Transcript ONLINE SELF-STUDY - Environment, Health and Safety

ONLINE SELF-STUDY
Machine Guarding
Machine Guarding
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The following online training course provides employees with
machine guarding information concerning processes,
equipment, and operations that are specifically conducted
at UNC Chapel Hill.
Employees will be introduced to the different types of
machine guarding methods, types of motions and actions,
and preventative strategies, and procedures to follow when
using machine guards or in the absence of machine guards.
Additional machine guarding information not covered in
detail within this particular training can be found at
www.osha.gov and under the UNC IMAC Manual: Machine
Guarding Policy.
References Covered in Training:
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OSHA 29 CFR 1910.212 (General Requirements for All Machines).
Machine Guarding OSHA e-Tool.
Introduction
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According to OSHA there are approximately 18,000 amputations,
lacerations, crushing injuries, and abrasions per year. There are also 800
deaths per year that are associated with improper or no machine
guarding. The majority of these types of injuries and deaths could have
been prevented by having proper machine guarding in place.
Machine guarding is the method used to prevent body parts and unwanted
objects from coming into contact with moving or dangerous parts of
machinery. If machine guarding is not in place, serious bodily harm or
death could occur.
Machine guarding is required by OSHA for any machine part, function, or
process that has the potential of causing an injury. Machine guarding also
differs for every machine due to the varying physical characteristics and
the operators involvement in how the machine is ran.
Introduction
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Employees often work with job specific types of machines long enough that it
becomes second nature to operate the machine. This can become potentially
hazardous since:
Continuous repetition can lead to a lack of concentration when operating the
machine.
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The operator believes that they are skillful enough with the piece of equipment
that the machine guard is not needed and they proceed to remove the guard.
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A dangerous situation is created in both of these scenarios for the operator
and employees that may be working around the machine during the time of
operation.
Never take for granted the security of working with the same machine.
Remember to always be alert and conscious of all moving machine parts no
matter how simple the operation of the machine may be.
Introduction
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Types of injuries that have the potential of occurring from improper or
no machine guarding are:
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Pinched, crushed, or severed limbs such as fingers, toes, hands, feet, arms, or
legs. Several examples of machines on campus that have the potential for
causing these types of injuries include: Trash compactors, lawn mowers,
printing machines, power saws, wood cutting machines, metal cutting
machines, etc.
Eye injury or blindness. Examples of machines on campus that have the
potential for causing these types of injuries include: Abrasive wheel
grinders, table saws, portable power saws, drill presses, etc.
Cuts, punctures, or abrasions. Types of machines that may cause these types
of injuries include: Drill presses, table saws, various wood working machines,
metal forming/cutting machines, etc.
Introduction
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Hazardous activities are considered to be situations that may present a
potential hazard to the operator or employees working around the machine
during operation. Examples of hazardous activities while operating any
machine includes:
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Normal production operations.
Machine set-up/threading/preparation.
Machine inspection.
Clearing jams.
Machine adjustments.
Cleaning of machine.
Lubricating of machine parts.
Maintenance of machine.
Do not wear loose clothing or jewelry, the material may become
entangled or caught in the machine. Once caught, these items can
cause the employee to become entangled in or pulled into the
machine.
Components of Machines
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A machine consist of three basic mechanical
components:
 Point
of Operation.
 Power Transmission Devices.
 Operating Controls (Other Moving Parts)
**Note: Even though machines have these three
basic components, this does not mean that
every machine has the same machine guarding.
Components of Machines
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Point of Operation: Where work
is performed on the material.
Points of operation must be
machine guarded. (i.e. - Cutting,
forming, etc.)
Power Transmission Devices: This
is the mechanical component that
transmits energy to the part of
the machine that performs the
work. (i.e. - Flywheels, pulleys,
belts, connecting rods, etc.)
Operating Controls (Other
Moving Parts): Are all of the
parts on a machine that move
while the machine is operating.
(i.e. - Reciprocating, rotating, etc.)
Operating
Controls
Power
Transmission
Device
Point of
Operation
Other Examples
Point of Operation on a Bench
Grinder
Power Transmission
Devices properly being
guarded on an
S & Drive Machine
Other Examples
Guard
Point of operation being properly
guarded on a drill press
Operating controls on a drill press
Hazardous Motions
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There are 4 types of hazardous motions that are
associated with machines:
 Rotating Motion.
 Reciprocating Motion.
