Subpart O - Machine Guarding OTI 501 Paul A. Schlumper, PE, CSP

Subpart O - Machine Guarding OTI 501 Paul A. Schlumper, PE, CSP
Subpart O - Machine
OTI 501
Paul A. Schlumper, PE, CSP
We Will Cover:
Machine Guarding Principles
Subpart O - Highlights
Mock Plant Walk-Through
Why are machines not guarded?
No one would stick their arm, hand,
finger, head, etc. in there.
No one is supposed to be back there, in
there, around it while it is running.
The machine came that way; it never had
a guard.
I’ve been doing it this way for twenty
years without any problems.
Why are machines not guarded? (cont.)
The guard is in the way
The OSHA inspector didn’t say anything
about it.
We’ll put it back on if OSHA comes.
Machine Guarding Requirements
Prevent contact
Be secure
Protect from falling objects
Create no new hazards
No interference
Maintainability and accessibility
Where machine hazards occur:
Point of operation
Mechanical power transmission
Other moving parts
Methods of machine safeguarding
Physical guards
Safeguarding devices
Presence sensing
Safety controls and trips
Subpart O - Machinery and Machine
211 - Definitions
212 - General requirements
213 - Woodworking machinery
215 - Abrasive wheel machinery
216 - Mills and calendars
217 - Mechanical power presses
218 - Forging machines
219 - Mechanical power transmission
General Requirements for all
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.
The guard shall be such that it does not
offer an accident hazard in itself
The point of operation of machines whose
operation exposes an employee to injury,
shall be guarded
Special hand tools for placing and
removing material shall be such as to
permit easy handling of material in the
danger zone. Such tools shall not be in
lieu of other guarding required by this
section, but can only be used to
supplement protection provided.
Usually require guarding:
Guillotine cutters
Shears (including alligator shears)
Power presses
Milling machines
Power saws
Portable power tools
Forming rolls and calendars
When the periphery of the blades of a fan
is less than seven (7) feet above the floor
or working level, the blades shall be
guarded. The guard shall have openings
no larger than 1/2 inch.
Machines designed for a fixed location
shall be securely anchored to prevent
walking or moving.
Woodworking Machinery
All belts, pulleys, gears, shafts, and
moving parts shall be guarded in
accordance with the specific
requirements of 1910.219.
It is recommended that each powerdriven woodworking machine be
provided with a disconnect switch that
can be locked in the off position.
Combs (featherboards) or suitable jigs
shall be provided at the workplace for
use when a standard guard cannot be
A mechanical or electrical power control
shall be provided on each machine to
make it possible for the operator to cut
off the power from each machine without
leaving his position at the point of
On applications where injury to the
operator might result if motors were to
restart after power failures, provision
shall be made to prevent machines from
automatically restarting upon restoration
of power.
Each circular hand-fed ripsaw shall be
guarded by a hood which shall
completely enclose that portion of the
saw above the table and that portion of
the saw above the material being cut.
The hood and mounting shall be
arranged so that the hood will
automatically adjust itself to the
thickness of and remain in contact with
the material being cut without
considerable resistance.
Each hand-fed circular ripsaw shall be
furnished with a spreader to prevent
material from squeezing the saw or being
thrown back on the operator.
Each hand-fed circular ripsaw shall be
provided with non-kickback fingers or
dogs so located as to oppose the thrust or
tendency of the saw to pick up the
material or throw it back toward the
Each circular crosscut table saw shall be
guarded by a hood which shall meet all
the requirements of 1910.213(c)(1) for
hoods for circular resaws.
The upper hood shall completely enclose
the upper portion of the blade down to a
point that will include the end of the saw
arbor… The sides of the lower exposed
portion of the blade shall be guarded to
the full diameter of the blade by a device
that will automatically adjust itself of the
thickness of the stock and remain in
contact with the stock.
Each radial saw used for ripping shall be
provided with non kickback fingers or
dogs located on both sides of the saw...
An adjustable stop shall be provided to
prevent the forward travel of the blade
beyond the position necessary to
complete the cut in repetitive operations.
Installation shall be in such a manner
that the front end of the unit will be
slightly higher than the rear, so as to
cause the cutting head to return gently to
the starting position when released by the
Ripping and ploughing shall be against
the direction in which the saw turns. The
direction of the saw rotation shall be
conspicuously marked on the hood.
All portions of the saw blade (bandsaws)
shall be enclosed or guarded, except for
the working portion of the blade between
the bottom of the guide rolls and the
Each hand-fed jointer with a horizontal
cutting head shall have an automatic
guard which will cover all the section of
the head on the working side of the fence
or gage.
Each hand-fed jointer with horizontal
cutting head shall have a guard which
will cover the section of the head back of
the gage or fence.
The cutting heads of each wood shaper,
hand-fed panel raiser, or other similar
machine not automatically fed, shall be
enclosed with a cage or adjustable guard
so designed as to keep the operator’s
hand away from the cutting edge.
Cutting heads on wood-turning lathes,
whether rotating or not, shall be covered
as completely as possible by hoods or
Belt sanding machines shall be provided
with guards at each nip point where the
sanding belt runs on to the pulley.... The
unused run of the sanding belt shall be
guarded against accidental contact.
The mention of specific machines in
paragraphs (a) thru (q) and this
paragraph (r) of this section, inclusive, is
not intended to exclude other
woodworking machines from the
requirements that suitable guards and
exhaust hoods be provided to reduce to a
minimum the hazard due to the point of
operation of such machines.
