MACHINE SAFEGUARDING 101
- Amputations are among the most severe and disabling workplace injuries that often result in permanent disability.
Approximately 60 percent of all workplace amputations were caused by machinery, such saws, presses, conveyors, milling machines, drill stands, bending, rolling or shaping machines, powered and non-powered hand tools, and other materials handling activities.
Understanding the mechanical components of machinery and the hazardous mechanical motion that occurs at or near these components in conjunction with machinery operation will help employees avoid injury.
Primary safeguarding includes devices and methods that protect (e.g., prevent employee contact with hazardous machine areas) employees from machine hazards.
- In addition, a hazardous energy control (lockout/tagout) program needs to complement machine safeguarding methods in order to protect employees during potentially hazardous servicing and maintenance work activities.
Three types of mechanical components present amputation hazards:
Point of Operation is the area of the machine where the machine performs work – i.e., mechanical actions that occur at the point of operation, such as cutting, shaping, boring, and forming.
Power-Transmission Apparatus is all components of the mechanical system that transmit energy, such as flywheels, pulleys, belts, chains, couplings, connecting rods, spindles, cams, and gears.
Other Moving Parts are the parts of the machine that move while the machine is operating, such as reciprocating, rotating, and transversing moving parts as well as lead mechanisms and auxiliary parts of the machine.
Safeguarding is essential for protecting employees from needless and preventable injury.
Primary safeguarding methods refers to machine guarding techniques that are intended to prevent or greatly reduce the chance that an employee will have an amputation injury. Refer to the 29 CFR 1910, Subpart O for specific guarding requirements.
Machine safeguarding must be supplemented by an effective energy control (lockout/tagout) program that ensures that employees are protected from hazardous energy sources during machine servicing and maintenance work activities. Lockout/tagout plays an essential role in the prevention and control of workplace amputations. In terms of controlling amputation hazards, employees are protected from hazardous machine exposure either by: 1) effective machine safeguarding, or 2) lockout/tagout where safeguards do not protect employees from hazardous energy during servicing and maintenance operations.
Additionally, there are some servicing activities, such as lubricating, cleaning, releasing jams and making machine adjustments that are minor in nature and are performed during normal production operations. It is not necessary to lockout/ tagout a machine if the activity is routine, repetitive and integral to the production operation provided that you use an alternative control method that affords effective protection from the machine’s hazardous energy sources.
The employer is responsible for safeguarding machines. The guards and devices used need to be compatible with a machine’s operation and designed to ensure safe operator use. The 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 as a guarding method that interferes with the operation of the machine may cause employees to override them. To ensure effective and safe operator use, guards and devices should suit the operation.
ANSI B11.19-2019 (Performance Requirements for Risk Reduction and other means of Reducing Risk) provides valuable guidance as the standard addresses the design, construction, installation, operation and maintenance of the safeguarding used to protect employees from machine hazards. The following safeguarding method descriptions are, in part, structured like and, in many ways are similar to this national consensus standard.
ANSI B11.19-2019 defines risk reduction measures as the protection of personnel from hazards by the use of guards, safeguarding devices awareness devices, safeguarding methods, or safe work procedures. The following ANSI B11.19 definitions describe the various types of safeguarding:
Guard: A barrier that provides protection from a hazard.
Safeguarding Device: A device that provides protection from a hazard by preventing or detecting exposure to a hazard zone.
Awareness Means: A barrier, signal or sign that warns individuals of an impending, approaching or present hazard.
Safeguarding Method: Risk reduction measures implemented to protect individuals from hazards by the physical arrangement of distance, holding, openings, or positioning of the machine or machine system so that a hazard cannot be reached.
Safe Work Procedure(s): Formal written documentation developed by the user that describes steps that are to be taken to safely complete tasks where hazardous situations can be present or hazardous events are likely to occur.
Two primary methods are used to reduce risk on machinery: guards, and some types of safeguarding devices. Guards provide physical barriers that prevent access to danger areas. Safeguarding devices either prevent or detect operator contact with the point of operation or stop potentially hazardous machine motion if any part of an individual’s body is in or near to the point of hazard on a machine. Both types of safeguards need to be properly designed, constructed, installed, used and maintained in good operating condition to ensure employee protection.
Criteria for Reducing Risk
- Risk reduction measures should prevent employee contact with the hazard area during machine operation.
- Risk reduction measures should not create additional hazards.
- Risk reduction measures should be secure, tamper-resistant, and durable.
- Risk reduction measures should not interfere with normal operation of the machine.
- Risk reduction measures should allow for safe lubrication and maintenance.
