Accident Prevention Manual for Business Industry Engineering Technology

Accident Prevention Manual for Business & Industry: Engineering & Technology 13 th edition National Safety Council Compiled by Dr. S. D. Allen Iske, Associate Professor University of Central Missouri

CHAPTER 6 SAFEGUARDING

3 Safeguarding • A primary method to reduce worksite hazards • Prevents personnel from contact with moving parts • Key is to identify hazards • Includes barriers, guards, signs, lockout/tagout, safety design, enclosures, fences

Definitions • Safeguarding—Any means of preventing personnel from coming in contact with moving parts of machinery or equipment, that would potentially cause harm • Device—a mechanism or control designed for safeguarding at the point of operation • Guard—barriers designed for safeguarding • Enclosure—safeguarding by fixed physical barriers that are mounted on or around the machine to prevent accidents • Fencing—safeguarding by means of a locked fence or rail • Location—safeguarding when a hazard is physically inaccessible under normal operating conditions or use

Definitions (Cont. ) • Nip points or bites—the hazardous area created by two or more mechanical parts, rotating in opposite directions within the same plane • Pinch point—the point where any body part can be caught between two moving parts or one fixed and one moving • Point of operation—the area of a machine where material is positioned or work is performed on material • Power transmission—all mechanical parts (gears, cams, shafts, pulleys, belts, clutches) that transmit energy and motion from a source of power to equipment or a machine • Shear points—the hazardous area created by the cutting movement of a mechanical part

Point-of-Operation Protection Devices • Openings used for safeguarding • should not exceed 3/8” • prevents entry or contact • first 1. 5” from danger line should not exceed 1/4” opening

Point-of-Operation Safeguards • Guard construction • must be sturdy and secure (substantially constructed) • secured to minimize distortion or movement. • sufficiently strong to withstand stress and exposure • usually made of metal

Point-of-Operation Safeguards (Cont. ) • Proper guard characteristics: • integration with machine • adequate construction, durability, and strength • handle workpiece in-feed and ejection • protection from the hazards • ease of inspection and maintenance • tamper-proof or foolproof • Proper guard should NOT: • Create additional hazards • Interfere with production • Cause work discomfort

Point-of-Operation Safeguards (Cont. ) • Types of safeguards • built-in safeguards • barrier guards • interlocking barrier guards • automatic safeguard devices • guarding by location • Substitution • Match machine or equipment to the operator • Study and review Table 6–A

Types of Safeguards • Built-in safeguard • factory made, conforms to the machine—appearance, placement, and function • eliminates hazards • withstands normal wear and tear • costs less than improvised/modified safeguard

Types of Safeguards (Cont. ) • Barrier guard • prevents physical access to dangerous point of operation or work area • usually adjustable for different sets of tools or kinds of work • once adjusted, must not be moved or detached

Types of Safeguards (Cont. ) • Interlocking barrier guard • can be electrical, mechanical, pneumatic or combination • prevents operation of machine control mechanism until guard moves into predetermined position • when open, machine cannot operate and mechanism is locked. • when machine is in motion or operation, guard cannot be opened until machine comes to rest or fixed position

Interlocking Barrier Guards • Effective interlocking barriers must meet three requirements: • guard hazardous area before machine can be operated • stay closed until the rotating equipment is at rest • prevent operation of the machine if the interlocking device fails

Types of Safeguards • Automatic safeguarding devices • prevent operator from coming in contact with dangerous parts of a machine while the machine is in motion • stop the machine in the event of a sub-normal operating condition (shuts down operation) • types of devices: • presence-sensing devices • pull-backs • restraints • two-handed controls

Guarding by Location • Location of the exposed part will be sufficient for guarding purposes. • OSHA 29 CFR 1910. 219 • All exposed parts of horizontal shafting seven (7) feet or less from floor or working platform, excepting runways used exclusively for oiling or running adjustments, shall be protected by a stationary casing enclosing shafting completely or by a trough enclosing sides and top or sides and bottom of shafting as location requires.

