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J o h n W . M r o s z c z y k , P h D , P E , C S P N o r t h e a s t C o n s u l t i n g E n g i n e e r s , I n c . D a n v e r s , M A 0 1 9 2 3

MACHINE SAFEGUARDING IN MANUFACTURING

OBJECTIVES

�  Recall machine safeguarding issues in manufacturing

�  Become aware of the how hazards arise with automatic machines

�  Become aware of unique hazards with laser and robot systems

�  Gain an appreciation of human factors issues �  Take action on machine hazards in your workplace

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OUTLINE

A. Hierarchy of Safeguarding B. OSHA and ANSI standards C. Machine tools D. Automation E. Controls F. Elements of Risk Assessment G. Human Factors Issues H. Laser Machining I. Robots

WHY MACHINE GUARDING IS IMPORTANT

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HIERARCHY OF SAFEGUARDING

1st Level: Fixed barrier guard secured with special fasteners, locked barrier guard, interlocked barrier guard, presence sensing 2nd Level: Adjustable barrier guard not

requiring operator intervention 3rd Level: Fixed and adjustable barrier guard without interlocks

4th Level: Awareness guards, alarms

5th Level: Administrative procedures

ADMINISTRATIVE PROCEDURES

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OSHA 1910 STANDARDS

Subpart O-Machinery and Machine Guarding 1910.212 (a)(1)- One or more methods of machine guarding shall be provided to protect the operator and other employees in the machine area from hazards such as those created by the point of operation, ingoing nip points, rotating parts, flying chips and sparks. Examples of guarding methods are-barrier guards, two-hand tripping devices, electronic safety devices, etc.

OSHA 1910 STANDARDS-SPECIFIC MACHINES

1910.213 Woodworking 1910.215 Abrasive Wheels 1910.216 Mills and Calenders 1910.217 Mechanical Power Presses 1910.218 Forging Machines 1910.219 Mechanical Power Transmission Apparatus 1910.243 Portable Power Tools 1910.261 Pulp, Paper, Paperboard Mills. 1910.262 Textiles 1910.263 Bakery Equipment 1910.264 Laundry Machines 1910.265 Sawmills 1910.266 Logging

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ANSI B11 MACHINE STANDARDS

ANSI B11.1 Safety Requirements for the Construction, Care, and Use of Mechanical Power Presses

ANSI B11.2 S B11B11afety Requirements for the Construction, Care, and Use of Hydraulic Power Presses

ANSI B11.3 Safety Requirements for the Construction, Care, and Use of Mechanical Power Press Brakes

ANSI B11.4 Safety Requirements for the Construction, Care, and Use of Shears

ANSI B11.5 Safety Requirements for the Construction, Care, and Use of Ironworkers

ANSI B11MACHINE STANDARDS

ANSI B11.6 Safety Requirements for the Construction, Care and Use of Lathes

ANSI B11.7 Safety Requirements for the Construction, Care, and Used of Cold Headers and Cold Formers

ANSI B11.8 Safety Requirements for the Construction, Care, and Use of Drilling, Milling, and Boring Machines

ANSI B11.9 Safety Requirements for the Construction, Care, and Use of Grinding Machines

ANSI B11.10 Safety Requirements for the Construction, Care, and Use of Metal Sawing Machines

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ANSI B11 MACHINE STANDARDS

ANSI B11.11 Safety Requirements for Gear and Spline Cutting Machines

ANSI B11.12 Safety Requirements for Roll-Forming and Roll-Bending Machines

ANSI B11.13 Safety Requirements for the Construction, Care, and Use of Single and Multiple –Spindle Automatic Screw, Bar, and Chucking Machines

ANSI B11.14 Coil Slitting Machines-Safety Requirements for

Construction, Care , and Use

ANSI B11.15 Safety Requirements for Pipe, Tube, and Shape Bending

ANSI B11 MACHINE STANDARDS

ANSI B11.16 Safety Requirements for Powder/Metal Compacting Presses

ANSI B11.17 Safety Requirements for Horizontal Hydraulic Extrusion Presses

ANSI B11.18 Safety Requirements for Construction, Care, and Use of Machines and Machinery Systems for Processing Strip, Sheet, or Plate From Coiled Configuration