Guards usually are preferable to other control methods because they are physical barriers that enclose dangerous machine parts and prevent employee contact with them. To be effective, guards must be strong and fastened by any secure method that prevents the guard from being inadvertently dislodged or removed. Guards typically are designed with screws, bolts and lock fasteners and usually a tool is necessary to unfasten and remove them. Generally, guards are designed not to obstruct the operator’s view or to prevent employees from doing a job.
In some cases, guarding may be used as an alternative to lockout/tagout because employees can safely service or maintain machines with a guard in place. For example, polycarbonate and wire-mesh guards provide greater visibility and can be used to allow maintenance employees to safely observe system components. In other instances, employees may safely access machine areas, without locking or tagging out, to perform maintenance work (such as machine cleaning or oiling tasks) because the hazardous machine components remain effectively guarded.
Guards must not create additional hazards such as pinch points or shear points between guards and other machine parts. Guard openings should be small enough to prevent employees from accessing danger areas.
Safeguarding devices are hazard reduction implements that, when properly designed, applied and used, will prevent inadvertent access by employees to hazardous machine areas by:
• Preventing hazardous machine component operation if your hand or body part is inadvertently placed in the danger area;
• Restraining or withdrawing your hands from the danger area during machine operation;
• Requiring the use of both of your hands-on machine controls (or the use of one hand if the control is mounted at a safe distance from the danger area) that are mounted at a predetermined safety distance; or
• Providing a barrier which is synchronized with the operating cycle in order to prevent entry to the danger area during the hazardous part of the cycle.
A. Types of Safeguarding Devices
Fixed: A device that allows for stock feeding but does not permit operator to reach the danger area.
Adjustable: A device that adjusts for a variety of production operations.
Self-Adjusting: A device that moves according to the size of the stock entering point of operation. The device is in place when machine is at rest and pushes away when stock enters the point of operation.
Presence-Sensing Devices: A device that creates a sensing field, area or plane to detect the presence of an individual or object and provides an output signal.
Shield: A barrier used to contain or deflect material or energy within the confines of the machine, or to reduce the potential of tooling parts or workpieces from being ejected from the machine.
Interlocking Shields: The interlock switch is designed to disengage power as well as prevent machine start-up when the interlocked shield is not properly in-place in front of the hazard.
These types of engineering controls, which either prevent the start of or stop hazardous motion, may be used in place of guards or as complimentary devices when guards are either inappropriate for the application, or do not adequately enclose the hazard. In order for these safeguarding devices to accomplish this requirement, they must be properly designed and installed. Other safeguarding devices (probe detection and safety edge devices) that merely detect, instead of prevent, inadvertent access to a hazard are not considered primary safeguards.
B. Types of Machine Safeguarding Devices
Restraint Devices: Wrists are connected by cords and secured to a fixed anchor point which limit operator’s hands from reaching the point of operation at any time.
Presence-Sensing Devices: A device that creates a sensing field, area, or plane to detect the presence of an individual or object and provides an output signal.
Pressure Sensitive Mats: Sensor-based floor mat integrated into a machine’s control system to stop operation when a predetermined weight is applied to the mat. A manual reset switch must be located outside the protected zone.
Two-Hand Control Device: An actuating control that requires the synchronous use of both of the operator’s hands to initiate a machine cycle and concurrent use during the hazardous portion of the machine cycle.
Two-Hand Trip Device: An actuating control that requires the synchronous use of both if the operator’s hands to initiate a machine cycle (on full-revolution clutch machines).
Type “A” Gate (movable barrier): Applicable to mechanical power presses. Provides a barrier between point of hazard and the operator (or other employees) until completion of machine cycle.
Type “B” Gate (movable barrier): Applicable to mechanical power presses. Provides a barrier between point of hazard and the operator (or other employees) during the downstroke portion of a machine cycle.
Other safeguarding methods, such as those described in ANSI B11.19-2019 may also provide employees with some protection from machine hazards. Additional presence-sensing devices, awareness devices, safeguarding methods and safe work procedures are described in this section. These methods provide a lesser degree of employee protection than the primary safeguarding methods and they are considered secondary control measures as they do not prevent employees from placing or having any part of their bodies in the point of hazard on a machine.
Secondary safeguarding methods are acceptable only when guards or safeguarding devices (that prevent you from being exposed to machine hazards) cannot be installed due to reasons of in-feasibility. Where it is feasible to use primary safeguarding methods, secondary safeguarding methods may supplement these primary control measures; however, these secondary safeguarding methods must not be used in place of primary safeguarding methods.
