My interpretation of Brian's note was that it is not the environment that
was explosive, but the product itself. He described the product as a
" small laboratory device" containing up to a gallon of solvent. I take
solvent to mean a highly volatile fuel, based on the examples given.
Without knowing any of the pertinent standards, I would suggest:
1. Placing ALL electronics in metal fire enclosures with as few and as
small openings as possible.
2. Thermally insulate all electronics and other possible heat sources
from the solvent container or its vapors.
3. Avoid the use of any electronics in the container, unless specifically
designed and "listed" for such use.
4. Be VERY careful about managing the solvent vapors, both within and
outside of the container. Perhaps a charcoal filter could be used to
absorb released vapors.
5. Be aware that the slightest spark or arc can explode any vapors. This
is still the leading theory in the crash of the plane off Long Island.
6. After doing all the above, I would recommend using this device only
under an appropriate vented hood, to ensure that someone turning on
a nearby PC did not initiate a catastrophe.
Regards,
George Alspaugh
Dear Brian,
A number of standards exist which describe the constructional and test
requirements of electrical apparatus for use in potentially explosive
atmospheres. The applicable standards would depend on the intended country
of use. The following tables gives a list of the applicable standards for
electrical equipment for use in Zone 1. Intrinsically Safe equipment could
be used in Zone 0 which is the highest risk.
Type of Protection Europe USA
IEC
General Requirements EN50014 ANSI/ISA S12.0.01(IEC79-0 Mod) IEC
60079-0
Flameproof EN50018 ANSI/ISA S12.22.01(IEC79-1 Mod) IEC
60079-1
Pressurized Enclosures EN50016
IEC 60079-2
Powder Filling EN50017 ANSI/ISA S12.25.01(IEC79-5 Mod) IEC 60079-5
Oil Immersion EN50015 ANSI/ISA S12.26.01(IEC79-6 Mod) IEC 60079-6
Increased Safety EN50019 ANSI/ISA S12.16.01(IEC79-7 Mod) IEC
60079-7
Intrinsic Safety EN50020 ANSI/UL 913
IEC 60079-11
Encapsulation EN50028 ANSI/ISA S12.23.01(IEC79-18 Mod) IEC
60079-18
In the USA the National Electrical Code Article 500 allows the use of either
Zone or Division Classification, but the number of types of protection is
not as varied, being limited to Intrinsic safety [ANSI/UL 913]
Explosionproof [ANSI/UL1203] Purged and Pressurised [NFPA496]. ANSI
standards based on IEC60079-11, and IEC60079-2 are currently under
development.
In all of the above cases certification by a Notified Body in Europe and a
NRTL in the USA are required. A lower level of risk [Zone 2 or Division 2]
also exists, and this may be self certified in some countries. In the US the
standard to use is ANSI/ISA S12.12, in Europe EN50021 and the IEC standard
is IEC60079-15.
If you have any questions please do not hesitate to contact me directly.
Nicholas Ludlam
Factory Mutual Research
Tel: (781) 255 4847
Fax: (781) 762 9375
-----Original Message-----
From: Brian At Work [mailto:[email protected]]
Sent: Wednesday, July 28, 1999 11:49 AM
To: IEEE Group
Subject: Flamible Liquids and Vapors
Hello Group,
Our company is working on a small laboratory device, about the size of a
computer tower, that contains, in addition to electronic components, about 1
gallon (3.8 liter) of a solvent chemical. The solvent can be one or a
combination of several different chemicals such as acetone, methanol,
ethanol, etc..
These chemicals and/or vapors are flammable and could possibly cause a fire
or explosion under the right conditions.
Protection against the ignition or explosion of a flammable liquid is not
directly covered in the EN61010 safety standard (or not as I have found).
Is there another standard that addresses these requirements more
specifically? Does anyone with experience in this area have some advice or a
summary of requirements they could give me?
Thank you for your time,
Brian Kunde
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