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Standard Interpretations - Table of Contents
• Standard Number: 1910.147

August 30, 2011

Ms. Michele D. Jones
Functional Safety Team Lead
BP Exploration (Alaska) Inc.
P.O. Box 196612
Anchorage, Alaska 99519-6612

Dear Ms. Jones:

Thank you for your February 14, 2011 letter to the Occupational Safety and Health Administration's (OSHA's) Seattle Regional Office. Your letter was forwarded to the Directorate of Enforcement Programs (DEP) for response. You had questions regarding OSHA's Control of hazardous energy (lockout/tagout) standard (§1910.147) and the use of local valves as a means of equipment isolation for energy control. Your paraphrased scenarios, questions, and our responses follow.

Scenario 1: A worker replaces the pressure gage device or other instrumentation on a process line or a piece of operating (running) equipment. The task involves three steps. First, the device being replaced is isolated from its energy source by closing a valve. Second, the pressure in the device is bled, usually by slightly loosening a connection (fitting) to bleed off any trapped fluid and pressure. Third, the device is removed and replaced.

You stated that this work task can be generally completed in a short time period and is always within arm's reach of the worker performing the task. You believe the worker has total and exclusive control of the valve at all times so as to prevent the unexpected release of hazardous energy. In the event that the worker leaves the work area, the valve is locked out and tagged out (LOTO) per your Energy Isolation Policy. Also, per your Energy Isolation Policy other personnel are made aware when this task is being performed and personnel are trained and periodically audited to ensure that they never leave the job without proper LOTO. During your telephone communication with a representative of my staff, you compared this to the exclusive control provision for cord- and plug-connected electric equipment.

Question: Does the replacement of the pressure gage device or other instrumentation on a process line or a unit of equipment while that line or equipment is running require lockout and tagging of the isolation valve?

Response: Yes, with limited exceptions, the §1910.147 standard requires control of the release of stored energy via lockout or via tagout where the energy isolating device is not capable of being locked out. Unless the requirements of 8 1910.147, including written procedures and the application of locks or tags, or both; are followed, the proximity of the worker to the valve is not a sufficient means for the control of hazardous energy.

You stated that the time period to complete the task is usually short and that you believe the worker, who is in arm's reach, has total control of the valve at all times. In the scenario that you pose, it could happen that the worker is pulled from or leaves the work area for an emergency or other urgent need, without locking out and tagging out the device, per your Energy Isolation Policy.

Regarding your belief that the operator has exclusive control of the valve similar to that permitted by 29 CFR §1910.147(a)(2)(iii)(A), this particular exception is limited by its own terms to cord- and plug-connected electric equipment1. OSHA also considered whether the other minor servicing and maintenance exceptions under §1910.147(a)(2) applies and determined that the exceptions are not applicable to the scenario you described.

Additionally, the standard requires that all sources of hazardous energy be controlled. If the pressure gage device (or other instrumentation) has another source of energy, such as an electrical connection, that energy source would also require hazardous energy control according to §1910.333(b), which also mandates written procedures as well as the application of locks and tags.

Scenario 2: A worker cleans or replaces the filter on a pumping system. Filters are generally set up in parallel (operating and standby) with isolation valves upstream and downstream of the filter and a drain valve on the filter unit. Alternatively, the piping to each filter can be set up (arranged) such that a duplex valve assembly (two ball valves in an integral housing with a common valve operating handle) can isolate an individual filter by the operation (turning) of a single handle.

To clean or replace the filter, the worker closes the upstream and downstream valves of the filter unit to be worked on or isolates the unit via the duplex valve assembly. He or she then relieves the pressure by slightly loosening a connection or slightly opening the drain valve, then fully opens the valves, drains the filter housing, and opens the housing to clean or replace the filter. Upon completion, the worker returns the filter to service.

Similar to Scenario 1 above, the task takes a few minutes to complete and the worker has exclusive control of both isolation valves, which are within arm's reach at all times.

Question: Is it permissible to clean or replace a filter unit without locking out or tagging of the local upstream and downstream isolation valves?

Response: No. Please refer to the rationale given in the response to the first scenario.

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.


Thomas Galassi, Director
Directorate of Enforcement Programs

  1910.0147(a)(2)(iii): This standard does not apply to the following:

§1910.147(a)(2)(iii)(A): Work on cord and plug connected electric equipment for which exposure to the hazards of unexpected energization or start up of the equipment is controlled by the unplugging of the equipment from the energy source and by the plug being under the exclusive control of the employee performing the servicing or maintenance.  [Return to Text]

Standard Interpretations - Table of Contents

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