A probe detection device (sometimes referred to as a halo or ring guard), such as that found on Rockford System’s Detect-A-Finger devices, detects the presence or absence of a person’s hand or finger by encircling all or part of the machine hazard area. The Detect-A-Finger stops or prevents a hazardous machine cycle or stroke if interrupted, thereby reducing the likelihood of injuring yourself in the point of operation. These types of detection devices are commonly used on spot welders, riveters, staplers and stakers when other primary risk reduction methods are not possible. However, probe detection devices do not prevent inadvertent access to the point-of-operation danger area; rather, they serve as a warning mechanism and are designed to prevent the initiation of the machine cycle if an employee’s hand or finger(s) are too close to the hazard area.
A edge safety device (sometimes called a bump switch) is another type of safeguard that detects the presence of an employee when they are in contact with the device’s sensing edge. An edge safety device protects employees by initiating a stop command when the sensing surface detects the presence of a person; however, they do not usually, when used by themselves, prevent inadvertent access to machine danger areas. Therefore, additional risk reduction measures and safeguarding devices must be provided to prevent employee exposure to a machine hazard.
Awareness devices warn employees of an impending, approaching or present hazard. The first type is an awareness barrier which allows access to machine danger areas, but it is designed to alert the employee to the fact that they are too close to a particular hazard. Awareness signals, through the use of recognizable audible or visual signals, are other devices that alert employees to an approaching or present hazard. Lastly, awareness signs are used to notify employees of the nature of the hazard and to provide instructions and training information. OSHA 1910.145 and ANSI Z535 1-4 provide design, application, and use specifications for accident prevention (danger, caution, safety instruction) signs and (danger, caution, warning) tags.
Safeguarding methods protect employees from hazards through the physical arrangement of distance, material holding/handling, openings or the positioning of the machine components to ensure that the operator cannot reach the hazard. Some safeguarding work methods include safe distance safeguarding, safe holding safeguarding and safe opening safeguarding. Requirements for these secondary control measures may be found in ANSI B11.19-2019. Proper training and supervision are essential to ensure that these secondary safeguarding methods are being used properly. Safeguarding work methods may require the use of awareness devices, including the use of accident prevention signs where there is a need for warning or safety instruction.
Safeguarding by Distance
Safeguarding by safe distance (or by location) may involve operator positioning at a predetermined minimum safe distance so that the operator cannot physically reach the hazard.
Another example of a safe distance safeguarding method is the use of gravity feed methods that reduce or eliminate employee exposure to machine hazards as the part slides down a chute into the point of operation. Automatic and semiautomatic feeding and ejection methods can also protect the employee by minimizing or eliminating employee exposure with potentially hazardous machinery components. An employee 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. Figures 18 and 19 illustrate different types of automatic feeding and ejecting methods.
Safe Work-Piece Holding
Operator’s hands are maintained away from the hazardous portion of the machine cycle by requiring that both hands are used to hold or support the work-piece, or by requiring that one hand holds the work-piece while the other hand operates the machine. 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. The operator’s body parts are out of the machine hazard area during the hazardous portion of the machine cycle. However, this work method only protects the operator.
Safe Opening Safeguarding
This method limits access to the machine hazardous areas by the size of the opening or by closing off the danger zone access when the work-piece is in place in the machine. Operators are prevented from reaching the hazard area during the machine operation; however, employee access to the danger area is not adequately guarded when the work-piece is not in place. Refer to Rockford Systems’ OSHA Guard Opening Scale and ANSI/CSA Guard Opening Scale.
Safe work procedures are formal, written instructions which describe how a task is to be performed. These procedures should incorporate appropriate safe work practices, such as prohibiting employees from wearing loose clothing or jewelry and requiring the securing of long hair with nets or caps. Clothing, jewelry, long hair, and even gloves can get entangled in moving machine parts.
Complementary equipment is used in conjunction with selected risk reduction methods and, by itself, not a safeguarding method. Some common complementary equipment used to augment machine safeguarding include:
Emergency Stop Devices
Emergency stop devices are designed to be used in reaction to an incident or hazardous situation and, as such, are not considered machine safeguarding. These devices, such as buttons, cable-pulls, or pressure-sensitive body bars, neither detect nor prevent employee exposure to machine hazards; rather they initiate an action to stop hazardous motion when an employee recognizes a hazard and actuates them.
Work-holding equipment is not used to feed or remove the work-piece, but rather to hold it in place during the hazardous portion of the machine cycle. Clamps, jigs, fixtures, back gauges and holders are examples of work-holding equipment. This equipment may be used to reduce or eliminate the need for an employee to place their hands in the hazard area.
