OSHA - Machine Guarding

OSHA - Machine Guarding

Course Description

This course focuses on OSHA guidelines pertaining to the proper use of safeguards to protect operators of machinery from injury.

Accreditation: KLA Education Services LLC is accredited by the State of California Board of Registered Nursing, Provider # CEP16145.

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Course Objectives

Upon completion of the course the course particpant will be able to:

  • Describe at least two of the main causes of machine accidents.
  • List three of the requirements for safeguards.
  • List 5 machinery parts that pose hazards when unguarded or improperly guarded.
  • List at least five types of machine guards.
  • List at least three types of devices used to safeguard machines
  • Describe a situation that warrants machine guarding and an appropriate method of guarding the machine or part in order to prevent injury or accident.


Course Content

Introduction

  • Crushed hands and arms, severed fingers, blindness - the list of possible machinery-related injuries is as long as it is horrifying. Safeguards are essential for protecting workers from needless and preventable injuries.
  • A good rule to remember is: Any machine part, function, or process which may cause injury must be safeguarded.
  • Where the operation of a machine can injure the operator or other workers, the hazard must be controlled or eliminated.
  • Regulatory Reference: 29 CFR 1910, Subpart O

Causes of Machine Accidents

  • Reaching in to “clear” equipment

  • Not using Lockout/Tagout

  • Unauthorized persons doing maintenance or using the machines

  • Missing or loose machine guards

Where Mechanical Hazards Occur

  • Point of operation

  • All parts of the machine which move, such as:

    • flywheels, pulleys, belts, couplings, chains, cranks, gears, etc.

    • feed mechanisms and auxiliary parts of the machine

    • reciprocating, rotating, and transverse moving parts

  • In-running nip points

Point of Operation

  • That point where work is performed on the material, such as cutting, shaping, boring, or forming of stock must be guarded.
  • Regulatory Reference: OSHA 1910.212(a)(3)(i) & (ii)

Rotating Parts

C:\My Documents\Outreach Training\GRDFIG1.TIF

In-Running Nip Points

  • In-running nip point hazards are caused by the rotating parts on machinery. There are three main types of in-running nips.
  • Parts can rotate in opposite directions while their axes are parallel to each other. These parts may be in contact (producing a nip point) or in close proximity to each other (where the stock fed between the rolls produces the nip points). This danger is common on machinery with intermeshing gears and rotating cylinders.
  • Another type of nip point is created between rotating and tangentially moving parts; for example, a chain and a sprocket, a rack and pinion, or the point of contact between a power transmission belt and its pulley.
  • Nip points can also occur between rotating and fixed parts which create a shearing, crushing, or abrading action; for example, spoked handwheels or flywheels, screw conveyors, or the periphery of an abrasive wheel and an incorrectly adjusted work rest.

C:\My Documents\Outreach Training\GRDFIG2.TIFRotating Cylinders

C:\My Documents\Outreach Training\GRDFIG3.TIF

Counter-clockwise from top: Belt & Pulley ; Chain & Sprocket ; Rack & Pinion

Requirements for Safeguards

  • Prevent contact - prevent worker’s body or clothing from contacting hazardous moving parts

    • A good safeguarding system eliminates the possibility of the operator or other workers placing parts of their bodies near hazardous moving parts.

  • Secure - firmly secured to machine and not easily removed

    • 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 and be firmly secured to the machine.

  • Protect from falling objects - ensure that no objects can fall into moving parts

    • A small tool which is dropped into a cycling machine could easily become a projectile that could strike and injure someone.

  • Create no new hazards - must not have shear points, jagged edges or unfinished surfaces

    • A safeguard defeats its own purpose if it creates a hazard of its own such as a shear point, a jagged edge, or an unfinished surface which can cause a laceration. The edges of guards, for instance, should be rolled or bolted in such a way that they eliminate sharp edges.

