MACHINE SAFEGUARDING IN MANUFACTURING. John W. Mroszczyk, PhD, PE, CSP. Northeast Consulting Engineers, Inc. Danvers, MA OBJECTIVES

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1 MACHINE SAFEGUARDING IN MANUFACTURING John W. Mroszczyk, PhD, PE, CSP Northeast Consulting Engineers, Inc. Danvers, MA 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 1

2 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 2

3 HIERARCHY OF SAFEGUARDING 1 st Level: Fixed barrier guard secured with special fasteners, locked barrier guard, interlocked barrier guard, presence sensing 2 nd Level: Adjustable barrier guard not requiring operator intervention 3 rd Level: Fixed and adjustable barrier guard without interlocks 4 th Level: Awareness guards, alarms 5 th Level: Administrative procedures ADMINISTRATIVE PROCEDURES 3

4 OSHA 1910 STANDARDS Subpart O-Machinery and Machine Guarding (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 Woodworking Abrasive Wheels Mills and Calenders Mechanical Power Presses Forging Machines Mechanical Power Transmission Apparatus Portable Power Tools Pulp, Paper, Paperboard Mills Textiles Bakery Equipment Laundry Machines Sawmills Logging 4

5 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 5

6 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 6

7 MECHANICAL POWER PRESSES MECHANICAL POWER PRESS FULL REVOLUTION Point of operation guards Two-Hand trip Pull backs Restraints Type A Gates 7

8 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 8

9 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 9

10 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,

11 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, 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,

12 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, 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,

13 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 13

14 OPENINGS IN BARRIERS Minimum Distance (in.) Smallest Opening (in.) Slotted Square distance opening hazard SAFETY DEVICE SAFETY DISTANCE Ds = K(Ts + Tc + Tr ) + Dpf 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. HAZARD Ds Dpf Safety mat 14

15 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 15

16 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. 16

17 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 17

18 RISK ASSESSMENT Alternative uses of the machine Cleaning and maintenance of the machine Foreseeable misuse RISK ASSESSMENT Operator error Wear and tear 18

19 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 19

20 JHA MEAT BLENDING MACHINE Potential Task Hazards Preventive Measures Climb stairway to platform Turn machine off, enter machine Worker falls into machine Worker forgets to turn machine off, enters machine Coworker turns machine on Design grate over opening Interlock on grate 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 20

21 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 21

22 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 22

23 DELIBERATE RISKS AND SHORTCUTS Install interlocks that are more difficult to defeat HUMANS CAN BE IN A HURRY 23

24 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 24

25 PERFORM STEPS OUT OF SEQUENCE Use sequential control or fully automate LASER MACHINING 25

26 LASER MACHINING Laser radiation hazards Laser effluent hazards Malfunction in beam delivery system Electrical hazards Toxic gases produced by laser process Ignition of flammable vapors 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. 26

27 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 27

28 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 28

29 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. 29

30 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! 30

31 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 31

32 ENGINEERING CONTROLS Presence sensing devices, barriers, interlocks AWARENESS BEACON LIGHTS 32

33 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 33

34 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? 34

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

36 RESOURCES Hagan, et al, editors. Accident Prevention Manual for Business and Industry, Engineering and Technology, 13 th Edition. National Safety Council OSHA Technical Manual (OTM) Section IV: Chapter 4 INDUSTRIAL ROBOTS AND ROBOT SYSTEM SAFETY National Safety Council, Safeguarding Concepts Illustrated, 6 th 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

37 RESOURCES ANSI/RIA R15.06 Industrial Robots and Robot Systems- Safety Requirements OSHA Instruction PUB SEP 21, 1987 Office of Science and Technology Assessment Subject: Guidelines for Robotics Safety owadisp.show_document? p_table=directives&p_id=1703 RESOURCES OSHA Publication 3067 Concepts and Techniques of Machine Safeguarding. 37

38 ANY QUESTIONS??? 38