"Moving machine parts have the potential to cause severe workplace injuries, such as crushed fingers or hands, amputations, burns, or blindness. Safeguards are essential for protecting workers from these preventable injuries. Any machine part, function, or process that may cause injury must be safeguarded. When the operation of a machine or accidental contact injure the operator or others in the vicinity, the hazards must be eliminated or controlled."

--OSHA on "Machine Guarding"

5 Most Common Ways of Machine Guarding

1. Barrier Guards
2. Presence Sensing Devices (PSD)
3. Pullbacks/Restraints
4. Two-hand Controls/Two-hand Trip
5. “A” and “B” Gates

Barrier Guards

These are designed to keep the operator’s hands and arms from entering the “danger zone” as prescribed by the particular machine. They are appropriate safeguards for full revolution and part revolution mechanical power presses. They are usually the first point-of-operation safeguard considered for machines.

Regulation: 29 CFR 1910.217

• Barrier guards on power presses must prevent the entry of hands or fingers into the point of operation by reaching through, over, under or around the guard.
• The barrier guards must conform to maximum permissible openings tables.
• The barrier guard itself must not create pinch points between the guard and moving machine parts.
• The guard must not be easily removable.
• The guard must not interfere with machine inspection.
• The barrier guard must offer maximum visibility of the point of operation consistent with the other requirements.

Presence Sensing Devices

These are designed to automatically stop the machine stroke if sensing field is interrupted. Proper use provides protection not only for operators but also for other employees in the area. They are one of the most common safeguards for automatic feed part revolution clutch presses, and have many requirements that must be met before they can be installed as point-of-operation safeguards.

Regulation: 29 CFR 1910.217

• Presence sensing devices (PSD) cannot be used on machines using full revolution clutches.
• A PSD must protect the operator by preventing or stopping normal stroking of the press if the operator’s hands are inadvertently placed in the point of operation. The PSD must also be interlocked into the control circuit so that the slide motion will stop the downstroke from continuing if any part of the operator's body is within the sensing field at that time.
• Guards must be used to protect all areas of entry to the point of operation not protected by the PSD.
• PSDs cannot be used as a tripping means to initiate slide motion.
• Should a failure occur within the system, the PSD must be constructed so that the normal stopping action is still applied when required, but prevents the start of the next stroke until the failure is corrected. The failure must be indicated by the system.
• “Muting” or bypassing of the PSD during the upstroke of the press slide is permitted for parts ejection, circuit checking, and feeding.
• The safety distance from the sensing field to the point of operation must be greater than the distance determined by the safety distance formula.

Pullbacks/Restraints

Pullbacks

These are safeguarding devices on both full and part revolution power presses. They are similar to restraints, but are designed to pull the operator’s hands away from the area of the closing dies (point of operation) during each stroke of the power press.

Regulation: 29 CFR 1910.217

• Attachments must be connected to and operated by the press slide or upper die.
• Attachments must be adjusted to prevent the operator from reaching into the point of operation or to withdraw the operator’s hands from the point of operation before the dies close.
• A separate pullout device must be provided for each operator if more than one operator is used on the press.
• Each pullout device in use must be inspected and checked for proper adjustment at the start of each operator shift, following a new die set-up, and when operators are changed. Necessary maintenance or repair on both must be performed and completed before the press is operated.
• Inspection and Maintenance Records. It is the responsibility of the employer to make periodic and regular safety inspections and keep accurate records of them.

Restraints

Sometimes referred as “holdouts,” restraints are similar to pullbacks and are appropriate safeguards for both full and part revolution mechanical power presses. When properly anchored, restraints are adjusted so that the operator can never reach the point of operation. The size and type of restraint depends on the size and type of press.

Regulation: 29 CFR 1910.217

• A holdout or a restraint device must protect the operator by preventing the operator from inadvertently reaching into the point of operation at all times and must include attachments for each of the operator’s hands.
• Attachments must be securely anchored and adjusted and separate set of restraints must be provided for each operator if more than one is required on a press.

