Chapter Five - General Safety

Shop Equipment and Machinery

CHESS has a variety of equipment in its machine shop, each with potential hazards.  Before using any equipment in the shop, you must be trained to use it and checked out by the Machine Shop Supervisor.

General Guidelines for Shop Safety:

• Eye Protection:  grinding, cutting and drilling of metal and wood generate airborne particles.  Always wear safety glasses, goggles, or shields.

• Foot Protection:  always wear sturdy, closed-toed shoes to protect your feet from wood and metal wastes on shop floors, and from heavy objects that can crush feet and toes.  A safety shoe and boot truck visits CHESS regularly - check with your supervisor or the Shop Supervisor for information on where to buy safety shoes.  CHESS personnel are allowed to purchase one pair of safety shoes annually.

• Hand Protection:  to prevent cuts, burns, sprains and repetitive motion injuries, be proactive about protecting yourself. Wear appropriate gloves (unless you are using equipment with unforgiving rotating parts), and remove watches and jewelry before you start work. Don't handle shop chemicals or operate machinery with your bare hands, and don't ignore safety guards on machinery. Always inspect equipment and machinery for wear, dull cutting blades, or broken parts before you begin work.  Use the correct tool for the job.  If you are lifting and carrying heavy objects, be aware of narrow doorways where your hands can get caught and crushed: when stacking heavy objects, keep your hands on either side, not underneath, to avoid crushing your fingers.

• Clothing:  be aware, especially when working with equipment with moving parts, of hair and clothing that could become trapped in machinery.  Tie back long hair, remove neckties, and roll up long sleeves.  Wear a safety apron to protect your body from flying particles of metal or wood.

• Housekeeping:  clean up after yourself.  Put away materials when you are finished with them.  Roll up power cords and return them to their appropriate storage places.  Do not leave machines running unattended.

Think ahead before you begin any project:  What are the steps necessary to complete it and what are the potential hazards?  Consider other people working in your area and let them know if you are doing work that may create a potential safety hazard for them.

Basics of Machine Safeguarding

Crushed hands and arms, severed fingers, blindness - the list of possible machinery related injuries is a long as it is horrifying.  There seems to be as many hazards created by moving machine parts as there are types of machines.  Safeguards are essential for protecting workers form 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 or accidental contact with it can injure the operator or others in the vicinity, the hazard must be either controlled or eliminated.

This section describes the various hazards of mechanical motion and action and presents some techniques for protecting workers from these hazards.

Where Mechanical Hazard Occur

Dangerous moving parts in these three basic areas need safeguarding:

1. The point of operation:  that  point where work is performed on the material, such as cutting, shaping, boring, or forming of stock.

2. Power transmission apparatus:  all components of the mechanical system which transmit energy to the part of the machine performing work.  These components include flywheels, pulleys, belts, connecting rods, couplings, cams, spindles, chains, cranks, and gears.

3. Other moving parts:  all parts of the machine which move while the machine is working.  These can include reciprocating, rotating, and transverse moving parts, as well as feed mechanisms and auxiliary parts of the machine.

Hazardous Mechanical Motions and Actions

A wide variety of mechanical motions and actions may present hazards to the worker.  These can include the movement of rotating members, reciprocating arms, moving belts, meshing gears, cutting teeth, and any parts that impact or shear.  These different types of hazardous mechanical motions and actions are basic to nearly all machines, and recognizing them is the first step toward protecting workers from the danger they present.  The basic types of hazardous mechanical motions and actions are:

Motions

• rotating (including in-running nip points)

• reciprocating

• transverse

Actions

• cutting

• punching

• shearing

• bending

Brief examination of each of these basic types:

Motions:

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

Collars, couplings, cams, clutches, flywheels, shaft ends, spindles, and horizontal or vertical shafting are some examples of common rotating mechanisms which may be hazardous.  The danger increases when bolts, nicks, abrasions, and projecting keys or set screws are exposed on rotating parts.

In-running nip point hazards are caused by rotating parts on machinery.  There are three main types of in-running nips.

1. 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.  In the latter case the stock fed between the rolls produces the nip points.  This danger is common on machinery with intermeshing gears, rolling mills, and calendars.

2. Another nip point is created between rotating and tangentially moving parts.  Some examples would be:  the point of contact between a power transmission belt and its pulley, a chain and a sprocket, or a rack and pinion.

