Safeguarding is essential for protecting employees from needless and preventable injury. A good rule to remember is:
Any machine part, function, or process that may cause injury must be safeguarded.
In this article, the term 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 OSHA general industry (e.g., Subpart O) and construction (e.g., Subparts I and N) standards for specific guarding requirements.
Many of these standards address preventive methods (such as using barrier guards or two-hand tripping devices) as primary control measures; while
other OSHA standards allow guarding techniques (such as a self-adjustable table saw guard) that reduce the likelihood of injury. Other less protective
safeguarding methods (such as safe work methods) that do not satisfactorily protect employees from the machine hazard areas are considered secondary
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 work activities either by: 1) effective machine safeguarding, or 2) lockout/tagout where safeguards are rendered
ineffective or 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 and should consider this need when purchasing machinery. Almost all new machinery is available with safeguards installed by the manufacturer, but used equipment may not be.
If machinery has no safeguards, you may be able to purchase safeguards from the original machine manufacturer or from 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. If possible, 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 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.
The Performance Criteria for Safeguarding [ANSI B11.19-2003] national consensus standard 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.
The Performance Criteria for Safeguarding [ANSI B11.19-2003] defines safeguarding 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 prevents exposure to an identified hazard.
Safeguarding device: A device that detects or prevents inadvertent access to a hazard.
NOTE: The 1990 ANSI B11.19 term Safeguarding device was modified to Safeguarding (Protective) Device in the revised 2003 ANSI standard and the new term includes a detection component. Devices that detect, but do not prevent employee exposure to machine hazards are not considered by OSHA to be primary safeguarding methods.
Awareness device: A barrier, signal or sign that warns individuals of an impending, approaching or present hazard.
Safeguarding method: Safeguarding implemented to protect individuals from hazards by the physical arrangement of distance, holding, openings, or positioning of the machine or machine production system to ensure that the operator cannot reach the hazard.
Safe work procedures: Formal written instructions developed by the user which describe how a task is to be performed.
Primary Safeguarding Methods
Two primary methods are used to safeguard machines: 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 within the hazardous portion of the 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 Machine Safeguarding
- Prevents employee contact with the hazard area during machine operation.
- Avoids creating additional hazards.
- Is secure, tamper-resistant, and durable.
- Avoids interfering with normal operation of the machine.
- Allows 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. (See Table 1 and Figures 9 through 12 for commonly used machine guards.)
|Types of Machine Guards
||Method of Safeguarding
||Barrier that allows for stock feeding but does not permit operator to reach the danger area.
- Can be constructed to suit many applications.
- Permanently encloses the point of operation or hazard area.
- Provides protection against machine repeat.
- Allows simple, in-plant construction, with minimal maintenance.
- Sometimes not practical for changing production runs involving different size stock or feeding methods.
- Machine adjustment and repair often require guard removal.
- Other means of protecting maintenance personnel often required (lockout/tagout).
||Barrier that adjusts for a variety of production operations.
- Can be constructed to suit many applications.
- Can be adjusted to admit varying stock sizes.
- May require frequent maintenance or adjustment.
- Operator may make guard ineffective.
||Barrier that moves according to the size of the stock entering point of operation. Guard is in place when machine is at rest and pushes away when stock enters the point of operation.
- Off-the-shelf guards are often commercially available.
- Does not provide maximum protection.
- May require frequent maintenance and adjustment.
|Interlocking Barrier Guards
||Shuts off or disengages power and prevents machine start-up when guard is open. Should allow for inching of machine.
- Allows access for some minor servicing work, in accordance with the lockout/tagout exception, without time-consuming removal of fixed guards.
- May require periodic maintenance or adjustment.
- Movable sections cannot be used for manual feeding.
- Some designs may be easy to defeat.
- Interlock control circuitry may not be used for all maintenance and servicing work.
[Content with recognition to OSHA]
Controlling Amputation Hazards Part 2