Explosion Protection Theory and Practice

Transcription

1 Explosion Protection Theory and Practice

2 explosion protection worldwide with installation examples This brochure on explosion protection is designed to help installation technicians, design engineers and operators of plants located in explosive atmospheres. Most often hazardous areas are equated to chemical and petrochemical industries. A potential hazardous atmosphere could exist with applications in food/beverage or automative industries (paint applications) which may usually seem harmless. explosion protection is often seen in connection with gases. however, explosive atmospheres can also be generated by dusts. Chemical and petrochemical industries Off-shore plants PhoeNix CoNTACT Coal-mining

3 Contents Page 1. Physical Background 4 2. explosion Protection Standards, Regulations and Directives 5 3. installation and Protection Methods 7 4. Zones and Divisions 9 5. Types of Protection identification and Marking intrinsic Safety Surge Voltage Protection in the hazardous Area (ex Area) ex-approved Modular Terminal Blocks Cable/Conductor Routing and Conduit Systems ip Protection Type, NeMA Classification What is NAMUR? Smart-Compatible Devices Application/installation examples Terms and Abbreviations Principles of Signal Transmission 39 in the first part of this brochure, the basics of explosion protection is explained with intention of making you aware of the particular risks involved. explosion protection around the world is based mainly on european and American standards and directives. The second part provides support for the user of electrical equipment for the hazardous area. There is a comprehensive explanation of what explosion protection criteria must be observed. in addition to information on MCR instrumentation devices for intrinsically safe circuits, you will also find information on modular terminal blocks and surge voltage protection for the hazardous area. You will find additional information about the products listed in this brochure in the Phoenix Contact catalogs. Use the fax order form on the back cover of this brochure to order these catalogs. PhoeNix CoNTACT

4 1. Physical Background Complete Combustion Complete combustion is a rapid oxidation process. It is also referred to as a "destructive fire", a process in which a combustible material is decomposed exothermally where there is a sufficient supply of oxygen. As the speed with which the shock wave emanating increases, the process is referred to as deflagration, explosion or detonation in this order. In the case of complete combustion, the damage caused increases significantly in proportion to speed of the shock wave emanating. Oxygen If an explosive material is combined with oxygen, an explosive mixture is created. In the case of gases, the ratio of concentrations determines whether an explosion is possible. The mixture can only be ignited if the concentration of the material in air is within the lower (LEL) and upper (UEL) explosive limits. Some chemically unstable materials (e.g. acetylene, ethylene oxide) can also enter into exothermal reactions without oxygen as a result of spontaneous decomposition. The upper explosive limit (UEL) shifts to 100 volume percent. In the case of gases under pressure, the explosive ranges change. Dusts can also be grouped into a lower explosion or flammability limit (at approx g/m 3 ) and an upper explosion or flammability limit (at approx. 2 6 kg/m 3 ). Acetone Acetylene Speed of the shock wave emanating Deflagration cm/s Ammonia Explosion Detonation m/s km/s Butane Explosion An explosion can occur if there is a combination of a flammable material, oxygen and a source of ignition. If one component is missing no exothermal reaction will occur. Diesel fuel Carbon monoxide Methane Gasoline Carbon disulfide Lower explosion limit Upper explosive limit Hydrogen Explosive material Oxygen Volume percent of combustible materials Examples for explosive areas of gases under normal pressure Source of ignition Sources of ignition Prerequisites for an explosion Explosive material A flammable material which is present as a gas, vapor or dust is called an explosive material. In the case of vapors or dusts, an explosive atmosphere is created if the drop or particle size is smaller than 1 mm. Vapors, aerosols and dusts occurring in practice have particle sizes between and 0.1 mm. Dusts with larger particle sizes are not flammable. Source of ignition Sparks Arcs Hot surfaces Flames and hot gases Electrical systems Static electricity Electrical equalizing currents Electromagnetic waves in the range of 3 x x Hz High frequency x Hz Lightning strike Ionizing radiation Ultrasound Examples of reasons for explosions mechanically created sparks (e.g. caused by friction, impact or abrasion processes), electric sparks short circuit, switching operations power in electric systems, heaters, metal-cutting, heating up during operation due to combustion reactions, sparks during welding protective low voltages ( U < 50 V) can still generate enough energy to ignite an explosive atmosphere. opening/closing of contacts, loose contact separately arranged conductive parts, many plastic materials reverse currents from generators, body/earth contact in the case of faults, induction laser beam for distance measurement, especially: focusing radio signals, industrial high-frequency generators for heating, drying, cutting, etc. atmospheric weather disturbances X-ray apparatus, radioactive material, absorption of energy leads to heating up absorption of energy in solid/liquid materials leads to heating up 4 Phoenix Contact Adiabatic compression and shock waves Exothermal reactions sudden opening of valves chemical reaction

5 2. Explosion Protection Standards, Regulations and Directives ATEX Free commodity trade in Europe Two directives are relevant for explosion protection in the European Union's "new approach". Target group Directive Common designation* Manufacturer 94/9/EC ATEX 100a ATEX 95 Operator 1999/92/EC ATEX 118a ATEX 137 The manufacturer directive through the times Council directive 94/26/EC, adapted to technical progress; Council directive 79/196/EEC (List of harmonized standards generation D) Council directive 97/53/EC, adapted to technical progress; Council directive 79/196/EEC (List of harmonized standards generation E) Directive 82/130/EEC, adapted with directive 98/65/EC (List of harmonized standards generation D and E) Council directive 94/9/EC * The directive is based on an article of the treaty establishing the European Community. The number of the article has changed. The term ATEX is derived from French, "ATmosphère EXplosive". Certification Putting on the market North American Hazardous Location Systems Based on the North American Hazardous Location System (Hazloc), fundamental rules are laid down for explosion protection. In the US, these are stated in the National Electrical Code (NEC), and in Canada in the Canadian Electrical Code (CEC) Among the main institutions of the system are: Underwriters Laboratories Inc. (UL), CSA International (CSA), Institute of Electrical and Electronics Engineers (IEEE), The Instrumentation, Systems and Automation Society (ISA), Mine Safety and Health Administration (MSHA), National Electrical Manufacturers Association (NEMA), National Fire Protection Association (NFPA), United States Coast Guard (USCG), Factory Mutual Research (FM). ATEX Manufacturer directive 94/9/EC Until now, certificates of conformity have been issued by the testing agencies. The directives for devices of generations A to E are the basis for this. These directives will, however, be replaced by the directive 94/9/EC as of July 1st, As early as 1997, Phoenix Contact supported the "new approach" of the European commission and approved all equipment in accordance with the directive 94/9/EC. From July 1st, 2003, electrical equipment may only be allowed on the market for the first time if it complies with directive RL 94/9/EC. Equipment group II "Surface installations" s" Hazardous areas Equipment group I "Mining installations" Areas with a firedamp hazard = coal-mining Equipment group and category In order to determine the appropriate procedure to be used for conformity assessment, the manufacturer must first decide which equipment group and category the product belongs to, based on its intended use (see table below). Equipment group I: Equipment for use in mining industries (coal-mining) and the related surface installations which are at risk from mine gases and/or combustible dusts. Equipment group II: Equipment for use in all other areas that might be endangered by an explosive atmosphere. The equipment groups are assigned to categories in the directive 94/9/EC. Categories M1 and M2 are determined for equipment group I. Three categories - 1, 2 and 3 are defined in equipment group II. The correlation between category and zones is made in the operator directive 1999/92/ EC. Equipment group Category Degree of protection I M1 very high safety degree Protection guarantee In the case of failure of one installation protection measure, a second protection measure guarantees the necessary safety, or That the necessary degree of safety is guaranteed when two independent errors occur. Operating conditions For reasons of safety, it must be possible to continue operating a product even if the atmosphere is potentially explosive. I M2 high safety degree It must be possible to switch off these products if an explosive atmosphere occurs. In normal operation, the protective measures must still guarantee the required safety even in difficult conditions, or if equipment is treated roughly or ambient influences have changed. II 1 very high Two independent protective measures. Safe if two faults occur independent from one another. II 2 high Safe in normal operation and if common faults occur. Equipment can still be used in zones 0, 1, 2 (G) and 20, 21, 22 (D) and continue to be operated. Equipment can still be used in zones 1, 2 (G) and 21, 22 (D) and continue to be operated. II 3 normal Safe in normal mode. Equipment can still be used in zones 2 (G) and 22 (D) and continue to be operated. Phoenix Contact 5

6 Conformity assessment The classification of electrical equipment according to equipment group and category is the basis for conformity assessment. The illustration shows this relationship. Except for category 3 equipment, an EC type examination is required for the conformity assessment. The modules are tested by a notified body. An example illustrates this fact: CE 0344 CE: EC conformity, 0344: notified body, here: KEMA. Conformity assessment in acc. with 94/ /9 9/ EC Group II Group I Category 1 M1 M2 Category 2 Category 3 * Group I EC type examination * Module D QA Production or product test c 0344 Module E QA Product or conformity with design c 0344 Module A Internal production control c 0344 Individual test c 0344 * possible as an option, similar procedure EC type examination The EC type-examination certificate certifies that the test has been carried out by a notified body. Notified bodies are determined by the EU. The certificate constitutes the documentation for the operator. Notified body in acc. with 94/4/EC (extract) Testing body Country Identification PTB Germany 0102 DMT (BVS) Germany 0158 TÜV Nord Germany 0032 DQS Germany 0297 IBExU Germany 0637 BAM Germany 0589 BASEEFA (2001 Ltd) Great Britain SCS Great Britain 0518 INERIS France 0080 LCIE France 0081 LOM Spain 0163 KEMA Netherlands 0344 CESI Italy 0722 DEMKO Denmark 0539 NEMKO Norway Phoenix Contact

7 ATEX operator directive 1999/92/EC Extract from RL 1999/92/EC: (1) Article 137 of the treaty provides that the Council may adopt, by means of Directives, minimum requirements for encouraging improvements, especially in the working environment, to guarantee a better level of protection of the health and safety of workers. (7) Directive 94/9/EC of the European Parliament and of the Council of 23 March 1994 on the approximation of the laws of the Member States concerning equipment and protective systems intended for use in potentially explosive atmospheres (5) states that it is intended to prepare an additional Directive based on Article 137 of the Treaty covering, in particular, explosion hazards which derive from a given use and/ or types and methods of installation of equipment. Note: In many areas, national law requires that the plants be tested. This is carried out by independent experts. 3. Installation and Protection Methods Installation General If systems are installed in hazardous areas, a great number of measures must be taken. When selecting equipment, cables/ conductors and construction, particular requirements must be met. In any case of doubt, we recommend including additional experts in the planning stage. Risk assessment Prior to installation, the operator of a system must carry out a risk assessment. On the basis of the risk assessment, the zones must be laid down and the permitted equipment selected. Every plant must be examined for its specific characteristics. Check list: (possible procedure) Recognizing the risk Probability of an explosive atmosphere occurring Presence of ignition sources Which materials are processed in the plant? What are the conditions necessary for the raw materials, semi-finished and finished products to be present in an explosive concentration? The physical correlations described on page 4 must be taken into account. Ignition sources that can cause materials in the process to ignite must be identified. Presence: permanent, frequent, seldom or very seldom. The interaction between individual parts of the system and the material being processed must be also be taken into account in the assessment. Assessing the explosion risk The operator of a plant must carry out a detailed assessment. The assessment is based on the standards EN , EN and EN The zones are determined on the basis of the assessment. The assessments must be recorded in the documentation. Documentation of explosion protection The documentation is crucial for the safe operation of the plant in the hazardous area. The documentation is created prior to installation and must be updated whenever there are alterations or additions. If changes are made to the plant, all influencing variables described must be taken into account. Example for the structure of the documentation Person responsible for the object Description of the structural and geographic characteristics Description of procedures Materials data Risk assessment with name Plan of site and building, ventilation and air supply Description of the plant from the point of view of explosion protection List of data with characteristics of relevance to an explosion see adjacent check list Areas with explosive atmospheres The employer/operator: divides areas in which explosive atmospheres may occur into zones. guarantees that the minimum requirements are applied. marks the entrances to areas with explosive atmospheres. In directive 1999/92/EC, annex II, the correlation between the category in acc. with 94/9/EC and the zone is made. Correlation in acc. with 1999/92/EC Effects of the explosion Possible risks If an explosion occurs despite these measures, the possible risks must be examined. Can chain reactions occur, what is the extent of damage to the buildings and what effect does the explosion have on other parts of the plant. It is possible for interactions that could never occur in the individual system to occur with neighboring systems. The risk assessment requires a high degree of experience and the correct evaluation. If there is any doubt, it is advisable to refer to other experts. Risk assessment is the basis for all other measures, including the operation of the system. Protection concepts Organizational measures Identification of hazardous areas The hazardous area is identified by means of a danger sign. Warning signs for the hazardous area Division into zones, safety categories applied Training, written instructions, clearance for work Zone Category 0, , 21 1, 2 2, 22 1, 2, 3 Phoenix Contact 7