Two-hand Controls/Two-hand Trip

Two-hand Controls

These are safeguarding devices in the single stroke mode of operation on part revolution clutch presses. It is similar to the two-hand trip; this device keeps the operators hands away from the point of operation during the entire machine stroke.

Regulation: 29 CFR 1910.217

• Press operations requiring more than one operator must provide each operator with separate two-hand controls where each set must be engaged to complete a machine stroke. The removal of a hand from any control button will stop the slide.
• Each two-hand control must meet the construction requirements of paragraph 29 CFR 1910.217(b)(7)(v).
• The safety distance between each hand control device and the point of operation must be greater than the distance determined by the safety distance formula.
• Two-hand controls’ position must be fixed so that only a supervisor of safety engineer is capable of relocating them.

Two-hand Trip

These are safeguarding devices used on a full revolution clutch power press only. It requires the joint operation of two trigger buttons located away from the “danger zone” of the press. It is similar to two-hand controls in that it requires the operator’s hands to be away from the point of operation to activate the machine stroke, but differs in that activation of the machine stroke requires only a "trip" of the controls whereas a two-hand control requires continued pressure.

Regulation: 29 CFR 1910.217

• When used in press operations requiring more than one operator, separate two hand trips must be provided for each operator, and must be designed to require concurrent application of both operators to activate the slide.
• A two-hand trip shall have the individual operator's hand controls protected against unintentional operation and have the individual operator's hand controls arranged by design and construction and/or separation to require the use of both hands to trip the press and use a control arrangement requiring concurrent operation of the individual operator's hand controls.
• The safety distance between the two-hand trip and the point of operation must be greater than the distance determined by the safety distance formula. 
• Like two-hand control devices, two-hand trips’ position must be fixed so that only a supervisor or safety engineer is capable of relocating the controls.

“A” Gates/”B” Gates

Type "A" and "B" Gates are both recognized methods for power press safeguarding. The "A" gate is used in both full and part revolution clutch presses while the "B" gate is for part revolution presses only.

Type “A” Gates

These protect the operator during the entire machine stroke. This means the gate will not open until after the crankshaft rotation is complete (360°) and the machine is stopped at top dead center. Although Type "A" Gates can be used on either part or full revolution clutch presses, best safety practice is the "A" gate should be used only on full revolution clutch presses.

Type “B” Gates

These protect the operator during the downstroke only. The gate starts to open before the crankshaft rotation is complete (generally after 180° crankshaft rotation). The gates must open on the upstroke of the machine cycle before the crankshaft rotation is complete.

Regulation: 29 CFR 1910.217, 29 CFR 1910.212

• In both cases (“A” & “B” Gates), operators must be prevented from placing their hands or any other body parts in the point of operation during the die-closing portion of the press stroke.
• The guard itself must comply with applicable standards.

History

Since the beginning of mankind, humans have adapted a sense of using the right tool for the job. In ancient times, it was tying rocks or bones to sticks for use as a hammer or sharpened to make hunting easier. Essentially, they established that using crude items could be used to make life easier. Ergonomics is just that, an applied science (not just a buzzword for marketers!) of work. That is, it’s intended to maximize productivity of workers by reducing/eliminating fatigue or discomfort. The literal definition of ergonomics, as Dictionary.com states, is “the study of the relationship between workers and their environment.” Also known as “biotechnology,” and first coined by Wojciech Jastrzebowski in 1857.

However, these early adoptions were merely used to optimize tasks. Ergonomics has since evolved into learning how to include worker safety and health by addressing muscle force, cardiovascular activity, maximum weight, etc. This is seen by Frederick Winslow Taylor in the 19^th century in which he used his “Scientific Method” (AKA ergonomics) to assist coal workers in tripling their productivity by designing shovels that were lighter and smaller. Also in the 1900s Frank and Lillian Gilbreth further expanded Taylor’s methods by coming up with the “Time and Motion Studies.” This was meant to reduce the amount of unnecessary motions required to perform a task. With this approach, they reduced the number of motions bricklayers used (from 18 to 4.5) and allowed them to increase productivity from 120 bricks per hour to 350.

