D: Fabrication And Maintenance Practices
Design and construct equipment
to protect personnel. First-line and backup safeguards should be provided
to prevent personnel from accessing energized circuits. Establish periodic
tests to verify that these protective systems are operative.
D1: Equipment Acceptability
Electrical equipment is
considered safe only when it is used as specifically intended by its
listing and design. Equipment must not be altered beyond the original
design intent, and must not be used for any purpose other than that
for which it was constructed.
Any equipment that is being
recommissioned must be examined and/or tested, as appropriate, to verify
the status of all safety features and the integrity of construction.
- Electrical equipment
should be listed or labeled by a Nationally Recognized Testing Laboratory
- The division responsible
for the equipment must maintain all documentation pertaining to the
design safety features of the equipment, including any test data. This
documentation must be available to any safety inspector.
- The inspector may
require that equipment that is not NRTL-listed undergo inspection and/or
testing for conformance to standards. Such testing should be documented
and submitted to EH&S for approval. The inspection record must specify,
- Equipment identification;
- Evaluator name,
date, mailstop, and extension;
- Standard to which
equipment is being evaluated;
- Specific tests,
results, and areas of examination;
- Any conditions of
product acceptability or limitations of use.
Equipment Safety Practices
- Cable Clamping:
A suitable mechanical-strain-relief device such as a cord grip, cable
clamp, or plug must be used for any wire or cable penetrating
an enclosure where external movement or force can exert stress on the
internal connection. Grommets, adlets, or similar devices must not be used as strain relief.
- Emergency Lighting:
Make emergency lighting available in case normal lighting fails when
work is being conducted on energized components. (Emergency lighting
is not necessary for Class 1A and 1B work. See Hazard Class Charts in Appendix P).
- Flammable and Toxic
Material Control: Keep the use of flammable or toxic material to a minimum.
A catch basin or other approved method must be provided to prevent the
spread of these materials should the normal component case fail.
- Isolation: Isolate
all sources of dangerous voltage and current with covers and enclosures.
Access to lethal circuits (greater than 50V) must be either via screw-on
panels (each containing no fewer than four screws or bolts) or via interlocked
doors, panels, covers, etc. The frame or chassis of the conductive enclosure
must be bonded to electrical ground with a conductor capable
of handling any potential fault current.
- Lighting: Provide
adequate lighting for easy visual inspection.
- Disconnecting Means
and Overload Protection: Provide overload protection and well-marked
disconnects. Local “off” controls must be provided on remote-controlled
- All disconnects
and breakers must be clearly labeled to identify the loads they control.
- Power: All ac and
dc power cabling to equipment not having a separate external ground
but having line-to-line or line-to-ground voltage greater than 50V must
have an equipment-grounding conductor unless cabling is inside an interlocked
enclosure, rack, grounded wireway, or conduit, or feeds a commercial double-insulated or UL-listed ungrounded device. If the grounding of
equipment introduces a greater hazard, the equipment must not be grounded.
- Rating: Operate
all conductors, switches, resistors, etc., within their design capabilities.
Pulsed equipment must not exceed either the average, the rms, or the
peak rating of components. The equipment must be derated as necessary
for the environment and the application of the components.
- Safety Grounding
of Capacitive Components: Use automatic-discharge devices on equipment
with stored energy of 100J or more. Suitable and visible manual-grounding
devices must also be provided to short-to-ground all dangerous equipment
while work is being performed.
- Electrical Equipment
Rooms: Place an identifying label or sign on the door when equipment
that may require servicing, manipulation, or inspection is concealed
in an equipment closet or otherwise is obscured behind doors or panels.
- Reuse of Circuit
Breakers: Do not purchase used or reconditioned circuit breakers from
vendors outside LBNL. Reuse of LBNL circuit breakers is permitted only
after the circuit breaker has been tested by the Electric Shop.
The following specifications
apply to circuits operating at greater than 50V, or storing more than
100J. An enclosure may be a room, a barricaded area, or an equipment
- Access: Interlock
easily opened doors, hinged panels, etc., that allow ready access to exposed energized components so that the act of opening de-energizes
the circuit. Automatic discharge of stored-energy devices must be provided.
H (Inductor and Magnet Hazards) in this chapter.
- Doors: Doors should
be key-locked, and the same key should also be used for the locks in
the control-circuit interlock chain, if applicable. This key must not
be able to be removed from the door unless the door is closed and locked.
- Heat: Mount heat-generating
components, such as resistors, so that heat is safely dissipated and
does not affect adjacent components.
- Isolation: Ensure
that the enclosure physically prevents contact with live circuits. The
enclosure can be constructed of conductive or nonconductive material.
If conductive, the material must be electrically bonded and connected
to a good electrical ground. These connections must be adequate to carry
all potential fault currents.
- Seismic Safety:
Secure all racks, cabinets, chassis, and auxiliary equipment against
movement during earthquakes. (See PUB 3000, Chapter 23, Seismic Safety.)
- Strength: Ensure
that enclosures are strong enough to contain flying debris caused by
- Ventilation: Ensure
that ventilation is adequate to prevent overheated equipment, and to
purge toxic fumes produced by an equipment fault. Ventilation openings
must not be obstructed.
- Visibility: Ensure
that enclosures large enough to be occupied by personnel allow exterior
observation of equipment and personnel working inside the enclosure.
- Warning Indicators:
When systems other than conventional facilities represent Class 4A or
3B or 4B hazards (see Hazard Class Charts Appendix Q), provide those
systems with at least one of these safety measures:
- A conspicuous visual
indicator that is clearly visible from any point where a person might
make hazardous contact or entry.
- A clearly visible
primary circuit breaker or “off” control button on the front of
- Be aware, however,
that industrial systems may vary from these standards.
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