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Machine Machine SafetySafety

Safeguarding any machine part that may cause injury.

Objectives:

1. To identify causes of machine related accidents

2. To provide ways of machine safeguarding

3. To articulate the importance of LOTO

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Machine accidents is caused of any of the following actions:

1. an individual making unwanted contact with a moving part of a machine

2. something flying from the machine

3. a machine malfunction, including mechanical and electrical energy sources failure

4. workpiece movement during a forming or cutting process

Effects of Machine Related Accidents

Can Result to Severe Injuries

Loss of Trained and Skilled Employee

Loss in Productivity

Damaged Equipment

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Where Mechanical Hazards Occur

The point of operation:

That point where work is performed on the material, such as cutting, shaping, boring, or forming.

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.

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Hazardous Mechanical Motions

• Rotating – turning around on an axis or center

• Reciprocating – the back and forth movements of a machine part

• Traversing – continuous straight line motion of a machine element in either direction

Hazards associated with Rotating Motions

Rotating coupling with projecting bolt

Rotating shaft and pulley with projecting key and set screw

Rotating pulley with spokes and projecting burr

Catching Body Parts

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Pinch Points / Nip Points Hazards

In-running nip points draw objects in and the effect is crushing or shearing injury.

Rotating Parts in Opposite Direction

Pinch Points Between Rotating Part and Tangentially Moving Part

Chain and Sprocket

Rack and Pinion

Belt and Pulley

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Pinch PointsBetween a Rotating Part and Fixed Parts

Cutting Hazards from Rotating Parts

• caught by• flying particles • sparks

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Reciprocating Machine Movements

During the back-and-forth or up-and-down motion, a worker can be struck by a moving part or caught between a moving and a stationary part. These are normally referred to as pinch points or caught-between hazards.

BendingPunching Shearing

Reciprocating Motion

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Traversing Motion

This motion is hazardous due to continuous straight line action and in-running nip points. Pinch and shear points are also created between a fixed or other moving object.

Purpose of Machine Safeguarding:Purpose of Machine Safeguarding:

To minimize the risk of injury to machine operators or other persons from hazardous machine parts, materials being processed, or scrap.

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Methods of Machine Safeguarding

GUARDS

• Fixed

• Interlocked

• Adjustable

• Manually adjustable

• Self-adjusting

DEVICES

• Presence sensing device

• Pullback device

• Restraint device

• Safety control devices

• Tripwire cable

• Two-hand Control

• Emergency Stop Button

Guards are barriers that prevent entry of an individual’s hands or other body parts into a hazard area.

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Fixed Barrier GuardThis type of guard is attached to a fixed surface and encloses the hazard. When in place, it prevents anyone from going over, around, under or through it to the hazard. The principal advantage of the fixed enclosing guard is that it always prevents access to the hazard area.

Movable guards w/ interlocking switches

This type prevents machine motion until the guard is moved into place. The interlocking method may be mechanical, electrical, pneumatic, or a combination of these. To be effective, interlocking guards must:

1.Enclose the point of operation before the machine can be operated.

2. Keep the point of operation enclosed before the hazardous part of the machine motion ceases.

3. Prevent operation of the machine if the interlock fails.

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Adjustable Guard

This type of guard can be positioned to accommodate a variety of operations or work and when properly adjusted provides adequate protection from the hazard at the point of operation. Adjustment of the guard should only be performed during setup.

Self-Adjusting GuardProvides a barrier which moves according tothe size of the stock entering the danger area.

Requirements for Machine GuardsSafeguards must meet these minimum general requirements:

•Prevent employee contact with hazardous moving parts•Secured and durable•Prevent falling materials into moving parts•Create no new hazards•Must not interfere with worker productivity•Should allow for proper and safe lubrication

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Any mechanical or electrical devices designed to protect a worker’s hands or other body parts from coming into contact with a hazardous motion of a machine.

Pullbacks and Restraint Devices

Holdout and restraint devices are cable and wristlet systems tha t attached to an operator’s hands and to the machine’s moving slide or ram, or to a fixed object away from the point of operation. They are usually used on machines having reciprocating motions.

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Two-hand Controls

Two-hand controls are operator controls that require an operator to hold both controls down during the hazardous portion of the machine’s stroke.

Presence-sensing Devices

These are designed, constructed, and arranged to create a sensing field, area, or plane that will detect in its field the presence of an opaque object.

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Emergency Stop

o Emergency stop button

o Grabwire switch or tripwire switch

Protective Shields

Provides some protection from flying particles, splashing cutting oils or coolants

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HOLDER, JIGS, PUSH STICKS

Control of All Energy Sources

Through

Lockout/Tagout System

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Lock-out/Tag-out System (LOTO)

The standard for the control of hazardous energy sources which covers maintenance of machines in which the unexpected start up of machines or release of stored energy could cause injury to employees.

Sources of Hazardous Energy

• Electrical – the uncontrolled current and voltage in electrical circuits

• Mechanical – exposed crushing or cutting parts of equipment or loose parts

• Thermal – such as steam or due to chemical reaction

• Potential - stored energy that may be due to gravity, hydraulics, pneumatics, vacuum or springs

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nLockout devices:

nA device that utilizes a positive means such as a lock either key or combination type, to hold an energy isolating device in the safe position and prevents the energizing of a equipment

nIncluded are blank flanges

nTagout devices:

nA warning device, such as a tag and a means of attachment

nCan be securely fastened to an energy isolating device in accordance with an established procedure to indicate that the energy isolating device and the equipment being controlled can not be operated until the tag is removed

Sequence of Lockout

• Notify the person in-charge/operator that maintenance of the equipment will be conducted.

• Person in-charge/operator shall identify the type and magnitude of energy that the machine utilizes.

• Deactivate the energy-isolating device(s) so that the machine or equipment is isolated from the energy source(s)

• Application of lock-out devices• Stored or residual energy must be dissipated or

restrained• Verification of equipment isolation

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Removal of Lock-out

• Ensure that the equipment components are operationally intact and it is safe to operate.

• Check the work area to ensure that all employees are safe.

• Notify person in-charge of job completion.• Remove lockout/tagout devices.

Summary:

1. Machine safety is preventing access to dangerous motions or preventing dangerous motions to access.

2. Machine safeguarding is generally accomplished by the use of machine guards and safety devices.

3. The lockout/tagout system is an effective safety program when performing maintenance activity.

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