The basics of explosion protection >

R.STAHL explosion protection >

8 > explosion pressure resistant construction > avoiding flammable substances(replacement technologies) > explosion relief devices > explosion suppression by means of extinguishers The principle of integrated explosion protectionrequires following explosion protection measures in a certain sequence. Preventing explosive atmospheres(Primary Explosion Protection) The term primary explosion protection refers to all precautions, which prevent a hazardous explosive atmosphere from being created.This can be achieved by: > inerting (addition of nitrogen,carbon dioxide etc.) Mitigation of the explosion...

> ComponentsӔ means any item essential to thesafe functioning of equipment and protective systems but with no autonomous function. > An explosive atmosphereӔ is a mixture with air,under atmospheric condition, of flammable substances in the form of gases, vapours, mists, > Protective systemsӔ is the definition for designunits, which are intended to halt incipient explosions immediately and/or to limit the effective range of explosion flames and explosion pressures. Protective systems may be integrated into equipment separately and placed on the market for use as autonomous systems. Definitions...

> putting into service > use > assembling and dismantling Operating instructions > maintenance (servicing and emergency repair) The operating instructions of the manufacturer must clearly define the intended use of the equipment by the operator.The minimum requirements for the operating instruction are amongst others: Information on safe > installation > adjustmentIf necessary, special conditions for safe use have to be specified and should include notes on possible misuse that may occur as experience has shown. Manufacturers Declaration of Conformity Equipment and systems can be placed on the...

Table 7: Electrical Apparatus for Explosive Gas Atmospheres EN (old)EN (new)IECGeneral requirementsEN 50 014EN 60079-0IEC 60079-0Flameproof enclosures dӔEN 50 018EN 60079-1IEC 60079-1 Pressurized enclosures pӔEN 50 016EN 60079-2IEC 60079-2 Powder filling qӔEN 50 017EN 60079-5IEC 60079-5 Oil immersion oӔEN 50 015EN 60079-6IEC 60079-6 Increased safety e"EN 50 019EN 60079-7IEC 60079-7 Intrinsic safety ӓiEN 50 020EN 60079-11IEC 60079-11 Type of protection ԓnEN 50 021EN 60079-15IEC 60079-15 Encapsulation ԓmEN 50 028EN 60079-18IEC 60079-18 Intrinsically safe systemsEN 60079-25IEC 60079-25 Electrical...

16 4. Technical Principles4.1 Zone Classification Hazardous areas are classified into zones to facili-tate the selection of appropriate electrical appa- ratus as well as the design of suitable electrical installations. Information and specifications for the classification into zones are included in IEC 60079-10.The greatest potential risk has to be taken intoaccount when classifying the potentially explosive areas into zones and determining the necessary protective measures. If there is no expert (skilled person) available inthe company to verify the risk of explosion and to determine the necessary...

Table 9: Explosion Groups Explosion group Maximum experimental safe gap Minimum ignition current ratio*IIA > 0,9> 0,8IIB0,5 0,90,45 ֖ 0,8 IIC< 0,5< 0,45 *rel. to methane = 1 R.STAHL explosion protection >

Fig. 5: Combination of Types of Protection Emergency Light Fitting C-Lux 6108 Ex e Ex em Ex e Ex m Ex de Ex de Ex de Ex d Ex e Ex e R.STAHL explosion protection >

Minimum ignition energy Associated apparatus The minimum ignition energy of a gas/air and vapour/air mixture is the smallest level of electri- cal energy which occurs while a capacitor is discharging, and which may still be sufficient to ignite the most ignitable mixture of a gas or vapour and air at atmospheric pressure and 20C.An essential aspect of the type of protectionГIntrinsic Safety is reliability with regard to the observance of voltage and current limit values, even if determined faults may occur. Intrinsically safe apparatus and intrinsically safe components from related equipment...

Fig.6: Electric Isolators IS pac Table 15: Levels of protection of intrinsically safe electrical circuits Level of protection iaӔElectrical apparatus of level of protection iaԔshall not be capable of causing ignition in normal operation and when one fault occurs or when a combination of any two faults occurs.Safety factor1.5:During normal operation and in case of one faultSafety factor 1.0:Two independent faults Level of protection ibӔElectrical apparatus of level of protection ibԔshall not be capable of causing ignition in normal operation or when one fault occurs.Safety factor1.5:During normal...

direct entry, the connecting cables are entered directly into the flameproof enclosure. Only cable glands that have been specially certified for this purpose may be used for this type of entry. 29 5.3 Methods of Installation Essentially, three systems are used for electricalinstallations in hazardous areas: indirect entry, the cables and linesare conducted via cable glands into a connection chamber in the type of protection Increased SafetyӔ and connected to the terminals also pro- vided in Increased SafetyӔ.From here, the individual wires are conducted via flameproof bushings into the flameproof...

For potentially explosive atmospheres the termhazardous (classified) locationsӔ is used in North America.These are defined in Articles 500 and 505 of the National Electrical Code (NEC) in the USA and in Section 18 and Annex J of the Canadian Electrical Code (CEC) in Canada. Hazardous locations are locations, where fire or explosion hazards may exist due to flammable gases, vapours or mists (Class I), combustible dusts (Class II), or ignitable fibres or flyings (Class III).Based on the likelihood or risk that an ignitableconcentration of a flammable substance will be present the hazardous locations...

Class I, II & III, Division 1 and 2 The approved electrical equipment for Class I, Class II and Class III, Division 1 and Division 2 must be marked to show the following information: 1. Class(es), Division(s) (optional except for Division 2)2. Gas/dust group(s) 3. Operating temperature or temperature class(optional T5 and T6)Example: Class I Division 1 Groups C D T4 33 (2) Zone EquipmentEquipment meeting one or more types of protection described in Article 505 of the NEC or Section 18 of the CEC shall be marked with the following in the order shown: 1. Class (optional in Canada) 2. Zone (optional...