8 Worldwide overview of standards Overview of standard protection methods for electrical equipment Protection methods General requirements USA basis Principle EN standard IEC standard (factually identical to EN) Basis for safety categories EN , EN , EN , EN FM (USA) EN IEC FM 3600 (ISA ) UL (USA) CSA (Canada) China GB Intrinsic safety EEX i Limiting energy EN AEx i NEC505 FM 3610 UL2279 Pt.11 CSA-E79-11 Ex i IEC GB (IS) NEC504 FM 3610 UL913 CSA-157 Increased safety EEx e Constructional measures through EN AEx e NEC505 spacing and dimensioning FM 3600 (ISA ) UL2279 Pt.11 CSA-E79-7 Ex e IEC GB Non-incendive (NI) NEC500 Constructional measures through spacing Explosion-proof (XP) NEC500 Constructional measures through enclosure FM 3611 UL 1604 CSA-213 FM 3615 e.g. Housing: UL 1203 Flameproof enclosure EEx d Constructional measures through EN AEx d NEC505 enclosure FM 3600 (ISA ) UL2279 Pt.1 CSA-E79-1 Ex d IEC GB Encapsulation EEx m Exclusion of potentially explosive EN AEx m NEC505 atmosphere FM 3600 (ISA ) UL2279 Pt.18 CSA-E79-18 Ex m IEC GB Oil immersion EEx o Exclusion of potentially explosive EN AEx o NEC505 atmosphere FM 3600 (ISA ) UL2279 Pt.6 CSA-E79-6 Ex o IEC GB Powder filling EEx q Exclusion of potentially explosive EN FM 3622 AEx q NEC505 atmosphere FM 3600 (ISA ) UL2279 Pt.5 CSA-E79-5 Ex q IEC GB Pressurization (purged) EEx p Exclusion of potentially explosive EN AEx p NEC505 atmosphere CSA-E79-2 Ex p IEC GB Type X NEC500 FM 3620 NFPA496 Type Y NEC500 FM 3620 NFPA496 Type Z NEC500 FM 3620 NFPA496 Protection Method "n" EEx n Improved industrial quality EN AEx n NEC505 FM 3600; (ISA ) UL2279 Pt.15 CSA-E79-15 Intrinsically safe electrical systems "i-sys" Ex n IEC GB Power limitation in interconnected EN IEC GB intrinsically safe circuits Dust explosion protection Dust; protection through housing design EN (DIP) NEC500 NFPA 70 Abbreviations based on the NEC 500 in North America XP IS AIS ANI PX, PY, PZ APX, APY, APZ NI DIP Explosion-proof Intrinsically safe apparatus Associated apparatus with intrinsically safe connections Associated non-incendive field wiring circuit Pressurized Associated pressurization systems/components Non-incendive apparatus and non-incendive field wiring apparatus Dust ignition-proof Installation, standards for operator Designation EN standard IEC standard China (factually identical to EN) Explosion protection part 1: basics and methods EN Electrical operating equipment for potentially gas-explosive areas introduction of the areas Electrical operating equipment for potentially gas-explosive areas Electrical equipment in potentially explosive areas Electrical operating equipment for use in areas with combustible dusts; part 1-2: selection, installation and maintenance EN IEC GB EN IEC GB EN Phoenix Contact

9 4. Zones and Divisions Europe Potentially explosive areas are allocated to standard zones that are distinguished according to two types: potentially gas-explosive areas and potentially dust-explosive areas. The zones are defined for gases in EN and for dusts in EN Furthermore, the standard EN was created on the basis of the mandate of the European Commission (KEU) and the European Free Trade Zone (EFTA) to the European Standardization Committee (CEN). This is to support the EC directives (ATEX) 94/9/EC and 1999/92/EC. The zones are divided based on the frequency of the occurrence of potentially explosive atmospheres. Gases and dust can also occur at the same time. The zones were assigned precise time specifications for gases in the explosion protection rules of the Trade Association for Chemicals in Germany These values are not mentioned in the standards, because it appears that it is not possible to make a generally valid statement. For this reason, one must weigh up how to judge the frequency of occurrence in every individual risk assessment. Potentially gas-explosive areas Zones Zone 0 Zone 1 Zone 2 Type of danger continuous, long periods, frequent occasional normally not, only for a short period North America National Electrical Code (NEC) in the USA Article Contents 500 General requirements for divisions of class I, II and III 501 Requirements for division of class I 502 Requirements for division of class II 503 Requirements for division of class III 504 Requirements for division of class I, II and III in relation to intrinsic safety (IS) 505 General and special requirements for the zone of class I Canadian Electrical Code (CEC) in Canada Regulation Contents General requirements for class I / zone and class II and III / division Requirements for class I, zone 0 requirements Requirements for zone 1 and 2, class I Requirements for division of class II Requirements for division of class III Appendix J General and special requirements for the division of class I In the USA, zones or divisions are divided up according to the National Electrical Code (NEC). The comparison with the IEC/ CENELEC zone division can only be regarded as a general approximation. The conversion must be checked in individual cases. Electrical operating equipment can be used especially for division 2. The same operating equipment can only be used in zone 2 with additional testing and certification. The possibilities are shown in the simplified assignment diagram. The basis for explosion protection in North America is the National Electric Code (NEC) in the USA and the Canadian Electrical Code (CEC) in Canada. The listed excerpts of the NEC and CEC refer to explosion protection. CLASS I (gases and vapors) CLASS II (dusts) CLASS III (fibers) Group A (acetylene) Group B (hydrogen) Group C (ethylene) Group D (propane) Group E (metal dust) Group F (coal dust) Group G (grain dust) No subgroups Potentially dust-explosive areas* Old division in Germany New division in Germany Type of danger Zone 10 Zone 20 continuous, long periods, frequent Zone 21 occasional IEC/CENELEC Zone 0 Zone 1 Zone 2 Zone 11 Zone 22 normally not, only for a short period * General assignment, must be checked in individual cases. USA: NEC 505 Zone 0 Zone 1 Zone 2 USA: NEC 500 Division 1 Division 2 In Germany, dusts were previously divided into two zones. When standards were revised as a result of European directives, the zone division was also divided into three zones for dusts as well, throughout Europe. However, it must be taken into account that zones 10 and 11 cannot be transferred to the new zone division without checking. Explosive material Class Group Explosive material Class Group Gas / vapor or liquid I A, B, C, D Gas / vapor or liquid I A, B, C, D Dust II E, F, G Dust II F, G Fibers III Fibers III Phoenix Contact 9

10 Understanding classes and divisions Division Explosive atmosphere Class I, division 1 Gas, liquid and vapor Can also occur under normal operating conditions, can occur frequently during repair, maintenance or due to lack of sealing, or can become a source of ignition in the case of an operation failure. Class I, division 2 Gas, liquid and vapor Normally in closed systems in which flammable concentrations are prevented by ventilation or connected to the area that is assigned to class I, division 1, for which the danger exists that flammable concentrations can occur. Class I, zone 0 Gas, liquid and vapor Continuous, long periods, frequently present. Class I, zone 1 Gas, liquid and vapor Occurs under normal conditions, can occur frequently during repair, maintenance or due to lack of sealing, can become a source of ignition in the case of an operation failure or is connected to the area that is assigned to class, zone 0, for which the danger exists that flammable concentrations can occur. Class I, zone 2 Gas, liquid and vapor Normally not, only for short periods in connection with the area that is assigned to class 1, zone 1, for which the danger exists that flammable concentrations can occur. Class II, division 1 Dust Can also occur under normal conditions, frequently during repair, maintenance or due to lack of sealing. Can become a source of ignition in the case of an operation failure, or electrically conductive dust occurs in a dangerous amount. Class II, division 2 Dust Normally not present in a flammable concentration in the air, does not endanger the normal operation of the electrical plant. Occurs during seldom operation failures of the plant, or dust hinders reliable heat discharge. Class III, division 1 Fibers Areas in which easily flammable fibers are processed or transported. Class III, division 2 Fibers Areas in which easily flammable fibers are stored or transported. Simplified assignment diagram for the USA Operating equipment marked with *: Permissible areas of application NEC class I, div. 1 OK in NEC class I, zone 1 and 2 NEC class I, div. 2 OK in NEC class I, zone 2 NEC class I, zone 1 Not permissible in NEC class I, div. 1 NEC class I, zone 2 OK in NEC class I, div. 2 NEC AEx OK in NEC zone 0, 1, 2, as marked NEC AEx Not permissible for NEC class I, div. 1 NEC AEx OK in NEC class I, div. 2 IEC zone 1 IEC zone 2 IEC EEx or Ex Not permissible for NEC purview Not permissible for NEC purview Not permissible for NEC purview * When this mark is given, it can be used to derive the permissible area of application. Assignment is only possible in the indicated direction. Example for zone division Valve Zone 1 Zone 0 Zone 2 Sink 10 Phoenix Contact Example: Tank for flammable liquids (acc. to EN )

11 5. Types of Protection The basis for the standardized protection methods are the requirements for the surface temperature, clearance and creepage distances, the identification of electrical operating equipment, the assignment of the electrical operating equipment to the area of application and the degrees of protection. Everything that goes beyond the basic requirements are specified in the respective protection method. Classification in groups Due to its characteristics, coal mining is assigned group I. This group was previously characterized by the term "susceptible to firedamp". All other potentially explosive areas are assigned to group II. Examples include the petrochemical industry, the chemical industry and silo plants with flammable dusts. The term "potentially explosive" (old abbreviation "Ex") stands for the electrical operating equipment of the current group II. For intrinsic safety, flame-proof enclosures and type of protection "n" subgroups IIA, IIB, Group II "Surface installations" Potentially explosive atmospheres Group I "Underground installations" Areas with a firedamp hazard = coal mining Temperature class group I The temperatures are designed for the requirements in coal mining. Methane is present as a gas and dust results from the coal. Permissible surface Condition temperature of group I [ C] 150 with deposits of coal dust on the operating equipment 450 without deposits of coal dust on the operating equipment Temperature class of group II The explosive atmosphere can be prevented from igniting when the surface temperature of the operating equipment is lower than the ignition temperature of the surrounding gas. The surface temperature is valid for all parts of an electrical apparatus that can come into contact with the explosive material. The majority of the gases can be assigned to the temperature classes T1 to T3. In the USA its referred as the T rating. Clearance and creepage distances Clearance and creepage distances must be maintained for intrinsic safety, increased safety and type of protection "n". Clearance distance Creepage distance Clearance and creepage distance The term clearance distance is defined as the shortest connection between two potentials through the air. The creepage distance is the shortest connection between two potentials over a surface. A minimum distance must be maintained, depending on the comparative tracking index of the material. The minimum distances for clearance and creepage distances are specified in the corresponding protection methods. and IIC are distinguished in group II. Group IIC contains gases with the highest flammability. In the case of intrinsic safety and protection method "nl", the classification is determined by the minimum ignition current (MIC). The gap (MESG) determines the subgroups for "flame-proof enclosures" and for protection method "nc". Example: Note: The ATEX directive 94/9/EC refers to device groups. These are identical to the groups according to EN standard. Permissible surface temperatures [ C] for group II: temperature classes in Europe and the USA Temperature limits with dust In the case of potentially dust-explosive areas, the maximum surface temperature is given as a temperature value [ C]. There is no classification into groups. The permissible temperatures for each type of dust normally have to be determined through experiments. Modular terminal blocks are used in a housing in safety category EEx e IIC T6. In this case, the maximum permissible current strength must be calculated so that the temperature class T6 is also maintained at the modular terminal blocks. The housing is designed with the IP protection type IP 54, but the explosive gas can still intrude into the housing. For this reason, it is not sufficient only to regard the surface temperature of the housing. Phoenix Contact 11

