November 13, 1996

APS TECHNICAL UPDATE - No. 13

Subject: Beamline Electrical Safety Guideline

Attached is a Beamline Electrical Safety Guideline (R. Salazar). The purpose of this document is to provide a convenient basic electrical guideline for beamline personnel installing, maintaining, modifying, repairing and using electrical systems on the experiment floor. The selected regulations cited in this guide are not intended as a substitute for the complete regulations, and the references should be consulted for specific cases not covered in this document.

For additional information contact:

Julie Cross - User Technical Interface
jox@aps.anl.gov
Telephone - 630.252.0592

Updated: October 4, 2007

 

Beamline Electrical Safety Guideline

Version 1.1

Roderick C. Salazar

December 3, 1996

BEAMLINE ELECTRICAL SAFETY GUIDELINE

 1.0 INTRODUCTION

1.1 Purpose. The purpose of this document is to provide basic electrical guidelines for beamline personnel installing, maintaining, modifying, repairing and using electrical systems on the experiment hall floor. General electrical safety practices and requirements are presented so that electrical hazards are minimized or eliminated. The references for this document are National Electrical Code 1993 (NFPA 70), NEC Handbook 1993, Title 29 Code of Federal Regulation Part 1910, Subpart S, Electrical Surveillance Guide (prepared by DOE, Oak Ridge Field Office), DOE Electrical Safety Guideline 1993, Electrical Safety Review Checklist (NSLS), and the Argonne National Laboratory Environmental, Safety and Health Manual.

1.2 Regulation and Citation. The selected regulations cited in this guide, from the above references, are not intended as a substitute for the complete regulations. The references should be consulted for specific cases not covered in this document or for cases requiring a more detailed examination for compliance. For these cases, the person selected as having electrical authority jurisdiction shall be responsible for interpreting the applicable codes and regulations and approve equipment, assemblies, or materials.

 

2.0 GENERAL REQUIREMENTS

2.1 Approval. Common electrical equipment and materials are typically evaluated by testing facilities, which then list, label, or identify approved products that meet nationally recognized standards. Equipment and materials are to be used for their intended purpose.

2.2 Examination, Installation and Use of Equipment.

2.2.1 Examination. Electrical equipment shall be free from recognized hazards that are likely to cause death or serious physical harm. The following shall be considered when determining the safety of equipment:
    1. suitability of installation and use
    2. sufficient mechanical strength and durability
    3. proper electrical insulation
    4. heating affects under condition of use
    5. arcing affects
    6. type, size, voltage, current capacity and specific use
    7. other factors that provide safeguards to personnel using or in contact with electrical equipment

2.2.2 Installation and Use. Listed or labeled equipment shall be used and installed according to any supplied instructions.

2.3 Splices. Conductors shall be spliced or joined with splicing devices suitable for that use or by brazing, welding, or soldering. Splices, joints, and free ends of conductors shall be insulated with insulation equivalent to that of the conductors or with insulating devices suitable for the purpose.

2.4 Arcing Parts. Equipment under normal operation that produces arcs or sparks shall be enclosed and isolated from combustible materials.

2.5 Marking. Electrical equipment shall be marked with the manufacturer's name, trademark, or other descriptive markings. As necessary, other markings shall be provided giving voltage, current, wattage, or other ratings. ANL ESH recommends that equipment hardwired to the electrical power distribution system be labeled as follows:
    1. type of equipment
    2. voltage
    3. source identification and location
    4. load identification and location

All labels and markings shall be durable enough to withstand the local environment.

2.6 Identification of Disconnecting Means and Circuits. Unless clearly evident, each disconnecting or overcurrent device for service, feeder, branch circuit, motors, and other equipment shall be legibly marked to indicate its intended purpose. All labels and markings shall be durable enough to withstand the local environment.

2.7 Working Space About Electric Equipment (600 Volts, Nominal, or Less). Sufficient access and working space shall be provided and maintained about all electric equipment to permit ready and safe operation and maintenance of such equipment.

