B6: MACHINE GUARDING REQUIREMENTS
There seem to be as many hazards created by moving machine parts as there
are types of machines. Safeguards are essential for protecting operators
from preventable injuries.
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Scope and Application
The Occupational Safety and Health Administration
(OSHA) requires guarding for any machine where machine parts, functions,
or processes may cause injury. The need for machine guarding may be found
in machine shops in academic departments, maintenance shops, print shops,
and other areas where mechanical equipment is used.
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Any machine part, function, or process that might cause injury must
be safeguarded. When the operation of a machine or accidental contact
with it could injure the operator or others in the vicinity, the hazards
must be either controlled or eliminated.
Where Mechanical Hazards Occur
Dangerous moving parts in three basic areas require safeguarding:
- The point of operation:
that point where work is performed on the material, such as cutting,
shaping, boring, or forming of stock.
- Power transmission apparatus:
all components of the mechanical system that 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 that move while the machine is working.
These may include reciprocating, rotating, and transverse moving
parts, as well as feed mechanisms and auxiliary parts of the machine.
Hazardous Mechanical Motions and Actions
A wide variety of mechanical motions and actions may present hazards
to the operator. These can include the movement of rotating members,
reciprocating arms, moving belts, meshing gears, cutting teeth, and
any parts that impact or shear. These different types of hazardous
mechanical motions and actions are basic in varying combinations to
nearly all machines, and recognizing them is the first step toward
protecting operators from the danger they present.
The basic types of hazardous mechanical motions and actions are:
- rotating (including in-running nip points)
Requirements for Safeguards
Protective Clothing and Personal Protective Equipment
Safeguards must meet these minimum general requirements:
Prevent contact: The
safeguard must prevent hands, arms, and any other part of a operator's
body from making contact with dangerous moving parts. A good safeguarding
system eliminates the possibility of the operator or another worker
placing parts of their bodies near hazardous moving parts.
Secure: Operators should
not be able to easily remove or tamper with the safeguard, because
a safeguard that can easily be made ineffective is no safeguard
at all. 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.
Protect from falling objects:
The safeguard should ensure that no objects can fall into moving
parts. A small tool dropped into a cycling machine could easily
become a projectile that could strike and injure someone.
Create no new hazards:
A safeguard defeats its own purpose if it creates a hazard such
as a shear point, a jagged edge, or an unfinished surface that could
cause a laceration. The edges of guards, for instance, should be
rolled or bolted in such a way to eliminate sharp edges.
Create no interference:
Any safeguard that impedes an operator from performing the job quickly
and comfortably might soon be overridden or disregarded. Proper
safeguarding may actually enhance efficiency since it relieves the
operator's apprehensions about injury.
Allow safe lubrication:
If possible, workers should be able to lubricate the machine without
removing the safeguards. Locating oil reservoirs outside the guard,
with a line leading to the lubrication point, will reduce the need
for the operator or maintenance operator to enter the hazardous
Engineering controls that eliminate the hazard at the source and
do not rely on the operator's behavior for their effectiveness offer
the best and most reliable means of safeguarding. Therefore, engineering
controls are the first choice for eliminating machine hazards. But
whenever engineering controls are not available or are not fully capable
of protecting the operator, operators must wear protective clothing
or personal protective equipment (see Section B4,
Personal Protective Equipment).
To provide adequate protection, the protective clothing and equipment
must always be:
- appropriate for the particular hazards
- maintained in good condition
- properly stored when not in use, to prevent damage or loss
- kept clean, fully functional, and sanitary.
Protective clothing is, of course, available for different parts
of the body. Hard hats offer protection to the head from the
bumps and falling objects when the operator is handling stock;
caps and hair nets may be used to keep the operator's hair
from being caught
in machinery. If machine coolants could splash or particles could
fly into the operator's eyes or face, then face shields, safety
glasses, or similar kinds of protection might be necessary. Hearing
protection may be needed when operators operate noisy machines.
To guard the trunk of the body from cuts or impacts from heavy
rough-edged stock, there are protective coveralls, jackets, vests,
aprons, and full-body suits. Operators may protect their hands
arms from the same kinds of injury with special sleeves and gloves.
Safety shoes and boots, or other acceptable foot guards, shield
feet against injury in case the operator must handle heavy stock
that could drop.
It is important to note that protective clothing and equipment may
create hazards. A protective glove that could become caught between
rotating parts, or a respirator face piece that hinders the wearer's
vision, for example, require alertness and continued attentiveness
whenever they are used.
Other parts of the operator's clothing may present additional safety
hazards. For example, loose-fitting shirts might possibly become entangled
in rotating spindles or other kinds of moving machinery. Jewelry,
such as bracelets and rings, may catch on machine parts or stock and
lead to serious injury by pulling a hand into the danger area.
Even the most elaborate safeguarding system cannot offer effective
protection unless the operator knows how to use it and why. Specific
and detailed training is therefore a crucial part of any effort to
provide safeguarding against machine-related hazards. Thorough operator
training should involve instruction or hands-on training in the following:
- a description and identification of the hazards associated with
- the safeguards themselves, how they provide protection, and the
hazards for which they are intended
- how to use the safeguards and why
- how and under what circumstances safeguards can be removed, and
by whom (in most cases, repair or maintenance personnel only)
- what to do (e.g., contact the supervisor) if a safeguard is damaged,
missing, or unable to provide adequate protection.
This kind of safety training is necessary for new operators and
maintenance or setup personnel, when any new or altered safeguards
are put in service, or when operators are assigned to a new machine
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Roles and Responsibilities
- Ensure machines are equipped with appropriate safeguards.
- Provide personal protective equipment to operators, when necessary.
- Provide machine specific training to operators.
- Ensure operators do not defeat machine safeguards.
- Provide assistance in machine safeguard development.
- Assist in selection of personal protective equipment.
- Assist in development of specific training, when needed.
- Provide periodic audits of machine guarding.
- Operate machines with all safeguards in place.
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For More Information
Contact an EHS Safety Engineer at 258-5294.
A manual published by OSHA, Machine Guarding Concepts & Techniques,
is available through EHS.
A Machinery and Machine Guarding Self-Audit Checklist is available
through EHS or may be downloaded either as a PDF
or a customizable Word
A copy of OSHA’s regulation, Machinery
and Machine Guarding, 29 CFR 1910 Subpart O, is available through
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