12 Intrinsic safety protection method Ex i The intrinsic safety category, as opposed to other categories (e.g. increased safety), refers not only to individual equipment, but to the entire circuit that is intrinsically safe. The protection is in the circuit and not in the housing. A circuit is described as intrinsically safe if no spark or thermal effect can cause an explosive atmosphere to ignite. Suitable measures must guarantee that the energy in intrinsically safe operating equipment is so low that an explosive atmosphere cannot be ignited even in the case of a defect. In the case of intrinsically safe electrical apparatus, all circuits are intrinsically safe and depending on their overall protection method, this equipment can be used directly in the designated zones or divisions. Associated apparatus has both intrinsically safe and non-intrinsically safe circuits. They are generally implemented in the safe area but the connecting lines do extend into the hazardous area. Therefore, the associated apparatus must also comply with the above-mentioned categories, i.e. associated apparatus which is connected with a sensor or actuator in zone 0, Div. 1 must be equipment from category 1. Possibilities of pressurization Pressurization Static With compensation of the leakage losses Increased safety Ex e In protection method "increased safety", voltages up to 11 kv can be brought into the potentially explosive area. Increased safety is especially suitable for supplying motors, lights and transformers. The protection principle is based on constructional measures. Clearance and creepage distances are determined for the live parts, divided into voltage levels. This prevents electrical sparks. In addition, at least the IP protection type (EN 60529) IP 54 must be fulfilled. Limiting the surface temperature ensures that explosive atmosphere cannot be ignited at any place, even inside the housing, during operation. The housing does not prevent gas from entering. Flame-proof Enclosures Ex d In flame-proof enclosures an explosion is contained. An explosion that occurs inside is not able to ignite the explosive atmosphere surrounding the housing. This leads to very robust housings. The housings have covers and insertion points to accommodate cables and lines. The maximum permitted gap that is present is dimensioned in such a way that it prevents the explosion from being carried over from inside the housing to the surrounding explosive atmosphere. In the case of cable and conductor leads in the protection type Ex d, it is not permitted to grease the thread or remove rust with a wire brush. The gap could be changed as a result and the protection principle destroyed. The manufacturer s specifications must be observed. In the USA a similar method used is called explosion proof. (xp) (see page 8) With continuous circulation Compressed air Without correction Compensation of the leakage losses Continuous correction Operating states --- Pre-purging phase: The housing is purged and any explosive atmosphere that is present is removed from the housing. Encapsulation, powder filling or oil emersion Ex m, Ex q, Ex o The principle of the protection methods "molded encapsulation", "sand encapsulation" and "oil encapsulation" safety categories is to surround possible sources of ignition in an electrical apparatus with the potting compounds, sand or oil. This prevents the ignition of the explosive atmosphere. Voltages from kv can also be reached with these protection methods. Details can be found in the standards (see page 8). Pressurization (purged) Ex p The positive pressure or inert gases describes methods that use overpressure to prevent an explosive atmosphere from entering the housings or the control room. The ambient pressure around the housing is always lower than inside. Three forms of pressurization are possible (see table at the bottom left). In the case of static pressurization, the housing must be hermetically sealed. No loss of pressure occurs. More common, however, are methods in which the pressurization is maintained by compensating the leakage losses or by constant circulation. The overpressure is usually created by simple compressed air. Pressurization (purged) methods Ex p requires a monitoring unit that reliably switches off the electrical operating equipment inside the housing as soon as sufficient pressurization is no longer present. The monitoring unit must be designed in a different protection method, so that it can also be operated without pressurization. Operating equipment can now be operated inside the enclosure. Nevertheless, a source of ignition must not develop if the pressurization decreases, as a result of the temperature of the operating equipment. In the USA this method used is referred to as purged with three forms X,Y,Z. (see page 8) Operating phase: The overpressure in the housing is monitored. If it decreases, the electrical operating equipment inside the housing is switched off. 12 Phoenix Contact

13 Type of protection "n" Protection method "n" can be described as an improved industrial quality that is designed for normal operation. A fault scenario examination as with the intrinsic safety category is not performed. This can only be applied for group II and the use of electrical operating equipment in zone 2. The manufacturer specifies the technical data for normal operation. In the method "n", five different versions are distinguished, which can be derived in part from the well-known increased safety, intrinsic safety, flame-proof encapsulation, pressurization and encapsulation and molded encapsulation safety categories. This method was developed based on the US protection method "non-incendive" (NI) and was introduced in Europe as a standard in Classification of protection method "n": EEx n in Europe Abbreviation Meaning Comparable to Method Divisions of group II A Non-sparking EEx e Occurrence of arcs, sparks or hot surfaces is minimized C R Sparking equipment Restricted breathing housing partly EEx d, EEX m Enclosed break device Non-incendive components Hermetically sealed, sealed or encapsulated installations None --- Intrusion of explosive gases is limited None L Power-limited EEX i Power limitation so that neither sparks nor thermal effects cause an ignition P Simplified pressurized encapsulation * different in North America and Europe EEx p Intrusion of explosive gases is prevented by overpressure, monitoring without disconnection IIA, IIB, IIC IIA, IIB, IIC None Subdivision of type of protection "n" in North America Designation acc. to NEC Energy limited, "nc" * Hermetically sealed, "nc" Non-incendive, "nc" Non-sparking, "na" Restricted breathing, "nr" Sealed device, "nc" Simplified pressurization, "np" ** * different in North America and Europe ** referred to as type X, Y and Z in the USA Dust explosion protection in Europe The dust explosion protection for group II acc. to EN limits the entrance of dust into housings by requiring an IP protection for housings acc. to the standard EN In addition, the maximum surface temperature that can ignite the dust is specified. Higher temperatures can occur inside the housing, however. In these cases, special instructions are necessary for opening the housing. For group I, which is designed for coalmining, the dust explosion protection (coal dust) is already covered by the standards EN ff. Requirements for housings of group II, dust (D) Category IP protection (EN ) IP6X IP6X IP5X Housing Dust-proof Dust-proof Dust-protected Ambient temperature -20 C to + 40 C -20 C to + 40 C -20 C to + 40 C Max. surface temperature* of the housing * A temperature value is given in Celsius. Measurement based on ambient temperature 40 C Measurement based on ambient temperature 40 C Measurement based on ambient temperature 40 C US type of protection acc. to NEC Explosion-proof Dust ignition-proof For operating equipment of this protection type, additional requirements are made for explosion protection. The temperature is specified to a value that is considered safe in relation to the surroundings. This includes products such as: Motors and generators Monitoring devices for industrial and process control applications (industrial control equipment, process control equipment) Electrically operated valves The ignition of dust or dust accumulation by arcs, sparks or heat is prevented. Non-incendive Non-sparking Hermetically sealed Sealed device A short circuit or thermal effect is not able to ignite a flammable gas-air or vapor-air mixture that is specified by the manufacturer under certain operating conditions. The electrical operating equipment does not have any parts that normally cause arcs, sparks, or thermal effects with which an explosive atmosphere can be ignited. The electrical operating equipment is completely sealed so that no explosive atmosphere can enter from outside. This is realized by welding or other melting methods. The operating equipment is designed in such a way that it cannot be opened, has no function parts on the outside and is totally sealed. Sparking parts or hot surfaces can be located inside the equipment. Phoenix Contact 13

14 6. Identification and Marking Identification in Europe acc. to ATEX and EN standards Electrical apparatus Identification acc. to EN E Ex ia IIC T6 Electrical equipment Identification acc. to ATEX X c 02 II 1 GD 0102 Current year of manufacture Type-examination in acc. with 94/9/EC (ATEX) Electrical equipment EC type-examination certificate TÜV 01 ATEX 1750 Temperature class (for electrical equipment used directly in the Ex area) Group Protection method Explosion-protected Certified to CENELEC standard EN 50 Atmosphere (G = Gas, D = Dust) Category Equipment group Notified body, production (e.g. PTB) Certificate no. Type-examination in acc. with 94/9/EC (ATEX) Year of EC type-examination certificate Notified body Associated apparatus Identification acc. to EN [E Ex ia] IIC Associated apparatus Group Protection method Explosion-protected Certified to CENELEC standard EN 50 Identification acc. to ATEX X c 02 II (1) GD 0102 Current year of manufacture Type-examination in acc. with 94/9/EC (ATEX) Associated apparatus Atmosphere (G = Gas, D = Dust) Category Equipment group Notified body, production (e.g. PTB) EC type-examination certificate TÜV 01 ATEX 1750 Certificate no. Type-examination in acc. with 94/9/EC (ATEX) Year of EC type-examination certificate Notified body Component Identification acc. to EN Identification acc. to ATEX Current year of manufacture Type-examination in acc. with 94/9/EC (ATEX) EC type-examination certificate E Ex e II T6 Temperature class (for electrical equipment used directly in the Ex area) Group Protection method Explosion-protected Certified to CENELEC standard EN X 02 II 2 GD Atmosphere (G = Gas, D = Dust) Category Equipment group Notified body, production (e.g. PTB) Components are excepted from the c marking. TÜV 01 ATEX 1750 U Certificate no. Type-examination in acc. with 94/9/EC (ATEX) Year of EC typeexamination certificate Notified body 14 Phoenix Contact

15 Dust explosion protection for electrical equipment Identification acc. to EN Identification acc. to ATEX Current year of manufacture Type-examination in acc. with 94/9/EC (ATEX) EC type-examination certificate IP 66 T = 180 C X c 02 II 1 D 0102 TÜV 01 ATEX 1750 Temperature IP protection in acc. with EN Atmosphere (D = Dust) Category Equipment group Notified body, production (e.g. PTB) Certificate no. Type-examination in acc. with 94/9/EC (ATEX) Year of EC type-examination certificate Notified body Associated apparatus Identification Component Identification Phoenix Contact 15

16 Identification USA Identification US Standard in acc. with NEC 500 Deviation in ambient temperature IS / II,I / 1 / CDEFG / T6, T5 Ta = 70 C; ; Type 4X, 6P Type of housing Control document Temperature class Group Division Class Safety category Identification US Standard in acc. with NEC 505 Deviation in ambient temperature I / 1 / AEx ia / IIB / T6, T5 Ta = 70 C; ; IP 54 Type of housing Control document Temperature class Group, Gas group Degree of protection American National Standard approved Zone Class Associated apparatus Classification of the electrical equipment 1M68 Certifying body in the USA: here UL; c for Canada; us for the USA UListed CD-No: Control drawing no. (Control document) Suitable for Class I, Div. 2, Groups A, B, C and D installation; providing intrinsically safe circuits for use in Class I, Div. 1, Groups A, B, C and D; Can be used in Div 2* for Class I: Gases Gases A: Acetylene B: Hydrogen C: Ethylene D: Propane Class II, Groups E, F and G; and Class III, Hazardous Locations Dusts suitable for circuits in Div 1* Fibers * Acc. to NEC Phoenix Contact