 Transverse Motion.
 In-running Nip Points (Pinch Points)
Hazardous Motions
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Rotating Motion: Is a circular motion that is generated from a variety of
mechanisms on machines.
Rotating parts on a machine can ‘grab’ an employee through minor contact
which can force the hand, arm, or any other body part into a dangerous
position. The danger increases when projections such as set screws, bolts,
nicks, abrasions, and projecting keys are exposed on rotating parts. The
danger also increases if loose clothing is being worn or if an employee has
long hair.
Collars, couplings, cams, clutches, flywheels, shaft ends, spindles, meshing
gears, and horizontal or vertical shafting are some examples of common
rotating mechanisms which may be hazardous.
Rotating Shaft End
Hazardous Motions
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Reciprocating Motions: Is a back-and-forth
or up and-down motion that can strike or pin an
employee between a moving part and a fixed
object.
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Can be hazardous because, during the back-andforth or up-and-down motion, a worker may be
struck by or caught between a moving part and a
stationary part. An example of this would be a
forming machine.
Hazardous Motions
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Transverse motion: This refers to
movement in a straight and continuous
line. This type of motion creates a
hazard because a worker may be
struck or caught in a pinch or shear
point by the moving part. An
excellent example of a transverse
motion would be a conveyor belt or
belt sander.
Belt Sander
Hazardous Motions
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In-Running Nip Points: Pinch points develop
when two parts move together and at least
one moves in a circular motion. In-running
nip points occur when machine parts move
toward each other or when one part moves
past a stationary object. (ex. Gears, rollers,
belt drives, and pulleys)
Pinch point hazards are caused by rotating parts
on machinery. There are 3 main types of inrunning nip points:
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Parts can rotate in opposite directions while their
axes are parallel to each other. These parts can
either be in contact with one another or within close Sheet Metal Roller
proximity. Examples of parts that rotate in opposite
directions are gears, rolling mills, and calendars.
Hazardous Motions
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3 Main Types (cont’d…)
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Nip points are also created between rotating and tangentially moving
parts. Examples of this type would be the point of contact between a
power transmission belt and its pulley, a chain and a sprocket, and a
rack and pinion.
Nip points can also occur between rotating and fixed parts which
create a shearing, crushing, or grinding action. Several examples of
this include spoke hand wheels or flywheels, screw conveyors, or the
periphery of an abrasive wheel and an incorrectly adjusted work rest
and tongue.
Nip Point
Pulley
Hazardous Actions
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The 4 types of hazardous actions that are
associated with machines are:
 Cutting
Action.
 Punching Action.
 Shearing Action.
 Bending Action.
Hazardous Actions
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Cutting Action: May involve rotating, reciprocating, or transverse
motion.
The danger of cutting action exists at the point of operation where
finger, arm, and body injuries can occur, and where flying chips or
scrap material can strike the head, face, and eyes. Hazards are
present at the point of operation when cutting wood, metal, or other
materials.
Several examples of mechanisms involving cutting hazards include
bandsaws, circular saws, boring and drilling machines, turning
machines (lathes), and milling machines.
Router
Hazardous Actions
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Punching Action: Results when
power is applied to a slide (ram)
for the purpose of blanking,
drawing, or stamping metal or
other types of materials.
The danger of this type of action
occurs at the point of operation
where stock is inserted, held, and
withdrawn by the employee.
Examples of machines used for
punching operations are power
presses and iron workers.
Hazardous Actions
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Shearing Action: When power is applied to a slide or knife that is used to
trim or shear metal or other materials.
The hazard occurs at the point where the employee inserts, holds, or
withdraws the stock by hand.
Examples of machines used for shearing operations are mechanically,
hydraulically, or pneumatically powered shears.
Guard
Shear
Metal Shear with proper guard in
place.
Hazardous Actions
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Bending Action: Occurs when power is applied to
a slide in order to draw, turn, or stamp metal or
other materials into a specified shape.
A hazard occurs at the point of operation where
stock is inserted, held, and withdrawn.
Equipment that uses bending action includes power
presses, press brakes, and tube benders.
Tube Bender
Manual Break (Bends Sheet Metal)
Safeguarding Requirements
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All safeguards (machine guards) must meet or
exceed the following 6 requirements set forth by
OSHA:
 Prevent
Contact.
 Be Secured to the Machine, Floor, Wall, etc.
 Protect from Falling Objects.