“Formal” ergonomics is generally credited to the development of more complicated machinery in WWI and WWII. As aircrafts, tanks and other complex machines were being developed; human errors were piling up, resulting in catastrophes. Non-combat casualties were an outcome of bad engineering and design. This begged the necessity of better results through better designing, and the most “modern” form of ergonomics (how we know it today) is now becoming the norm.

Engineers and psychologists are working together in collaboration to improve our daily lives through better design. A multi-disciplinary approach has been taken to include anthropologists, industrial engineers, cognitive scientists and physiologists in order to understand the human operators and to design systems and machines to fit said user.

Today, most of us know ergonomics in a workplace context. As the average worker in America works for about 8 hours a day, the need for ergonomic office furniture and practices is of the upmost importance. The idea is to be sure that as technology and design make our homes safer and more comfortable, and in the case of the workplace, to increase productivity, increase comfort and prevent injuries and fatigue.

Hazards Associated with Ergonomics

Back injuries - Common back injuries include sprains, herniated disks and fractured vertebrae. Lower back pain is often the result of incorrect lifting methods/habits and poor posture.

• Tips include:

• Properly train employees on appropriate lifting techniques

• Utilize material handling equipment (carts, dollies, hand trucks)

• Encourage stretching for employees to reduce muscle strain

Carpal tunnel syndrome - A nervous system disorder causing parethesia (limbs falling sleep), pain and numbness. Carpal tunnel can be caused by environmental factors such as heavy manual work or work with vibrating tools. There is even a small amount of clinical data to suggest that lighter, repetitive tasks can cause it. This includes activities when frequent/constant wrist flexion is needed or when there is pressure against the underside of the wrist.

With May (Electrical Safety Month) coming to a close, Safety Training Services, Inc. would like to offer 10 tips to remember for those who work near overhead power lines (when working outside):

1. Survey your surroundings. Always be aware of the location of power lines, particularly when using long tools (e.g. ladders). Don’t assume…assess.

2. Obey the 10 foot rule. As in, do not work or use equipment within 10 feet of overhead lines. You may feel lucky and think “I won’t come in contact with the power line.” However, the electricity can arc to nearby objects and people and assuming you have enough time to think before being barbequed better than my dad’s grilled chicken, you’ll remember these words.

3. Be careful when working on your roof. That includes cleaning gutters, installing antennas and satellite dishes or any repair work. Oh….and during winter, those holiday lights, be especially careful putting those 250 strands up, thank you Mr. Griswold.

4. Never climb trees near power lines. Limbs & branches can bend or break off and obviously, you can fall off. Didn’t you learn this as a child?

5. Never trim trees near power lines. Leave that to a professional.

6. Always follow safety procedures, no matter how boring and mundane they seem. Just remember, “Working safely may get old, but so do those who practice it.”

7. Assume all power lines are energized. Do not use metal ladders near them; instead use appropriate American National Standards Institute (ANSI)-approved ladders for work near energized power lines. With respect to electricity, one wrong move could be your last.

8. Train yourself/your workers. You/they should be versed in emergency communication and proper techniques for providing aid to someone after an electrical accident.

9. Use Safety Watches or Spotters. Their only duties should be observing the work and communicating with the operator to ensure the equipment never gets closer than 10 feet to a power line. Were you in boy/girl scouts as a kid? Remember the “buddy system!”

10. Don’t be a hero! Keep a safe distance from any victim who is/was in direct contact with electricity. Call 911 immediately! Do not try to touch victim because you may be electrocuted. 

The best way to avoid injury from power lines is to make the choice to stay committed to safety. All rules & regulations are useless unless they’re observed. Safe work habits should be consistent and ongoing.

Remember, as OSHA states it, “no building, equipment, deadline or profit is worth a human life.”

Safety Training Services, Inc. provides appropriate training for several safety topics, including but not limited to: OSHA General Industry, OSHA Construction Industry, NFPA 70E Arc Flash Training, HAZWOPER, Confined Space Entry and Rescue. Call or contact us for a free quote on safety training! Consulting Services, Rescue Services and Equipment sales & rentals also available. Or schedule a visit to come by (or us to you) and see what we can offer your company today!