ONLINE SELF-STUDY

Machine Guarding

Machine Guarding The following online training course provides

employees with machine guarding information concerning processes, equipment, and operations that are specifically conducted at UNC Chapel Hill.

Employees will be introduced to the different types of machine guarding methods, types of motions and actions, and preventative strategies, and procedures to follow when using machine guards or in the absence of machine guards.

Additional machine guarding information not covered in detail within this particular training can be found at www.osha.gov and under the UNC IMAC Manual: Machine Guarding Policy.

References Covered in Training: OSHA 29 CFR 1910.212 (General Requirements for All

Machines). Machine Guarding OSHA e-Tool.

Introduction

According to OSHA there are approximately 18,000 amputations, lacerations, crushing injuries, and abrasions per year. There are also 800 deaths per year that are associated with improper or no machine guarding. The majority of these types of injuries and deaths could have been prevented by having proper machine guarding in place.

Machine guarding is the method used to prevent body parts and unwanted objects from coming into contact with moving or dangerous parts of machinery. If machine guarding is not in place, serious bodily harm or death could occur.

Machine guarding is required by OSHA for any machine part, function, or process that has the potential of causing an injury. Machine guarding also differs for every machine due to the varying physical characteristics and the operators involvement in how the machine is ran.

Introduction

Employees often work with job specific types of machines long enough that it becomes second nature to operate the machine. This can become potentially hazardous since: Continuous repetition can lead to a lack of concentration when operating the machine. The operator believes that they are skillful enough with the piece of equipment that the machine guard is not needed and they proceed to remove the guard.

A dangerous situation is created in both of these scenarios for the operator and employees that may be working around the machine during the time of operation.

Never take for granted the security of working with the same machine. Remember to always be alert and conscious of all moving machine parts no matter how simple the operation of the machine may be.

Introduction

Types of injuries that have the potential of occurring from improper or no machine guarding are:

Pinched, crushed, or severed limbs such as fingers, toes, hands, feet, arms, or legs. Several examples of machines on campus that have the potential for causing these types of injuries include: Trash compactors, lawn mowers, printing machines, power saws, wood cutting machines, metal cutting machines, etc.

Eye injury or blindness. Examples of machines on campus that have the potential for causing these types of injuries include: Abrasive wheel grinders, table saws, portable power saws, drill presses, etc.

Cuts, punctures, or abrasions. Types of machines that may cause these types of injuries include: Drill presses, table saws, various wood working machines, metal forming/cutting machines, etc.

Introduction Hazardous activities are considered to be situations that

may present a potential hazard to the operator or employees working around the machine during operation. Examples of hazardous activities while operating any machine includes:

Normal production operations. Machine set-up/threading/preparation. Machine inspection. Clearing jams. Machine adjustments. Cleaning of machine. Lubricating of machine parts. Maintenance of machine.

Do not wear loose clothing or jewelry, the material may become entangled or caught in the machine. Once caught, these items can cause the employee to become entangled in or pulled into the machine.

Components of Machines

A machine consist of three basic mechanical components: Point of Operation. Power Transmission Devices. Operating Controls (Other Moving Parts)

**Note: Even though machines have these three basic components, this does not mean that every machine has the same machine guarding.

Components of Machines Point of Operation: Where

work is performed on the material. Points of operation must be machine guarded. (i.e. - Cutting, forming, etc.)

Power Transmission Devices: This is the mechanical component that transmits energy to the part of the machine that performs the work. (i.e. - Flywheels, pulleys, belts, connecting rods, etc.)

Operating Controls (Other Moving Parts): Are all of the parts on a machine that move while the machine is operating. (i.e. - Reciprocating, rotating, etc.)

Power Transmis

sion Device

Operating Controls

Point of Operation

Other Examples

Point of Operation on a Bench Grinder

Power Transmission Devices properly being guarded on an S & Drive Machine

Other Examples

Point of operation being properly guarded on a drill press

Guard

Operating controls on a drill press

Hazardous Motions

There are 4 types of hazardous motions that are associated with machines: Rotating Motion. Reciprocating Motion. Transverse Motion. In-running Nip Points (Pinch Points)

Hazardous Motions

Rotating Motion: Is a circular motion that is generated from a variety of mechanisms on machines.

