Control risk with lockout/tagout

How to perform equipment maintenance safely

PRACTICAL WELDING TODAY® JULY/AUGUST 2006

July 11, 2006

By:

Lock-out/tag-out procedures are critical when you're dealing with equipment or machines powered by electricity, steam, hydraulics, gas, compressed air, or a combination of sources.

In March 2002 a California welder was asked by his supervisor to remove a jammed piece of metal from the hydraulic door of a scrap metal shredder. As he'd done several times before, the man grabbed his ladder, torch, and padlock and went to the hopper.

While lying across the top edge of the door, he cut away the obstruction with the torch. Once he succeeded, though, the hydraulic door—which still was under pressure—closed upward on the man. He was crushed to death.

Two co-workers testified that the welder said he had secured the system, but the padlock he was supposed to use to lock out the system was recovered from his clothing.

Such occurrences serve as graphic reminders that anytime you're dealing with equipment or machines powered by electricity, steam, hydraulics, gas, compressed air, or a combination of sources, always remember to follow prescribed lockout/tagout (LOTO) procedures.

What Lockout/Tagout Means

The Occupational Safety and Health Administration (OSHA) LOTO standard (29 CFR1910.147) mandates criteria for de-energizing equipment during servicing and maintenance operations to prevent unexpected energization or start-up. Lockout refers literally to installing a lock (keyed or combination) on an energy-isolating device. Tagout refers to placing tags or labels on those devices to warn others not to restore energy to them.

To avoid an incident, never assume someone else has completed LOTO. You are responsible for your own safety. If you need to weld any energized equipment or machines, you should follow these step-by-step procedures:

  1. Locate and identify isolating devices to confirm switches, valves, or other energy-isolating devices for equipment LOTO.
  2. Notify all affected employees that lockout/tagout is going to occur. (Authorized employees must know the machine type, its energy magnitude, and the hazards.)
  3. Shut down the equipment/machine with normal stopping procedures.
  4. Isolate the equipment/machine from the energy sources by locking or tagging it out with assigned individual locks or tags. Only the worker completing the work will have control over the key.
  5. Bleed or release all potentially hazardous stored or residual energy, including trapped air, gas, and chemicals. Safely dissipate or restrain stored energy (such as that in springs and hydraulic systems) by repositioning, blocking, or bleeding.
  6. Verify equipment/machine isolation before servicing or maintenance work.
  7. Service equipment/machinery with a buddy, both wearing proper personal protective equipment (PPE)—insulated gloves, sleeves, insulated tools, and protective helmet.

Before lockout or tagout devices are removed and energy is restored, the authorized employee must:

  1. Inspect the work area to ensure that nonessential items have been removed and that machine or equipment components are intact and can operate properly.
  2. Check the area around the machine or equipment to ensure that all employees have been positioned or removed safely.
  3. Notify affected employees immediately after removing locks or tags and before starting equipment or machines.
  4. Ensure that locks or tags are removed only by those authorized employees.

Additional safety tasks are required for special circumstances, such as testing or repositioning equipment during service. Situations involving on-site contractors, multiple shifts, or new personnel also may require special LOTO procedures.

In cases like these, OSHA allows locks or tags to be removed temporarily and machine or equipment re-energization only when necessary. When this occurs, re-energization also requires that the authorized employee:

  1. Clear the machines or equipment of tools and materials.
  2. Remove employees from the immediate area.
  3. Remove the LOTO devices as specified in your company plan.
  4. Energize and proceed with testing or positioning.
  5. De-energize all systems, isolate the machine or equipment from the energy source, and reapply lockout or tagout devices as specified.

If a machine can't be locked out, it must be tagged out with a tag that can't be removed or cut away easily. Clearly, tags affixed to energy-isolating devices don't provide the physical restraint of locks, but they still can prevent injury. All tags should be legible and understandable and must be made of materials that can withstand your workplace's environmental conditions. They should be attached using fasteners that can't be removed easily. And once a tag is applied, it should be removed only by the person qualified to apply it.

Employees who perform or are affected by LOTO procedures must receive training at least once a year. According to OSHA regulations, "Employees must understand the purpose, function, and restrictions of the energy control program and that authorized employees possess the knowledge and skills necessary for the safe application, use, and removal of energy controls."

Welders in particular should be mindful of additional energy-related issues, such as the distance people should stay clear of work being done (see sidebar). Also remember:

  • Don't perform housekeeping duties near exposed energized parts unless a barrier or insulating device is used.
  • Keep weld-initiating control circuits less than 120 volts AC root mean square (RMS) for stationary equipment, and not over 36 VAC RMS for portable equipment.
  • For welding capacitors, insulate and enclose (via doors with interlocks and wired contacts into the control circuit) resistance welding equipment and control panels (with over 550 V RMS). Design contacts and doors to interrupt power when opened. Add a manual switch or positive device as an extra safety measure.
  • Lock, interlock, or guard remote welding control panels on overhead platforms or in separate rooms by physical barriers and signage when not being serviced.
  • When working with electrical circuits, use circuit breakers to open, reverse, or close circuits under load conditions. Make sure circuits are checked before they're re-energized and overcurrent protection can't be modified.
  • Inspect the cords on portable electrical equipment to ensure safety, and never pick up or hang equipment by its cord.

LOTO procedures are essential. According to OSHA, its LOTO policy prevents approximately 120 fatalities and more than 28,000 lost workdays each year. Welding carries risks, but when you take responsibility for your own safety, you can control those risks.

Keeping your distance
When authorized employees are performing service on machines or equipment that has been locked out and tagged out, it's vital that other qualified individuals maintain a certain distance from the welding machine as a guideline. The distance depends on the voltage range in use. When conducting work, use the following chart:
Voltage Range (AC)
Phase to Phase

< 300 V
>300 V, < 750 V
>750 V, < 2 kV
>2 kV, < 15 kV
>15 kV, < 37 kV
>37 kV, < 87.5 kV
>87.5 kV, < 121 kV
>121 kV, < 140 kV
Minimum Approach Distance
Avoid Contact
1' (30.5 cm)
1'6" (46 cm)
2' (61 cm)
2'6" (91 cm)
3'6" (107 cm)
4' (122 cm)
4'6" (137 cm)
Note: Unqualified employees are required to adhere to the 10-ft. minimum at all times.

Shari Falkenburg, MS, OTR, CPE, is risk control director, workers' compensation, for CNA, 800-262-6241, www.cna.com. CNA underwrites Fabricators & Manufacturers Association-endorsed insurance programs and is a longtime partner in FMA safety programs.

The purpose of this article is to provide general information, rather than advice or opinion. It is accurate to the best of the author's knowledge as of the date of the publication. Accordingly, this article should not be viewed as a substitute for the guidance and recommendations of a retained professional. In addition, CNA does not endorse any coverages, systems, processes, or protocols addressed herein unless they are produced or created by CNA.

CNA is a service mark registered with the U.S. Patent and Trademark Office. Copyright© 2006, Continental Casualty Company. All rights reserved.



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