All knives and cutting heads of
woodworking machines shall be kept
sharp, properly adjusted, and firmly
secured. Where two or more knives are
used, they shall be properly balanced.
All cracked saws shall be removed from
Abrasive-Wheel Machinery
Work rests shall be adjusted closely to
the wheel with a maximum opening of
one-eighth inch to prevent the work from
being jammed between the wheel and the
rest, which may cause wheel breakage.
The distance between the wheel
periphery and the adjustable tongue or
the end of the peripheral member at the
top shall never exceed one-fourth inch.
Immediately before mounting, all wheels
shall be closely inspected and sounded by
the user (ring test) to make sure they
have not been damaged.
Mills and Calendars in the Rubber
and Plastics Industries
A safety trip control must be provided in
front and back of each mill. It must be
accessible and operate readily on contact.
It must be one of the following:
Pressure-sensitive body bar
Safety triprod
Safety tripwire cable or wire
A safety triprod, cable or wire must be
provided across each pair or in-running
rolls extending the length of the face of
the rolls. It must be readily accessible
and operate whether pushed or pulled.
On both sides of the calendar and near
each end of the face of the roll, there
must be a safety trip cable or wire.
Mills must stop within 1 1/2 percent of
the peripheral no-load surface speed in
feet per minute.
Calendars must stop within 1 3/4 percent
of the peripheral no-load surface speed in
feet per minute. There is an exception for
speeds above 250 feet per minute.
Mechanical Power Presses
Press brakes, hydraulic and pneumatic
power presses, bulldozers, hot bending
and hot metal presses, forging presses
and hammers, riveting machines and
similar types of fastener applicators are
excluded from the requirements of this
Machines using full revolution clutches
shall incorporate a single-stroke
The pedal mechanism shall be protected
to prevent unintended operation.
A pad with a nonslip contact area shall be
firmly attached to the pedal.
A two-hand trip shall have the individual
operator’s hand controls protected
against unintended operation and be
arranged to require use of both hands.
Two-hand trip systems on full revolution
clutch machines shall incorporate an
antirepeat feature.
If two hand trip systems are used on
multiple operator systems, each operator
shall have a separate set of controls.
Two-hand controls must incorporate an
anti repeat feature, require use of both
hands, be protected against unintended
operation, have one set of controls for
each operator.
If foot control is provided, the selection
between hand and foot control must be
supervised by the employer.
A main power disconnect switch, capable
of being locked only in the off position
shall be provided with every power press
control system.
When required by paragraph (c)(5), the
control system shall be constructed so
that a failure within the system does not
prevent the normal stopping action but
does prevent initiation of a successive
stroke until the failure is corrected.
When required by paragraph (c)(5),
brake monitors must be constructed as to
automatically prevent the activation of a
successive stroke if the stopping time or
braking distance deteriorates to a point
where the safety distance requirements
are not met.
It shall be the responsibility of the
employer to provide and insure the use of
point of operation guards or properly
applied and adjusted point of operation
devices on every operation performed on
a mechanical power press. See Table O10.
Safety distance will be greater than the
distance determined by the following
Ds = 63 inches/second X Ts where Ts is the
stopping time of the press measured at
approximately 90 degree position of
crankshaft rotation (seconds)
It shall be the responsibility of the
employer to establish and follow a
program of periodic and regular
inspections of power presses.
It shall be the responsibility of the
employer to insure the original and
continuing competence of personnel
caring for, inspecting, and maintaining
power presses.
The employer shall train and instruct the
operator in the safe method of work
before starting work on any operation
covered by this section.
The employer shall provide clearance
between machines. Ample room for
cleaning machines, handling material,
work pieces, and scrap shall also be
The employer shall, within 30 days,
report all point of operation injuries to
operators or other employees.
Forging Machines
Mechanical Power-Transmission
This section does not apply to the
following belts operating at 250 fpm or
Flat belts 1 inch or less wide
Flat belts 2 inches wide or less with no
fasteners or metal lacings
Round belts 1/2 inch or less in diameter
Single-strand v-belts 13/32 inches wide or
Vertical and inclined belts if not more
than 2 1/2 inches wide, traveling at less
than 1000 fpm, if free from metal lacings
or fastenings may be guarded with a nip
point belt and pulley guard.
Flywheels located so that any part is 7
feet or less above the floor or platform
shall be guarded.
Wherever flywheels are above working
areas, guards shall be installed having
sufficient strength to hold the weight of
the flywheel in the event of a shaft or
wheel mounting failure.
Horizontal, vertical, and inclined shafting
must be enclosed.
Projecting shaft ends shall present a
smooth edge and end and shall not
project more than 1/2 the diameter of the
shaft unless guarded by non rotating cap
or safety sleeves. Unused keyways shall
be filled up or covered.
Pulleys less than 7 feet above the floor or
platform must be guarded.
Pulleys with cracks or pieces broken out
of rims shall not be used.
With some exceptions, horizontal,
vertical, and inclined belts must be
Gears must be guarded.
Guarding of hand operated gears is
highly recommended.
All sprocket and chains must be enclosed
unless more than 7 feet above the floor or
When frequent oiling must be done,
openings with hinged or sliding selfclosing covers must be provided.
Collars shall be cylindrical, and screws or
bolts used in collars shall not project
beyond the largest periphery of the
Couplings shall be constructed so as to
present no hazard from bolts, nuts,
setscrews, or revolving surfaces.
Wood guards may be used in the
woodworking and chemical industries or
other industries where conditions would
cause rapid deterioration or where its
location outdoors would make metal
guards and railings undesirable. In all
other industries, wood guards must not
be used.
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