts. A good safeguarding system eliminates the possibility of the operator or another worker placing parts of their bodies near hazardous moving parts.

• Secure: Workers should not be able to easily remove or tamper with the safeguard, because a safeguard that can easily be made ineffective is no safeguard at all. Guards and safety devices should be made of durable material that will withstand the conditions of normal use. They must firmly be secured to the machine.

FSM

Source: OSHA.