  • Create no interference - must not prevent worker from performing the job quickly and comfortably

    • Any safeguard which impedes a worker from performing a job quickly and comfortably might soon be overridden or disregarded. Proper safeguarding can actually enhance efficiency since it can relieve the worker’s apprehensions about injury.

  • Allow safe lubrication - if possible, 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 worker to enter the hazardous area.

Methods of Machine Safeguarding

  • Guards

    • fixed

      • Provides a barrier - a permanent part of the machine, preferable to all other types of guards.

      • As a general rule, power-transmission apparatus is best protected by fixed guards that enclose the danger area. For hazards at the point of operation, where moving parts actually perform work on stock, several kinds of safeguarding are possible.

      • Regulatory Reference: 1910.212(a)(2)

    • interlocked

      • When this type of guard is opened or removed, the tripping mechanism and/or power automatically shuts off or disengages, and the machine cannot cycle or be started until the guard is back in place.

      • An interlocked guard may use electrical, mechanical, hydraulic, or pneumatic power or any combination of these. Interlocks should not prevent “inching” by remote control, if required. Replacing the guard should not automatically restart the machine.

    • adjustable

      • Provides a barrier which may be adjusted to facilitate a variety of production operations.

      • Adjustable guards are useful because they allow flexibility in accommodating various sizes of stock, but, because they require adjusting, they are subject to human error.

    • self-adjusting

      • Provides a barrier which moves according to the size of the stock entering the danger area.

      • Provides a barrier which moves according to the size of the stock entering the danger area.

  • Devices

    • presence sensing

    • pullback

      • Utilizes a series of cables attached to the operator’s hands, wrists, and/or arms

      • Primarily used on machines with stroking action

      • Allows access to the point of operation when the slide/ram is up

      • Withdraws hands when the slide/ram begins to descend

    • restraint

      • Uses cables or straps attached to the operator’s hands and a fixed point

      • Must be adjusted to let the operator’s hands travel within a predetermined safe area

      • Hand-feeding tools are often necessary if the operation involves placing material into the danger area

    • safety controls (tripwire cable)

      • Device located around the perimeter of or near the danger area

      • Operator must be able to reach the cable to stop the machine

      • Tripwire cables must be manually reset to restart the machine.

    • safety controls (two-hand control)

      • Requires constant, concurrent pressure to activate the machine

      • The operator’s hands are required to be at a safe location (on control buttons) and at a safe distance from the danger area while the machine completes its closing cycle

      • This kind of control requires a part-revolution clutch, brake, and brake monitor if used on a power press as shown.

      • A similar device, known as a two-hand trip, requires concurrent application of both of the operator’s control buttons to activate the machine cycle, after which the hands are free. This device is used with machines equipped with full-revolution clutches. The trips must be placed far enough from the point of operation to make it impossible for the operators to move their hands from the trip buttons or handles into the point of operation before the first half of the cycle is completed to prevent them from being accidentally placed in the danger area prior to the slide/ram or blade reaching the full “down” position.

    • gates

      • Movable barrier device which protects the operator at the point of operation before the machine cycle can be started

      • If the gate does not fully close, machine will not function

      • Another potential application of this type of device is where the gate is a component of a perimeter safeguarding system. Here the gate may provide protection not only to the operator but to pedestrian traffic as well.

  • Location/distance

    • Locate the machine or its dangerous moving parts so that they are not accessible or do not present a hazard to a worker during normal operation.

    • Maintain a safe distance from the danger area.

    • One approach to safeguarding by location is shown in this photo. Operator controls may be located at a safe distance from the machine if there is no reason for the operator to tend it.

    • Another approach is to locate the machine so that a plant design feature, such as a wall, protects the worker and other personnel. Enclosure walls or fences can also restrict access to machines. Another possible solution is to have dangerous parts located high enough to be out of the normal reach of any worker.

