Mike, I am a chemical engineer at Arch
Chemicals. People have asked me several times if it is code compliant to use battery powered equipment
in Class 1 Division 1 or Class 1 Division 2 areas. I have looked in the NEC and have not found anything
on low voltage battery powered equipment. I have always defaulted to using equipment in nitrogen-purged
boxes if they are not intrinsically safe or do not meet the code requirements. Could I use a small
scale that is powered by a battery pack that could be charged as high as 14.5 volts?
Please let me know as this question has
been gnawing at me for three years. I would love to be able to give my safety department a definite
From Vickers, Julie C. MESA JCVickers@archchemicals.com
Process Engineer, Arch Chemicals
From: Kain, Steve
The NEC does not differentiate between
voltage levels or battery/line powered devices in Class I, Division 1 or 2 locations. The mandate
is to ensure that energy accidentally released because of a circuit fault is below the minimum energy
required to ignite whatever gas or material is present in the atmosphere. If this is not possible,
the conductors/electronics/contacts/equipment must be enclosed in an explosionproof enclosure, which
cools the exhaust gasses below the temperature required to ignite the atmosphere. NEC requirements
1) Apparatus must be classified as explosionproof
2) Enclosure must be purged and pressurized
in accordance with NFPA 496-1998 or
3) All circuitry must be classified as
"Intrinsically Safe" or
4) Device may be enclosed in an oil bath
5) Device may be hermetically sealed such
that no external atmosphere can penetrate to electronics/contacts/wiring.
From: arcs and sparks
I never thought about blowing myself up
to the carpenter in the sky by using a cordless tool... I suppose its possible huh...maybe she should
use air tools with lots of hose:)
From: Dale Kessler
First, I would need to know the type of
facility in which this equipment is being placed. This would, in my opinion determine the NFPA Standard,
which would cover the operation. Is this chemical plant, refinery, or distillery? It makes a big difference.
I do not believe that voltage is the issue. The ability to generate a source of ignition is the key.
Non-incendive circuits and equipment rated for the environment. If the manufacturer does not make
a housing suited for this environment then he is back to a nitrogen purge.
However, in my experience there is usually
another way. Longer leads to a safe area, explosion proof housings, properly rated equipment. Remember
if do not produce enough heat to exceed the auto-ignition temperature you cannot have a fire. Again,
it comes down the governing body having jurisdiction. They would also be a great source of information.
No one wants an unsafe installation.
From: Rowland, John
The answer to the question is to refer
to NEC 500-4 where it refers to the ANSI/ISA S12.12-1994 standard on Nonincendive Electrical Equipment
for use in Class I and II, Division 2 and Class III, Divisions 1 and 2 Hazardous (Classified) Locations.
If you go to the charts, you will find the igniting currents say for example for hydrogen - 12 volts
and 5 amps. Using this information and the flashpoint or auto-ignition point to as a test against
any hot components then an engineering judgment call can be made to you concern. One thing to keep
in mind is the battery. The non-incendive batteries have a SCR type current limited circuit to shut
off the battery if a short or high current occurs beyond the battery terminals. If you device has
a current limiting fuse that could serve as the same purpose. Motorola uses the SCR and just by changing
batteries, their radio can be for use in a Division 1 area.
From: John Doty
We are also working on getting hazardous
location UL1604 approval for a battery based system - only ours is using a large 100Ahr+ battery for
solar electric applications. There are many issues to resolve and any information on the topic would
be greatly appreciated.
From: Roger Strand
I am of the opinion that unless the item
is specifically listed for Class 1 Division 1 or Division 2 it does not belong in that atmosphere.
There is enough stored energy to cause ignition in most all of these devices. I know that flashlights
used in these atmospheres have to be explosion proof. I do not see any reason that makes other battery
devices have any less stringent requirements.
