Electrical
Equipment and Safety StandardsSafety is always a
consideration when using electrical equipment. Some
common concerns are contamination due to unsanitary
equipment, protection from and limits on electromagnetic
interference, and meeting strict safety requirements in
potentially explosive environments. Customers rely on
certifying agencies such as 3A, Factory Mutual, Canadian
Standards Association, and others to ensure safety in
these applications. These agencies examine, test, and
certify that each product has been designed to meet
specific standards for sanitary applications, hazardous
locations, or specific electrical situations. Unlike
independent testing laboratories who are unauthorized to
issue any label but their own, certifying agencies
enable the manufacturer to mark approved products with
the corresponding standard committee's label, ensuring
the end user that these products have been tested and
meet those specific standards.
Certifying
Agencies
Sanitary
Equipment
3A:
Sanitary Standards Administrative Council
 The
objective of the 3A Sanitary Standards Committee is to
formulate standards and accepted practices for equipment
and systems used to process milk and milk products. Such
standards are developed through the cooperative efforts
of local, state, and federal sanitarians, equipment
manufacturers, and equipment users so that the standards
are acceptable to those involved in the sanitary aspects
of dairy and related industries. The 3A Symbol
Administrative Council authorizes manufacturers to
display the 3A symbol on processing equipment that is in
compliance with 3A Sanitary Standards.
USDA:
United States Department of Agriculture
The Federal Meat and
Poultry Products Inspection Acts authorize the USDA to
require that the slaughter of animals and the subsequent
processing of meat and poultry products be done in a
sanitary manner. The Food Safety Inspection Service (FSIS)
inspects to USDA sanitary guidelines for equipment and
facilities engaged in these operations. As of November
1997, the USDA no longer approves product to these
guidelines but rather requires the facility engaged in
these processes to combine equipment in their plant that
will pass a USDA Inspection. The manufacturer of the
equipment will be solely responsible for ensuring their
product will meet the USDA guidelines for inspection.
Hazardous
Locations Equipment
FM:
Factory Mutual Research Corporation
 The
Factory Mutual Approvals Division determines the safety
and reliability of equipment, materials, or services
utilized in hazardous locations in the United States and
elsewhere. Factory Mutual certifies to NEC (National
Electrical Code) standards for hazardous locations, NEC
Standard 500 (Division classification) and also to the
new NEC Standard 505 (Zone classification), which
attempts to harmonize American and European
classifications. For a product to receive approval, it
must meet two criteria. First, it must perform
satisfactorily, reliably, and repeatedly as applicable
for a reasonable life expectancy. Second, it must be
produced under high quality control conditions. Factory
Mutual also has interlaboratory agreements and can
certify to Canadian and European standards.
CSA:
Canadian Standards Association
 The
association includes Canadian consumers, manufacturers,
labor, government, and other regulatory agencies among
its actively participating influences. These groups work
together to generate standard requirements (CSA
standards) that demonstrate product quality, enhance
market acceptability, and improve quality and safety
control procedures in manufacturing and construction for
the Canadian marketplace. The standards generated by CSA
are the cornerstone for determining a product's
eligibility for certification in hazardous locations in
Canada. CSA also performs product evaluation, testing,
and ongoing inspection to these standards, and also to
American and European standards through new
interlaboratory agreements.
INERIS/
NEMKO/ LCIE/ BASEEFA
 These
are some of the recognized European approval agencies
that have certified Viatran transmitters to Cenelec
(European Committee for Electrotechnical
Standardization) and/or IEC (International
Electrotechnical Commission) standards for hazardous
locations. Cenelec attempts to harmonize the electrical
standards of its member countries. Generally, IEC
standards are used. However, in certain instances where
IEC standards are considered too vague, Cenelec defines
more precise requirements. The member nations of Cenelec,
which include and exceed those of the EEC (European
Economic Community), are bound to adhere to these
international regulations.
Hazardous
Locations Classifications
For an
area to be classified as hazardous, the following three
requirements for a Fire Triangle must be present
simultaneously:
Flammable
gas, dust, or fiber
Ignition
source
Air/oxygen.
Hazardous locations are broken into Divisions, Zones,
Classes and Groups. These enable the manufacturer to
specify exactly the type of hazardous location for which
the product has been certified. The first classification
describes the presence of flammable material in a
hazardous location, either continuously, intermittently,
or abnormally. The apparatus grouping states what type
of flammable material is present: either gas, dust, or
fiber. The temperature codes indicate the maximum
temperature the device's external enclosure can reach.
This is summarized in Table 1.
Table
1: Hazardous
Locations Classifications
| Classification |
IEC,
Cenelec
NEC 505 Codes |
NEC
500
CSA Codes |
|
Classification |
IEC,
Cenelec
NEC 505 Codes |
NEC
500
CSA Codes |
| Material
Presence |
|
|
|
Max
Surface Temp. |
|
|
| Continuously
Present |
Zone
0 |
Division
1 |
|
450
°C |
| T1 |
| T1 |
|
| Intermittently
Present |
Zone
1 |
Division
1 |
|
300
°C |
T2 |
T2 |
| Abnormally
Present |
Zone
2 |
Division
2 |
|
280
°C |
|
T2A |
| Apparatus |
|
|
|
260
°C |
|
T2B |
Gas & Vapors |
|
|
|
230
°C |
|
T2C |
| Acetylene |
Group
IIC |
Class
I/Group A |
|
215
°C |
|
T2D |
| Hydrogen |
Group
IIB |
Class
I/Group B |
|
200
°C |
T3 |
T3 |
| Ethylene |
Group
IIB |
Class
I/Group C |
|
180
°C |
|
T3A |
| Propane |
Group
IIA |
Class
I/Group D |
|
165
°C |
|
T3B |
| Methane |
Group
I |
N/A |
|
160
°C |
|
T3C |
|
Dust |
|
|
|
135
°C |
T4 |
T4 |
| Metal |
N/A |
Class
II/Group E |
|
120
°C |
|
T4A |
| Coal |
N/A |
Class
II/Group F |
|
100
°C |
T5 |
T5 |
| Grain |
N/A |
Class
II/Group G |
|
85
°C |
T6 |
T6 |
| Fibers
(All) |
N/A |
Class
III |
|
|
|
|
Protective
Concepts
For a
product to be approved for a hazardous location, it must
be designed so that an explosion of the flammable or
combustible material surrounding the device does not
occur. There are different methods of protection to
achieve this. Viatran uses the three most accepted
methods in the pressure transmitter market: Intrinsic
Safety, Explosion Proof (Flame Proof), and Suitable for
Use in Hazardous Locations.