Rotating parts on a machine can ‘grab’ an employee through minor contact which can force the hand, arm, or any other body part into a dangerous position. The danger increases when projections such as set screws, bolts, nicks, abrasions, and projecting keys are exposed on rotating parts. The danger also increases if loose clothing is being worn or if an employee has long hair.

Collars, couplings, cams, clutches, flywheels, shaft ends, spindles, meshing gears, and horizontal or vertical shafting are some examples of common rotating mechanisms which may be hazardous.

Rotating Shaft End

Hazardous Motions

Reciprocating Motions: Is a back-and-forth or up and-down motion that can strike or pin anemployee between a moving part and a

fixedobject.

Can be hazardous because, during the back-and-forth or up-and-down motion, a worker may be struck by or caught between a moving part and a stationary part. An example of this would be a forming machine.

Hazardous Motions

Transverse motion: This refers to movement in a straight and continuous line. This type of motion creates a hazard because a worker may be struck or caught in a pinch or shear point by the moving part. An excellent example of a transverse motion would be a conveyor belt or belt sander.

Belt Sander

Hazardous Motions

In-Running Nip Points: Pinch points develop when two parts move together and at least one moves in a circular motion. In-running nip points occur when machine parts move toward each other or when one part moves past a stationary object. (ex. Gears, rollers, belt drives, and pulleys)

Pinch point hazards are caused by rotating parts on machinery. There are 3 main types of in-running nip points: Parts can rotate in opposite directions while

their axes are parallel to each other. These parts can either be in contact with one another or within close proximity. Examples of parts that rotate in opposite directions are gears, rolling mills, and calendars.

Sheet Metal Roller

Hazardous Motions

3 Main Types (cont’d…) Nip points are also created between rotating and

tangentially moving parts. Examples of this type would be the point of contact between a power transmission belt and its pulley, a chain and a sprocket, and a rack and pinion.

Nip points can also occur between rotating and fixed parts which create a shearing, crushing, or grinding action. Several examples of this include spoke hand wheels or flywheels, screw conveyors, or the periphery of an abrasive wheel and an incorrectly adjusted work rest and tongue.

Pulley

Nip Point

Hazardous Actions

The 4 types of hazardous actions that are associated with machines are: Cutting Action. Punching Action. Shearing Action. Bending Action.

Hazardous Actions

Cutting Action: May involve rotating, reciprocating, or transverse motion.

The danger of cutting action exists at the point of operation where finger, arm, and body injuries can occur, and where flying chips or scrap material can strike the head, face, and eyes. Hazards are present at the point of operation when cutting wood, metal, or other materials.

Several examples of mechanisms involving cutting hazards include bandsaws, circular saws, boring and drilling machines, turning machines (lathes), and milling machines.

Router

Hazardous Actions

Punching Action: Results when power is applied to a slide (ram) for the purpose of blanking, drawing, or stamping metal or other types of materials.

The danger of this type of action occurs at the point of operation where stock is inserted, held, and withdrawn by the employee.

Examples of machines used for punching operations are power presses and iron workers.

Hazardous Actions

Shearing Action: When power is applied to a slide or knife that is used to trim or shear metal or other materials.

The hazard occurs at the point where the employee inserts, holds, or withdraws the stock by hand.

Examples of machines used for shearing operations are mechanically, hydraulically, or pneumatically powered shears.

Metal Shear with proper guard in place.

Guard Shear

Hazardous Actions

Bending Action: Occurs when power is

applied to a slide in order to draw, turn, or stamp metal or other materials into a specified shape.

A hazard occurs at the point of operation where stock is inserted, held, and withdrawn.

Equipment that uses bending action includes power presses, press brakes, and tube benders.

Tube Bender

Manual Break (Bends Sheet Metal)

Safeguarding Requirements

All safeguards (machine guards) must meet or exceed the following 6 requirements set forth by OSHA: Prevent Contact. Be Secured to the Machine, Floor, Wall, etc. Protect from Falling Objects. Does NOT Create a New Hazard. Does NOT Create an Interference. Allows for Safe Lubrication.