ANSI B11.19 Performance Criteria for Safeguarding

ANSI B11.20 Safety Requirements for Integrated Manufacturing Systems

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MECHANICAL POWER PRESSES

MECHANICAL POWER PRESS FULL REVOLUTION

 Point of operation guards

 Two-Hand trip

 Pull backs

 Restraints

 Type “A” Gates

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MECHANICAL POWER PRESS PART REVOLUTION

  Point of operation guards

  Two-Hand controls

  Pull backs

  Presence – sensing

  Restraints

  Type “A” and “B” Gates

POWER PRESS BRAKES

 Presence sensing

 Two-hand control  Restraints/pullbacks

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FORMING AND BENDING MACHINES

 Barrier guards are usually not practical  Hold down or foot

controls   Trip device

SHEARING MACHINES

Adjustable point of operation guard Foot pedal controls Two hand controls Presence sensing devices

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AUTOMATION

INJURIES INVOLVING AUTOMATIC EQUIPMENT

�  54% Intervening after a malfunction �  20% Changing settings or making adjustments �  16% Performing normal operation

�  10% Preventative maintenance

Ref: Chinniah and Bourbonneire , “Automation Safety”, Professional Safety, December, 2006.

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SAFEGUARDING METHODS

Fixed Barrier Guard-An enclosure that prevents access into the danger zone. Kept in place by fasteners that require tools to remove the guard Problems with automation �  Guard is removed for setup

Ref: Backstrom and Doos, “Problems with Machine Safeguards in Automated Installations” International Journal of Industrial Ergonomics, 2000.

SAFEGUARDING METHODS

Interlocked Guard-Prevents start-up of a machine and stops machine when guard is removed Problems with automation- �  Interlock does not stop machine in danger zone �  Interlock is bypassed �  Interlocked gate open while workers operating machine in manual mode Ref: Backstrom and Doos, “Problems with Machine Safeguards in Automated Installations” International Journal of Industrial Ergonomics, 2000.

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SAFEGUARDING METHODS

Two-hand control- Requires the use of both hands simultaneously to initiate and maintain operation Problems with automation- �  Buttons on two-hand control activated by mistake as operator stretched over control �  Co-worker reached into danger zone while operator two

hands on control Ref: Backstrom and Doos, “Problems with Machine Safeguards in Automated Installations” International Journal of Industrial Ergonomics, 2000.

SAFEGUARDING METHODS

Presence –sensing devices-detects intrusion into danger zone such as pressure sensitive mats and light curtains Problems with automation- �  Fails to stop all machine movement �  A co-worker starts machine while operator still in danger zone Ref: Backstrom and Doos, “Problems with Machine Safeguards in Automated Installations” International Journal of Industrial Ergonomics, 2000.

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MAINTENANCE/REPAIR/CLEANING

�  LOTO �  If power to machine is needed to jog machine, do maintenance, set up machine, etc. -use pendant control with key protected jog mode.

GUARDING BY LOCATION

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Minimum Distance (in.) Smallest Opening (in.) Slotted Square 0.000-.250 0.5 0.5 .251-.375 2.5 1.9 .376-.625 3.5 2.6 .626-1.250 6.5 6.5 1.251-1.875 17.5 17.5 1.876-5.000 36.0 36.0

hazard opening

distance

OPENINGS IN BARRIERS

SAFETY DEVICE SAFETY DISTANCE

HAZARD Safety mat

Dpf

Ds = K(Ts + Tc + Tr ) + Dpf

Ds Ds= minimum distance between device and hazard K = speed constant 63 in/sec or about 5 ft/sec Ts=worst stopping time for machine Tc=worst stopping time for control system Tr = response time of safety device Dpf=minimum travel distance toward hazard within presence sensing field that may occur before a stop is signaled.

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CONTROLS

Need to bypass safeguards while machine is powered: � Hold to run or jog control � Portable pendant control with an emergency stop button � Means to limit speed or power of machine

CONTROLS Prevent inadvertent actuation �  Recess controls or provide a raised barrier around control � Place controls so that they are unlikely to be accidentally hit � Require sequential application of a force in at least two directions

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CONTROLS Require a manual restart if the machine is in automatic mode and the control system stops the machine, or if an interlocked guard is removed

CONTROLS An emergency stop should be located on every control panel.

