Machine Guarding

Working with many companies in the manufacturing and construction industries, there are times when I observe a piece of equipment or an employee utilizing a small hand tool that has had the machine guard either removed or modified. We must, as safety professionals remind them of OSHA 1910.212 and 1926.300. But to sit in a training session and quote OSHA to employees of different “life” backgrounds can sometimes be challenging. We must be creative and entertaining enough to keep their attention, in hopes that they retain what is being taught.

Why do we have Guards?

• For the average person the time needed to react to an unexpected sensation is about one second.

What can happen in one second?

• A human eye can only blink twice in one second.
• At rest the human heart beats once per second.

Incident Worker was in the process of checking gauges when suddenly he felt a pulling motion on his right hip and back side. His coveralls had become entangled in an unguarded shaft and were being sheared off. Unable to escape or break free of the drawing motion the worker was able to reach the motor clutch and disengage the equipment, thus ending the ordeal. In the period of approximately 15-20 seconds from the initial contact with the rotating equipment, the workers right leg portion of his coveralls including his right pant leg and undergarments had been pulled off from the hip down and completely sheared. The worker only received a minor friction burn to the right hip and buttock region, as his hip was against the shaft at the time of shut down.

Cause The investigation determined the immediate cause of the incident was inadequate guards on rotating equipment. The belt and wheel portion of the motor did have the required guard in place but the center potion had been cut out allowing the crankshaft to protrude out approximately 2 inches past the protective guard.

Why do we have Guards?

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.

Rotating motion can be dangerous; even smooth, slowly rotating shafts can grip hair and clothing, and through minor contact force the hand and arm into a dangerous position. Injuries due to contact with rotating parts can be severe.

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.

The danger increases when projections such as set screws, bolts, nicks, abrasions, and projecting keys or set screws are exposed on rotating parts.

Nip Points

In-running nip points (or pinch points) are a special danger arising from rotating or reciprocating parts. They occur whenever machine parts move toward each other or when one part moves past a stationary object.

Parts of the body may be caught between or drawn into the nip point and crushed, mangled, or severed.

Traverse motions of conveyor belts and other material traveling over rolls can create nip-points.

Crush hazards

Exist when a worker may be struck by or caught between a moving and a stationary part.

This can include vehicles and rolls of paper.

Reciprocating motions may be hazardous because, during the operation a back-and-forth or up-and-down motion is present.

Exist when a worker may be struck by or caught between a moving and a stationary part.

This can include vehicles and rolls of paper.

Reciprocating motions may be hazardous because, during the operation a back-and-forth or up-and-down motion is present.

Cutting and shearing

Cutting actions may involve rotating, reciprocating, or transverse motion.

The danger of cutting action exists at the point of operation. Finger, arm and body injuries can occur and where flying chips or scrap material can strike the head, particularly in the area of the eyes or face.

Shearing action involves parts of machinery that move past each other or stationary objects.

The danger exists at the point of operation.

Other Hazards

• Any source of heat that can cause a burn

Extreme Cold

• Any source of cold that could freeze tissue

Other types of energy

 High and low voltage electricity

Stored energy

• High pressure steam, air, or fluids

 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.
• 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.

Fabricated guards should be made of metal

• Wood is only acceptable under certain conditions where exposure to certain chemicals will quickly corrode metal
• Just because a guard is not specifically made for a machine, does not mean a guard does not have to be in place.

Guarding 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.

Think in terms of the largest and smallest person who may make contact

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.

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 could cause the object to easily become a projectile that could strike someone, and cause serious injury.

Falling People are objects too!

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.

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.

If access points are provided they must be secured at all times

Inspection

Does the design, material & construction of the guard create a hazard?

Is the guard free of:    

Burrs?

Sharp Edges?

Pinch Points?

Are guards securely attached?

This can be accomplished through the use of many different types of fasteners

Think nuts and bolts, not duct tape and string.

Access doors and inspection covers must be secured as well.

Secured= having to take a deliberate action to open.

Are guards securely attached?

This can be accomplished through the use of many different types of fasteners.

Think nuts and bolts, not duct tape and string.

Access doors and inspection covers must be secured as well.

Secured= having to take a deliberate action to open.

Is the Guard recognizable as a “Guard”?

Accomplished through color:

Guards may need additional labelling.

Paint:

are guards a color which will standout from surrounding equipment?

Safety Yellow is a common color. Safety Orange is also used.

Do markings and paint follow the mill wide paint standards?

Are guards placed far enough from the hazard?

There are Standards on safe distances.

The standards were developed to determine guard mounting distances based on the maximum opening sizes in the guarding.

The standards ensures that any body part which can fit through a guard opening won’t be able to contact the hazard inside.

Hazards can be at the point of operation as well as in area of machine and material movement

Unit Heaters

Check for insulation hot pipes

Is the fan guarded?

Is the guard loose?

How far from the floor?

Unguarded surfaces should be 8’ above the walking or standing surface.

How does the wiring look?

Temporary or permanent use?

Cords in good condition?

E-Stops and other Machine Guarding aides to inspect.

Guarding aides are used in addition to conventional safe guards:

E-stops and Safety Trip Controls

Gates

Photoelectric Barriers/Light Curtains

Awareness Barriers

Special Hand Tools

Machine Guarding aides are designed to supplement guards not replace them

Need to be accessible and easy to reach

Not blocked, covered, hidden, or guarded

Have to be self latching

Switches will remain open until manually reset

Prevents machines from being restarted automatically

Have to be tested periodically

Check for inspection records

E-Stop Button requirements

Palm type button

Also know as mushroom

Red in color

Yellow back ground

Requirements for E-Stop button design come from NFPA 79

E-Stop Lanyard requirements

Red cable

Easily identifiable

Readily available at the point of operation

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.

Safety Trip Controls

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.

Once tripped a separate action to restart a machine is required.

Tools should be in good condition:

No splinters, taped handles, etc.

Be sure they are of adequate design and construction for the task

Be sure guards are being used first, and tools are compatible with guards