Current through Register Vol. 54, No. 45, November 9, 2024
Section 39.199 - Guarding or isolating live parts(a) Ungrounded current-carrying parts of electrical utilization equipment, such as bus bars, conductors, and terminals, operating at over 150 volts to ground and not isolated by elevation at least 8 feet above floor line shall, if practicable, be provided with suitable permanent enclosures or other guards arranged so as to prevent persons or conducting objects from inadvertently coming in, or being brought into, contact with the parts in question and at the same time so as to permit ready access to authorized persons for making adjustments or repairs, unless excepted under the provisions of subsection (b). Enclosures may consist of suitable casings or suitable insulating coverings. The continuous insulating covering of conductors should be depended upon only when the circuit is grounded or entirely unexposed to leakage or induction from higher voltage circuits, and when it is impracticable to install more suitable guards. It should be depended upon then only when the covering is not exposed to liability of mechanical injury, and is very substantial, thoroughly dry, and contains no noninsulating flameproofing compound or oil-soaked rubber. It is recommended that in addition to the protection afforded by such coverings the insulating mats or platforms called for in subsection (b) be used. If it is necessary that covers, casings, or barriers at any time be removed from the otherwise exposed current-carrying parts which they guard, while these parts are alive, the covers, casings or barriers should be of insulating material, or so arranged that they are not readily brought in contact with the live parts. Mats may be of wood, held together by wood pins, or of cork matting, linoleum or rubber. The material and construction should be suitable for the voltage concerned and for the prevailing conditions. If subject to moisture or to accumulations of conducting dust, flyings, or chips, mats should present surfaces minimizing the hazards from these sources. Reference should be made to § 39.214 (relating to guarding conductors).(b) If current-carrying parts at over 150 volts to ground are necessarily exposed, ungrounded, and within 8 feet from the floor line, surrounding conducting floors and other noncurrent-carrying surfaces within reach shall be covered with suitable insulating platforms, mats or other insulating devices. Reference should also be made to § 39.198 (relating to working space about electrical equipment). The guarding of current-carrying parts obviates the necessity for such insulating devices, and when the use of the latter is impracticable, from the nature of the location or processes carried on, guards should always be used.(c) Except on fenced rights of way or other locations to which only qualified persons are admitted, trolley or crane collector wires and third rails, whether indoors or out, shall be so isolated by elevation, or be provided with suitable guards so arranged that persons do not inadvertently touch the current-carrying parts while in contact with the ground, or with conducting material connected to the ground, and shall be provided with warning signs effective whenever the conductors are alive. Damp wood, concrete floors, and metal parts of crane cabs are considered as grounded. Trolley-contact conductors indoors shall be so supported that in case of a single break, contact with the floor is not made. Reference should be made to § 39.106 (relating to isolating live parts by elevation).(d) Bare parts at different potentials shall be effectively separated. Such parts in circuits of large capacity or operating at over 300 volts shall, if practicable, unless provided with the enclosure or other guard specified in subsection (a), be provided with suitable barriers, if otherwise they would be liable to be short circuited by tools or other conducting objects. This section cited in 34 Pa. Code § 39.191 (relating to applicability); 34 Pa. Code § 39.192 (relating to scope); 34 Pa. Code § 39.193 (relating to modification or waiver of provisions); 34 Pa. Code § 39.197 (relating to grounding); 34 Pa. Code § 39.201 (relating to storage batteries, transformers, and lightning arresters); 34 Pa. Code § 39.212 (relating to mechanical and thermal protection); 34 Pa. Code § 39.214 (relating to guarding conductors); 34 Pa. Code § 39.219 (relating to grounding or isolating service conduits); 34 Pa. Code § 39.246 (relating to guarding current-carrying parts); and 34 Pa. Code § 39.291 (relating to guarding live and moving parts).