MSHA Machine Guarding

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MSHAMachine Guarding
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Introduction to Guarding

• Many accidents result from persons working on or
  around moving machinery. These accidents could
  have been prevented by the installation and
  proper maintenance of guarding. The goal of this
  training is to make the guarding of all equipment
  as easily understood as possible and re-enforce
  the safe working procedures that must always be
  in place around dangerous equipment.

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MSHA Regulations

• 56/57.14107(a) Moving machine parts shall be
  guarded to protect persons from contacting gears,
  sprockets, chains, drive, head, tail and take-up
  pulleys, flywheels, couplings, shafts, fan
  blades, and similar moving parts that can cause
  injury.
• 56/57.14107(b) Guards shall not be required where
  the exposed moving parts are at least seven feet
  away from walking or working surfaces.

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Accidents and Injuries

• For the period 1990-1997
• there were 3,300 lost time injuries involving
  conveyor belts
• 39 miners were killed working around an unguarded
  conveyor belt
• 170 miners were permanently disabled as the
  result of working around an unguarded conveyor
  belt

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Effective Guarding

• An effective guard should have several
  characteristics in design and construction
• Be considered a permanent part of the equipment
• Afford maximum protection to operator
• Prevent access to danger zone during operation
• Be convenient and not interfere with efficiency
  of the operation
• Be designed for each specific machine
• Be durable and constructed strong enough to
  resist normal wear
• Not present a hazard in itself

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Maintenance

• When the installation of guards is complete, the
  employees who will work around the equipment or
  maintain it during operation should be properly
  trained to replace guards immediately after they
  are removed. Removal of guards should only take
  place after the equipment is properly
  de-energized and locked out. Supervisors,
  maintenance personnel, oilers, and all laborers
  working in the immediate area must be aware of
  the hazards around such equipment.

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Guard Selection

• The selection of a guarding method to be used may
  depend upon a number of factors such as space
  limitations, production methods, size of
  available stock, frequency of use, and type of
  equipment. Moving machine parts, nip points, and
  pinch points must be guarded individually rather
  that restricting access to the areas by
  installation of a railing. Guards should never
  create a greater hazard to employees working with
  or near the equipment.

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Type of Guards

• Materials for guards should be carefully
  selected. In most cases, guards of bar stock,
  sheet metal, perforated metal, expanded metal, or
  heavy wire mesh are more effective than other
  materials.
• Larger guards are frequently made of pipe or of a
  structural steel frame supporting wood, solid
  sheet metal, or wire mesh that will provide a
  positive barrier against moving parts.

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Type of Guards

• Guards of wood have limited application because
  their durability and strength, high replace cost
  and flammability may pose greater risk to
  employees who must work on or around equipment
  with this type of material construction.
• Guardrails and toeboards are frequently installed
  around flywheels, hoisting and other equipment
  where a hazards from falling objects exist,
  provide additional safeguards around moving parts
  and machinery.

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Type of Guards

• The application of guards constructed using
  expanded metal or mesh has several advantages
  over other materials.
• The area guarded can be inspected without
  removing the guard.
• Grease fittings and oil cups can be placed
  through openings without cutting large holes in
  the guard.
• Smaller particles of spilled materials (fines)
  can pass through the guard with minimal build-up
  of materials.

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Self Cleaning Tail Pulley

• The example on the right shows a self-cleaning
  tail pulley with an inadequate guard. The guards
  are placed too far away from the fins and pulley,
  leaving pinch points exposed to the operator.

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Self Cleaning Tail Pulley

• Self-cleaning tail pulleys should be guarded in
  this manner so that the employee is protected
  from the pinch points of the equipment and those
  created by the transfer chute.

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Tail Pulley Guards

• The guard for the tail pulley shown here does not
  cover the rotating parts. Side guards are
  effective when placed close to the pulley and
  extend a sufficient distance so that pinch points
  cannot be reached from the front, top or back.

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Working on Energized Equipment

• Remote areas, guarded by location, usually do not
  need to be guarded. However, if work is performed
  at such a location the equipment must be
  de-energized, locked locked and employees
  provided with a safe means of access.