Safeguarding Requirements

Prevent Contact: The safeguard must prevent hands, feet, arms, legs, or any other part of the body from making contact with dangerous moving parts. A good safeguard system eliminates the possibility of the

operator or another worker placing his hands near hazardous moving parts. The best practice is to interlock machine control and guards so the machine is inoperable unless the guards are in place.

Be Secured to the Machine, Floor, Wall, etc.: Workers should not be able to remove or tamper with the safeguard. A safeguard that can easily be made ineffective is not a safeguard at all. Guards and safety devices should be made of durable

material that will withstand the conditions of normal use. They must be firmly secured to the machine.

Safeguarding Requirements

Protect From Falling Objects: The guard should ensure that no objects can fall into moving parts. (Example: A small tool which dropped into a machine that is spinning in a cyclical motion could cause the object to easily become a projectile (flying object) that could strike someone, and cause serious injury.)

Does NOT Create a New Hazard: 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 lacerations. The edges of guards should be rolled or bolted in such

a way that they eliminate sharp edges.

Safeguarding Requirements

Does NOT Create Interference: Any safeguard which impedes a worker from performing the job quickly and comfortably may be used improperly to make the job easier or even discarded while the work is being conducted. Proper safeguarding can actually enhance efficiency by

relieving the stresses placed on the employee of thinking about the possibility of an injury when using an unguarded or improperly guarded piece of equipment.

Allows for Safe Lubrication: If possible, one should be able to lubricate or service the machine with the safeguard in place. Locating oil reservoirs outside the guards with lines

leading to the lubrication points will reduce the need for the operator or maintenance workers to enter the hazardous area.

Safeguarding Requirements

OSHA Maximum Permissible Openings for Guards:Distance of Opening

from Point of Operation (Inches)

Maximum Width of Openings (Inches)

½ to 1 ½ ¼

1 ½ to 2 ½ ⅜

2 ½ to 3 ½ ½

3 ½ to 5 ½ ⅝

5 ½ to 6 ½ ¾

6 ½ to 7 ½ ⅞

7 ½ to 12 ½ 1 ¼

12 ½ to 15 ½ 1 ½

15 ½ to 17 ½ 1 ⅞

17 ½ to 31 ½ 2 ⅛

Over 31 ½ 6

Other Machine Guarding Aides

Machine guard aides include: Safety Trip Controls. Gates. Photoelectric Barriers/Light Curtains. Awareness Barriers. Special Hand Tools.

Other Machine Guard Aides

Safety Trip Control Safety trip controls provide

a quick means for deactivating the machine in an emergency situation.

A pressure-sensitive body bar, when depressed, will deactivate the machine. If the operator or anyone trips, loses balance, or is drawn toward the machine, applying pressure to the bar will stop the operation.

Other examples include emergency stop buttons, and emergency pull cords.

Other Machine Guarding Aides Gates

The gate is a moveable barrier that protects the operator at the point of operation before the machine cycle can be started. Gates are designed to be operated with each machine cycle.

To be effective: The gate must be interlocked so

that the machine will not begin a cycle unless the gate guard is in place.

The gate must be in the closed position before the machine can function. If the gate is not permitted to descend to the fully closed position, the machine will not operate. ‘Gate’ on an

automatic bottle washer

Other Machine Guarding Aides Photoelectric

The photoelectric (optical) presence-sensing device uses a system of light sources and controls which can interrupt the machine's operating cycle. These are also known as ‘light curtains’. If the light curtain is broken, the machine instantly stops and will not cycle. This device must be used only on machines which can be stopped before the worker can reach the danger area. The design and placement of the guard depends upon the time it takes to stop the mechanism and the speed at which the employee's hand can reach across the distance from the guard to the danger zone.

Once the ‘light’ barrier is broken, the equipment must not be restarted while any employee is in the danger zone.

Photoelectric Barriers

Other Machine Guarding Aides Awareness Barrier: Serves as a reminder to a

person that he or she is approaching the danger area. Even though the barrier does not physically prevent a person from entering the danger area, it calls their attention to it. Awareness barriers are not considered an adequate

means of prevention when continual exposure to the hazard exists. An awareness barrier can be used in conjunction with a proper guard, but should never be the only method of ‘guarding’ an area.

