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12.1 Introduction #
One or more methods of machine guarding shall be provided to protect the operator and other employees in a machine area from hazards, such as those created by a point-of-operation, in-running nip points, rotating parts, flying chips, sparks, etc. Guards shall be affixed to the machine where possible and secured elsewhere, if for any reason attachment to the machine is not possible. The guard shall be such that it does not create an accident hazard in itself. When power operated tools are designed to accommodate guards, they shall be equipped with such guards when in use. Belts, gears, shafts, pulleys, sprockets, spindles, drums, flywheels, chains, or other reciprocating, rotating or moving parts of equipment shall be guarded if such parts are exposed to contact by employees or otherwise create a hazard.
At present, there are no governmental regulations for safety requirements specifically for robotic or autonomous equipment. It should be expected that state safety enforcement agencies will use the MIOSHA “general duty clause” to justify enforcement actions, where they will apply the existing machine guarding requirements outlined in this chapter to robots and autonomous equipment (i.e., the machine guarding requirements should be considered to apply to robots and autonomous equipment).
Reference Regulations: Guards For Power Transmission (MIOSHA Part 7)
12.2 Autonomous Vehicles #
The U-M supports the safe use of unmanned systems – on or off of U-M properties – in the course of research, educational activities, and other endeavors in the pursuit of the University’s mission. The area of unmanned system research and use is complex and ever-evolving. The Office of Research has established the Institutional Autonomous Systems Committee (IASC) to review all applications for use of these systems in an outdoor setting. Use of autonomous vehicles inside of facilities is at the discretion and approval of the Facility Manager for the building of interest, and approval will not be granted without adequate measures in place to assure the safety of everyone in the area of use and the protection of sensitive building systems. To that end, U-M EHS has created the following guidance:
Indoor Operation of Unmanned Aircraft Systems (UAS) Guideline – This Guideline applies to the indoor use of UAS by anyone on the University of Michigan (U-M) Ann Arbor, Flint, and Dearborn campuses, and other U-M properties (e.g., Biological Station, Pellston, MI; Stinchfield Woods, Pinckney, MI; Camp Davis, Jackson, WY). This Guideline also applies to the indoor use of UAS by U-M faculty, students, and staff for U-M sanctioned events off of U-M property. This Guideline covers UAS flights in both general public spaces (atriums, lobbies, etc.) as well as in controlled classroom and laboratory settings.
12.3 Where Mechanical Hazards Occur #
Dangerous moving parts have three basic areas that require safeguarding: #
- The Point-of-Operation: that point where work is performed on the material, such as cutting, shaping, boring, or forming of stock.
- The Power Transmission Apparatus: 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: 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 and ejection mechanisms, and auxiliary parts of the machine.
Types of hazardous mechanical motions that require safeguarding: #
- Rotating Motion
- Reciprocating Motion
- Transversing Motion
- Cutting Action
- Punching Action
- Shearing Action
- Bending Action
- In-Running Nip Points
Machine guarding is meant to protect workers during normal production activities. All of the following actvities are considered “servicing and/or maintenance activities” which fall under Lockout Tagout (chapter 13) requirements:
- Machine Setup/Preparation
- Machine Inspection
- Clearing Jams
- Machine Adjustments
- Cleaning of the Machine
- Lubricating the Machine
- Scheduled and Unscheduled Maintenance
Non-Mechanical Hazards #
While this machine guarding typically focuses primarily on concepts and techniques for safeguarding employees from mechanical hazards (moving parts), machines present a variety of other non-mechanical hazards that should not be ignored. Hazardous energy sources, other than safeguarding moving parts, can impact your safety and affect the safe operation of machines, including:
- Electricity
- Hydraulics
- Pneumatics
- Thermal
- Pressure
- Gravity
- Noise
- Harmful Substances
12.4 Types of Machine Guards #
- Fixed
- Interlocked
- Adjustable
- Self-adjusting
12.5 Types of Machine Safeguarding Devices #
Presence Sensing Devices #
Disengages the machine when something is detected in the hazard zone:
- Photoelectric
- Radiofrequency
- Electromagnetic
Restraint Devices #
Prevents the operator from reaching into the hazard zone
Pullback Devices #
As the machine cycles, the operator’s hands are pulled out of the hazard zone
Safety Trip Controls (stops the machine when the controls are tripped):
- Pressure sensitive body bar
- Safety trip-rod
- Two-hand Control
- Two-Hand Trip
Gates #
Provides a barrier between hazard zone and operator or other personnel
Guarding by Location and Distance #
Position machines so that the dangerous moving parts of a machine are not accessible, or do not present a hazard to the worker during the normal operation of the machine. Minimum distance required from floor to danger zone is 7 feet.
Complementary Equipment: #
- Emergency Stop Devices
- Work-Holding Equipment
- Feeding and Ejection Methods
- Foot Controls
- Miscellaneous Aids. Awareness barriers, shields, special hand tools.
12.6 EHS Support and Inspections #
EHS conducts regular inspections of all machine shops and Makerspaces to ensure compliance with regulations and University safety policies. EHS is also available to provide safety information and support to units that have or are planning on installing machine shops or Makerspaces. Information and resources, such as specific tool safety requirements and safety checklists are available on the EHS web site.
12.7 Machine Specific Safeguarding Standards #
- ANSI B5.52M-1980 (R1994), Presses, General Purpose, Single Point, Gap Type, Mechanical Power (Metric)
- ANSI B5.37—1970 (R1994), External Cylindrical Grinding Machines—Centerless
- ANSI B5.42—198 (R1994), External Cylindrical Grinding Machines—Universal
- ANSI B7.1—2000, Use, Care, and Protection of Abrasive Wheels
- ANSI B11.1-2001, Safety Requirements for Mechanical Power Presses
- ANSI B11.3-2002, Safety Requirements for the Construction, Care, and Use of Power Press Brakes
- ANSI B11.4-2003, Safety Requirements for Construction, Care, and Use of Shears
- ANSI B11.8-2001, Safety Requirements for Manual Milling, Drilling and Boring Machines with or without Automatic Control
- ANSI B11.9—1975 (R2005), Safety Requirements for the Construction, Care, and Use of Grinding Machines
- ANSI B11.12-1996, Safety Requirements for Construction, Care, and Use of Roll-Forming and Roll-Bending Machines
- ANSI B11.14—1996, Coil Slitting Machines Safety Requirements for Construction, Care and Use
- ANSI B11.19-2003, Performance Criteria for Safeguarding
- ANSI B20.1-57, Safety Code for Conveyors, Cableways, and Related Equipment [incorporated by reference in 1926.555(a)(8)]
- ANSI B65.1-2005, Safety Standard—Printing Press Systems
- ANSI B65.2-2005, Binding and Finishing Systems
- ANSI O1.1-2004, Safety Requirements for Woodworking Machinery
- ANSI/CEMA 350-2003, Screw Conveyors for Bulk Material
- ANSI/CEMA 401-2003, Unit Handling Conveyors—Roller Conveyors—Non-powered
- ANSI/CEMA 402-2003, Unit Handling Conveyors—Belt Conveyors
- ANSI/CEMA 403-2003, Unit Handling Conveyors—Belt Driven Live Roller Conveyors
- ANSI/CEMA 404-2003, Unit Handling Conveyors—Chain Driven Live Roller Conveyors
- ANSI/CEMA 405-2003, Unit Handling Conveyors—Slat Conveyors
- ANSI/CEMA 406-2003, Unit Handling Conveyors—Line-shaft Driven Live Roller Conveyors
- ANSI/ASME B20.1-2003, Safety Standard for Conveyors and Related Equipment