 Does NOT Create a New Hazard.
 Does NOT Create an Interference.
 Allows for Safe Lubrication.
Safeguarding Requirements
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Prevent Contact: The safeguard must prevent hands, feet, arms,
legs, or any other part of the body from making contact with
dangerous moving parts.
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A good safeguard system eliminates the possibility of the operator or
another worker placing his hands near hazardous moving parts. The
best practice is to interlock machine control and guards so the machine is
inoperable unless the guards are in place.
Be Secured to the Machine, Floor, Wall, etc.: Workers should not
be able to remove or tamper with the safeguard. A safeguard that
can easily be made ineffective is not a safeguard at all.
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Guards and safety devices should be made of durable material that
will withstand the conditions of normal use. They must be firmly secured
to the machine.
Safeguarding Requirements
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Protect From Falling Objects: The guard should ensure that
no objects can fall into moving parts. (Example: A small
tool which dropped into a machine that is spinning in a
cyclical motion could cause the object to easily become a
projectile (flying object) that could strike someone, and
cause serious injury.)
Does NOT Create a New Hazard: A safeguard defeats its
own purpose if it creates a hazard of its own, such as a
shear point, a jagged edge, or an unfinished surface which
can cause lacerations.
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The edges of guards should be rolled or bolted in such a way
that they eliminate sharp edges.
Safeguarding Requirements
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Does NOT Create Interference: Any safeguard which impedes a
worker from performing the job quickly and comfortably may be
used improperly to make the job easier or even discarded while the
work is being conducted.
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Proper safeguarding can actually enhance efficiency by relieving the
stresses placed on the employee of thinking about the possibility of an
injury when using an unguarded or improperly guarded piece of
equipment.
Allows for Safe Lubrication: If possible, one should be able to
lubricate or service the machine with the safeguard in place.
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Locating oil reservoirs outside the guards with lines leading to the
lubrication points will reduce the need for the operator or maintenance
workers to enter the hazardous area.
Safeguarding Requirements
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OSHA Maximum Permissible Openings for Guards:
Distance of Opening from
Point of Operation (Inches)
Maximum Width of Openings
(Inches)
½ to 1 ½
¼
1 ½ to 2 ½
⅜
2 ½ to 3 ½
½
3 ½ to 5 ½
⅝
5 ½ to 6 ½
¾
6 ½ to 7 ½
⅞
7 ½ to 12 ½
1¼
12 ½ to 15 ½
1½
15 ½ to 17 ½
1⅞
17 ½ to 31 ½
2⅛
Over 31 ½
6
Other Machine Guarding Aides
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Machine guard aides include:
 Safety
Trip Controls.
 Gates.
 Photoelectric
Barriers/Light Curtains.
 Awareness Barriers.
 Special Hand Tools.
Other Machine Guard Aides
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Safety Trip Control
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Safety trip controls provide a
quick means for deactivating the
machine in an emergency situation.
A pressure-sensitive body bar,
when depressed, will deactivate
the machine. If the operator or
anyone trips, loses balance, or is
drawn toward the machine,
applying pressure to the bar will
stop the operation.
Other examples include
emergency stop buttons, and
emergency pull cords.
Other Machine Guarding Aides
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Gates
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The gate is a moveable barrier that
protects the operator at the point of
operation before the machine cycle can be
started. Gates are designed to be
operated with each machine cycle.
To be effective:
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The gate must be interlocked so that the
machine will not begin a cycle unless the
gate guard is in place.
The gate must be in the closed position
before the machine can function. If the gate
is not permitted to descend to the fully
closed position, the machine will not operate.
‘Gate’ on an
automatic bottle
washer
Other Machine Guarding Aides
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Photoelectric
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The photoelectric (optical) presencesensing device uses a system of light
sources and controls which can interrupt
the machine's operating cycle. These
are also known as ‘light curtains’. If the
light curtain is broken, the machine
instantly stops and will not cycle. This
device must be used only on machines
which can be stopped before the
worker can reach the danger area.
The design and placement of the
guard depends upon the time it takes
to stop the mechanism and the speed
at which the employee's hand can
reach across the distance from the
guard to the danger zone.
Once the ‘light’ barrier is broken, the
equipment must not be restarted while
any employee is in the danger zone.
Photoelectric
Barriers
Other Machine Guarding Aides
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Awareness Barrier: Serves as a reminder to a person that
he or she is approaching the danger area. Even though the
barrier does not physically prevent a person from entering
the danger area, it calls their attention to it.
