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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
3a.gif (545 bytes)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
fm.gif (409 bytes)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
csa.gif (426 bytes)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.

ex.gif (498 bytes)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
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
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

CE Marking

ce.gif (350 bytes)"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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