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Standard Interpretations - (Archived) Table of Contents
• Standard Number: 1910.147(a)(2)(ii)
• Status: Archived

Archive Notice - OSHA Archive

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

June 21, 2002

Mr. Mark Wilhelm
5321 Midland Road
Midland, VA 22728-2135

Dear Mr. Wilhelm:

Thank you for your inquiry to the Occupational Safety and Health Administration's (OSHA's) Philadelphia, PA Regional Office. Your letter has been referred to the [Directorate of Enforcement Programs (DEP)] for an answer to your specific questions regarding the application of OSHA's "Control of Hazardous Energy (Lockout/Tagout)" 1910.147 standard. This letter constitutes OSHA's interpretation only of the requirements discussed and may not be applicable to any questions not delineated within your original correspondence. Your paraphrased scenario, proposed alternative, question, and our response are provided below.

Scenario: The scenario involves a tool change process where the carriers and tooling in an intermittent motion packaging machine are changed to accommodate a different package footprint. The electronic control system guides the operators through this process, providing direction and timing information regarding the tool change, which actually requires several steps: changing the carriers, the seal and cut station, and the discharge components.

Changing the carriers involves standing in the normal operator position, removing a carrier by pulling the carrier out of its detent, and indexing the machine such that the next carrier can be removed. This process is repeated until all carriers are removed from the machine. No guards have to be removed for this process, and all interlocks are in place.

Currently, officials are requiring lockout/tagout between each carrier index, which is extremely time consuming. This lockout/tagout procedure causes the computer of the machine to re-boot each time the machine is powered up, and resets the tool change procedure screens, etc.

Alternative: Tool change procedures for the machine currently require the seal and cut station to be changed first to allow preheating of the tool while the other tool change tasks are completed. Newer versions of the machine software give the user the option of doing the tool change and then the carrier change or the carrier change and then the tool change. Choosing "Carrier Change" mode first would allow the carriers to be changed at the beginning of the tool change cycle. We could change the software in the machine to accommodate this option.
  1. We would choose "Carrier Change" mode first and change the carriers. Changing the carriers is not intrusive, no guards are removed, and all safeties are still in place.
  2. To address the machine re-boot issue, and Tool Change Procedure and Screen reset, we could change the e-stop on the operator side of the machine to a lockable e-stop. The e-stop breaks all control power and power to the servo drive, and would "control the power" that provides carrier motion. Pressing the e-stop would also dump the air. This e-stop could be locked.
  3. With the e-stop locked, Air and Control power are controlled. The air inlet could also be locked out if necessary to further "control the power" for the die closing system. Power stays on the PLC, and touchscreen and timers continue to work.
  4. Die change would then take place with the locks (e-stop and air) in place. Operators would push "Tool Change complete," and record the time.
  5. Locks would then be removed. Air would be restored, the e-stop pulled, and the machine would again be operational.
Question: Are the proposed alternative procedures adequate as safeguards during these referenced production changes?

Reply: The work that you have described constitutes a "servicing and/or maintenance" activity, as that phrase is defined in the Control of hazardous energy (lockout/tagout) standard. See 29 C.F.R. §1910.147(b) (defining "servicing and maintenance" inter alia to include making machine tool changes and machine adjustments). The standard covers the servicing and maintenance of machines and equipment in which the unexpected energization or start up of the machines or equipment, or the release of stored energy, could cause injury to employees. OSHA representatives who observed the carrier and tool changing operation determined that employees may be subjected to hazardous energy during the carrier and tool changing process. Thus, employers who change the carriers and tools on the motion packaging machine must comply with the provisions of the standard, unless the work falls within one of the exceptions to the standard.

In your letter you suggest that the carrier and tool change is similar to a minor tool change or minor adjustment and should be considered within the exception for minor servicing activities. Pursuant to this exception, minor servicing activities, which take place during normal production operations, are not covered by the lockout/tagout standard, if they are routine, repetitive, integral to the production operation and there is an alternative, effective means of employee protection applied in lieu of lockout or tagout. However, from your limited description of the activity, it appears that one or more of these criteria cannot be met and that an employer would be required to comply with the provisions of the lockout/tagout standard.1

In order to comply with the standard in the scenario that you have described, an employer would need to develop an energy control procedure that accounts for all types of hazardous energy associated with the servicing and maintenance activity. The steps that you have described would be sufficient to isolate hazardous electrical and pneumatic energy, if they use a mechanical device that physically prevents the transmission or release of both types of hazardous energy. For example, if the e-stop switch that you described separates all current carrying conductors from the carrier's electrical servo drive and also prevents the release (and re-accumulation) of hazardous pneumatic energy through mechanical means, the e-stop switch could be used as an energy isolation device to prevent employee exposure to hazardous energy. On the other hand, if the e-stop switch does not physically disconnect the conductors and mechanically control the pneumatic energy, the e-stop is not an "energy isolation device" and cannot be used exclusively to control hazardous energy. 2

You have also indicated that the e-stop also would be locked. As you infer, the energy isolation device must be locked or tagged in accordance with the provisions of the standard prior to the initiation of servicing or maintenance activity. The locking and tagging provisions of the standard are detailed in paragraph (c)(5) of 1910.147.

Please be aware that isolation of hazardous energy and the locking or tagging of the energy isolation device are only two facets of hazardous energy control. The additional steps that must be followed prior to the initiation of servicing or maintenance activity are detailed in paragraph (d) of 1910.147.

As you may know, the state of Virginia operates its own occupational safety and health program under a plan supervised by federal OSHA. This letter interprets only the provisions of the federal standard, 29 C.F.R. §1910.147. State plans are required to promulgate regulations that are, "at least as effective" as the federal standards, but they may also be more stringent. To obtain the state of Virginia's opinion on this issue, you should contact:
Virginia Department of Labor and Industry
Jeffery Brown, Commissioner
Powers-Taylor Building
13 South 13th Street
Richmond, Virginia 23219
Phone: (804) 786-2377
Fax: (804) 371-6524

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 If you have any further questions, please feel free to contact the [Office of General Industry Enforcement] at (202) 693-1850.


Richard E. Fairfax, Director
[Directorate of Enforcement Programs]

1For example, it does not appear that the servicing activities, even if they were deemed to be "minor," are conducted during normal production operations. Further, your description does not provide a basis for concluding that the activities are "routine, repetitive, and integral to the use of" the machine. [ back to text ]

2Given the information in your letter, we are unable to determine whether the e-stop works in a manner such that it would constitute an "energy isolation device" for purposes of the standard. Our attempts to get additional detail from you regarding the manner in which the e-stop functions were unsuccessful. [ back to text ]

Archive Notice - OSHA Archive

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

Standard Interpretations - (Archived) Table of Contents

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