3. Nip points can occur between rotating and fixed parts which create a shearing, crushing, or abrading action.  Examples are:  spoked handwheels or flywheels, screw conveyors, or the periphery of an abrasive wheel and an incorrectly adjusted work rest.

Reciprocating motions may be hazardous because, during the back-and-forth or up-and-down motion, a worker may be struck by or caught between a moving and a stationary part.

Transverse motion (movement in a straight, continuous line) creates a hazard because a worker may be struck or caught in a pinch or shear point by the moving part.

Actions

Cutting action involves rotating, reciprocating, or transverse motion.  The danger of cutting action exists at the point of operation where finger, head, and arm injuries can occur and where flying chips or scrap material can strike the eyes or face.  Such hazards are present at the point of operation in cutting wood, metal, or other materials.  Typical examples of mechanisms involving cutting hazards include bandsaws, circular saws, boring or drilling machines, turning machines (lathes), or milling machines.

Punching action results when power is applied to a slide (ram) for the purpose of blanking, drawing, or stamping metal or other materials. The danger of this type of action occurs at the point of operant where stock is inserted, held, and withdrawn by hand.  Typical machinery used for punching operations are power presses and iron workers.

Shearing action involves applying power to a slide or knife in order to trim or shear metal or other materials. A hazard occurs at the point of operation where stock is actually inserted, held, and withdrawn.  Typical examples of machinery used for shearing operations are mechanically, hydraulically, or pneumatically powered shears.

Bending action results when power is applied to a slide in order to draw or stamp metal or other materials, and 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 tubing benders.

Requirements for Safeguards

What must a safeguard do to protect workers against mechanical hazards?  Safeguards must meet these minimum general requirements:

Prevent contact:  The safeguard must prevent hands, arms, or any other part of a worker's body from making contact with dangerous moving parts.  A good safeguarding system eliminates the possibility of the operator or another worker placing their hands near hazardous moving parts.

Secure:  Workers should not be able to easily remove or tamper with the safeguard, because 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.  They must be secured to the machine.

Protect from falling objects:  The safeguard should 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:  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.

Allow safe lubrication:  If possible, one should 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 operator or maintenance worker to enter the hazardous area.

Non-mechanical Hazards

All power sources for machinery are potential sources of danger.  When using electrically powered or controlled machines, for instance, the equipment as well as the electrical system itself must be properly grounded.  Replacing frayed, exposed, or old wiring will also help to protect the operator and others from electrical shocks or electrocution.  High pressure systems, too, need careful inspection and maintenance to prevent possible failure from pulsation, vibration, or leaks.  Such a failure could cause explosions or flying objects.

Machines often produce noise (unwanted sound) and this can result in a number of hazards to workers. Not only can it startle and disrupt concentration, but it can interfere with communications, thus hindering the worker's safe job performance. Research has linked noise to a whole range of harmful health effects, from hearing loss and aural pain to nausea, fatigue, reduced muscle control, and emotional disturbances. Engineering controls such as the use of sound- dampening materials, as well as less sophisticated hearing protection, such as ear plugs and muffs, have been suggested as ways of controlling the harmful effects of noise. Vibration, a related hazard which can cause noise and thus result in fatigue and illness for the worker, may be avoided if machines are properly aligned, supported, and, if necessary, anchored.

Because some machines require the use of cutting fluids, coolants, and other potentially harmful substances, operators, maintenance workers, and others in the vicinity may need protection.  These substances can cause ailments ranging from dermatitis to serious illnesses and disease.  Specially constructed safeguards, ventilation and protective equipment and clothing are possible temporary solutions to the problem of machinery-related chemical hazards until these hazards can be better controlled or eliminated form the workplace.

Training

Even the most elaborate safeguarding system cannot offer effective protection unless the worker knows how to use it and why.  Specific and detailed training is therefore a crucial part of any effort to provide safeguarding against machine-related hazards.  Thorough operator training should involve instruction or hands-on training in the following:

1. a description and identification of the hazards associated with particular machines;

2. the safeguards themselves, how they provide protection, and the hazards for which they are intended;

3. how to use the safeguards and why;

4. how and under what circumstances safeguards can be removed, and by whom (in most cases, repair or maintenance personnel only; and

5. what to do (e.g., contact supervisor) if a safeguard is damaged, missing, or unable to provide adequate protection.

This kind of safety training is necessary for new operators and maintenance or setup personnel, when any new or altered safeguards are put in service, or when workers are assigned to a new machine or operation.

Last Update: 2006-09-21