LOTO: the equipment maintenance, repair, and installation safety standard

Lock-out, tag-out (LOTO) standards are the most violated, the most cited, and the most dangerous-to-ignore safety standards around. To improve machine safety and lower risk, LOTO standards are needed for industrial equipment in five situations. These are ...

07/13/2010


Lock-out and tag-out (LOTO) standards, per the Occupational Safety and Health Administration (OSHA), apply in situations where industrial equipment, automated equipment in particular, is out of service, but may be operated as part of installation, maintenance, or modification activity.

There are five situations where LOTO standards are needed for industrial equipment:

  • construction;
  • install and set up;
  • adjustments, inspections, modifications;
  • lubricating, cleaning or un-jamming; and
  • tool changes.

LOTO standards require that all power circuits to the equipment in question be deactivated. Simply shutting the equipment off at the control circuits (such as an E-stop) is not enough. Power from the mains to the equipment must be cut using an energy isolation device. An energy isolation device is a mechanical device that physically prevents the transmission or release of energy, including but not limited to:

  • a manually operated electrical circuit breaker;
  • a disconnect switch; or
  • a manually operated switch by which the conductors of a circuit can be disconnected from all ungrounded supply conductors.

The reason E-Stops, safety mats, light curtains, interlock switches, etc. are not considered energy isolation devices is because they are elements of control circuits. Therefore, they may prevent control signals from reaching the device, but leave the power circuits (e.g., power to a motor drive) live.

Minor servicing activities, such as simple tool changes and adjustments, which take place during normal production operations, are not covered by OSHA’s LOTO standard if they are routine, repetitive, and integral to the use of the equipment for production. However, this exception applies only if the work is performed using alternative measures which provide effective protection.

The OSHA LOTO standard doesn’t address situations where tasks to be performed are not minor servicing, but must have power supplied to perform them. For example, using a teach pendant for robotic equipment, where employees have to be next to the robots – which may violate the LOTO standard.

OSHA recognizes such situations exist and has provided an alternative per ANSI Z244.1. According to this standard, when LOTO is not used for tasks that are routine, repetitive, and integral to the production process, or traditional LOTO prohibits the completion of those tasks, then “an alternative method of control” shall be used.

Appropriate alternative protective systems ensure that a device or system will stop, or prevent initiation of hazardous motion, or release of hazardous energy, in the event of a single component failure within the device or system. Typical alternative protective systems may include:

  • a hardware based, control-reliable safety interlock system; and/or
  • a safety-rated multiple-channel programmable logic controller, when manufactured specifically for safety applications, and applied per manufacturer’s instructions.

 

To know when LOTO is required, the following general rules of thumb can be used to determine LOTO’s necessity:

  • always use lockout during servicing and maintenance;
  • always use effective alternative protection for minor servicing activities;

In other situations, where it is not feasible to lockout, document the reasons, conduct a risk assessment, and provide the proper level of protection.

More information about LOTO can be found at the OSHA Website – www.osha.gov, which includes a section on training. There, you can find links to OSHA Education Centers.

As an example of such education centers, James Washam, safety specialist at Machine Safety Specialists, based in Cincinnati, notes that “the University of Cincinnati has a program where they present OSHA courses for training purposes.” There are also free OSHA consultation services provided by the states, which OSHA funds throughout the country.

Searching on the Web for keyword phrases like “OSHA training” will yield links to third-party companies who will also provide training for engineers tasked with setting up safety procedures. Many of them, like Washam’s Machine Safety Specialists, also provide consulting services to help companies protect themselves with regard to safety issues.

Several OSHA-related resources can also be found at www.safetybase.com.

Additional resources include:            

  • ANSI B11.19 Criteria – Performance for Safeguarding, 2003;
  • NFPA 79 – Electrical Standard for Industrial Machinery; and
  • ANSI standards specifically related to your equipment.

While application of LOTO-related best practices can be a complex subject, it is one that simply cannot be ignored. Engineers responsible for installing automated systems need to be aware of what is required by relevant standards and when those activities must be performed.

- Control Engineering tutorial, www.controleng.com



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