September 26, 2002
Mr. Marvin B. Moore
Refining and Supply Company
2800 Decker Drive
P.O. Box 3950
Baytown, TX 77522-3950
Dear Mr. Moore:
Thank you for your May 8, 2001 letter to the Occupational Safety and Health Administration's (OSHA's) Houston North Area Office. Your letter was referred to OSHA's [Directorate of Enforcement Programs] for an answer to your questions regarding safe working clearances for unqualified persons who work near insulated shielded cables. This letter constitutes OSHA's interpretation only of the requirements discussed and may not be applicable to any situations not delineated within your original correspondence.
Your specific question was whether OSHA would consider the American National Standard Institute standard C2-1997, Section 12, Subsection 124, paragraph C.2 (Shields or Enclosures) as appropriate guidance for employees working near insulated shielded conductors. Because of your reference to this requirement, which is quoted below, we assume that you use the term "shielded conductor" to refer to a conductor that is guarded as specified in the ANSI/IEEE standard rather than a single-conductor cable with a metallic sheath, which is also known as a shielded conductor. (In any event, whether or not a conductor has metallic sheath has no bearing on the answer.) Your question apparently arises from your belief that OSHA general industry standards 1910.269 and 1910.333 do not provide safe working clearances or guarding requirements for unqualified employees working near insulated and shielded conductors.
The referenced section of ANSI/IEEE C2 is provided here for clarity.
Shields or Enclosures
Please note that the scope of Part 1 of ANSI C2 reads as follows:
Guards less than 100 mm (4 in) outside of the guard zone shall completely enclose the parts from contact up to the heights listed in column 2 of Table 124-1. They shall be not closer to the live parts than listed in column 4 of Table 124-1, except when suitable insulating material is used with circuits of less than 2500 V to ground. If more than 100 mm (4 in) outside the guard zone, the guards shall extend at least 2.60 m (8 ft, 6 in) above the floor. Covers or guards, which must at any time be removed while the parts they guard are live, shall be so arranged that they cannot readily be brought into contact with live parts.
Part 1 of this code covers the electric supply conductors and equipment, along with the associated structural arrangements in electric supply stations, that are accessible only to qualified personnel. It also covers the conductors and equipment employed primarily for the utilization of electric power when such conductors and equipment are used by the utility in the exercise of its function as a utility.
OSHA's relevant electrical standards are contained in §1910.269 and Part 1910, Subpart S. Section 1910.269 covers "power generation, transmission, and distribution installations that are accessible only to qualified employees." It also covers work on or directly associated with such installations. (See §1910.269(a)(1) for the full scope of §1910.269.) Subpart S covers electric utilization systems and electrical safety-related work practices for all employees working on or near such installations. It also covers electrical safety-related work practices for unqualified employees working near electric power generation, transmission, and distribution installations. (See §§1910.302 and 1910.331 for the full scope and application of Subpart S.) The general rule for both standards is that unqualified employees must not have access to unguarded energized parts.
Guarding of rooms and spaces containing electric supply equipment in power generation stations and substations covered by §1910.269 is addressed in paragraphs (u)(4) and (v)(4). These paragraphs require these rooms and spaces to be enclosed so as to keep unqualified employees from entering, unless the equipment is guarded as required in Subpart S. (See the discussion of paragraph (u)(4) in the preamble to final rule §1910.269 at 59 FR 4418 - 4419.) Thus, if electric supply equipment is not installed in accordance with Subpart S, unqualified employees must not be able to enter rooms or spaces containing the equipment. In addition, paragraphs (u)(5) and (v)(5) cover guarding of equipment, whether or not it is installed in locations accessible to qualified employees only. These four paragraphs recognize that equipment can be guarded by location within room and spaces accessible only to qualified employees, and "Notes" following paragraphs (u)(5) and (v)(5) recognize compliance with ANSI/IEEE C2-1987 as an acceptable form of guarding by location. The later edition of the ANSI/IEEE standard noted in your letter may be used for this purpose as well. Rule 124 contains the relevant requirements in the 1997 and 2002 editions of that standard.
Guarding of live parts of electric utilization equipment covered by Subpart S is addressed in §1910.303(g)(2) for parts energized at 50 to 600 volts and in §1910.303(h)(2) for parts energized at more than 600 volts. Paragraph (g)(2) requires guarding by approved enclosures or by locating the parts so that they are not accessible to unqualified persons. Paragraph (h)(2) requires higher voltage installations to be either completely within metal enclosed equipment or in a location that is locked to keep unqualified employees out. When guards are removed to enable qualified employees to work on equipment, the employer must install temporary barriers to prevent unqualified employees from gaining access to energized parts as required by §1910.335(a)(2)(ii).
Note 2 to Table S-1 indicates that insulated wire and insulated busbars operating at not more than 300 volts are not considered to be live parts.
This note applies to paragraph (g)(2) as well. If they operate at more than 300 volts, energized insulated wire and busbars are live parts and must be guarded as required in §1910.269(u)(4) or (v)(4) or §1910.303(g)(2) or (h)(2) as applicable. No minimum approach distances are necessary for such installations, because, as long as the equipment is installed in accordance with OSHA standards, unqualified employees should not be able to approach them too closely in the first place.
[This document was edited on 3/29/2005 to strike information that no longer reflects current OSHA policy. For current OSHA policy on guarding live parts, go to: 07/01/2005 - Update to 09/26/2002 letter.]
Employers should note that the standards referenced in this letter should not be considered inclusive of all standards that may apply. Employers are advised to review current published OSHA regulations and contact local area/regional OSHA offices for regulations and guidance that apply to a particular situation or hazard.
Thank you for your interest in occupational safety and health. We hope this information is 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.
Richard E. Fairfax, Director
Directorate of Enforcement Programs