17 7. Intrinsic Safety Signal system around 1910 Principle Safety category "Intrinsic safety" Ex i is based on the principle of limiting the current, voltage and stored energy within an electric circuit. When limiting voltage and current, the following applies for the maximum power: P o = U o 2 4R The maximum permissible values are determined by the ignition limit curves according to in EN There are a total of four ignition limit characteristic curves for the gas groups I, IIA, IIB and IIC. They are grouped according to the ignition energy. The ignition limit curves are determined by means of spark test apparatus as described in EN "ia" in conjunction with galvanic isolation. Intrinsic safety is based on the consideration of faults in order to rule out the danger of explosion. This does not, however, provide any conclusions as to the operational safety. This means that a total functional failure of the equipment can be permissible as seen from the point of view of explosion protection. Electrical equipment can be used in zone 0, Div. 1 according to the category. Associated apparatus is usually installed in the safe area. Only the intrinsically safe circuits are routed into the hazardous area, according to the category. The principle of intrinsic safety > voltage limited > current limited > stored energy limited Electrical equipment, intrinsic safety Associated apparatus, intrinsic safety Intrinsic safety does not reduce the flammable material and/or the oxidizer. The ignition of an explosive mixture is prevented if electrical sparks and thermal effects are ruled out. In order to keep the electrical spark below the ignition limit, the voltage is limited. The thermal effect, in other words, excessively hot surfaces, is ruled out by limiting the current. Limiting the energy prevents the electrical equipment and its surfaces from becoming too hot. This is also true of the sensors connected to the intrinsically safe circuits. Energy may be stored in capacitors (condensers) or inductors (coils) within the intrinsically safe circuit. Hazardous area Safe area Block diagram for limiting voltage and current. The Zener diode becomes conductive at a defined voltage level. The higher voltage is discharged over the Zener diode and the voltage in the electrical circuit is limited in the Ex area. A resistor connected in series limits the current in the hazardous area. I max = I o = U o R Electrical equipment and associated apparatus An intrinsically safe circuit consists of at least one electrical equipment and one associated apparatus. The circuits of the electrical equipment fulfill the requirements of intrinsic safety. Electrical equipment may only be connected to circuits without intrinsic safety via associated apparatus. Associated apparatus has both intrinsically safe circuits and circuits without intrinsic safety. The circuits are isolated using Zener barriers or galvanic isolators. In EN , the term "safety barrier" is used to refer to this technique. Intrinsically safe electrical equipment and intrinsically safe parts of associated apparatus are classified according to EN in categories "ia" and "ib". Category "ia" is always safer than "ib". Category "ia" or "ib" defines whether protection is maintained with one or two faults in the protective circuit. For intrinsically safe circuits going into zone 0, standard (EN chap. 12.3) recommends the preferential use of category Category* Faults Permissible zones ia Under normal operating conditions, not able to cause ignition if one fault or a combination of two faults occurs. 0, 1, 2 ib Under normal operating conditions, not able to cause ignition if one fault occurs. 1, 2 * Category, in acc. with EN , is not identical with the term used in directive 94/9/EC Phoenix Contact 17

18 Associated apparatus with/without galvanic isolation Ex side Without electrical isolation: Zener barrier Safe area Simple electrical equipment (EN ) Type Condition Examples passive components Energy storing devices No energy contribution Precisely defined characteristics, the values of which must be taken into account in the overall safety of the system. Resistor, switch, potentiometer, distributor box, simple semiconductor components, Pt 100 Coil, Capacitor Intrinsic safety installations The central idea with regard to installation The entire intrinsically safe circuit must be protected against energy from other sources entering, and against electrical and magnetic fields. The installation technician or operator is responsible for the intrinsic safety installation, and not the manufacturer. Ex side With electrical isolation: Galvanic isolator barriers Safe area Associated apparatus can be designed in a further safety category in order for it to be installed in zone 2, Div. 2 or maybe even in zone 1, Div. 1. Energy sources Maximum values: U 1.5 V, I 100 ma, P 25 mw Thermocouple, Photocell Identification of hazardous areas The hazardous area is identified by means of a warning sign. Simple electrical equipment, intrinsic safety Associated apparatus, intrinsic safety Warning signs for the hazardous area Intrinsically safe circuits with associated apparatus To aid planning and installation, it is advisable to keep the operating instructions and EC type-examination certificates of the associated apparatus used at hand. These must be referred to for the necessary parameters. The first step is to verify the data according to the following table. Hazardous area Safe area Simple electrical equipment Simple electrical equipment does not require certification. It must be assigned to a temperature class and conform with any other applicable requirements of EN The maximum temperature can be calculated from power P o of the associated apparatus and the temperature class determined. Dimensioning of intrinsically safe circuits Potentially explosive area Safe area PLC 4 20 ma Common designations Europe USA For electrical equipment: Max. permissible voltage Max. permissible current Internal capacitance Internal inductance For associated apparatus: Max. open-circuit voltage Max. short-circuit current Max. permissible capacitance Max. permissible inductance U i I i C i L i U o I o C o L o V max I max C i L i V oc I sc C a L a 18 Phoenix Contact

19 Checking the use in the hazardous area Criteria Equipment group, Electrical equipment II, G, D Associated apparatus II, G, D Category 1, 2, 3 (1), (2), (3) Group IIA, IIB, IIC IIA, IIB, IIC Zone 0, 1, 2 0, 1, 2 Type of protection Temperature class EEX ia, EEx ib T1 T6 -- [EEX ia], [EEx ib] The next step is to check the electrical data of the intrinsically safe circuit (voltage, current, power, capacitance and inductance). The system parameters are seen as complying if the system has certification. In the intrinsically safe circuit, all capacitances and inductances must be taken into account and compared with capacitance C o and inductance L o of the associated apparatus. In practice, it is particularly important to observe the capacitance, since this can considerably restrict the length of cables or conductors. As a reference value, capacitance C C can be taken to be approx nf/km and inductance L C approx mh/km. Where there is any doubt, always assume the worst case. with several pieces of associated apparatus The interconnection of several associated apparatus is not permitted for use in zone 0. If an intrinsically safe circuit for applications in zone 1 and zone 2 contains more than one associated apparatus, proof must be provided from theoretical calculations or test with the spark tester (in acc. with EN ). It must be taken into account whether a current addition is present. It is therefore recommended to have the evaluation performed by an expert. Examples for the interconnection of several intrinsically safe circuits with a linear current-voltage characteristics are listed in appendix A and B of EN When associated operating equipment with nonlinear characteristics are interconnected, the evaluation on the basis of the open-circuit voltage and the short-circuit current does not lead to the result. The calculations can be performed on the basis of the PTB report PTB-ThEx-10 "Interconnection of non-linear and linear intrinsically safe circuits". However, here graphic methods are used to evaluate the intrinsic safety up to zone 1. Galvanic isolator barriers versus Zener barriers Comparison of galvanic isolator barriers and Zener barriers Condition Sensor, actuator Galvanic isolator barriers: can be connected to ground, but not in zone 0 Zener barriers cannot be connected to ground Equipotential bonding not necessary necessary Faults in measurement (ground loops) Leakage currents in Zener diodes Temperature coefficients in limiting resistors Different potentials for intrinsically safe circuit and evaluation circuit not possible not possible none permitted possible possible present not permitted Installation work less higher due to reliable grounding In order to prevent difficulties during installation that can occur due to grounding, the IS products from Phoenix Contact always have electrical isolation. Grounding in intrinsically safe circuits Potential differences can arise when intrinsically safe circuits are grounded. These must be taken into account when considering the circuits. Intrinsically safe circuits may be isolated to ground. The danger of electrostatic charging must be considered. The connection via a resistance R = MΩ to discharge electrostatic charges is not a ground connection. An intrinsically safe circuit may be connected to the equipotential bonding system if this is only done at one point within the electrically isolated, intrinsically safe circuit. This condition is fulfilled by an electrical isolator. X-Note If a grounding is necessary at the sensor/ actuator due to the function, this must be done immediately outside of zone 0. Systems with Zener barriers must be grounded to them. Mechanical protection against damage must also be provided if necessary. These circuits may not be grounded at another point. All electrical operating equipment that does not pass the voltage test with at least 500 V to ground must be grounded. Permitted conductor cross sections for connection to earth Number of conductors At least two separate conductors One conductor Conductor cross section min. 1.5 mm 2 min. 4 mm 2 Condition Each individual conductor can carry the greatest possible current In the case of galvanic isolation of supply and signal circuits, the faults and/or transient currents in the equipotential leads must be taken into account. Service and maintenance No special authorization (e.g. fire certificate) is required for servicing intrinsically safe circuits. The conductors of the intrinsically safe circuit can be shortcircuited or interrupted without causing an explosion. Electrical equipment can be replaced (or modules unplugged) without the system having to be switched off. Soldering is not permitted. No dangerous contact currents or voltages occur in intrinsically safe circuits, so they pose no danger to people. The measurement of intrinsically safe circuits requires approved, intrinsically safe measuring instruments. If the data from these measuring instruments is not taken into account, additional energy can enter into the intrinsically safe circuit. The permissible maximum values may be exceeded and the requirements for intrinsic safety will no longer be fulfilled. The same holds true for all testers that are to be used. Distance between EEx i and Non-Ex Intrinsically safe circuits Light blue cable in hazardous area Circuits to the PLC in the safe area Structure of a control cabinet with intrinsically safe circuits Phoenix Contact 19

20 Cables/conductors for zone 0, 1 and 2 When cables/conductors are installed, they must be protected against mechanical damage, corrosion, chemical and thermal effects. This is a binding requirement in the intrinsic safety category. The accumulation of explosive atmosphere in shafts, channels, tubes and gaps must be prevented. Flammable gases, vapors, liquids and dusts must not be able to spread over them. Within the potentially explosive area, cables/conductors should be laid without interruption wherever possible. If this cannot be done, the cables/conductors may only be connected in a housing that is designed with a protection type that is approved for the zone. If this is also not possible due to installation reasons, the conditions from the standard EN must be fulfilled. These conditions will not be discussed here. Cables/conductors for zone 1 and 2 Cable/ conductor Fixed operating equipment Portable, transportable equipment Requirement Sheath External sheath Thermoplastic,thermosetting plastic, elastomer or metalinsulated with a metal sheath Heavy plolychloroprene, synthetic elastomer, heavy rubber tubing or comparable sturdy structure The following also hold true for intrinsically safe circuits, outside of the potentially explosive area as well: Protection against the intrusion of external power. Protection against external electrical or magnetic fields. Possible cause: Highvoltage overhead conductor or singlephase high-voltage conductors. Single-core non-sheathed conductor of intrinsically safe and non-intrinsically safe circuits may not be routed in the same conductor. In the case of proven, metal-sheathed or shielded cables/conductors, intrinsically safe and non-intrinsically safe circuits can be laid in one and the same cable duct. In the control cabinet, the intrinsically safe circuits should be as clearly marked as possible. The standard does not stipulate a uniform process, but only indicates that identification should preferably be in light blue. The neutral conductors of power cables are also usually identified with blue. In this case, intrinsically safe circuits should be identified in a different way, to prevent mix ups. A clear arrangement and spatial separation is advantageous in the control cabinet. Conductive shields may only be grounded at a place that is usually in the non-explosive area. See also the section "Grounding in intrinsically safe circuits" (see page 19). Three special cases are allowed in which the shield can be grounded several times. Distances to connection terminal blocks Between different intrinsically safe circuits The clearance distances between terminal blocks of different intrinsically safe circuits must be at least 6 mm. The clearance distances between the conductive parts of the connection terminal blocks and conductive parts that can be grounded must be at least 3 mm. Intrinsically safe circuits must be clearly identified. Between intrinsically safe and other circuits At modular terminal blocks, the distance between the conductive parts of intrinsically safe circuits and the conductive parts of nonintrinsically safe circuits must be at least 50 mm. The spacing can also be created using a separating plate made of insulation material or a grounded metal plate. Cables/conductors of intrinsically safe circuits may not come into contact with a non-intrinsically safe circuit, even if they should become separated from the modular terminal block. The cables/conductors must be correspondingly shortened during installation. Minimum 1.0 mm 2 crosssectional area Flexible Version Light rubber tubing without/with polychloroprene sheathing Heavy rubber tubing without/with polychloroprene sheathing Plastic-insulated conductor, comparable heavy rubber tubing The cables and conductors must be selected accordingly for intrinsically safe circuits: Selection criteria for cables/conductors for the intrinsic safety Criterion Condition Note Isolated cables/ conductors Diameter of individual conductors Fine-strand conductors Multi-strand cables/ conductors Parameters Test voltage 500 V AC 0.1 mm Protect against unsplicing Permitted (C C and L C ) or (C C and L C / R C ) Conductor-ground, conductor-shield and shield-ground For fine-strand conductors as well e.g. with ferrules Take into account the error monitoring from EN if in doubt: worst-case Special cases for grounding conductive shields in intrinsically safe circuits a b c Reason Shield has a high resistance, additional shielding against inductive interferences Equipotential bonding between both ends Multiple grounding via small capacitors Conditions Sturdy ground conductor (min. 4 mm 2 ), insulated ground conductor and shield: insulation test 500 V, both grounded at one point, Ground conductor fulfills the requirements for intrinsic safety and is taken into account in the proof High guarantee that the equipotential bonding is guaranteed Total capacitance not over 10 nf Several intrinsically safe circuits can be routed in multi-conductor cables. Spacing acc. to EN , ch or fig. 1. Special requirements in zone 0, Europe The standard EN "Special requirements for the construction, testing and labeling of electrical equipment for equipment group II, category 1G" (corresponding to the ATEX directive 94/9/ EC) supplements EN ff. This describes further requirements for using operating equipment with other protection method as intrinsic safety in zone Phoenix Contact