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Return Idlers

• Return idlers should be guarded where someone
  could be injured while working or passing
  underneath the belt. It is important to guard
  these areas when clearance is less than seven
  feet from the walking surface.

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Return Idlers

• Here are two acceptable methods of guarding
  return idlers so that grease fittings can be
  accessed without removing the guards. The mesh
  openings can be large enough to let fines fall
  through but not allow a person to reach through.

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Head Pulleys
Unguarded and guarded head pulley and drive unit
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Stop Cords

• Stop cords provide additional safeguards for
  employees. The cord must be located so it can be
  reached by anyone falling on or against the belt.
  It must be sufficiently taut to assure the drive
  motor will be de-energized when the stop cord is
  pulled.

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Conveyor Railings

• The installation of a railing may be provided in
  lieu of conveyor guarding. The railing must be
  placed above belt level to prevent contact with
  the moving belt. When cable is used, it must be
  kept tight and free of burrs.

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Take-up Pulleys
Unguarded and guarded take-up pulley
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Applying Belt Dressings

• MSHA regulations state that belt dressing shall
  not be applied manually while the belts are in
  motion, unless an aerosol-type dressing is used.
  Mesh guarding allows access without exposing the
  operator.

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Counterweights

• Pinch points of take-up pulleys may be located
  above the ground so as to be guarded by location,
  however counterweights must be guarded to prevent
  access or blocked with a bar to prevent the
  counterweight from dropping to the ground.

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Drive Shafts

• Drive shafts with protruding set screws, keys and
  key ways must be guarded to prevent persons from
  the hazard created by rotating parts.

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Power Take-off Shafts

• Portable crushing machinery may have a power
  take-off shaft that can be best guarded by
  enclosing the shaft with a guard that is
  constructed of two halves, totally enclosing the
  drive shaft.

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Drive Couplings

• Drive couplings should be totally enclosed as
  shown in the illustration on the right.

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Drive Belt Pulleys

• The standard guard for a drive belt is inadequate
  because it allows an employee to reach behind the
  guard and access the rotating parts during
  maintenance operations.

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Drive Belt Pulleys

• Where access is possible, the belts and pulleys
  should be totally enclosed, preventing accidental
  contact with moving machine parts.

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Belt Breakage
Unguarded and guarded drive belt and pulley
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Protruding Shafts

• An effective way of guarding a protruding shaft
  is to put a sleeve with an end cap.
• Shafts ends, other than keyed shafts must be
  guarded when they protrude further than half the
  distance of the diameter of the shaft.

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Fan Inlets

• Fan inlets should be guarded regardless of
  location to not only prevent contact with moving
  blades but to also prevent free flying blades to
  injury an employee.

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Flywheel Guards

• A flywheel may be considered guarded by location
  where it is located at least seven feet above the
  walking or working surface.

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Flywheel Guards

• Where a build-up of material changes the distance
  of the walking or working surface, a guard must
  be installed to prevent contact by employees.

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Classifiers

• Since it is not practical to guard each
  classifier, a railing can be installed to
  restrict access and prevent employees from
  falling into a hazard.

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Dryers
Unguarded and guarded trunnions on a dryer
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Safe Maintenance

• Dont manually apply belt dressing if a conveyor
  belt is in motion. Only pressurized dressings can
  be put on while a conveyor is running.
• Always put a guard back in place when youre done
  working on a machine.
• Dont try to dislodge rocks form pulleys while
  the conveyor is running.
• Block conveyors against hazardous motion before
  repairing or servicing machinery.

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Working Smart

• Examine each work area at the start of each shift
  for guards that may need to be replaced.
• Lock and TAG out all power switches before you
  work on any machinery.
• Align conveyor belts from a safe location where
  the belt cant grab you.
• Stay clear of suspended loads during installation
  of repair of a conveyor.
• Check stop cords periodically to see if they
  work.
• Use a safety belt and harness when working from
  elevated work areas.
• Keep all walkways free and clean of hazards.

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Summary

• Guarding remains the number one citation issued
  by the Mine Safety and Health Administration.
• Historical data proves that working around
  unguarded equipment and machinery is always more
  dangerous than working around guarded equipment.
• Work safe - Guard all machinery