2.7.1 Working Clearance. Equipment likely to require examination, adjustment, servicing or maintenance while live shall have a working space in the direction of access not less than indicated in the following table. Additionally, the workspace may not be less than 30" wide in front of the electric equipment. The distances are measured from the live parts if they are exposed, otherwise from the front of the enclosure or opening of enclosed parts.

WORKING CLEARANCE

Minimum Clear Distance for Condition 1

Nominal Voltage
to Ground

Condition A

(ft)

Condition B

(ft)

Condition C

(ft)
0 to 150 Volts

3

3

3
151 to 600 Volts

3

3.5

4

1Conditions:
    1. Exposed live parts on one side and no live or grounded parts on the other side of the working space, or exposed live parts on both sides effectively guarded by suitable wood or other insulating material. Insulated wire or insulated busbars operating below 300 volts are not considered live parts.
    2. Exposed live parts on one side and grounded on the other side.
    3. Exposed live parts on both sides of the workspace.

2.7.2 Clear Space. Working clearance shall not be use for storage, and normally enclosed live parts that have been exposed for inspection or servicing the working space, if in a general area, shall be suitably guarded.

2.7.3 Access and Entrance to Working Space. At least one entrance shall be provided to give access to the working space.

2.7.4 Front Working Space. Equipment that contains normally exposed live parts shall have a minimum of 3 feet clearance in front of such equipment.

2.7.5 Illumination. Adequate illumination shall be provided for all working spaces.

2.7.6 Head Room. Working space shall have a minimum of 6 feet 3 inches of headroom.

2.8 Guarding of Live Parts. Live parts of electric equipment operating at 50 volts or more shall be guarded against accidental contact. Listed below are approved means of guarding:
    1. use of cabinets or other form of enclosures
    2. controlled room, vault, or similar enclosure accessible only to qualified persons
    3. partitions or screens arranged so that access is limited only to qualified persons
    4. by elevation of 8 feet or more

The means used to guard exposed live parts shall be of suitable strength to prevent physical damage. Conspicuous warning signs shall be posted on the entrances to rooms or enclosures where exposed live parts are located.

2.9 Conditions for over 600 Volts, Nominal. Requirements for equipment operating at 600 volts or more are not presented in this document. The references cited in Section 1.1 should be consulted for these requirements.

3.0 WIRING DESIGN AND PROTECTION

3.1 Use and Identification of Grounded and Grounding Conductors

3.1.1 Identification of Conductors. A conductor used as a grounded conductor or as an equipment-grounding conductor shall be identifiable and distinguishable from all other conductors.

3.1.2 Polarity of Connections. Grounded conductors may not be attached to any terminal or lead so as to reverse designated polarity.

3.1.3 Use of Grounding Terminals and Devices. Grounding terminals or grounding-type devices may not be used for purposes other than grounding.

3.2 Services. Means shall be provided to disconnect all conductors from the service conductors. The disconnecting means shall indicate whether the switch is open or closed. The switch shall be located in an accessible location near the point-of-service entrance.

3.3 Overcurrent Protection (600 volts, nominal, or less).

3.3.1 Protection of Conductors and Equipment. Conductors and equipment shall be protected from overcurrent. Current handling capacities shall not be exceeded.

3.3.2 Grounded Conductors. Unless all conductors are disconnected simultaneously, a grounded conductor shall not be disconnected by the overcurrent device.

3.3.3 Disconnection of Fuse and Thermal Cutouts. Disconnecting means shall be provided for all cartridge fuses and thermal cutouts on circuits operating over 150 volts to ground.

3.3.4 Location In or On Premises. Location of overcurrent devices shall be readily accessible and away from sources of physical damage or ignitible materials.

3.3.5 Arcing or Suddenly Moving Parts. Overcurrent devices shall be located or shielded in a way as to prevent burns or other injuries due to their operation.

3.3.6 Circuit Breakers. A circuit breakers shall clearly indicate whether it is in the open (off) or closed (on) position. Circuit breakers installed vertically shall have the up position to mean closed (on).