From: Tom Baker
Look at the UL Red Book "Hazardous
Locations Equipment Directory”. Equipment that is UL Listed for the hazardous location is listed,
from baby bassinets to flashlights. The UL Red Book (and any of the UL books) is valuable in that
there is general application information on each listing category. You should consult the following
UL Standard UL913 "Intrinsically Safe
Apparatus and Associated Apparatus for use in Class I, II and III, Division 1, Hazardous Locations"
UL Standard UL1604 "Intrinsically
Safe Apparatus and Associated Apparatus for use in Class I, II and III, Division 2, and Class III
Note. There are products listed by other
testing labs, which would not be shown in the UL directories. In addition, some testing labs will
use the UL standards with their product evaluations and listing.
I do not believe I have ever seen a listed
C1 D1 or D2 battery tool, such as a drill for a hazardous classified area. The reasons may be a limited
market or the expense of listing and labeling.
From: Denise Sullivan
Interesting question, been discussed for
years without an officially documented answer. The closest I can respond is a meeting I had with an
OSHA Field Representative for the Northeast. His decision indicates that not all cordless tools are
the same, and I had to verify that the tool would NOT produce a spark around the armature when in
use. He did this by testing it in a confined space with an Argon gas. He also required that the battery
for the tool be removed and inserted outside the confined area of work. The company I was working
in uses battery-powered scales in all three of their main production areas. The OSHA inspector indicated
the battery change sequence was the only requirement he wanted implemented.
This occurred in year 1997, about August,
in a paint manufacturing plant in Mass. The plant is part of an International Company, so I would
have to gain their permission to forward any written documents.
Contact the manufacturer and ask them to
supply you with the specifications as to whether it is "Explosionproof" equipment. I would
also contact Underwriters Labs to see if is listed for Hazardous environments. Otherwise, just one
little spark will ruin your whole day.
From: Lynn Adams
While the low voltage equipment may seem
safe and non-threatening, I would not recommend its use. The equipment is neither sealed to prevent
the entry of explosive gasses/contain and cool the products of combustion, nor is it of sufficiently
low power to be intrinsically safe. Likely, it could be used for many times without incident - BUT
we must protect against explosive hazard under abnormal and fault conditions as well.
The average batter pack is sufficient to
cause a spark. To evidence this, take a wire and cross the two ends of a simple 1.5 volt D battery.
Momentary contact will cause a substantial spark; continuous contact can heat the wire to ignition
temperature. Note that there are flashlights approved for use in mines and hazardous locations. They
include provisions to disconnect the battery from the lamp if the outer envelop of the bulb is shattered.
From: Don Edgerley
Please be extremely cautious with any power
tool ac or battery powered in a hazardous location they have armatures that spark. My thoughts would
be to use pneumatic tools in a hazardous location and non-spark tools that were made of brass or aluminum
or a material that would not produce a spark. I at times work in areas with gases that would explode
and even if the area was purged, there is always the chance of a little gas there. Check with a local
Fire Department, they may be able to point you in the right direction.
From Rich Burman, UL
Hi Mike, Hopefully, this information will help resolve the controversy.
First, it should be noted that technically the NEC does not apply to portable, battery-powered devices.
The Article 100 definition of "equipment" states that the "equipment " is part
of an electrical installation. These devices, since they do not connect to the electrical power that
is part of the installation, are not covered by the NEC. That is not true of portable, cord-connected
equipment (see 501-11 for example). The fact that the NEC does not cover does not apply to portable,
battery-powered devices does not mean that they are not a potential source of ignition. NEC Panel
14 accepted a proposal to focus on this subject, due to the widespread use of cell phones, pagers,
etc. in classified areas. If ultimately accepted, it would include these devices within the scope
of Chapter 5 of the NEC.
Although the NEC does not currently cover these devices, they still pose a potential risk of ignition,
and need to be suitable for the area they will be used. In Class I, Division 1 locations, the permitted
protection techniques are:
- Intrinsically Safe
In Class I, Division 2 locations, they are:
- Any of the above for Division 1
- Nonincendive circuits, components, equipment
- Hermetically sealed or sealed components
- Oil immersion
UL Lists battery operated devices for both Division 1 and 2,
but these are mostly gas detectors, pagers, and instruments of various types, but no power tools.
For tools, it is very difficult to comply with any of the above protection techniques for various
reasons. In most well regulated facilities, they either use air-operated tools or get "hot work"
permits before using the tools in classified location.
Rich Berman, Research Manager
Underwriters Laboratories Inc.