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Machine Guarding

Shop Safety

2.0. General: 

Injuries resulting from contact with moving machine parts may be severe and often result in permanent disability. Two methods of machine guarding are: power transmission machinery guarding which includes all equipment from the prime mover to the point of operations; and point-of-operation guarding where the actual work of the machine takes place. 

2.1. Optimum Machinery Locations: 

For maximum safety, machines should be located to provide sufficient space for the operator to handle materials and perform most job  operations without interference from his own equipment or from other operators  nearby.  When possible, machines designed for fixed locations should be securely  anchored. Those machines using shock mounting pads should be installed according to manufacturer's recommendations. Top heavy machines should be firmly secured to prevent tipping. Lights should be at the point of operation and in the immediate area.  Lights that create a stroboscopic effect should not be used for illumination around moving machinery elements. Antiskid material, mats, etched floor, etc., are  encouraged to prevent slips and falls.  

2.2. Principles of Safe Machine Design:  

The most effective means of machine   guarding is by safe design and construction.  For safety and economy, machinery  should be purchased  with "built in" safeguards that meet OSHA requirements. They should be designed to give maximum operator protection without interfering  adjustments or lubrication, machine guards should be designed with hinged or  removable sections. 

2.3. Mechanical Guards:

When machinery and powered transmission equipment are not guarded as part of their design suitable mechanical guards such as enclosure or  barricades should be installed.  Machinery should not be used until made safe. 

  1. Construction Materials:  

    Machine guards constructed locally should be made of screening, expanded, perforated or latticed metal, reinforced as needed with maximum opening of 1/4".  Wooden or plastic guards should normally not be used because of their lack of durability.  Where fumes or manufacturing  conditions cause rapid deterioration of steel guards, other metals or materials should be used.  Guards should not have sharp edges, burrs or projections. 

  2. Removal of Permanently Installed Guards: 

    Guards should not be removed from any machine without proper authorization.  The machine should be turned off, power supply disconnected and the switch padlocked.  When a machine is equipped with removable guards, it should also be equipped with an interlock control device that will stop the machine if the guard is removed.

2.4. Machine Controls: 

Machine controls should be conveniently located for the operator. Stop switches should never be made inaccessible by covering or blocking off.  Power controls should be of a type that can be locked in the off position when necessary.  Suitable identification signs should be posted at control switches. Machine operators should not leave machinery running unattended.  

2.5. Mechanical Power Transmission Equipment:  

Guarding power transmission equipment involves providing adequate protection from the prime mover to the point of operation.  

  1. Flywheels: 

    When any portion of a flywheel is less than 7' above the floor or work platform, it should be completely enclosed in a suitable metal guard.  If a flywheel is unusually large, or protrudes through a work floor, it should be guarded by complete metal enclosures or guardrails and toe boards.  Flywheel rotations (RPM) should be maintained within the manufacturer's rated limits at all times. 

  2. Shafting: 

    Exposed shafting less than 7' above the floor should be completely enclosed in a stationary metal guard.  Suitable trough guards should be used to cover exposed parts of shafts to ensure enclosure on all sides.   

  3. Pulleys:  

    Pulleys should be rigged at a distance exceeding the width of the belt being used.  Where circumstances make this impossible, guides should be provided to prevent the belt from jumping the sheave. When pulleys are exposed to possible contact by personnel or installed less than 7' above the floor, the hazard points must have a cover.  

  4. Belt, Rope and Chain Drives:  

    These devices should be guarded when located less than 7' above the floor or at any height over work areas and passageways where material can come into contact with the hazard points.  

  5. Gears, Sprockets, and Chains: 

    These items located less than 7' above the floor or work area should be enclosed by guards.  When gears, sprockets or chains are more than 7' above a work area they should also be enclosed.  

  6. Shaft Ends and Shaft Keys: 

    Shaft ends projecting within 7' of the floor should be rounded smooth.  Shaft ends should not be allowed to protrude a distance greater than 1/2  of the diameter of the shaft beyond the end of the bearing unless protected by non-rotating casings. Exposed keyways, less than 8' above the floor, should be covered or filled. 

  7. Collars and Couplings: 

    Revolving collars should be cylindrical, with no projections beyond the periphery of the collar.  Any projection on the couplings should be covered with safety sleeves when it extends beyond the coupling flange.  

  8. Clutches:  

    Clutches and moving clutch parts closer than 7' to a working surface, should be enclosed in an approved stationary guard.  

2.6.Point of Operation Guarding:  

This method of guarding involves safeguarding the point(s) where cutting, shaping, drilling or forming is performed on the machine. Built-in safety devices are the most effective point-of-operation guards.  Machinery not equipped with proper safeguards to provide the type of operator protection defined in this manual should not be purchased.  When machine design does not give this type of operator protection, locally produced safeguards should be provided.  Each locally designed point-of-operation safety device should be simple in design and reliable in operation.  It should be installed as a permanent part of the machine. The device should be so designed and constructed that the operator will not be able to place any part of the body into the hazard points of the machine.  The guard should be attached so that essential inspections and adjustments can be performed without hazard to the operator.  

  1. Mechanical Guards: 

    Protective metal barriers or enclosures should be used at the points-of-operation.  Adequate guards should be placed on all sides of the hazard points where the operator can come into contact with moving parts.  

  2. Feeding Devices:  

    Machine operators should use mechanical feeding devices when possible, to avoid contact with moving parts. Stock feeding should be done by conveyor, revolving disk, gravity or separate piece of stock from a safe loading point.  Blanking dies should be equipped with spring clips strong enough to hold materials on the dies. Jigs and fixtures should be adequately secured to prevent slipping, turning or tipping.  

  3. Interrupting Devices: 

    For operations where any part of the operator's body has to be placed in a dangerous position to the machine, interrupting devices should be provided to automatically stop the machine when safety guards are bypassed or the operator moves from the normal operating position.  

  4. Remote Controls:  

    Ram-type machinery, such as power presses and drop hammers, should be provided with two-hand controls. Remote controls that require the operator to run the equipment at a distance from the point-of-operation may also be used.  The machine should be mechanically fed or loaded by hand, then put into operation by a remote control that is at a safe distance from the actual machining.