3.3.7 Over 600 Volts, Nominal. Short-circuit protection is to be provided for feeders and branch circuits operating over 600 volts.

3.4 Supports, Enclosure and Equipment Grounding.

3.4.1 Support and Enclosures for Conductors. Metal cable trays, metal raceways, and metal enclosures shall be grounded.

3.4.2 Service Equipment Enclosures. Metal enclosures for electrical service equipment shall be grounded.

3.4.3 Fixed Equipment. Exposed non-current-carrying metal parts of fixed equipment that may become energized shall be grounded.

4.0 WIRING METHODS

4.1 General requirements. Metal raceway, cable armor, and other metal enclosures for conductors shall be joined together forming a continuous electric conductor. All boxes, fittings, and cabinets shall also be connected to form electrical continuity. Wiring shall not be installed in ducts used to transport dust or flammable vapors.

4.2 Temporary Wiring. Temporary electrical power and lighting shall be permitted during the periods of construction, remodeling, maintenance, repair, demolition, emergencies, tests, experiments, and developmental work. Otherwise, temporary wiring shall not be in place for more than 90 days. Wherever possible, a minimum overhead clearance of 7 feet shall be use when temporary wiring spans across open space. Wires spanning open floors shall have bridges for protection and to reduce trip hazards.

4.2.1 Extension Cords. Extension cords shall not be:
    1. used in place of fixed wiring
    2. connected in series
    3. spliced, tapped, or modified in any way
    4. concealed behind building structures
    5. attached to building surfaces
    6. run through building walls, ceilings, doorways, or windows
    7. wired so that an exposed male plug is energized

5.0 CABLE TRAYS

5.1 Uses Permitted. The following list of conductors are approved for installation in cable tray systems:
    1. mineral-insulated metal-sheathed cable
    2. armored cable
    3. metal-clad cable
    4. power-limited tray cable
    5. nonmetallic-sheathed cable
    6. shielded nonmetallic-sheathed cable
    7. multiconductor service-entrance cable
    8. multiconductor underground feeder and branch-circuit cable
    9. power and control tray cable
    10. other tray-approved factory-assembled, multiconductor control, signal, or power cables
    11. any approved conduit or raceway with its contained conductors

In an industrial establishment where maintenance and supervision assure that only qualified persons will service the installed tray system, the following list of cables are allowed:
    1. single conductor cables 250 kcmil or larger that are types listed and marked for use in cable trays
    2. multiconductor cable type of medium voltage (MV)

5.2 Uses Not Permitted. Cable tray system shall not be installed in hoist ways or in any area where it may be subject to physical damage.

5.3 Construction Specification. Cable tray systems must meet the following requirements:
    1. must have suitable strength and rigidity to provide adequate support
    2. must be free from sharp edges, burrs or projections that may damage cable insulation
    3. must be corrosion protected
    4. must have side rails or equivalent structures
    5. must have fittings or other suitable means for changes in direction and elevation runs
    6. must be made of flame-retardant material if nonmetallic

5.4 Installation. Cable trays shall be installed as a complete system for that particular run before cables are installed. Supports and cover shall be installed in places where added protection to the integrity of the cables is needed. Multiconductor cables rated 600 volts or less are permitted to be installed in the same cable tray. Cables rated 600 volts or more shall not be installed in the same cable tray with cables rated 600 volts or less except when separated by a solid fixed barrier or where cables over 600 volts are type metal-clad (MC). Cable trays are permitted to penetrate through partitions and walls or vertical platforms and floors provided that the openings are fire-stopped using approved methods to maintain fire resistance ratings. Cable trays shall be exposed and shall have sufficient access for installing and maintaining cables.

5.5 Grounding. Metallic cable trays that support electrical conductors shall be grounded. Steel or aluminum cable-tray systems are permitted to be used as a grounding conductor provided:
    1. the sections and fittings are identified
    2. the minimum cross sectional is met
    3. the sections and fittings are legibly and durably marked to show the cross sectional area
    4. bonding between sections and fitting are done according to bonding code