Types of Safeguards (Cont. ) • Substitution • Substitute a less hazardous machine or piece of equipment for a more hazardous one. • Eliminates or reduces machine hazards

Types of Safeguards (Cont. ) • Match operator to the machine • Workplace—arrange equipment to minimize work • Work height—adjust for operator • Controls and displays—make them readily accessible • Material handling aids—handles, hoists, belts, conveyors, lifts • Operator fatigue—reduced when job is well designed

Guarding Power Transmissions • Rotating, reciprocating, and transverse motions • In-running nip points • Cutting actions • Punching, shearing, and bending actions

Guarding Power Transmissions (Cont. ) • Methods of guarding actions and motions • Similar to point-of-operation safeguards. • Machine movements can be dangerous. • Guards must cover all moving parts. • Guards must allow for routine maintenance and service, but only when equipment is properly locked out. • Guards must be fixed in place with bolts, hinges, sliding doors, etc. • Guards must be durable.

Guarding Power Transmissions (Cont. ) • Types of mechanical actions and motions • rotating, reciprocating, and transverse motions • in-running nip points • cutting actions • punching, shearing and bending actions

Typical Nip Points

Guarding Power Transmissions (Cont. ) • Guarding Materials • Material must be sturdy. • Metal is preferred. • If visibility is required, use plastic, polycarbonate, or Lexan. • Use aluminum, another soft metal, or plastic if rust is a concern. • Wood has limited application due to lack of durability and strength, relatively high cost, combustibility, and tendency to splinter. • Provide ample ventilation through the guard.

Maintenance and Service • Plan for routine maintenance when designing guards. • Apply engineering techniques that reduce the frequency of, or eliminate, a job/task. • Design guards for easy routine maintenance access. • Equip machines with automatic controls for lubrication, adjustment, or service.

Control of Hazardous Energy Source • OSHA Standard 29 CFR 1910. 147 • Lockout/tagout procedures • Purpose • Scope • Sequence of Lockout • Restoring equipment to service • Other requirements

Lockout/Tagout Procedures • must be written • lockout preferred • tagout used when machine can’t be locked • combination of the two is best • strict compliance is required

Lockout/Tagout Procedures (Cont. ) • Purpose • minimum requirements • isolates energy for routine maintenance and service • guards against accidental restart

Lockout/Tagout Procedures (Cont. ) • Scope • All employees are required to comply with the restrictions and limitations imposed during use of lockout. • Authorized employees are required to perform the lockout in accordance with procedure. • All employees upon observing a machine or equipment piece that is locked out should not attempt to start, energize, or use that piece of equipment or machine.

Lockout/Tagout Procedures (Cont. ) • Sequence • Notify employees of servicing or maintenance on a machine or equipment—shut down and lock out. • Authorized employee refers to and follows procedures to identify the type and magnitude of energy source. • Shut down by normal procedure. • Deactivate the energy—isolating device—machine isolated from energy sources (lockout/tagout) • Dissipate stored or residual energy and gas/air/steam • Verify isolation before performing service. • Machine is now LOCKED OUT!

Lockout/Tagout Procedures (Cont. ) • Restore service • Remove non-essential items from the work area. • Make sure machine is intact. • Remove all employees from the area. • Put controls in neutral. • Remove locks and reenergize the equipment. • Notify employees that maintenance or servicing is completed. Equipment or machine is ready for use. • Group lockout—for a piece of equipment or power source, each employee shall have an individual lock and apply the lock to the device.

35 Lockout/Tagout Procedures (Cont. ) • Training • Train all employees in lockout/tagout. • Retrain annually. • Audit training program annually. • Conduct remedial training as needed for individuals for nonconformance actions. • Lockout equipment • Devices shall be durable, marked, color coded, or otherwise identified for each facility and supplied to authorized personnel. Correct tag labels and strength.

Robotics Safeguarding • Principal hazards • being struck by the moving parts of a robot while in the operating envelope or movement zone • caught between moving parts of the robot and other machinery or objects within or near the robots movement zone • being struck by objects or tools the robot has dropped or ejected

Robotics Safeguarding (Cont. ) • Safeguarding methods • Restrict robot movement zone to required range of motion for particular operation • Install an amber light on a robot, which turns on when the robot is “live” or operational. • Install barriers and fixed guards. • Have emergency stop or “deadman” buttons hardwired to robot power source and easy to reach. • Program so operator cannot place into automatic cycle until all interlocked gates are closed and operator is at master control panel outside of robot movement zone.

Guards and Noise • If well designed and mounted, guards: • may reduce noise • act as a barrier • absorb, reflect, or confine sound waves