21 8. Surge Voltage Protection in the Hazardous Area Surge voltages Surge voltages are an important topic where functional endurance and the availability of electrical equipment are concerned. Increasing automation, in conjunction with more and more powerful electronic components, involves a higher susceptibility to transient surge voltages. These interferences are disturbing pulses that quickly change through time and can reach amplitudes of several kv in a few microseconds. The most frequent cause for the occurrence of surge voltages is not lightning, as generally assumed, but switching transients at the facility. Electrostatic is also a considerable cause in many areas. Once a surge voltage has occurred, then malfunctioning, short-term functional interruptions or in the worst case, complete failures due to destruction can often occur. Modular terminal block with integrated surge voltage protection TT-EX(I)- 24DC IN 2 4 OUT Protection devices of the product series MCR-PLUGTRAB are especially userfriendly. The decoupling elements (resistors) are contained in the base element and remain in the circuit regardless of whether the protective plug is plugged into the base element or not. For use in potentially dust-explosive areas, the surge voltage protection devices must be installed in housings with a protetion level of at least IP 6X, directly before the volume to be protected. In the potentially gas-explosive area, an IP 4X housing is sufficient. If signal conductors of an intrinsically safe circuit lead into the inside of a container in which flammable liquids are stored, the surge voltage protection devices must be installed in a metal housing directly before the tank wall in accordance with TRbF 100 (Technical Regulations for Flammable Liquids). This must be connected with the tank in such a way that a secure equipotential bonding can be assumed. In order to prevent direct strikes in already protected conductors, the conductors must be routed between the housing and tank, for example in metal tubes. 1 unprotected 3 protected Protection circuit of the modular terminal block TT-EX(I)-24DC and the basic terminal blocks TT-PI-EX-TB The function principle can be easily explained using the above protection circuit as an example. When a surge voltage occurs, the suppressor diode operates first as the fastest component. The protection circuit is designed so that when the amplitude increases, the discharge current passes to the upstream discharge path, i.e. to the gas-filled surge arrester, before the suppressor diode can be destroyed. With this design, it is possible to attain a surge arresting capacity of 10 ka (8/20)µs with a very low and precise voltage threshold. If the discharge current remains low, then the upstream gas-filled surge arrester does not operate. This circuit provides the advantages of fast operating surge arresters with a low voltage threshold as well as a high surge arresting capacity at the same time in the case of a powerful surge voltage coupling. Surge voltage protection devices help to control this threat and thereby increase the life span of the protected installation. In instrumentation and data processing, the protection devices are connected into the signal circuit directly before the device interface to be protected. The connections of the surge arresters are labeled with "IN" and "OUT". During installation, make sure that "IN" points in the direction from which the surge voltage is expected. This enables the accurate functionality of multi-stage protection circuits function correctly. Basic terminal block with integrated surge voltage protection TT-PI-EX-TB Phoenix Contact 21

22 02-25 Ex-Basics Seite 22 Mittwoch, 27. November :28 08 Example: Holding tank In a tank farm for chemical products, disruptive errors can develop in the system software that cause the uncontrolled or simultaneous triggering of several valves and thus produce intense reactions. In order to prevent the inadmissibly high potential differences, an equipotential bonding is first set up between the control board and the holding tanks. If a lightning bolt discharges with ib (t) = 30 ka(10/350 µs), it is calculated according to IEC that only approx. 50% of the lightning current will be discharged into the ground if no risk analysis has been performed. If one assumes that the remaining 15 ka(10/350) µs initially only flows over the equipotential lead, the following maximum ohmic potential difference between the control board and the holding tank with a copper cross section of 95 mm2 : îb I RCU with RCU = 2 A ûr = = 17.3 ûr = 100 m IN 4 20 ma 4 20 ma + 24 VDC Cconductor = 20 nf Lconductor = 2 x 100 µf Ci 30 V Ii 200 ma Pi 1 W Ci1 = 0 nf Li1 20 nh PT 2X EX (I)-24 DC Ci3 < 5 nf Li3 < 1 µh Proof of intrinsic safety!! 1. Uo Ui Io Ii RCU 2. Co1 + Ci2 + Cconductor 3. Lo1 + Li2 + Lconductor +- TT-EX (I)-24 DC Ci2 < 2.5 nf Li2 < 1 µh -+ PI-EX-RPSS-I/I Uo = 28 V Io = 93 ma Po = 650 mw! Po Pi! + Ci3 Co! + Li3 Lo - GND -+ Co = 83 nf Lo = 4.3 mh L Level measurement: Protection of the controller by TERMITRAB TT-EX(I)-24DC and basic terminal block PI-EX-TB and 100 m mω mm2 m IN mω mm2 100 m 30 ka m 95 mm2 OUT 9, ma 4 20 ma + 24 VDC ûr = 273 V At first glance, the combination of equipotential leads and the required insulation strength of 500 V seems to offer sufficient protection from partial lightning currents in intrinsically safe systems. However, in addition to the resistance per unit length, every conductor also has an inductance per unit length L. For a round copper conductor, a crosssection-independent inductance per unit length L 1 µh/m is assumed in practice. Furthermore, a lightning current of the curve form (10/350) µs reaches its amplitude (here: 15 ka) in approx. 10 µs and is reduced to 50% after approx. 350 µs. This yields a rate of front current rise of dib(part) dt ib(part) t ib(part) t = îb(part) T1 ib(part) t = 1.5 = îb 30 ka = 2 T µs ka µs Phoenix Contact Cconductor = 20 nf Lconductor = 2 x 100 µf Ci 30 V Ii 200 ma Pi 1 W Ci1 = 0 nf Li1 20 nh TT-EX (I)-24 DC Ci2 < 2.5 nf Li2 < 1 µh Proof of intrinsic safety!! 1. Uo Ui Io Ii RCU 2. Co1 + Ci2 + Cconductor 3. Lo1 + Li2 + Lconductor L! Po Pi! + Ci3 Co! + Li3 Lo PI-EX-RPSS-I/I Uo = 28 V Io = 93 ma Po = 650 mw -+ - GND Co = 83 nf Lo = 4.3 mh Basic terminal block with integrated surge voltage protection TT-PI-EX-TB Ci3 = 3 nf Li3 = 1 µf Level measurement: Protection of the controller by the basic terminal block TT-PI-EX-TB with integrated surge voltage protection according to Faraday s law: ul (t) = - L ûl - L I The inductive voltage drop that occurs along the equipotential lead is calculated 22 OUT 9,2 ûl -1 dib(part) dt ib(part) t ka µh 100 m 1.5 m µs ûl -150 kv Intrinsically safe circuits that run between the holding tank and the control board are thereby destroyed. The potential difference at the protected volume can only be limited to harmless values by the consistent use of surge voltage protection devices.

23 9. Hazardous Approved Modular Terminal Blocks Modular terminal blocks are used as approved components in the potentially explosive area. They are used in connection spaces of Ex equipment. The use in zone 1 and 2 for gases and in 21 and 22 for dusts is therefore allowed. The requirements for IP protection are fulfilled by the connection space in accordance with the respective safety category. The approval of components serves as the basis for certifying a device or protection system. The modular terminal block is identified as a component by the certificate number (suffix "U" according to European standard) or the approval mark (e.g. UL: recognition mark A). Modular terminal blocks with the "increased safety" category must have identification. Information on the details can be found on page 14 in the section "Components". Increased safety Ex e Modular terminal blocks must also meet the requirements for the connection of external conductors. The standards for the increased safety form the basis for the test. The most important requirements for modular terminal blocks can be summarized as follows: Modular terminal blocks for external conductors must be generously dimensioned. Modular terminal blocks must be secured against loosening, fastened and designed so that the conductors cannot become undone. Modular terminal blocks must be designed to guarantee sufficient contact pressure without the conductors being damaged. This is particularly important in the case of multiple-wire (fine-strand) conductors that are used in terminal blocks for connecting conductors directly. Modular terminal blocks must be designed so that their contact pressure during normal operation is not altered by a change in temperature. Under no circumstances may insulating material parts be used to transmit the contact pressure. Modular terminal blocks that are intended for the connection of multi-wire conductors must be fitted with an intermediate elastic element. The technical data for modular terminal blocks in the hazardous area are specified by the type-examination and documented in the certificate. The basic data for the use of modular terminal blocks and accessories are: working voltage, nominal current, connectable conductor cross-sections, temperature range, temperature class. X--Note The standard modular terminal blocks with screw, spring-cage and fast connection technology from Phoenix Contact are approved worldwide for applications in the hazardous area. Further information can be found at: Phoenix Contact 23

24 Intrinsic safety Ex i With intrinsic safety, no special requirements are made for conductor connections concerning secured screws, solder connections, plug connections etc. This is due to the fact that the current, voltage and power values are so low in circuits proven to be intrinsically safe, that there is no danger of explosion. No special type tests or identifications are planned for passive components such as e.g. modular terminal blocks and plug connectors. Blue is the usual color for terminal Ex e and Ex i in the same housing In electrical equipment, such as e.g. terminal boxes, both intrinsically safe (Ex i) and (Ex e) circuits with increased safety can be combined. In this case, safe mechanical and, if necessary, also visual separation is stipulated. It must be taken into account that individual conductors do not come into contact with live parts of the other circuits when the wiring is disconnected from the modular terminal block. The distance between the modular terminal blocks must be at least 50 mm. Conventional wiring procedures must be Clearance distance through separating plate between intrinsically safe circuits and other circuits housings to clearly identify intrinsically safe electric circuits. This is why almost all modular terminal blocks from Phoenix Contact are also available in blue housings. Strict demands are placed on the clearance distances between adjacent terminal blocks and between terminal blocks and grounded metal parts. The clearance distance between the external connections of two neighboring intrinsically safe circuits must be at least 6 mm. The minimum clearance distance between non-insulated connections and grounded metal parts or other conductive parts, on the other hand, need only be 3 mm. Clearance and creepage distances as well as distances through rigid insulation are specified e.g. in EN , section 6.3 and table 4. X-Note In the data sheets, Phoenix Contact not only documents data for intrinsic safety, but also for the protection method "increased safety". followed to make contact between the circuits improbable even if a conductor were to come loose. In control cabinets with a higher wiring density, this separation is achieved by either insulating or grounded metallic partition plates. The distance between intrinsically safe and nonintrinsically safe electric circuits must also be 50 mm. Measurements are made in all directions around the partition plates. The distance may be less if the partition plates come within at least 1.5 mm of the housing wall. Metallic partition plates must be grounded and must be sufficiently strong and rigid. Metallic partition plates must be at least 0.45 mm thick; non-metallic insulating partition plates must be at least 0.9 mm thick. The Ex e circuits must be additionally protected in the housing by a cover (at least IP 30) if the end cover is allowed to be opened during operation. Otherwise, it is only permissible to open the end cover when the Ex e circuits are switched off. Corresponding warning signs must be provided. Clearance distances to intrinsically safe circuits and other circuits must also be observed even when there are several mounting rails. Separating plate between mounting rail to ensure clearance distance 24 Phoenix Contact