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Awareness barriers are not considered an adequate means of
prevention when continual exposure to the hazard exists. An
awareness barrier can be used in conjunction with a proper
guard, but should never be the only method of ‘guarding’ an
area.
For an employee to enter the danger area, an overt act must
take place, meaning, the employee must either reach or step
over, under or through the barrier.
An example of this would be a highly visible tape placed on a
table saw a few inches away from the point of operation.
Other Machine Guarding Aides
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Special Hand Tools: Are tools used specifically for placing and
removing material to permit easy handling of material(s) without the
operator placing a hand in the danger zone (i.e. – Push stick, push
block, etc.).
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Special hand tools should never be used in the place of other required
guards. They can, however, be used in conjunction with the required
machine guard. (i.e. – Push stick used for a table saw in conjunction with
a self adjusting table saw guard.)
Push Block
Fingerboard
Push Stick
Construction of Machine Guards
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Most machine guards can be purchased from the
manufacturer of the specified machine.
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Always check with the manufacturer of the machine to see
if they also produce safeguards for that particular machine.
Guards designed and installed by the builder/manufacture
offer two main advantages:
They usually conform to the design and function of the machine.
 They can be designed to strengthen the machine in some way or
to serve some additional functional purposes.
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Construction of Machine Guards
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Examples of Manufacturer Machine Guards:
Construction of Machine Guards
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Sometimes a guard is not produced by the manufacturer for a
particular machine because the machine pre-dates the use or
production of machine guards.
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If this is the case, then user built guards can be developed to serve the
purpose of machine guarding as long as they are fabricated to function
effectively and meet the specifications of proper machine guarding for
the specific machine they are developed for.
Note: Just because a guard is not specifically made for a machine,
does not mean a guard does not have to be in place.
Machine guarding is required on ALL machines where a risk of an injury
exists at the point of operation, or where exposed mechanisms/parts on
the machine may injure an employee if a guard is not in place.
Construction of Machine Guards
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Examples of Fabricated Machine Guards:
Before
After
Before
After
Machinery Maintenance & Repair
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Having superior maintenance and repair procedures
(i.e. – Job Safety Analysis, Standard Operating
Procedures) in place to reduce hazards can contribute
significantly to the safety of UNC-CH maintenance
personnel and machine operators. The following 4
things can make safe maintenance and repair work
difficult:
The variety and complexity of machines to be serviced.
 The hazards associated with their power sources.
 The special dangers that may be present during machine
breakdown.
 The severe time constraints often placed on maintenance
personnel.
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Machinery Maintenance & Repair
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The following safeguarding measures should be
taken in order to prevent hazards while servicing
machines:
 Notify
all affected employees (usually machine or
equipment operators or users) that the machine or
equipment must be shut down to service the machine or
perform maintenance.
 Stop the machine.
 Isolate the machine or piece of equipment from its
energy source.
Machinery Maintenance & Repair
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The following safeguarding measures should be taken in
order to prevent hazards while servicing machines
(cont’d…):
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Lockout/Tagout the energy source.
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**The danger of accident or injury is greatly reduced by
shutting off and locking out/tagging out all sources of energy.
Relieve any stored or residual energy.
 Verify that the machine or equipment is isolated from the
energy source.
 Once all maintenance and repair has been completed,
place and secure ALL guards back on the equipment before
turning it on.
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Machinery Maintenance & Repair
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The following list are exceptions to the general rules in
regard to safeguarding measures that should be followed in
order to prevent hazards:
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When the servicing or maintenance is not hazardous for an
employee. The supervisor, employee, or UNC Environment, Health
& Safety can deem servicing/maintenance as hazardous or nonhazardous. If there is a safety concern, contact UNC Environment,
Health & Safety before any servicing/maintenance is started.
When the servicing which is conducted is minor in nature.
Servicing is done as an integral part of production.
The employer utilizes alternative safeguards which provide
effective protection as required by 29 CFR 1910.212 or other
specific standards.
Machinery Maintenance & Repair
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The following list of specific steps must be followed in
order to return the machine or piece of equipment to
service. These steps include:
Inspection of the machine or equipment to ensure that all
guards and other safety devices are in place and
functional.
 Checking the area to ensure that energization and start up
of the machine or equipment will not endanger employees.
 Removal of the lockout devices.