Intrinsic
Safety
An
Intrinsically Safe piece of equipment is an electrical
device that is incapable of causing an ignition of the
prescribed flammable gas, vapor, or dust, regardless of
any spark or thermal effect that may occur in normal
use, or under any conditions of fault likely to occur in
practice. This means that the device design is limited
in such areas as PC Board layout, surface temperature,
protection of electrical components, and power supply to
the device. The devices are certified with either
specific Intrinsic Safety Barriers (Loop certification)
or general Intrinsic Safety Barrier parameters (Entity
certification). These barriers are used outside the
hazardous location and limit the amount of current,
voltage, capacitance, and inductance entering the
certified device. Often considered the safest and most
technically elegant approach, there are many benefits of
an Intrinsically Safe device to the customer. Expensive
and cumbersome explosion-proof enclosures and conduit
connections are not needed, electric shock is minimized,
and controls can be maintained without shutting down the
process.
Explosion
Proof / Flame Proof
An Explosion
Proof (or Flame Proof, as classified in IEC and Cenelec
standards) device is an electrical device designed with an
enclosure capable of withstanding, without damage, an
explosion within it of a specific gas, fiber, or dust. In
turn, it prevents ignition of these same materials surrounding
the enclosure by a spark or flame from the explosion within.
Factory Mutual formerly limited its Explosion Proof standard
by requiring that the explosive external material be able to
enter the device to cause an explosion. This excluded
hermetically sealed devices from approval consideration. FM
has recently modified their definition to include these
devices. This certification usually requires that devices be
designed with sturdy and durable enclosures with conduit
connections. The primary benefits of this type of protection
are that the device is not limited by low available power nor
does it restrict PC Board layout. Viatran has also designed
some of the smallest Explosion Proof devices in the industry.
Suitable for Use in
Hazardous Locations
Factory Mutual developed this unique
approval as a way for products to receive hazardous location
approvals that cannot conform to existing protection concepts.
There is no documented standard and the definition of this
certification is unique to each product. In Viatran's case,
this protection concept was utilized for our hermetically
sealed products that did not meet FM's former Explosion Proof
definition. Products that receive this approval are certified
to the same Divisions as a comparable Explosion Proof or
Intrinsically Safe device.
Table 2:
Code Examples
| Description |
NEC
500 |
NEC
505 |
CSA |
IEC |
Cenelec |
Intrinsically
Safe for all
gases, dusts, and fibers
continuously present at
external temperatures to 135°C
(Certified with Intrinsically
Safe barrier parameters |
Intrinsically
Safe
Entity for uses in
Class I, II, III, Div. 1
Groups A-G
hazardous locations |
Class
I, Zone 0,
AEx d IIC, T4 |
Certified
for Class I, Div. 1, Groups A-D,
Class II, Div. 2, Groups E-G,
Class III for hazardous
locations |
Ex
ia IIC T4 |
EEx
ia IIC T4 |
| Explosion
Proof for all gasses,
dusts, and fibers intermittently
present and at external
temperatures of 85 °C |
Explosion
Proof
for Class 1 Div. 1
Groups A-D
hazardous locations |
Class
I, Zone 1,
AEx d IIC, T6 |
Certified
for Class I, Div. 1, Groups A-D,
Class II, Div. 2, Groups E-G,
Class III for
hazardous locations |
Ex
d IIC T6 |
EEx
d IIC T6 |
| Suitable
for Use for all gases,
dusts, and fibers continuously
present |
Suitable
for Use
Class I, II, III, Div. 1
Groups A-G
hazardous locations |
N/A |
N/A |
N/A |
N/A |
CE
Marking
 "CE"
marking is a declaration from the manufacturer that their
product conforms to a specific Directive(s) adopted by the EEA
(European Economic Area) and is a requirement for the product
to be sold into any of the countries in this 18 member group.
CE is an abbreviation for the French phrase Conformité Européene,
meaning European Conformance. Unlike hazardous location
approvals, the manufacturers are solely responsible for
ensuring their product's conformance to these Directives which
were developed using IEC and Cenelec standards. The Directives
that affect transmitters are the EMC (Electromagnetic
Compatibility) and LVD (Low Voltage) Directives. These state
that the products must meet specific electromagnetic emission
and immunity, as well as electrostatic discharge standards.
Transmitters that meet EMC standards, as declared by the
manufacturer, must be able to withstand interference from the
radio frequency spectrum, electrostatic discharge, surges,
etc., without the unit's performance being affected. The
transmitter must also emit a minimum of the above charges so
that it does not affect other nearby electrical devices or
systems such as emergency communications or radio and
television broadcasts. The Low Voltage Directive addresses
basic electrical shock and fire hazard issues. These
directives are currently only a requirement for the EEA member
nations and are not required for products sold outside this
community.
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