Anyone involved in the design, installation, operation, or maintenance of industrial equipment is personally concerned with machine safety and safety procedures. There are two broad descriptions of machine safeguarding: prevention of contact with the hazard and control of the energy driving the hazardous operation. Machine barrier guarding is a way to avoid contact with a hazard, while lockout/tagout (LOTO) procedures and the use of control reliable circuits are ways to control the energy driving the operation. This paper provides information on the best uses of lockout/tagout and control reliable circuits.
Lockout/tagout (LOTO) is the required safety procedure for maintenance tasks and those that are not part of a machine's normal production process. If any employee is required to remove or bypass a machine guard, or is required to place any part of his body into a machine where work is performed or where any other zone of danger exists, the LOTO procedures must be followed.
The essence of the safety requirement is that the danger of any and all hazardous energy sources must be relieved and removed before anyone enters a machine for repair, maintenance or service. The associated regulations require that the method to do that on a machine be formalized, documented and communicated to anyone who works around the equipment.
Tagout is a similar process required if lockout is not possible. A prominent tag is placed on or near the energy isolation device warning against hazardous conditions if the equipment is energized. Use of a tagout device illustrates a feature necessary to any energy control program- the need for employee training and communication. A tagout device does not physically prevent the equipment from being energized, but with training in the proper procedures to apply and remove lockout and tagout devices, employees can be effectively protected.
Energy control by lockout or tagout is required for all tasks that are not routine, repetitive, or integral to the use of the machine for production. For example, changing a grinding wheel is not part of the normal production operation, so to do this, the grinder must be locked out or tagged out. Normal production operations and minor machine servicing are not regulated by the OSHA lockout/tagout regulation.
The increasing complexity of production processes and industrial equipment often precludes the use of LOTO to perform necessary work. The Occupational Safety and Health Administration (OSHA), the American National Standards Institute (ANSI) and other organizations have provided regulations and guidance to assess the level of risk present and apply alternative methods of personnel protection to decrease the risk to a tolerable level.
The federal regulation in the United States that governs the use of LOTO is OSHA regulation 1910.147. This standard establishes minimum performance requirements for the control of hazardous energy. NFPA 70 (National Electrical Code NEC) is listed as reference in Appendix A of OSHA 1910; therefore, the mandatory requirements of NEC are also mandatory OSHA requirements.
There are some exceptions where OSHA 1910.147 does not apply.