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Standard Interpretations - Table of Contents
• Standard Number: 1910.147; 1910.147(a)(2)(ii); 1910.147(b)

This letter constitutes OSHA's interpretation only of the requirements discussed and may not be applicable to any situation not delineated within the original correspondence.

February 26, 2007

Mr. Stephen Zbytowski, PE
Marketing Manager
1201 S Second
Milwaukee, WI 53204

Dear Mr. Zbytowski:

Thank you for your October 3, 2006 letter and follow-up e-mail to the Occupational Safety and Health Administration (OSHA). You requested an interpretation regarding the use of a disconnect system called ElectroGuard and OSHA's Control of hazardous energy (lockout/tagout), 29 CFR §1910.147, requirements for energy isolating devices. You also attached a product brochure, User Manual and referred to a now archived OSHA interpretation letter.
1 Your paraphrased product description, question, and reply follow:

System Description: The ElectroGuard system is used to de-energize electrical, hydraulic, and/or pneumatic energy in equipment and machinery. Although this system physically prevents the transmission of energy by locking out the equipment/machinery at the point of entry to the hazard via a Remote Lockout Station (RLS), it does so through the operation of control circuit devices.

Your brochure states that the ElectroGuard conforms to OSHA requirements for the control of hazardous energy. Your team of safety, product, and process engineers feels that the ElectroGuard system meets the requirements of a disconnect device and provides a method of de-energizing machinery and equipment during operation, service, and maintenance.

Question 1: Does the ElectroGuard system, which meets the following recognized standards, meet the energy isolating device definition, contained in 1910.147(b):

  • The National Electric Code (NEC) 2005 edition Section 430.109(a)(7), System Isolation Equipment;
  • NFPA 79-2002 Section 5.5.4(3) refers to Redundantly monitored, remotely operated contactor isolating system . . .;
  • ANSI Z244.1-2003 Section and Annex G references on Remote low-voltage lockout system?
Reply: No. Circuit control devices, such as the ElectroGuard system, are sometimes referred to as a remote low-voltage lockout system. Circuit control systems are not energy isolating devices as defined in §1910.147(b). As defined by the lockout/tagout (LOTO) standard, energy isolating devices are mechanical devices that physically prevent the transmission or release of energy. Thus, pursuant to the standard, circuit control devices such as the ElectroGuard cannot be used to control hazardous energy in situations other than minor servicing. (See Question 2 below.)

Although you believe that the ElectroGuard system operates in accordance with three recognized industry standards, based on the information you provided, we do not believe that the use of an ElectroGuard system in lieu of an energy control device is justified. If, however, you wish to provide more information demonstrating that the ElectroGuard provides the same level of protection as that mandated by the LOTO standard, you may apply for a variance. For further information on the variance application process, you may contact:
Office of Technical Programs and Coordination Activities
200 Constitution Avenue, NW, Room N-3655
Washington, DC 20210
Question 2: If used in accordance with all of the our User Manual's application, installation, trouble-shooting, preventive maintenance, and use requirements, would the ElectroGuard system constitute effective protection pursuant to the LOTO standard's minor servicing exception?

Reply: Yes, an ElectroGuard system will likely provide alternative measures which constitute effective protection under the minor servicing exception. See 29 CFR §1910.147(a)(2)(ii), note. In making this determination, it is important to apply this safety control system through a hazard analysis process on a case-by-case basis in order to ensure that it provides the required effective employee protection. For example, the system would need to be designed, installed, used, and maintained in accordance with the generally-recognized good engineering practices. Even if the system meets these criteria, please note that under the minor servicing exception, the ElectroGuard system may be used only to protect employees who are performing minor tool changes and adjustments, and other minor servicing activities that take place during normal production operations and are routine, repetitive, and integral to the use of the equipment for production.

Thank you for your interest in occupational safety and health. We hope you find this information helpful. OSHA requirements are set by statute, standards, and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at
http://www.osha.gov. If you have any further questions, please feel free to contact the Office of General Industry Enforcement at (202) 693-1850.


Edwin G. Foulke, Jr.

[Corrected 6/11/2007]

Standard Interpretations - Table of Contents

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