25 10. Cable/Conductor Leads and Conduit Systems Two installation techniques are used worldwide. In Europe, cable/conductor leads protection method "flame-proof Ex d in encapsulation" or "increased safety" are most commonly used. In the USA and Canada, the conduit system is traditionally used. Conductors (single wires) Sealing compound Mineral fiber wool (asbestos-free) Cable/conductor leads The cable/conductor leads are designed in protection method "pressure-tight encapsulation". This is flame-proof and is used in conjunction with flame-proof encapsulated housings. Designs can also be available with protection method "increased safety". The cable/conductor leads fulfill the requirements for IP protection here. They are used together with housings in protection method "increased safety". Cable system with direct entry Conduit system In the USA, value is especially placed on high mechanical protection of the cables/ conductors. For this reason, the conduit system has become very common in the USA. Conductor protection tube (Ex d) Ignition lock (seal) Comparison of cable/conductor leads with conduit system In comparison with the cable/conductor leads, the disadvantages of the conduit system can be seen in the time-consuming assembly. If the ignition lock is not properly sealed, then protection cannot be guaranteed. The cable/conductor leads, on the other hand, is designed so that the assembly does not depend on the respective fitting. During installation, the position of the opening is also decisive for the sealing compound. In addition, condensation can form very easily in conduit systems. This can lead to ground faults and short circuits as a result of corrosion. Cable system with indirect entry Conduit system Phoenix Contact 25

26 11. IP Protection, NEMA Classification IP protection IP 5 4 First characteristic numeral Degrees of protection against access to dangerous parts and solid foreign Second Degree of protection against water bodies charac- Short description Definition teristic numeral Short description Definition 0 Not protected 0 Not protected 1 Protected against touching dangerous parts with the back of one s hand. Protected against solid foreign bodies of 50 mm diameter and larger. 2 Protected against touching dangerous parts with a finger. Protected against solid foreign bodies of 12.5 mm diameter and larger. 3 Protected against touching dangerous parts with a tool. Protected against solid foreign bodies of 2.5 mm diameter and larger. 4 Protected against touching dangerous parts with a wire. Protected against solid foreign bodies of 1.0 mm diameter and larger. 5 Protected against touching dangerous parts with a wire. Dust-protected The access probe, a sphere 50 mm in diameter, must be at a sufficient distance from dangerous parts. The object probe, a sphere of 50 mm diameter, may not enter entirely 1 ). The segmented test finger, 12 mm in diameter, 80 mm long, must be at a sufficient distance from dangerous parts. The object probe, a sphere of 12.5 mm diameter, may not enter entirely 1 ). 1 Protected against dripping water. 2 Protected against dripping water when the housing is inclined at an angle of up to Vertically falling drops must not have any detrimental effect. Vertically falling drops must not have any detrimental effect when the housing is inclined at an angle of up to 15º on both sides of the perpendicular. 3 Protected against spray water. Water that is sprayed at an angle of up to 60 on both sides of the perpendicular must not have any detrimental effect. 4 Protected against splash water. The access probe, 2.5 mm in diameter, must not enter. 4K Protected against splash water with increased pressure. The object probe, 2.5 mm in diameter, may not enter at all 1 ). Water that is splashed against the housing from any direction must not have any detrimental effect. Water that is splashed against the housing with increased pressure from any direction must not have any detrimental effect. (acc. to DIN part 9 only applies to road vehicles) The access probe, 1.0 mm in diameter, must not enter. 5 Protected against jet water. Water that is splashed against the housing as a jet from any direction must not have any detrimental effect. The object probe, 1.0 mm in diameter, must not enter at all 1). 6 Protected against strong jet water. The access probe, 1.0 mm in diameter, must not enter. 6K Protected against strong splash water with increased pressure. The entrance of dust is not completely prevented, but dust may not enter in such an amount that the satisfactory operation of the device or the safety is impaired. Water that is splashed against the housing as a strong jet from any direction must not have any detrimental effect. Water that is directed against the housing as a jet with increased pressure from any direction must not have any detrimental effect. (acc. to DIN part 9, only applies to road vehicles) 6 Protected against touching dangerous parts with a wire. Dust-proof The access probe, 1.0 mm in diameter, must not enter. 7 Protected against the effects of temporary submersion in water. No intrusion of dust. Water must not enter in such an amount that it causes detrimental effects when the housing is temporarily submerged in water under standard pressure and time conditions. 1 ) The complete diameter of the object probe must not pass through an opening of the housing. Note If one characteristic numeral does not need to be specified, it must be replaced with the letter "X". Devices that are identified with the second characteristic numeral 7 or 8 do not have to fulfill the requirements of the second characteristic numerals 5 or 6, unless they have a double identification (e.g. IP X6/IP X7). No conditions are specified for IP X8. The conditions can be specified by the manufacturer. 8 Protected against the effects of continuous submersion in water. 9K Protected against water during high-pressure / jetstream cleaning. Water must not enter in such an amount that it causes detrimental effects when the housing is continuously submerged under water under conditions that are to be agreed upon between the manufacturer and the user. The conditions must be more difficult than those for the characteristic numeral 7, though Water that is directed against the housing with greatly increased pressure from any direction must not have any detrimental effect. (acc. to DIN part 9 only applies to road vehicles) NEMA classification NEMA Application Condition (based on NEMA standard 250) IP protection type* 1 Indoors Protection against accidental contact, limited amount of dirt IP 20 2 Indoors Intrusion of dripping water and dirt 3 Outdoors Protection against dust, rain, no damage when ice forms on the housing IP 64 3R Outdoors Protection against falling rain, no damage when ice forms on the housing IP 22 3S Outdoors Protection against dust, rain and hail; external mechanisms remain operable when ice forms IP 64 4 Indoors or outdoors Protection against splash water, dust, rain, no damage when ice forms on the housing IP 66 4x Indoors or outdoors Protection against splash water, dust, rain; no damage when ice forms on the housing; protected against corrosion IP 66 6 Indoors or outdoors Protection against dust, water jet and water during temporary submersion; no damage when ice forms on the housing IP 67 6P Indoors or outdoors Protection against water during longer submersion; protected against corrosion 11 Indoors Protection against dripping water; protected against corrosion 12, 12K Indoors Protection against dust, dripping water IP Indoors Protection against dust and splash water, oil and non-corrosive liquids IP 65 Important: The test conditions and requirements of the NEMA classification and IP protection (EN ) are not the same. IP protection types cannot be converted into NEMA classifications. 26 Phoenix Contact

27 I What is NAMUR? The term NAMUR (Standardization Association for Measurement and Regulation Technology in the Chemical Industry) applies to proximity switches. This type of sensor is ideally suited for intrinsically safe circuits. NAMUR sensor The proximity switch is equipped with an internal resistance. These are operated with a two-wire connection cable that is connected to the control input of a switching amplifier. The sensor is blocked when the value is below 1.2 ma and opened when the value is over 2.1 ma. Within these limits is an impermissible state. This ensures that unambiguous states are attained. Division of proximity switches 1st position/ 1 character Classification type I = inductive C = capacitive U = ultrasound D = photoelectrically diffuse reflecting light beam R = photoelectrically reflecting light beam 2nd position/ 1 character Mechanical installation conditions 1 = can be mounted flush 2 = cannot be mounted flush 3 = not determined 3rd position/ 3 character Design and size FORM (1 capital letter) A = cylindrical threaded sleeve B = smooth cylindrical sleeve C = rectangular with square cross-section D = square with square crosssection 4th position/ 1 character Switching element function A = N/O contact B = N/C contact P = can be programmed by user S = other 5th position/ 1 character Output type D = 2 DC connections S = other 6th position/ 1 character Type of connection 1 = integrated connection cable 2 = plug-in connection 3 = screw connection 9 = other 8th position/ 1 character NAMUR function N = NAMUR function T = photoelectrically direct light beam SIZE (2 numerals) for diameter or side length Note: This table is an extension of the table from EN (previously DIN ). NAMUR Sensor EX Safe area PLC NAMUR sensor in the field UB+ UB- UB+ UB 24 V Mains voltage I 3 ma ma 2 0 Switching points 2,1 1,2 Example of a continuous characteristic curve of a proximity sensor 2,1 Switching current difference Spacing Trav avel difference S s I1 Circuit design with a NAMUR sensor in the Ex area. NAMUR switching amplifier NAMUR switching amplifiers allow the following signals and characteristics of NAMUR sensors to be evaluated. a Operating range for changing the switching state I 1 : 1.2 ma to 2.1 ma, b Operating range for interrupting the control current circuit I 1 : 0.05 ma to 0.35 ma, c Monitoring range for interruptions I 0.05 ma, d Operating range for short circuits in the control circuit R: 100 Ω to 360 Ω, e Monitoring range for short circuits R 100 Ω. PI-EX-NAM/RNO-NE U V c b a I 1 I / ma Control input of the NAMUR switching amplifier d R = 360 Ω R = 100 Ω e I 1 1,2 s 0 Spacing S Example of a non-continuous characteristic curve of a proximity sensor Phoenix Contact 27

28 13. Smart-Compatible Devices In the process industry, a configuration must be performed or diagnostic data determined for a large number of analog field devices during commissioning and maintenance as well as during operation. To enable such communication to field devices, digital information is superimposed on the analog signal. For this purpose, all the involved devices must be "Smart"- compatible. In practice, the HART protocol has become established for this type of communication. Since this technology is currently the most widely used one and is the "de facto" standard, the "Smart" topic will be explained using this technology as a basis. With the HART protocol, the transmission of the digital information is modulated to the analog 4-20 ma signal with the help of frequency shift keying (FSK). In general, two possible operating modes are distinguished: "point-to-point" mode, in which communication is only possible to one field device connected in the 4-20 ma circuit, and "multi-drop" mode, in which up to 15 field devices in the circuit can be connected in parallel. These two operating modes basically differ in the fact that in "point-topoint" mode, the analog 4-20 ma signal can continue to be used in the usual way and transmits the desired process signal. In this case, additional data can also be transmitted in digital form. In "multi-drop" mode, a current signal of 4 ma is used in the field device as a carrier medium to transfer the exclusively digital information to and from the connected field devices. Analog signal superimposed with digital HART signal The devices can be connected in point-topoint mode as well as in multi-drop mode (with up to 15 stations). In the case of pointto-point mode, the ma signal remains available as a process signal as usual. For multi-drop mode, a load-independent, minimum current of 4 ma is needed for the analog signal. 20 ma 4 ma 2200 Hz 1200 Hz "0" "1" 1200 Hz "1" Digital signal 2200 Hz "0" 2200 Hz "0" Analog signal Using the additional digital signals, it is possible to perform diagnostics and configurations of HART-capable field devices in the system on this communication path. The aids that are used to implement this functionality depend on the technical infrastructure of the system installation. The diagnostics and configurations of the field devices can be carried out directly in the field as well as at the terminals of the interface devices with the help of a handheld device. If the HART data is transmitted to higher-level engineering tools with HART multiplexers or via I/O modules of the control level, then they can also be used e.g. by asset management systems. Asset management systems offer the possibility of performing configuration and diagnosis functions automatically and additionally provide the technical framework for archiving the field device data (e.g. parameter settings etc.). t Design with HART signal supply Depending on the physical structure, the control level can also use the HART communication to influence the field device (setpoint, measurement range change etc.) Smart transmitter EEx ia ϑ I EX Safe area Transmitter/converter [EEx ia] i 4-20 ma khz HARTconfiguration device from the control unit or to request additional data (e.g. process signals). In recent time, the use of HART information has been implemented in more and more applications. As in standard installations (without HART communication) as well, interface devices are used to connect the field devices (sensors and actuators) and the I/O level of the control unit. To transmit the data that has been modulated to the analog 4-20 ma signal reliably and without interference, the interface devices used for this must be "Smart"-compatible. That means that no influences on the HART signal may occur during operation, e.g. from filters. In the case of interface devices for signal level matching with electrical isolation or Ex isolation etc., the HART signal is decoupled in the interface device and transmitted separately. Otherwise, it would not be possible to transmit the data from these devices. In addition, the connected load in the circuit must also be taken into account. i 28 Phoenix Contact