 Re-energization of the machine or equipment.
 Notification of affected employees that the machine or
equipment may be returned to service.
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Feeding & Ejection Methods
Automatic Feed: The material is fed from rollers or another
automatic method.
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This eliminates the need for operator involvement in the danger
area.
Other guards such as fixed barrier guards are required for
operator protection.
Requires frequent maintenance due to the many moving parts
involved in the automatic feed process.
A disadvantage is that it may not be adaptable to different types
or sizes of materials.
Semiautomatic Feed: Material is fed by chutes, movable dies,
dial feed, plungers, or sliding bolster.
Feeding & Ejection Methods
Automatic Ejection: The material is ejected by air or mechanical means.
This method of ejection may create a hazard of blowing debris.
Disadvantages of the automatic ejection method include:
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The size of materials limits the use of this method.
Air ejection may present a noise hazard.
Semiautomatic Ejection: The material is ejected by mechanical means which
are started by the operator. The operator does not have to enter danger
area to remove material. Disadvantages of this method are:
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That other guards are required for operator protection.
It may not be adaptable to different sizes and shapes of materials being used.
Feeding & Ejection Methods
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Robotic Machines: Used to perform
work that is usually conducted by a
human.
Operator does not have to enter
danger area.
 Are suitable for operations where high
stress factors are present, such as heat
stress and noise levels 85 dB or higher.
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Disadvantages of Robots:
 Can create hazards themselves.
 Require maximum maintenance.
 Are suitable only to specific operations.
Pegasus Robotic Bedding
Machine
Feeding and Ejection Methods
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Robotic Machines (cont’d…)
 When
servicing or performing maintenance on robotic
equipment, always deenergize it before entering the
area and performing any work.
 Never depend on the stoppage of the automatic shut
off control circuit alone to cut all power to the robotic
machine.
Feeding and Ejection Methods
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Robotic Machines (cont’d…)
 ALL
employees must be clear from the danger area
once maintenance has been completed.
 The
danger zone is separated from the safe zone by light
curtains and a safety barrier consisting of a Plexiglas wall
that contains the robotic machinery.
 NEVER
bypass safety switches, light curtains, emergency
stop buttons, etc. when performing maintenance on
robotic machinery or any other type of machinery.
Lock out/tag out
Lock out/tag out is also an integral part of workplace safety. When
machine guarding must be removed for maintenance, proper lock
out/tag out procedures must be followed.
When performing maintenance do the following:
- Notify all affected employees that the machine or equipment
must be shut down to perform maintenance or servicing.
- Isolate the machine or piece of equipment from its energy
source.
- The energy source should be locked out or tagged out.
- Any stored or residual energy should be relieved from the
machine.
- The machine or equipment should be verified that it is isolated
from the energy source.
Lock Out/Tag Out
If you have any questions or concerns, contact your supervisor or UNC
Environment, Health & Safety for more specific LOTO procedures.
 Additional information concerning LOTO can be found on the UNC Environment,
Health & Safety website.

 Link:
http://www.ehs.unc.edu
 Link: http://www.ehs.unc.edu/manuals/imac/
 Contact Info: Kim Haley (843-2735
Standard References
Additional Information concerning Machine Guarding can be
found under:
 OSHA 1910.213 (Woodworking Machinery
Requirements)
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OSHA 1910.215 (Abrasive Wheel Machinery)
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Also addressed in UNC IMAC Manual Machine Guarding
Policy.
Also addressed in UNC IMAC Manual Machine Guarding
Policy as well as the Hand and Portable Power Tools Policy.
OSHA 1910.217 (Mechanical Power Presses)
OSHA 1910.217 App. A – D (Non-mandatory and
Mandatory Guidelines for Various Machines/Safeguards.)
OSHA 1910.218 (Forging Machines)
OSHA 1910.219 (Mechanical Power Transmission
Apparatus)
Summary
Machine guarding is important for your personal health
and safety and those that work around you. Before beginning
daily work activities, assess all work areas where machinery is
present and check for possible hazards/missing guards/etc.
Make sure that all guards on equipment are adjusted and
functioning properly. Guarding should never be removed
except for maintenance procedures. If machine guarding is not
in place do not use the equipment, and use proper procedures
to ensure that guarding is put in place.
If you have any questions or concerns about machine
guarding contact your departmental supervisor or UNC
Environment, Health, & Safety at 962-5507.