  • Feeding and ejection methods

    • automatic and/or semi-automatic feed and ejection

    • robots

      • Machines that load and unload stock, assemble parts, transfer objects, or perform other tasks

      • Best used in high-production processes requiring repeated routines where they prevent other hazards to employees

      • Robots may create hazards themselves. If they do, appropriate guards must be used. The most common technique is to use perimeter guarding with interlocked gates.

      • The American National Standards Institute (ANSI) safety standard for industrial robots, ANSI/RIA R15.06-1999, presents certain basic requirements for protecting the worker. However, when a robot is used in a workplace, the employer should accomplish a comprehensive operational safety and health hazard analysis and then implement an effective safeguarding system which is fully responsive to the situation. [Various effective safeguarding techniques are described in ANSI B11.19-1990 (R1997).]

      • Studies in Sweden and Japan indicate that many robot accidents did not occur under normal operating conditions, but rather during programming, program touch-up, maintenance, repair, testing, setup, or adjustment. During these operations, workers may temporarily be within the robot’s working envelope where unintended operation could result in injuries.

  • Miscellaneous aids

    • awareness barriers

    • protective shields

      • These do not give complete protection from machine hazards, but do provide some protection from flying particles, splashing cutting oils, or coolants.

    • hand-feeding tools

Holding Tools

  • Used to place and remove stock in the danger area

  • Not to be used instead of other machine safeguards, but as a supplement

  • Regulatory Reference: OSHA 1910.212(a)(3)(iii)

P:\REY\jpg-01\Holding tools.jpg

Examples of OSHA Machine Guarding Requirements

  • Guarding Fan Blades
    • When the periphery of the blades of a fan is less than 7 feet above the floor or working level, the blades must be guarded with a guard having openings no larger than 1/2 inch. Reference: 1910.212(a)(5)

  • Abrasive Wheel Machinery
    • Work rests on offhand grinding machines must be kept adjusted closely to the wheel with a maximum opening of 1/8-inch to prevent the work from being jammed between the wheel and the rest, which may result in wheel breakage. Reference 1910.215(a)(4). (Image on Left)

    • The distance between the wheel periphery and the adjustable tongue must never exceed 1/4-inch. (Image on Right)

A:\abrasive grinders.jpg

Machine Safety Responsibilities

  • Management

    • ensure all machinery is properly guarded

  • Supervisors

    • train employees on specific guard rules in their areas

    • ensure machine guards remain in place and are functional

    • immediately correct machine guard deficiencies

  • Employees

    • do not remove guards unless machine is locked and tagged

    • report machine guard problems to supervisors immediately

    • do not operate equipment unless guards are in place

Training

Operators should receive training on the following:

  • Hazards associated with particular machines

  • How the safeguards provide protection and the hazards for which they are intended

  • How and why to use the safeguards

  • How and when safeguards can be removed and by whom

  • What to do if a safeguard is damaged, missing, or unable to provide adequate protection

Summary

  • Safeguards are essential for protecting workers from needless and preventable machinery-related injuries

  • The point of operation, as well as all parts of the machine that move while the machine is working, must be safeguarded

  • A good rule to remember is: Any machine part, function, or process which may cause injury must be safeguarded

  • For more information on this subject, see the following OSHA publication available at www.osha.gov:

    • Concepts and Techniques of Machine Guarding – OSHA 3067

Course Evaluation

Please select the extent to the following was met. (Disagree..Agree)

1. Course met objectives?

(1) (5)

2. Applicability or usability of new information?

(1) (5)

3. Adequacy of the instructor's mastery of subject?

(1) (5)

4. Efficiency of course mechanics?

(1) (5)

Course Evaluation

Please select the extent to the following was met. (Disagree..Agree)

1. Course met objectives?

(1) (5)

2. Applicability or usability of new information?

(1) (5)

3. Adequacy of the instructor's mastery of subject?

(1) (5)

4. Efficiency of course mechanics?

(1) (5)

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