Other methods for safeguarding machines include guarding by location or distance and by feeding methods that prevent operator access to the point of operation.
Safeguarding by location involves positioning or designing a machine so that the hazardous parts are away from areas where employees work or walk, or alternatively, installing enclosure walls or fences that restrict access to machines.
The feeding process can be safeguarded by distance if the operators maintain a safe distance between their hands and the point of operation. For instance, if the stock is several feet long and only one end of the stock is being worked on, the operator may be able to hold the opposite end while performing the work. Safeguarding by distance is sometimes used during power press brake operations to ensure its effectiveness. This method of safeguarding requires close supervision and training.
Automatic and semiautomatic feeding and ejection methods can protect the worker by minimizing or eliminating direct contact with machinery. These methods typically require frequent maintenance, however, and are only protective for normal machine operation. Examples of semiautomatic feeding methods include:
§ Gravity feeds, where the part slides down a chute into the point of operation, and
§ Magazine feeding, where the worker places the part in a magazine which is then fed into the point of operation.
Automatic and semiautomatic ejection methods include pneumatic (jet of air), magnetic, mechanical (such as an arm), or vacuum.
Operators can use tools to feed work pieces into equipment to keep their hands away from the point of operation, but this should be done only in conjunction with the guards and devices described previously. Using hand tools requires close supervision to ensure that the operator does not bypass their use to increase production. Tools should be stored near the operation to encourage their use. To prevent repetitive trauma disorders, hand-feeding tools should be ergonomically designed for the specific task being performed.
Foot controls are not safeguards because they do not keep the operator’s hands out of the danger area. If you use them, they will need some type of guard or device, such as barriers or pullouts with interlocks capable of controlling the start up of the machine cycle. Using foot controls may increase productivity, but the freedom of hand movement allowed while the machine is operating increases the risk of a point of operation injury.
Foot controls must be guarded to prevent accidental activation by another worker or by falling material and not allow continuous cycling. They work best when the operator is in a sitting position. Always avoid the hazard of riding the pedal (keeping the foot on the pedal while not actively depressing it.)
Certain machines can be categorized based on the type of clutch they use — full-revolution or part-revolution. Differing modes of operation for these two clutches determine the type of guarding that can be used.
Once activated, full-revolution clutches complete a full cycle of the slide (lowering and raising of the slide) and cannot be disengaged until the cycle is complete. So, presence-sensing devices may not work and a worker must maintain a safe distance when using two-hand trips. Machines incorporating full-revolution clutches, such as power presses, must also incorporate a single-stroke device and anti-repeat feature.
The part-revolution clutch can be disengaged at any time during the cycle to stop the cycle before it completes the down stroke. For example, part-revolution presses can be equipped with presence-sensing devices, but full-revolution presses cannot. Likewise, hydraulic presses can be stopped at any point in the cycle, and their safeguarding is similar to guarding for part-revolution clutch presses.
Special hand tools may be used to place or remove stock, particularly from or into the point of operation of a machine. A typical use would be for reaching into the danger area of a press or press brake. Figure 1 shows an assortment of tools for this purpose. Holding tools should not be used instead of other machine safeguards; they are merely a supplement to the protection that other guards provide.
Figure 1: Holding tools
A push stick or block, such as those in Figure 2, may be used when feeding stock into a saw blade. When it becomes necessary for hands to be in close proximity to the blade, the push stick or block may provide a few inches of safety and prevent a severe injury. In the illustration, the push block fits over the fence.
Figure 2: Use of push stick or push block
Crushed hands and arms, severed fingers, blindness — the list of possible machinery-related injuries is as long as it is horrifying. There seem to be as many hazards created by moving machine parts as there are types of machines. Safeguards are essential for protecting workers from needless and preventable injuries.
A good rule to remember is:
Any machine part, function, or process which may cause injury must be safeguarded.
When the operation of a machine or accidental contact with it can injure the operator or others in the vicinity, the hazards must be either controlled or eliminated. In addition to techniques for protecting workers from the various hazards of mechanical motion presented in this chapter, you will find specific information related to preventing amputations — one of the most severe and disabling workplace injuries. These injuries result from using stationary machines such as saws, presses, conveyors, and bending, rolling, or shaping machines. They also occur from using powered and non-powered hand tools, forklifts, doors, trash compactors, and during materials handling activities.
To prevent worker injuries, both the employer and employees operating the equipment must be able to recognize the contributing factors, such as:
§ Mechanical components of machinery,
§ Mechanical motion that occurs at or near these components, and
§ Specific worker activities performed with the mechanical operation.
Machine safeguarding is the primary way to control crushing and amputation hazards associated with stationary machinery. Work practices, employee training, and administrative controls also play an important role in preventing and controlling these workplace hazards.
The Fair Labor Standards Act (FLSA) designates certain non-farm jobs as particularly hazardous for employees younger than 18. Generally, this worker group is prohibited from operating:
§ Band saws
§ Circular saws
§ Guillotine shears
§ Punching and shearing machines
§ Meatpacking or meat processing machines
§ Power-driven paper products machines
§ Power-drive woodworking machines
§ Power-driven metal forming machines
§ Power-driven meat slicers
If you are responsible for safeguarding machines, you need to consider guards when purchasing machinery. Most new machinery is available with safeguards installed by the manufacturer, but used equipment may not be.
In cases where machinery has no safeguards, you can purchase safeguards from the original machine manufacturer or an after-market manufacturer. You can also build and install the safeguards in-house. Safeguarding equipment should be designed and installed only by technically qualified professionals. In addition, the original equipment manufacturer should review the safeguard design to ensure that it will protect employees without interfering with the operation of the machine or creating additional hazards.
Regardless of the source of safeguards, the guards and devices you use should be compatible with a machine’s operation and designed to ensure safe operator use. The selection of safeguards should be based on:
§ Type of operation,
§ Size and shape of stock,
§ Method of feeding,
§ Physical layout of the work area, and
§ Production requirements all affect the selection of safeguards.
Also, safeguards should be designed with the machine operator in mind. To ensure effective and safe operator use, guards and devices should suit the operation. For example, if an operation is prone to jamming, installing a fixed guard may not work. An interlocked guard or presence-sensing device may be a more practical solution.
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