29 14. Application/Installation Examples Analog IN / OUT Digital IN / OUT Temperature Phoenix Contact 29

30 Analog IN Function The devices transmit analog signals from sensors in the field to a control unit, using electrical isolation. Input isolator: The sensor in the field is not supplied with power. Transmitter/converter: Additionally supplies the sensor with the required power. Field device Evaluation of the Ex code Associated apparatus Category of the field device corresponds to the assigned zone Type of protection is permitted in the assigned zone The gas is permitted in the assigned group and for the temperature class Associated apparatus is identified as such Category of the associated apparatus fulfills at least the category of the field device Type of protection of the associated apparatus is suitable for the field device Associated apparatus is suitable for the gas group of the field device (same or better quality) Smart transmitter/converter: Additionally modulated digital data signal is transmitted. Note: The operator determines the zone, the group and the temperature class for the field device, based on the performed risk analysis. Example of a circuit EX Safe area D ( A ) D ( B ) R ( A ) R ( B ) G N D 6 R S PSM-ME-RS232/RS485-P R S Ord.-Nr.: PLC Field device X II 1 G EEx ia IIB T6 Associated apparatus, e.g. PI-EX-ME-RPSS-I/I X II (1) GD [EEx ia] IIC Comparison of the safety-relevant data from the Ex approval (ATEX) Field device Cable/line Associated apparatus Example PI-Ex-ME-RPSS-I/I U i U o 28 V I i I o 93 ma P i P o 0.65 W C i + C c C o IIB = 650 nf IIC = 83 nf L i + L c L o IIB = 14 mh IIC = 2 mh 30 Phoenix Contact

31 R S R S Analog OUT Function The devices transmit analog signals from a control unit to an actuator in the field, using electrical isolation. Output isolator The output isolator can also be smartcompatible. In this way, actuators in the field can be configured using the HART protocol. Note: The operator determines the zone, the group and the temperature class for the field device, based on the performed risk analysis. Field device Evaluation of the Ex code Associated apparatus Example of a circuit Category of the field device corresponds to the assigned zone Type of protection is permitted in the assigned zone The gas is permitted in the assigned group and for the temperature class Associated apparatus is identified as such Category of the associated apparatus fulfills at least the category of the field device Type of protection of the associated apparatus is suitable for the field device Associated apparatus is suitable for the gas group of the field device (same or better quality) EX Safe area PSM-ME-RS232/RS485-P Ord.-Nr.: D ( A ) D ( B ) R ( A ) R ( B ) G N D 6 PLC Field device X II 1 G EEx ia IIB T6 Associated apparatus, e.g. PI-EX-ME-ID-I/I X II (1) GD [EEx ia] IIC Comparison of the safety-relevant data from the Ex approval (ATEX) Field device Cable/line Associated apparatus Example PI-Ex-ME-ID-I-I U i U o 12.6 V I i I o 87 ma P i P o 0.67 W C i + C c C o IIB = 830 nf IIC = 250 nf L i + L c L o IIB = 4.5 mh IIC = 1.2 mh Phoenix Contact 31

32 Digital IN NAMUR switching amplifier The devices transmit digital signals from sensors in the field to the control unit, using electrical isolation. On the control side, the signal is transferred to the control unit as a digital signal either through a relay or through a transistor This signal is created on the one hand by a switch or by a NAMUR sensor. In the case of switches, it is possible to implement the line interrupt detection at the same time with an additional resistance circuit. Field device Evaluation of the Ex code Associated apparatus Example of a circuit Category of the field device corresponds to the assigned zone Type of protection is permitted in the assigned zone The gas is permitted in the assigned group and for the temperature class Associated apparatus is identified as such Category of the associated apparatus fulfills at least the category of the field device Type of protection of the associated apparatus is suitable for the field device Associated apparatus is suitable for the gas group of the field device (same or better quality) EX Safe area 1 1 D ( A ) D ( B ) R ( A ) R ( B ) G N D 6 R S PSM-ME-RS232/RS485-P R S Ord.-Nr.: PLC With line interrupt detection Without line interrupt detection The resistance is used to ensure that a minimum current is always flowing, even when the switch is open. In this way, a line interrupt can be identified. Note: The operator determines the zone, the group and the temperature class for the field device, based on the performed risk analysis. Field device X II 1 G EEx ia IIB T6 Associated apparatus, e.g. PI-Ex-ME-2NAM/COC-24VDC X II (1) GD [EEx ia] IIC Comparison of the safety-relevant data from the Ex approval (ATEX) Field device Cable/line Associated apparatus Example U i Passive acc. to U o 10.5 V EN I i Passive acc. to I o 26 ma EN P i Passive acc. to P o 0.67 W EN C i + C c C o IIB 16.8 µf IIC 2.41 µf L i + L c L o IIB 160 mh IIC 45 mh 32 Phoenix Contact

33 Digital OUT Valve control block The valve control blocks PI-Ex- link a switch or power supply installed in the safe area to a device located in the hazardous area. Intrinsically safe solenoid valves, alarm modules or other intrinsically safe devices can be connected, and simple electrical devices such as LEDs can be operated. Field device Evaluation of the Ex code Associated apparatus Category of the field device corresponds to the assigned zone Type of protection is permitted in the assigned zone The gas is permitted in the assigned group and for the temperature class Associated apparatus is identified as such Category of the associated apparatus fulfills at least the category of the field device Type of protection of the associated apparatus is suitable for the field device Associated apparatus is suitable for the gas group of the field device (same or better quality) Dimensioning Example of a circuit Safe area R i IV Valve isolator R C ISV Solenoid valve R SV EX PWR U V U SV UB+ UB- PLC R i = internal resistance of the valve isolator U V = guaranteed voltage of the valve isolator without load R C = maximum permissible line resistance when valve isolator and valve are interconnected R SV = effective coil resistance of the solenoid valve (the copper resistance of the coil depends on the ambient temperature) I V = maximum current that the valve isolator can supply I SV = current needed by the solenoid coil in order for the valve to pick up or be stopped U SV = voltage that is present at the coil with I SP (copper resistance of the coil depends on the ambient temperature) The dimensioning takes place in several steps. Intrinsically safe electrical equipment X II 1 G EEx ia IIB T6 Example for valve control blocks PI-Ex-SD/22/45-C Associated apparatus, e.g. PI-Ex-SD/22/45-C X II (1) GD [EEx ia] IIC Text of the Ex data Valve isolator E[Ex ia] IIC, U o = 25 V, I o = 147 ma, P o = 0.92 W Valve EEx ia IIC, U i = 25 V, I i = 150 ma, P i = 2.1 W This means that the Ex data match U i U o, I i I o, P i P o Test of the function data Valve isolator U V = 21.4 V, R i = 190 Ω, I V = 45 ma Valve R SV 65 C = 566 Ω, I SV = 23 ma This means that the currents are suitable I V I SV Determining R C R C = U V - R i - R SV = 21.4 V Ω Ω = Ω I SV A The calculation yields the result that a resistance of 174 Ω is available for the cable. If a negative resistance results from the calculation, the function is not guaranteed. 1.Test of the safety data (Ex data) U i U o I i I o P i P o 2.Test of the function data I v I sv 3.Determining the max. permissible line resistance R C = U V I SV - R i - R SV R C > 0 Ω, otherwise the function is not ensured. Recommended value for cables / lines Conductor resistance (supply / return line) Cable capacity Cable inductance 0.5 mm 2 : 72 Ω/km 0.75 mm 2 : 48 Ω/km 1.5 mm 2 : 24 Ω/km approx. 0.8 nf/km approx. 180 mh/km Note: The operator determines the zone, the group and the temperature class for the field device, based on the performed risk analysis. Phoenix Contact 33

34 PWR Temperature Temperature measurement Safe area Temperature transducer Temperature transducers convert measurement signals from changeable resistors (Pt100 etc.) or thermocouples (e.g. J, K) into standard signals 0 20 ma, 4 20 ma. 2, 3, or 4-conductor measurement technology can be used for Pt100 resistors. Case I Pt100 ϑ EX PWR UB+ UB- PLC Case II 2-conductor short cables / lines 3-conductor long cables / lines UB+ UB- UB- 4-conductor long cables / lines Pt100 ϑ PLC Temperature measurement The temperature inside a heating oil tank is to be monitored. The measurement is done using a Pt100 resistor. This is defined as a simple electrical equipment. The resistance is passive. There are two possibilities for converting the measurement signal into a standard signal for the control unit. Field device Evaluation of the Ex code Associated apparatus Category of the field device corresponds to the assigned zone Type of protection is permitted in the assigned zone The gas is permitted in the assigned group and for the temperature class Associated apparatus is identified as such Case I The sensor signal is converted into a nonintrinsically safe standard signal in the temperature transducer. Category of the associated apparatus fulfills at least the category of the field device Type of protection of the associated apparatus is suitable for the field device Associated apparatus is suitable for the gas group of the field device (same or better quality) Case II The sensor signal is converted to a standard signal in an intrinsically safe temperature transducer. The intrinsically safe and nonintrinsically safe circuits are isolated in a separate device. Example of a circuit EX Safe area PWR Note: The operator determines the zone, the group and the temperature class for the field device, based on the performed risk analysis. Case I The measurement signal is carried from the Pt100 resistor via a signal line to the temperature transducer PI-Ex-RTD-I. In the measuring transducer, the temperature signal is converted to a standard signal, and the isolation between the intrinsically safe and non-intrinsically safe circuits takes place at the same time. The measuring transducer is an associated electrical equipment of the Type of Protection "intrinsic safety EEx ia". It is installed in a control cabinet in the safe area. In this case, the circuit does not require any further expense for electrical dimensioning. ϑ Intrinsically safe electrical equipment Pt100 2-wire connection X II 1 G EEx ia IIB T6 Associated apparatus, e.g. PI-Ex-RTD-I X II (1) GD [EEx ia] IIC Comparison of the safety-relevant data from the Ex approval (ATEX) Pt100 resistor Cable/line Associated apparatus Example PI-Ex-RTD-I 2-conductor 3-conductor Passive acc. to U o 1.1 V 6.6 V EN I o 4 ma 27 ma UB+ PLC P o 1 mw 50 mw + C c < C o IIA = 1000 µf IIB = 500 µf IIC = 22 µf + L c < L o IIA = mh IIB = mh IIC = 48.7 mh 34 Phoenix Contact

35 PWR Case II In the second case, the conversion of the temperature signal to a standard signal takes place near the measuring point, in other words in the hazardous area. The temperature sensor head MCR-FL-HT-TS-I- Ex is used for this purpose. The standard signal is then passed on to the transmitter/ converter PI-Ex-RPSS-I/I. This is installed in the safe area. The isolation of the intrinsically safe and non-intrinsically safe circuits takes place in the transmitter/converter. As in the first case, no special conditions have to be met for the Pt100 resistor and the sensor head. The safety-relevant data of the electrical equipment, the temperature sensor head and the transmitter/converter as related electrical equipment must be compared. The voltage, current and energy of the transmitter/converter that lead into the Ex area must be smaller than the permissible input values of the temperature sensor head. In addition, it is necessary to make sure that the sum of all capacitances and inductances in the intrinsically safe circuit do not exceed the data specified for the transmitter/ converter. These also include the technical data of the cables and lines of the intrinsically safe circuit. Example of a circuit ϑ Intrinsically safe electrical equipment Pt100 2-wire connection X II 1 G EEx ia IIB T6 Field device Evaluation of the Ex code Associated apparatus EX Intrinsically safe electrical equipment MCR-FL-HT-TS-I-Ex X II 1 G EEx ia IIB T6 Comparison of the safety-relevant data from the Ex approval (ATEX) Safe area Note: Associated apparatus necessary. Pt100 resistor Cable/line Electrical equipment Example MCR-FL-HT-TS-I-Ex Passive acc. to EN U o U i = 30 V I o I i = 100 ma P o P i = 750 mw + C c < C o C i 0 + L c < L o L i 0 Category of the field device corresponds to the assigned zone Type of protection is permitted in the assigned zone The gas is permitted in the assigned group and for the temperature class Associated apparatus is identified as such Category of the associated apparatus fulfills at least the category of the field device Type of protection of the associated apparatus is suitable for the field device Associated apparatus is suitable for the gas group of the field device (same or better quality) Example of a circuit EX Safe area UB- UB+ PLC Intrinsically safe electrical equipment MCR-FL-HT-TS-I-Ex X II 1 G EEx ia IIB T6 Associated apparatus, e.g. PI-Ex-RPSS-I/I X II (1) GD [EEx ia] IIC Comparison of the safety-relevant data from the Ex approval (ATEX) MCR-FL-HT-TS-I-Ex Cable/line Associated apparatus Example PI-Ex-RPSS-I/I U i = 30 V > U o 28 V I i = 100 ma > I o 93 ma P i = 750 mw > P o 650 mw C i 0 + C c < C o IIA = µf IIB = µf IIC = µf L i 0 + L c < L o IIA = mh IIB = mh IIC = 4.30 mh Phoenix Contact 35