For an employee to enter the danger area, an overt act must take place, meaning, the employee must either reach or step over, under or through the barrier.

An example of this would be a highly visible tape placed on a table saw a few inches away from the point of operation.

Other Machine Guarding Aides Special Hand Tools: Are tools used specifically for

placing and removing material to permit easy handling of material(s) without the operator placing a hand in the danger zone (i.e. – Push stick, push block, etc.). Special hand tools should never be used in the place of

other required guards. They can, however, be used in conjunction with the required machine guard. (i.e. – Push stick used for a table saw in conjunction with a self adjusting table saw guard.)

Push Block

Push Stick

Fingerboard

Construction of Machine Guards Most machine guards can be purchased from the

manufacturer of the specified machine. Always check with the manufacturer of the machine to

see if they also produce safeguards for that particular machine. Guards designed and installed by the builder/manufacture offer two main advantages: They usually conform to the design and function of the

machine. They can be designed to strengthen the machine in some

way or to serve some additional functional purposes.

Construction of Machine Guards Examples of Manufacturer Machine

Guards:

Construction of Machine Guards Sometimes a guard is not produced by the

manufacturer for a particular machine because the machine pre-dates the use or production of machine guards. If this is the case, then user built guards can be

developed to serve the purpose of machine guarding as long as they are fabricated to function effectively and meet the specifications of proper machine guarding for the specific machine they are developed for.

Note: Just because a guard is not specifically made for a machine, does not mean a guard does not have to be in place.

Machine guarding is required on ALL machines where a risk of an injury exists at the point of operation, or where exposed mechanisms/parts on the machine may injure an employee if a guard is not in place.

Construction of Machine Guards Examples of Fabricated Machine Guards:

Before

After

Before

After

Machinery Maintenance & Repair Having superior maintenance and repair

procedures (i.e. – Job Safety Analysis, Standard Operating Procedures) in place to reduce hazards can contribute significantly to the safety of UNC-CH maintenance personnel and machine operators. The following 4 things can make safe maintenance and repair work difficult: The variety and complexity of machines to be

serviced. The hazards associated with their power sources. The special dangers that may be present during

machine breakdown. The severe time constraints often placed on

maintenance personnel.

Machinery Maintenance & Repair The following safeguarding measures

should be taken in order to prevent hazards while servicing machines: Notify all affected employees (usually

machine or equipment operators or users) that the machine or equipment must be shut down to service the machine or perform maintenance.

Stop the machine. Isolate the machine or piece of equipment

from its energy source.

Machinery Maintenance & Repair The following safeguarding measures should

be taken in order to prevent hazards while servicing machines (cont’d…): Lockout/Tagout the energy source.

**The danger of accident or injury is greatly reduced by shutting off and locking out/tagging out all sources of energy.

Relieve any stored or residual energy. Verify that the machine or equipment is isolated

from the energy source. Once all maintenance and repair has been

completed, place and secure ALL guards back on the equipment before turning it on.

Machinery Maintenance & Repair The following list are exceptions to the general rules

in regard to safeguarding measures that should be followed in order to prevent hazards: When the servicing or maintenance is not hazardous for an

employee. The supervisor, employee, or UNC Environment, Health & Safety can deem servicing/maintenance as hazardous or non-hazardous. If there is a safety concern, contact UNC Environment, Health & Safety before any servicing/maintenance is started.

When the servicing which is conducted is minor in nature. Servicing is done as an integral part of production. The employer utilizes alternative safeguards which provide

effective protection as required by 29 CFR 1910.212 or other specific standards.

Machinery Maintenance & Repair The following list of specific steps must be

followed in order to return the machine or piece of equipment to service. These steps include: Inspection of the machine or equipment to ensure

that all guards and other safety devices are in place and functional.

Checking the area to ensure that energization and start up of the machine or equipment will not endanger employees.

Removal of the lockout devices. Re-energization of the machine or equipment. Notification of affected employees that the

machine or equipment may be returned to service.

