Machine Guarding & Lockout/Tagout Expert Article

A significant portion of our machine guarding investigations involve situations where machine guards are removed and/or workers place their hands and/or other body parts within a machine’s point-of-operation. The scope of these investigations will typically go beyond an evaluation of mechanical or electrical guards to include administrative protections such as lockout/tagout procedures.

In this article, facilities engineering and industrial safety expert, Todd Metcalfe, offers information on lockout/tagout within the context of industrial safety.

Machine Guarding Lockout Tagout Expert Witness


Adequate guards serve their purpose well in the prevention of injuries. However, there are times when guards need to be removed. This typically occurs during maintenance activities when technicians are servicing or maintaining machines and equipment. Such tasks may require some level of machine/equipment disassembly, including the removal of guards.

In such situations, the individual may turn the machine off using the controls provided on the machine. However, hazardous energy may remain within the system. This can include, but is not limited to: electrical, mechanical, hydraulic, and pneumatic.

The failure to control hazardous energy accounts for approximately 10% of serious industrial accidents.

Some examples of these are:

  • A jammed conveyor system suddenly releases, injuring a worker who is trying to clear the jam;
  • Internal wiring electrically shorts, shocking a worker who is repairing the equipment;
  • A worker turns on a machine, unaware that a technician is in harm’s way while making a repair.

A simple and required procedure to protect workers from hazardous energy is “Lockout/Tagout.” The Lockout/Tagout procedure can take several forms. Its specific use may be as simple as locking the handle on an electrical panel or securing the wheel on a steam valve using a chain.

In both cases, a lock with a unique key is utilized and that key remains under the exclusive control of its owner. A tag is applied at the control, to inform others of the lockout condition.  For items that are not hard-wired into a panel box, an electrical plug cover lockout device may be used:

Plugout expert example

Lockout/Tagout is mandated by OSHA Regulation 1910.147 The Control of Hazardous Energy (Lockout/Tagout). Selected sections from OSHA 1910.147 have been provided below for your reference.

  • 1910.147(a)(1)(i) - This standard covers the servicing and maintenance of machines and equipment in which the unexpected energization or start up of the machines or equipment or release of stored energy could cause injury to employees. This standard establishes minimum performance requirements for the control of such hazardous energy.
  • 1910.147(a)(3)(i) - This section requires employers to establish a program and utilize procedures for affixing appropriate lockout devices or tagout devices to energy isolating devices, and to otherwise disable machines or equipment to prevent unexpected energization, start-up or release of stored energy in order to prevent injury to employees.
  • 1910.147(b) – Definitions applicable to this section.
    • Lockout: The placement of a lockout device on an energy isolating device, in accordance with an established procedure, ensuring that the energy isolating device and the equipment being controlled cannot be operated until the lockout device is removed.
    • Lockout device: A device that utilizes a positive means such as a lock, either key or combination type, to hold an energy isolating device in the safe position and prevent the energizing of a machine or equipment. Included are blank flanges and bolted slip blinds.
    • Tagout: The placement of a tagout device on an energy isolating device, in accordance with an established procedure, to indicate that the energy isolating device and the equipment being controlled may not be operated until the tagout device is removed.
    • Tagout device: A prominent warning device, such as a tag and a means of attachment, which can be securely fastened to an energy isolating device in accordance with an established procedure, to indicate that the energy isolating device and the equipment being controlled may not be operated until the tagout device is removed.
  • 1910.147(c)(1) - Energy control program. The employer shall establish a program consisting of energy control procedures, employee training and periodic inspections to ensure that before any employee performs any servicing or maintenance on a machine or equipment where the unexpected energizing, start up or release of stored energy could occur and cause injury, the machine or equipment shall be isolated from the energy source, and rendered inoperative.

Additionally, Lockout/Tagout is supported by the American National Standard ANSI Z244.1 The Control of Hazardous Energy, Lockout/Tagout and Alternative Methods. ANSI standards are copyrighted and can be acquired through their webstore.

Robson Forensic possesses an extensive technical library that houses standards and reference materials dating throughout the modern industrial era. In many forensic investigations, our experts are able to reference industry specific resources to establish the relevant standard of care at the time that a piece of machinery or equipment was designed, built, or modified.

Workplace Safety & Machine Guarding Investigations

The industrial safety experts at Robson Forensic have designed, built, maintained, and operated a broad array of industrial machinery. Moreover, our experts have investigated countless incidents over the years involving all types of equipment. By retaining Robson Forensic, you are securing the full weight of our collective experience, knowledge, and resources toward the successful resolution of your matter.

For more information contact the author of this article or submit an inquiry.

Featured Expert

Todd Metcalfe, Facilities Engineering & Industrial Safety Expert

Todd Metcalfe

Facilities Engineering & Industrial Safety Expert
Todd is a Facilities Engineering and Industrial Safety Expert with over two decades of diverse experience in manufacturing and quality engineering for industrial machinery, heavy commercial vehicle… read more.


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