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RISK ASSESSMENT STEPS

�  Decide on the scope �  Identify tasks and hazards within that scope �  Assess the risk �  Implement safeguarding measures to reduce the risk �  Assess the residual risk �  Repeat the process

RISK ASSESSMENT �  Normal operation as defined in the manual �  Malfunction or failure of any of the components

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RISK ASSESSMENT �  Alternative uses of the machine

�  Cleaning and maintenance of the machine �  Foreseeable misuse

RISK ASSESSMENT �  Operator error

�  Wear and tear

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JOB HAZARD ANALYSIS

Four basic stages in conducting a JSA are: �  Selecting the job to be analyzed � Breaking the job down into a sequence of steps �  Identifying potential hazards � Determining preventive measures to overcome

these hazards

MEAT BLENDING MACHINE

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JHA MEAT BLENDING MACHINE

Potential Task Hazards Preventive Measures

Climb stairway to platform

Worker falls into machine

Design grate over opening

Turn machine off, enter machine

Worker forgets to turn machine off, enters machine

Interlock on grate

Coworker turns machine on

Interlock on grate

Interlock fails Add redundant interlock

HAZARD SEVERITY � Catastrophic- death, amputation, permanent disability �  Serious-serious debilitating injury (able to return to work after a period) � Marginal-significant injury requiring more than first aid, able to return to work at same job � Negligible-no injury or injury requiring no more than first aid, little or no lost work time 

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PROBABILITY OF OCCURRANCE

�  Frequent- Likely to occur often �  Probable-Will occur several times �  Occasional- Likely to occur sometime �  Remote- Unlikely, but possible �  Improbable- so unlikely as to be near zero

RISK ASSESSMENT MATRIX

--------------Severity of Harm------------------ Probability of Harm Catastrophic Serious Marginal Negligible Frequent 1A 2A 3A 4A Probable 1B 2B 3B 4B Occasional 1C 2C 3C 4C Remote 1D 2D 3D 4D Improbable 1E 2E 3E 4E  

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RISK ASSESSMENT MATRIX

Hazard Risk Assessment Suggested Action 1A, 1B, 1C, 2A, 2b, 3A Unacceptable, risk reduction is necessary 1D, 2C, 2D, 3B, 3C Unacceptable if personnel exposed to hazard 1E, 2E, 3D, 3E, 4A, 4B Acceptable with management review 4C, 4D, 4E Acceptable without management review

HUMAN FACTORS ASPECTS

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DELIBERATE RISKS AND SHORTCUTS

Install interlocks that are more difficult to defeat

HUMANS CAN BE IN A HURRY

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CONFUSION

Use gauges that are easy to interpret

Design and arrange controls so that they are easy to use.

LACK OF ATTENTION

Beacon lights can be used to alert the operator if a machine is in automatic mode

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PERFORM STEPS OUT OF SEQUENCE

Use sequential control or fully automate

LASER MACHINING

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� Laser radiation hazards � Laser effluent hazards � Malfunction in beam delivery system � Electrical hazards � Toxic gases produced by laser process � Ignition of flammable vapors

LASER MACHINING

CLASSES OF LASERS

Class I- cannot emit a hazardous level of optical radiation under normal operation Class II- do not have enough output power to injure a person, but may produce retinal injury when stared at for a long time.

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CLASSES OF LASERS

Class IIIA- cannot injure the unaided eye, but may cause injury if the light is collected, as with a lens Class IIIB-can produce injury if viewed directly Class IV-produce a hazardous beam and can also be a fire hazard.

LASER MACHINE SAFEGUARDING

�  All lasers should be constructed with interlocks that stop power to the laser if any shield is opened.

�  Access to laser systems should be restricted to trained personnel

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LASER MACHINE SAFEGUARDING

�  Class IIIB and IV Systems- Should be shielded and positioned so that the beam will not reach the eyes of skin of any worker. Workers should use special absorptive lens eyewear when working around these laser systems.

