MODULE 10
Machine Guarding Rule 1200 Part 1
Machine guarding is an integral part of any safety and health program. It is also one aspect of safety that
is too often violated.
This module will discuss
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Reasons for machine guarding
Various types of guards used in industry
Different motions and actions
The Basics of Machine Safety
Rule of Thumb
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Any machine part, function, or process that may cause injury must be safeguarded.
OSHA RULE 1200 (1201-1207): there are movements or actions that can affect you when
operating the machine, then it must be guarded in some way
Mechanical hazards
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Hazardous mechanical motions and actions
Movement of machine or equipment and any other part that may cause injuries
Hazardous mechanical motions:
o Rotating motion
 circular motion around an axis or center that may grip clothing or otherwise
force a body part into a dangerous location
 examples of common rotating mechanisms: collars, couplings, cams, clutches,
flywheels, shaft ends, spindles, meshing gears, horizontal or vertical shafting
 Nip-points
 points where parts of the hand, body or clothes can get caught inbetween
 parts rotating in opposite directions, parts rotating tangentially, parts
rotating close to a fixed part
o Reciprocating motion
 Back-and-forth or up-and-down motion
 A worker may be struck by or caught between a moving and a stationary part
o Transverse motion
 Movement in a straight, continuous line
 Be struck or caught in a pinch or shear point by a moving part
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Hazardous mechanical actions:
o Cutting action
 Point of operation where finger, arm, and body injuries can occur and where
flying chips or scrap material can strike the head, particularly in the area of the
eyes or face
 Examples of mechanisms involving cutting hazards: ban saws, circular saws,
boring or drilling machines, turning machines (lathes), milling machines
o Punching action
 Power is applied to a slide (ram) for the purpose of blanking, drawing, or
stamping metal or other materials.
 Point of operation where stock is inserted, held, and withdrawn by hand
 Typical machines used for punching operations: power presses, iron work
o Shearing action
 Applying power to a slide or knife in order to trim or shear metal or other
materials
 Point of operation where stock is usually inserted, held, and withdrawn
 Examples of machines used for shearing operations: mechanically, hydraulically,
pneumatically powered shears
o Bending action
 Power is applied to a slide in order to draw or stamp metal or other materials
 Point of operation where stock is inserted, held, and withdrawn
 Equipment that uses bending actions: power presses, press brakes, tubing
benders
Machine Guarding Rule 1200 Part 2
Areas that require machine guards:
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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 which transmit energy to the part of the
machine performing the work
- Flywheels, pulleys, belts, connecting rods, couplings, cams, spindles, chains, cranks, and
gears
Other moving parts
- All parts of the machine which moves while the machine is working
- Reciprocating, rotating, transverse moving parts, as well as feed mechanism and
auxiliary parts of the machine
IN GENERAL: any machine part, function, or process which may cause injury must be guarded
Requirements for machine guarding:
1. Must prevent contact
- Safeguards should prevent human contact with any potentially harmful machine part
2. Must be secured and durable
- Workers should not be able to render them ineffective by tampering with or disabling
them
3. Must provide protection against falling objects
- Objects that fall on a moving part can be thrown out, creating dangerous projectile
4. Must not create new hazards
- A safeguard with a sharp edge, unfinished surface or protruding bolts introduces new
hazards while protecting against the old
5. Must not create interference
- Such safeguards are likely to be disregarded or disabled by workers due to the pressure
of production deadlines
6. Must allow safe maintenance
- Safeguards should be designed to allow the more frequently performed maintenance
tasks (e.g., lubrication) to be accomplished without removal of guards
Importance of machine safety:
Because we know that machines can cause:
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Severe accidents
Loss of trained and skilled employee/s
Loss of production
Damage to equipment
Incurring training cost for new employee/s
Overtime cost
Possible litigation
Accident investigation
Lost time expense
Cost of machine down time
Cost of machine damage and repairs
Lost time due to time spent on accident investigation and other statutory requirements
Loss of production
Machine Guarding Part 3
1. Types of machine guards
a. Fixed enclosing guards
i. Permanent part mounted on the machine.
b. Adjustable guards
i. They allow flexibility in accommodating various sizes.
c. Interlocked guards
i. The tripping mechanism and/or power automatically shuts off or
disengage.
d. Self-adjusting guard
i. This guard protects the operator by placing a barrier between the danger
area and the operator.
e. Photoelectric light curtain
i. These devices emit a curtain of harmless infrared light beams in the fron
of the hazard area.
f. Pullback devices
i. These devices use a series of cables attached to the operators’ hands, wrist,
and or arms.
g. Restraint devices
i. These devices use cables or straps that are attached of the operators’ hands
at a fixed point so that the operators’ hands may travel only within a
predetermined safe area.
h. Safety trip controls
i. These devices use pressure sensitive body bar, when depressed, will
deactivate the machine.
i. Two-hand control
i. This ensures that both hands of the operator are in a safe position and
therefore cannot be in the hazard area.
j. Transparent shields
i. These are used to provide protection from flying particles, slashing, and
cutting debris.
k. Push stich or block
i. When it becomes necessary for hands to be in close proximity to the blade,
the push stick or block may provide a few inches of safety and prevent a
severe injury.
2. Any part, function, or process which many causes injury must be guarded.
3. When the operation of a machine or accidental contact with it can injure the operator or
others in the vicinity, the hazards must be either controlled or eliminated.