Feeding & Ejection Methods

Automatic Feed: The material is fed from rollers or another automatic method. This eliminates the need for operator involvement in

the danger area. Other guards such as fixed barrier guards are

required for operator protection. Requires frequent maintenance due to the many

moving parts involved in the automatic feed process. A disadvantage is that it may not be adaptable to

different types or sizes of materials.

Semiautomatic Feed: Material is fed by chutes, movable dies, dial feed, plungers, or sliding bolster.

Feeding & Ejection Methods

Automatic Ejection: The material is ejected by air or mechanical means. This method of ejection may create a hazard of blowing debris. Disadvantages of the automatic ejection method include: The size of materials limits the use of this method. Air ejection may present a noise hazard.

Semiautomatic Ejection: The material is ejected by mechanical means which are started by the operator. The operator does not have to enter danger area to remove material. Disadvantages of this method are: That other guards are required for operator protection. It may not be adaptable to different sizes and shapes of materials

being used.

Feeding & Ejection Methods

Robotic Machines: Used to perform work that is usually conducted by a human. Operator does not have to enter

danger area. Are suitable for operations where

high stress factors are  present, such as heat stress and noise levels 85 dB or higher.

Disadvantages of Robots: Can create hazards themselves. Require maximum maintenance. Are suitable only to specific

operations.

Pegasus Robotic Bedding Machine

Feeding and Ejection Methods Robotic Machines (cont’d…)

When servicing or performing maintenance on robotic equipment, always deenergize it before entering the area and performing any work.

Never depend on the stoppage of the automatic shut off control circuit alone to cut all power to the robotic machine.

Feeding and Ejection Methods Robotic Machines (cont’d…)

ALL employees must be clear from the danger area once maintenance has been completed. The danger zone is separated from the safe zone

by light curtains and a safety barrier consisting of a Plexiglas wall that contains the robotic machinery.

NEVER bypass safety switches, light curtains, emergency stop buttons, etc. when performing maintenance on robotic machinery or any other type of machinery.

Lock out/tag out

Lock out/tag out is also an integral part of workplace safety. When

machine guarding must be removed for maintenance, proper lock

out/tag out procedures must be followed.

When performing maintenance do the following:

- Notify all affected employees that the machine or equipment

must be shut down to perform maintenance or servicing.

- Isolate the machine or piece of equipment from its energy source.

- The energy source should be locked out or tagged out. - Any stored or residual energy should be relieved from

the machine.

- The machine or equipment should be verified that it is isolated

from the energy source.

Lock Out/Tag Out

If you have any questions or concerns, contact your supervisor or UNC Environment, Health & Safety for more specific LOTO procedures.

Additional information concerning LOTO can be found on the UNC Environment, Health & Safety website.

Link: http://www.ehs.unc.edu Link: http://www.ehs.unc.edu/manuals/imac/ Contact Info: Kim Haley (843-2735

Standard References

Additional Information concerning Machine Guarding can be found under:

OSHA 1910.213 (Woodworking Machinery Requirements) Also addressed in UNC IMAC Manual Machine

Guarding Policy. OSHA 1910.215 (Abrasive Wheel Machinery)

Also addressed in UNC IMAC Manual Machine Guarding Policy as well as the Hand and Portable Power Tools Policy.

OSHA 1910.217 (Mechanical Power Presses) OSHA 1910.217 App. A – D (Non-mandatory

and Mandatory Guidelines for Various Machines/Safeguards.)

OSHA 1910.218 (Forging Machines) OSHA 1910.219 (Mechanical Power

Transmission Apparatus)

Summary

Machine guarding is important for your personal health and safety and those that work around you. Before beginning daily work activities, assess all work areas where machinery is present and check for possible hazards/missing guards/etc. Make sure that all guards on equipment are adjusted and functioning properly. Guarding should never be removed except for maintenance procedures. If machine guarding is not in place do not use the equipment, and use proper procedures to ensure that guarding is put in place.

If you have any questions or concerns about machine guarding contact your departmental supervisor or UNC Environment, Health, & Safety at 962-5507.