LASER SAFEGUARDING

Nominal Hazard Zone – The space in which direct, reflected, or scattered radiation exceeds the Maximum Permissible Exposure (MEP) Interlocked gates, safety mats or light curtains should be used to prohibit entrance into the Nominal Hazard Zone when the laser is in operation

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REMOVE EFFLUENT

�  Integral ducting or other extraction systems to move effluent out of the system

INDUSTRIAL ROBOTS

“An automatically controlled, reprogrammable multipurpose manipulator programmable in three or more axes which may be either fixed in place or mobile or use in industrial automation applications.”

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ROBOT HAZARDS

  Hazards associated with robot systems are of the mechanical type.

  They are similar

to typical machine hazards EXCEPT……………..

ROBOTS ARE CONSIDERABLY MORE DANGEROUS THAN OTHER MACHINES

�  If the robot is not moving, DO NOT assume it is not going to move

�  If the robot is repeating a pattern, DO NOT assume it will continue with this pattern

�  Respect what the robot is capable of…even large robots are capable of swinging an 8 foot radius at speeds up to 200 in per second or about 17 feet per second!

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ROBOT HAZARDS

�  Robots are programmable, they might stop for a period of time, then suddenly start up �  Robots can change speed and direction �  Robots have a “teaching mode”.

BASIC THREE TYPES OF HAZARDS

�  Being struck by moving part of robot or items carried by robot �  Being trapped between a moving part of the robot and a fixed object �  Other hazard related to the robot task such as electric shock, toxic substances, burns

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ENGINEERING CONTROLS

Presence sensing devices, barriers, interlocks

AWARENESS

BEACON LIGHTS

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EXAMPLE OF A ROBOT CELL

CONCLUSION/SUMMARY

� Do a complete walk around of your facility, make note of all machine hazards, regardless of where they are located

� Consider human error � Consider repair, maintenance, cleaning (may need pendant controls, etc) � Design or install safeguarding measures

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CHECKLISTS

�  Have you made a survey of all mechanical hazards? �  Does all equipment have emergency stop button(s) that are

within easy reach of all operators and operators stations?   �  Are all emergency stop buttons colored red?   �  Can electric power to each machine be locked out for

maintenance or security?   �  Are all foot switches guarded? Require a second action?  

CHECKLISTS

  �  Have guards been provided throughout the plant to keep personnel

away from moving parts?   �  Are removable guards interlocked? Are the interlocks reliable?   �  Are pinch points, rotating parts, and other moving parts guarded?   �  Are openings in guards small enough or located far enough from the

hazard that personnel cannot reach into the hazardous area?   �  How can personnel access any of the moving parts?  

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CHECKLISTS

  �  Are all moving parts guarded, regardless of likelihood of

accessing the hazardous area?   �  Is there adequate space between pieces of equipment?   �  Are there perimeter fences with interlocked gates around

all robot systems and other automatic equipment ?   �  Are all pinch points guarded?  

RESOURCES

�  Mroszczyk, J. “Machine Safeguarding” Handbook of Loss Prevention Engineering, Joel Haight, Ed. Wiley-VCH.

�  Gallagher, V. “Guarding by Location:A Dangerous Concept, Professional Safety, Sept. 1990.

�  Safety Engineering, 4th Edition. ASSE �  NIOSH Machine Guarding-Assessment of Need Publication No 75-173

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RESOURCES �  Hagan, et al, editors. Accident Prevention Manual for

Business and Industry, Engineering and Technology, 13th Edition. National Safety Council

�  OSHA Technical Manual (OTM) Section IV: Chapter 4 INDUSTRIAL ROBOTS AND ROBOT SYSTEM

SAFETY �  National Safety Council, Safeguarding Concepts Illustrated,

6th Edition

RESOURCES

�  National Institute of Standards and Technology (NIST) Safety of Human-Robot Systems in Fixed Workcell Environments November 10, 2011

�  Professional Safety Handbook 2ns Edition, Joel

Haight, ed. ASSE

�  Scheel, P. “Robotic in Industry” Professional Safety, March 1993

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RESOURCES

  ANSI/RIA R15.06 Industrial Robots and Robot Systems-Safety Requirements

  OSHA Instruction PUB 8-1.3 SEP 21, 1987 Office of

Science and Technology Assessment Subject: Guidelines for Robotics Safety http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=DIRECTIVES&p_id=1703

RESOURCES

�  OSHA Publication 3067 Concepts and Techniques of Machine Safeguarding.

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ANY QUESTIONS???