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

2. 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

4. 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

5. 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

6. 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

9. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

19. Guarding by Location
Location of the exposed part will be sufficient for guarding purposes.
OSHA 29 CFR
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.

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

21. 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

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

24. 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.

25. 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

26. Typical Nip Points

27. 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.

28. 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.

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

30. 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

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

32. 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.

33. 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!

34. 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 non-conformance 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.

37. 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

38. 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.

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