Feeding and Ejection Systems
A feeding and ejection systems (e.g., a gravity fed chute; semi-automatic and automatic feeding and ejection equipment), by itself, does not constitute secondary safeguarding. However, the use of properly designed feed and ejection mechanisms can protect employees by minimizing or eliminating the need for them to be in a hazard area during the hazardous motion of the machine.
Operators can use tools to feed and remove material into and from machines so as to keep their hands away from a point of operation hazard. However, this must be done only in conjunction with any, or a combination of the hazard reduction devices described previously. Hand tools are not considered safeguarding devices, but rather are complimentary devices designed to allow employees’ hands to remain outside of the hazard area while feeding material, removing material, or clearing jams. Using hand tools requires close supervision to ensure that the operator does not bypass their use to increase production. It is recommended that these tools be designed and constructed of a “crushable” material (such as aluminum), and stored near the operation to promote their use.
Foot controls that are not securely fixed at a safe distance do not constitute a hazard reduction device because they do not keep the operator’s hands out of the point of hazard. Improperly used foot-actuated controls may increase productivity, but the freedom of hand movement increases the risk of a point-of-operation injury or amputation. Foot controls must be guarded to prevent accidental activation by another employee or by falling material.
If you use foot-actuated controls that are not single-control safeguarding devices, they will need to be utilized only when a primary means of hazard reduction is present.
As an employer, you need to consider housekeeping practices, employee apparel, and employee training. Implement good housekeeping practices to promote safe working conditions around machinery by doing the following:
- Remove slip, trip, and fall hazards from the areas surrounding machines;
- Use drip pans when oiling equipment;
- Remove waste stock as it is generated;
- Make the work area large enough for machine operation and maintenance; and
- Place machines away from high traffic areas to reduce employee distraction.
Employees should not wear loose-fitting clothing, jewelry, or other items that could become entangled in machinery, and long hair should be worn under a cap or otherwise tied back or contained to prevent entanglement in moving machinery.
Adequate instruction in the safe use and care of machines and supervised on-the-job training are essential in preventing amputation injuries. Only trained employees should operate machinery.
Train Employees in the Following:
- All hazards in the work area, including machine-specific hazards;
- Machine operating procedures, lockout/tagout procedures and safe work practices;
- The purpose and proper use of machine safeguards; and
- All procedures for responding to safeguarding problems such as immediately reporting unsafe conditions such as missing or damaged guards and violations of safe operating practices to supervisors.
In addition to employee instruction and training, employers need to provide adequate supervision to reinforce safe practices. Take disciplinary action to enforce safe work practices and working conditions.
OSHA’s lockout/tagout (LOTO) standard, 29 CFR 1910.147, establishes minimum performance requirements for controlling hazardous energy and it is intended to complement and augment machine safeguarding practices.
Because some minor servicing may have to be performed during normal production operations, an employer may be exempt from LOTO in some instances. Minor tool changes and adjustments and other minor servicing operations, which take place during normal production operations, are not covered by lockout/tagout if they are routine, repetitive and integral to the use of the machine for production and if work is performed using alternative effective protective measures that provide effective employee protection.
In short, a hazardous energy control program is a critical part of an overall strategy to prevent workplace amputations during machine servicing and maintenance activities, such as during the setting up of machines for production purposes, bypassing guards to clear jams or lubricate parts, and inspecting, adjusting, replacing, or otherwise servicing machine parts.
The machinery listed below cause amputation injuries, and appropriate safeguarding and hazardous energy control (lockout/tagout) methods are addressed in this section. Employers need to consult the OSHA standard for specific machinery to ensure compliance with all requirements.
Machinery Associated with Amputations
1. Mechanical Power Presses
2. Power Press Brakes
3. Powered and Non-Powered Conveyors
4. Printing Presses
5. Roll-Forming and Roll-Bending Machines
6. Shearing Machines
7. Food Slicers
8. Meat Grinders
9. Meat-Cutting Band Saws
10. Drill Presses
11. Milling Machines
12. Grinding Machines
Properly reducing and eliminating hazards likely to injure of kill an employee is not only required by law, but it also helps reduce risk and keep employees safe at work. Properly reducing hazardous exposure through properly safeguarding machinery can be a complex undertaking, and any safeguarding project should always begin with a risk assessment.
For more information about machine safeguarding, please call 1-800-922-7533 or refer to our Machine Safeguarding Seminars, which provide 2 days of in-depth instruction on the topics covered above (and more).