36 Application in the USA The differences between the North American system for hazardous locations and the European system acc. to ATEX are shown using associated electrical equipment as an example. Special attention must be paid to the different indices for intrinsically safe circuits. Dimensioning of intrinsically safe circuits Hazardous area Safe area PLC 4 20 ma Common designations Europe USA For electrical equipment: Max. permissible voltage Max. permissible current Internal capacitance Internal inductance For associated apparatus: Max. open-circuit voltage Max. short-circuit current Max. permissible capacitance Max. permissible inductance U i I i C i L i U o I o C o L o V max I max C i L i V oc I sc C a L a Application in the USA In the USA, it is necessary to make sure that approvals are granted for hazardous areas in acc. with NEC 500 as well as acc. to NEC 505. Parameters for electrical equipment: V max : max. permissible voltage I max : max. permissible current C i : internal capacitance L i : internal inductance Parameters for associated apparatus: V oc : max. open-circuit voltage I sc : max. short-circuit current C a : max. permissible capacitance L a : max. permissible inductance Field device U Comparison of the safety-relevant data from the Ex approval (ATEX) Associated apparatus, e.g. PI-EX-ME-RPSS-I/I U Listed 1M68 Dark blue for class I, div. 2, groups A, B, C and D installation; providing intrinsically safe circuits for use in class I, div. 1, groups A, B, C and D; class II, groups E, F and G; and class III, hazardous locations Field device Cable/line Associated apparatus Example PI-Ex-ME-RPSS-I/I U i U o 28 V I i I o 93 ma P i P o 0.65 W C i + C c C o IIB = 650 nf IIC = 83 nf L i + L c L o IIB = 14 mh IIC = 2 mh 36 Phoenix Contact

37 15. Terms and Abbreviations Hazardous area terms Potentially explosive or hazardous area An area in which a potentially explosive atmosphere is present or can be expected in such an amount that special measures are needed in the construction, set up and use of electrical equipment. Hazardous area component A part of any electrical equipment for potentially explosive areas or a module (except for Ex cable/line leads), identified by the symbol "U" that may not be used by itself in such areas and requires an additional certificate when installed in electrical equipment or systems for use in potentially explosive areas. "U" symbol "U" is the symbol that is used behind the certificate number of the part certificate to identify an Ex component. "X" symbol "X" is the symbol that is used as an addition after the certificate to identify special conditions for safe application. Note: The symbols "X" and "U" are not used together. Intrinsically safe circuit A circuit in which neither a spark nor a thermal effect can cause the ignition of a particular potentially explosive atmosphere. Electrical equipment All components, electric circuits or parts of electric circuits that are usually to be found within a single housing. Intrinsically safe equipment Apparatus in which all circuits are intrinsically safe. Associated apparatus Electrical equipment that contains both intrinsically safe and non-intrinsically safe circuits and is designed in such a way that the non-intrinsically safe circuits cannot influence the intrinsically safe ones. Note: This can also be seen in the square parentheses and the round parentheses of the identification. Associated equipment also has to be installed outside of the potentially explosive area. Simple electrical equipment Electrical equipment or a combination of components with a simple design, with precisely determined electrical parameters and that does not impair the intrinsic safety of the circuit in which it is to be used. Abbreviations U i = maximum input voltage The maximum voltage (peak value of the AC voltage or DC voltage) that can be applied to the connection elements of intrinsically safe circuits without affecting the intrinsic safety. That means no voltage higher than the value of the associated U i may be fed to this intrinsically safe circuit. A possible addition of voltage must also be taken into account. See also EN appendix B. I i = maximum input current The highest current (peak value of the alternating current or direct current) that can be fed in through the connection elements of the intrinsically safe circuits without destroying the intrinsic safety. That means no current higher than the value of the associated U i may be fed to this intrinsically safe circuit. A possible addition of current must be taken into account here as well. See EN appendix B here too. P i = maximum input power The maximum input power in an intrinsically safe circuit that can be implemented within an electrical equipment when it is connected to an external power supply. That means that no intrinsically safe circuit with a higher power than P i may be connected here either. Here, a possible addition of power should be taken into account as well. Note on U i, I i and P i : Often, only one or two of the terms U i, I i or P i are given in the information in the certificates of conformity or EC typeexamination certificates. In this case, there are no restrictions for the terms that are not mentioned, since a further, internal limitation has already been integrated in this electrical equipment. Phoenix Contact 37

38 U o = maximum output voltage The highest output voltage (peak value of the AC voltage or DC voltage) in an intrinsically safe circuit that can occur under idling conditions at the connection elements of the electrical equipment with any applied voltage, up to the maximum voltage including U m and U i. That means that U o is the maximum noload voltage that can be present at the terminals at maximum auxiliary power in the case of a fault. U o is also decisive for the maximum values of the maximum external capacitance C o of an ohmic limitation with a linear characteristic curve acc. to the figures A1, A2 and A3 as well as table A.2 in EN , appendix A. I o = maximum output current The maximum current (peak value of the alternating current or direct current) in an intrinsically safe circuit that can be taken from the connection terminals of the electrical equipment. That means that I o corresponds to the previous short-circuit current I k. I o is also decisive for the maximum values of the maximum external inductance L o in the figures A 1, A 4, A 5 and A 6 in EN , appendix A for application. P o = maximum output power The highest electrical power in an intrinsically safe circuit that can be taken from the electrical equipment. That means that when a sensor or actuator is connected to this intrinsically safe circuit, this power must be reckoned with, e.g. when heating up or with the load in relation to the associated temperature class. C i = Maximum internal capacitance Effective equivalent capacity at the connection elements for the internal capacitances of the electrical equipment. L i = maximum internal inductance Effective replacement inductance at the connection elements for the internal inductances of the electrical equipment. C o = maximum external capacitance The maximum value of the capacitance in an intrinsically safe circuit that can be applied to the connection elements of the electrical equipment without destroying the intrinsic safety. That means that this is the maximum value that all of the capacitances working outside of the electrical equipment may attain. This also includes the addition of all line capacitances and external capacitances of this circuit. In the case of a linear ohmic current limitation, the value of C o above all depends on U o. See also figure A 2 or table A2 EN appendix A2, A3. L o = maximum external inductance The maximum value of the inductance in an intrinsically safe circuit that can be connected to the connection elements of the electrical equipment. That means that this is the value that all of the inductances working outside of the electrical equipment may attain. This includes the addition of all line inductances and external inductances of this circuit. In the case of a linear ohmic current limitation, L o above all depends on I o. See also EN , appendix A, figure A 4. Note: The index i stands for "in"; the index o stands for "out". C c = cable or line capacitance Intrinsic capacitance of a cable or a line. This depends on the cable or line. It is generally between 140 nf/km and 200 nf/ km. L c = cable or line inductance Intrinsic inductance of a cable or a line. One reckons with approx. 0.8 mh/km. U m = maximum effective value of the AC voltage or maximum DC voltage The maximum voltage that may be connected to non-intrinsically safe connection elements of the associated apparatus without affecting its intrinsic safety. That means that e.g. a U m = 250 V can be specified for the supply voltage and a U m = 60 V for the output. See also EN , appendix Electrical equipment that is connected to non-intrinsically safe connection terminal blocks of associated apparatus may not be supplied with a supply voltage that is larger than the U m that is listed on the nameplate of the associated equipment. For the above example, this means: Further electrical equipment with a supply voltage of up to 250 V can be connected to the power supply of the associated apparatus. Only one piece of electrical equipment with a supply voltage of up to 60 V can be connected to the output of the associated apparatus. I n = rated fuse current The rated current of a fuse acc. to EN or according to the manufacturer s specification. This the rated current that is specified for a fuse in the end. T a or T amb = ambient temperature The ambient temperature T a or T amb must be listed on the nameplate and specified in the certificate when it is outside the range of -20 C and + 40 C. Otherwise, the certificate number is given the symbol "X". 38 Phoenix Contact

39 16. Principles of signal transmission Active isolation 3-way isolation Input isolation Repeater power supply Input signal IN OUT Output signal Input signal IN OUT Output signal Feeding the measuring transducer Input signal IN OUT Output signal POWER POWER POWER In the case of modules with this isolation system, all components that are connected to the input, output, or supply are protected from each other against interferences. All three ways (input, output, and supply) are correspondingly electrically isolated from one another. The 3-way isolation provides an electrical isolation between the measurement sensor and the controller as well as between the controller and actuator. On the input side, the modules need active signals. On the output side, they provide a filtered and amplified signal. In the case of modules with this isolation system, the electronics connected on the output side (e.g. the controller) are to be protected from interferences from the field. For this reason, only the input is electrically isolated from the output and the supply, which lie on the same potential. On the input side, the modules need active signals (e.g. from measuring transducers). On the output side, they provide a filtered and amplified signal e.g. from the controller. Transmitter/converters use the signalinput side not only for measured value acquisition, but also to provide the necessary power to the loop-powered measurement sensors connected on the input side. On the output side, they provide a filtered and amplified signal e.g. from the controller. The isolation technique of these modules corresponds to input isolation. Loop-powered isolation Loop-powered isolation, supplied on the input side Loop-powered isolation, supplied on the output side Loop-powered repeater power supply Feed-in via signal Input signal IN OUT Output signal Input signal IN OUT Feed-in via signal Output signal Feeding the measuring transducer Input signal IN OUT Feed-in via signal Output signal The modules receive the power needed for signal transmission and electrical isolation from the active input circuit. On the output side, a conditioned current signal is provided to the controller or to actuators. This loop-powered isolation allows signal conditioning (interrupting of earth loops) and filtering without an additional power supply. The modules obtain the power needed for signal transmission and electrical isolation from the active output circuit, ideally from a PLC input card that supplies power. On the output side, the loop-powered modules work with a ma standard signal. On the input side, the loop-powered isolator processes active signals. When this isolation technique is used, it is important to make sure that the active signal source connected on the output side (e.g. an active PLC input card) is able to supply the loop-powered isolator as well as to operate its load. The modules receive the power needed for signal transmission and electrical isolation from the active output circuit. The loop-powered transmitter/converter also provides the power obtained from the output circuit to a loop-powered measurement sensor connected on the input side. The measurement sensor uses the provided power to supply an signal that the loop-powered transmitter/converter electrically isolates and makes available on the output side. For this reason, in a loop-powered transmitter/converter, the signal and energy flows generally run in opposite directions from each other. Phoenix Contact 39

40 Further information on the products introduced here and on the world of solutions from Phoenix Contact can be found at industrial Connection Systems, Marking and Mounting Material Clipline industrial Plug Connectors pluscon Or contact us directly! PCB Connection Systems and electronic housings COmbiCOn PhoeNix CoNtaCt Gmbh & Co. KG Blomberg, Germany Phone: +49/52 35/3-00 Fax: +49/52 35/ Components and Systems automation Surge Protection TrabTeCh Signal Converters, Switching Devices and Power Supplies interface MNR / Printed in Germany PhoeNix CoNtaCt 2007